< draft-arkko-pppext-eap-aka-10.txt		draft-arkko-pppext-eap-aka-11.txt >
	J. Arkko		Network Working Group J. Arkko
	Internet Draft Ericsson		Internet Draft Ericsson
	Document: draft-arkko-pppext-eap-aka-10.txt H. Haverinen		Document: draft-arkko-pppext-eap-aka-11.txt H. Haverinen
	Expires: December 2003 Nokia		Expires: 27 April, 2004 Nokia
	June 2003		27 October, 2003
	EAP AKA Authentication		EAP AKA Authentication
	Status of this Memo		Status of this Memo
	This document is an Internet-Draft and is subject to all provisions		This document is an Internet-Draft and is subject to all provisions
	of Section 10 of RFC2026.		of Section 10 of RFC2026.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF), its areas, and its working groups. Note that		Task Force (IETF), its areas, and its working groups. Note that
	skipping to change at page 1, line 31 ¶		skipping to change at page 1, line 31 ¶
	Internet-Drafts are draft documents valid for a maximum of six		Internet-Drafts are draft documents valid for a maximum of six
	months and may be updated, replaced, or obsoleted by other documents		months and may be updated, replaced, or obsoleted by other documents
	at any time. It is inappropriate to use Internet-Drafts as		at any time. It is inappropriate to use Internet-Drafts as
	reference material or to cite them other than as "work in progress."		reference material or to cite them other than as "work in progress."
	The list of current Internet-Drafts can be accessed at		The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/ietf/1id-abstracts.txt		http://www.ietf.org/ietf/1id-abstracts.txt
	The list of Internet-Draft Shadow Directories can be accessed at		The list of Internet-Draft Shadow Directories can be accessed at
	http://www.ietf.org/shadow.html.		http://www.ietf.org/shadow.html.
			Comments should be submitted to the eap@frascone.com mailing list.
	Abstract		Abstract
	This document specifies an Extensible Authentication Protocol (EAP)		This document specifies an Extensible Authentication Protocol (EAP)
	mechanism for authentication and session key distribution using the		mechanism for authentication and session key distribution using the
	Universal Mobile Telecommunications System (UMTS) Authentication and		Universal Mobile Telecommunications System (UMTS) Authentication and
	Key Agreement (AKA) mechanism. UMTS AKA is based on symmetric keys,		Key Agreement (AKA) mechanism. UMTS AKA is based on symmetric keys,
	and runs typically in a UMTS Subscriber Identity Module, a smart		and runs typically in a UMTS Subscriber Identity Module, a smart
	card like device.		card like device.
	EAP AKA includes optional identity privacy support and an optional		EAP AKA includes optional identity privacy support and an optional
	re-authentication procedure.		re-authentication procedure.
	Table of Contents		Table of Contents
	Status of this Memo................................................1		Status of this Memo................................................1
	Abstract...........................................................1		Abstract...........................................................1
	1. Introduction and Motivation.....................................2		1. Introduction and Motivation.....................................3
	2. Terms and Conventions Used in This Document.....................4		2. Terms and Conventions Used in This Document.....................4
	3. Protocol Overview...............................................6		3. Protocol Overview...............................................6
	4. Identity Management............................................10		4. Operation......................................................11
	4.1. User Identity in EAP-Response/Identity.......................10
	EAP AKA Authentication June 2003		EAP AKA Authentication 27 October, 2003
	4.2. Obtaining Subscriber Identity via EAP AKA Messages...........12		4.1. Identity Management..........................................11
	4.3. Identity Privacy Support.....................................15		4.2. Re-authentication............................................25
	5. Re-authentication..............................................21		4.3. EAP/AKA Notifications........................................31
	6. Message Format.................................................26		4.4. Error Cases..................................................32
	7. Message Authentication and Encryption..........................27		4.5. Key Generation...............................................34
	7.1. AT_MAC Attribute.............................................27		5. Message Format and Protocol Extensibility......................35
	7.2. AT_CHECKCODE Attribute.......................................28		5.1. Message Format...............................................35
	7.3. AT_IV, AT_ENCR_DATA and AT_PADDING Attributes................30		5.2. Protocol Extensibility.......................................37
	8. Messages.......................................................31		6. Messages.......................................................37
	8.1. EAP-Request/AKA-Challenge....................................31		6.1. EAP-Request/AKA-Identity.....................................37
	8.2. EAP-Response/AKA-Challenge...................................35		6.2. EAP-Response/AKA-Identity....................................38
	8.3. EAP-Response/AKA-Authentication-Reject.......................36		6.3. EAP-Request/AKA-Challenge....................................38
	8.4. EAP-Response/AKA-Synchronization-Failure.....................37		6.4. EAP-Response/AKA-Challenge...................................39
	8.5. EAP-Request/AKA-Identity.....................................38		6.5. EAP-Response/AKA-Authentication-Reject.......................39
	8.6. EAP-Response/AKA-Identity....................................39		6.6. EAP-Response/AKA-Synchronization-Failure.....................39
	8.7. EAP-Request/AKA-Reauthentication.............................41		6.7. EAP-Request/AKA-Reauthentication.............................39
	8.8. EAP-Response/AKA-Reauthentication............................43		6.8. EAP-Response/AKA-Reauthentication............................40
	8.9. EAP/AKA Notifications........................................46		6.9. EAP-Response/AKA-Client-Error................................40
	9. Error Cases and the Usage of EAP-Failure and EAP-Success.......49		6.10. EAP-Request/AKA-Notification................................40
	9.1. Processing Erroneous Packets.................................49		6.11. EAP-Response/AKA-Notification...............................41
	9.2. EAP-Failure..................................................49		7. Attributes.....................................................41
	9.3. EAP-Success..................................................50		7.1. Table of Attributes..........................................41
	10. Key Derivation................................................50		7.2. AT_MAC.......................................................42
	11. IANA and Protocol Numbering Considerations....................52		7.3. AT_IV, AT_ENCR_DATA and AT_PADDING...........................43
	12. Security Considerations.......................................53		7.4. AT_CHECKCODE.................................................45
	12.1. Identity Protection.........................................53		7.5. AT_PERMANENT_ID_REQ..........................................47
	12.2. Mutual Authentication.......................................53		7.6. AT_ANY_ID_REQ................................................47
	12.3. Key Derivation..............................................53		7.7. AT_FULLAUTH_ID_REQ...........................................47
	12.4. Brute-Force and Dictionary Attacks..........................53		7.8. AT_IDENTITY..................................................48
	12.5. Integrity Protection, Replay Protection and Confidentiality.54		7.9. AT_RAND......................................................48
	12.6. Negotiation Attacks.........................................54		7.10. AT_AUTN.....................................................49
	12.7. Fast Reconnect..............................................55		7.11. AT_RES......................................................49
	12.8. Acknowledged Result Indications.............................55		7.12. AT_AUTS.....................................................49
	12.9. Man-in-the-middle Attacks...................................55		7.13. AT_NEXT_PSEUDONYM...........................................50
	12.10. Generating Random Numbers..................................55		7.14. AT_NEXT_REAUTH_ID...........................................50
	13. Security Claims...............................................55		7.15. AT_COUNTER..................................................51
	14. Intellectual Property Right Notices...........................56		7.16. AT_COUNTER_TOO_SMALL........................................51
	Acknowledgements and Contributions................................56		7.17. AT_NONCE_S..................................................51
	Authors' Addresses................................................56		7.18. AT_NOTIFICATION.............................................52
	Annex A. Pseudo-Random Number Generator...........................57		7.19. AT_CLIENT_ERROR_CODE........................................53
			8. IANA and Protocol Numbering Considerations.....................53
			9. Security Considerations........................................54
			9.1. Identity Protection..........................................55
			9.2. Mutual Authentication........................................55
			9.3. Key Derivation...............................................55
			9.4. Brute-Force and Dictionary Attacks...........................55
			9.5. Integrity Protection, Replay Protection and Confidentiality..55
			EAP AKA Authentication 27 October, 2003
			9.6. Negotiation Attacks..........................................56
			9.7. Fast Reconnect...............................................56
			9.8. Acknowledged Result Indications..............................56
			9.9. Man-in-the-middle Attacks....................................57
			9.10. Generating Random Numbers...................................57
			10. Security Claims...............................................57
			11. Intellectual Property Right Notices...........................58
			Acknowledgements and Contributions................................58
			Authors' Addresses................................................58
			Annex A. Pseudo-Random Number Generator...........................59
	1. Introduction and Motivation		1. Introduction and Motivation
	This document specifies an Extensible Authentication Protocol (EAP)		This document specifies an Extensible Authentication Protocol (EAP)
	mechanism for authentication and session key distribution using the		mechanism for authentication and session key distribution using the
	UMTS AKA authentication mechanism [1]. UMTS is a global third		UMTS AKA authentication mechanism [TS 33.102]. UMTS is a global
	generation mobile network standard.		third generation mobile network standard.
	EAP AKA Authentication June 2003
	AKA is based on challenge-response mechanisms and symmetric		AKA is based on challenge-response mechanisms and symmetric
	cryptography. AKA typically runs in a UMTS Subscriber Identity		cryptography. AKA typically runs in a UMTS Subscriber Identity
	Module (USIM). Compared to the GSM mechanism, UMTS AKA provides		Module (USIM). Compared to the GSM mechanism, UMTS AKA provides
	substantially longer key lengths and mutual authentication.		substantially longer key lengths and mutual authentication.
	The introduction of AKA inside EAP allows several new applications.		The introduction of AKA inside EAP allows several new applications.
	These include the following:		These include the following:
	- The use of the AKA also as a secure PPP authentication method in		- The use of the AKA also as a secure PPP authentication method in
	devices that already contain an USIM.		devices that already contain an USIM.
	- The use of the third generation mobile network authentication		- The use of the third generation mobile network authentication
	infrastructure in the context of wireless LANs and IEEE 802.1x		infrastructure in the context of wireless LANs
	technology through EAP over Wireless [2, 3].
	- Relying on AKA and the existing infrastructure in a seamless way		- Relying on AKA and the existing infrastructure in a seamless way
	with any other technology that can use EAP.		with any other technology that can use EAP.
	AKA works in the following manner:		AKA works in the following manner:
	- The USIM and the home environment have agreed on a secret key		- The USIM and the home environment have agreed on a secret key
	beforehand.		beforehand.
	- The actual authentication process starts by having the home		- The actual authentication process starts by having the home
	skipping to change at page 3, line 42 ¶		skipping to change at page 4, line 4 ¶
	key and a sequence number. The authentication vector contains a		key and a sequence number. The authentication vector contains a
	random part RAND, an authenticator part AUTN used for		random part RAND, an authenticator part AUTN used for
	authenticating the network to the USIM, an expected result part		authenticating the network to the USIM, an expected result part
	XRES, a session key for integrity check IK, and a session key for		XRES, a session key for integrity check IK, and a session key for
	encryption CK.		encryption CK.
	- The RAND and the AUTN are delivered to the USIM.		- The RAND and the AUTN are delivered to the USIM.
	- The USIM verifies the AUTN, again based on the secret key and the		- The USIM verifies the AUTN, again based on the secret key and the
	sequence number. If this process is successful (the AUTN is valid		sequence number. If this process is successful (the AUTN is valid
			EAP AKA Authentication 27 October, 2003
	and the sequence number used to generate AUTN is within the		and the sequence number used to generate AUTN is within the
	correct range), the USIM produces an authentication result, RES		correct range), the USIM produces an authentication result, RES
	and sends this to the home environment.		and sends this to the home environment.
	- The home environment verifies the correct result from the USIM. If		- The home environment verifies the correct result from the USIM. If
	the result is correct, IK and CK can be used to protect further		the result is correct, IK and CK can be used to protect further
	communications between the USIM and the home environment.		communications between the USIM and the home environment.
	When verifying AUTN, the USIM may detect that the sequence number		When verifying AUTN, the USIM may detect that the sequence number
	the network uses is not within the correct range. In this case, the		the network uses is not within the correct range. In this case, the
	USIM calculates a sequence number synchronization parameter AUTS and		USIM calculates a sequence number synchronization parameter AUTS and
	sends it to the network. AKA authentication may then be retried with		sends it to the network. AKA authentication may then be retried with
	a new authentication vector generated using the synchronized		a new authentication vector generated using the synchronized
	sequence number.		sequence number.
	For a specification of the AKA mechanisms and how the cryptographic		For a specification of the AKA mechanisms and how the cryptographic
	values AUTN, RES, IK, CK and AUTS are calculated, see reference [1].		values AUTN, RES, IK, CK and AUTS are calculated, see [TS 33.102].
	EAP AKA Authentication June 2003
	It is also possible that the home environment delegates the actual		In EAP AKA, the EAP server node obtains the authentication vectors,
	authentication task to an intermediate node. In this case the		compares RES and XRES, and uses CK and IK in key derivation.
	authentication vector or parts of it are delivered to the
	intermediate node, enabling it to perform the comparison between RES
	and XRES, and possibly also use CK and IK. Such delivery MUST be
	done in a secure manner. In EAP AKA, the EAP server node is such an
	intermediate node.
	In the third generation mobile networks, AKA is used both for radio		In the third generation mobile networks, AKA is used both for radio
	network authentication and IP multimedia service authentication		network authentication and IP multimedia service authentication
	purposes. Different user identities and formats are used for these;		purposes. Different user identities and formats are used for these;
	the radio network uses the International Mobile Subscriber		the radio network uses the International Mobile Subscriber
	Identifier (IMSI), whereas the IP multimedia service uses the		Identifier (IMSI), whereas the IP multimedia service uses the
	Network Access Identifier (NAI) [4].		Network Access Identifier (NAI) [RFC 2486].
	2. Terms and Conventions Used in This Document		2. Terms and Conventions Used in This Document
	The following terms will be used through this document:		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
			"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
			document are to be interpreted as described in [RFC 2119].
	AAA protocol		The terms and abbreviations "authenticator", "backend authentication
			server", "EAP server", "Silently Discard", "Master Session Key
			(MSK)", and "Extended Master Session Key (EMSK)" in this document
			are to be interpreted as described in [EAP].
	Authentication, Authorization and Accounting protocol		This document frequently uses the following terms and abbreviations:
	AAA server		AAA protocol
	The AAA server is responsible for storing shared secrets and		Authentication, Authorization and Accounting protocol
	other credential information necessary for the authentication of
	users. Cf. EAP server
	AKA		AKA
	Authentication and Key Agreement		Authentication and Key Agreement
			EAP AKA Authentication 27 October, 2003
	AuC		AuC
	Authentication Centre. The mobile network element that can		Authentication Centre. The mobile network element that can
	authenticate subscribers either in GSM or in UMTS networks.		authenticate subscribers either in GSM or in UMTS networks.
	Authenticator
	The entity that terminates the protocol carrying EAP used by the
	client, such as a Network Access Server (NAS) terminating the PPP
	link. The EAP server may be co-located in the Authenticator. In
	this case, the Authenticator may actually authenticate the user
	based on information received from the AAA server.
	EAP		EAP
	Extensible Authentication Protocol [5].		Extensible Authentication Protocol [EAP].
	EAP AKA Authentication June 2003
	EAP server
	The network element that terminates the EAP protocol. Typically,
	the EAP server functionality is implemented in a AAA server.
	GSM		GSM
	Global System for Mobile communications.		Global System for Mobile communications.
	NAI		NAI
	Network Access Identifier [4].		Network Access Identifier [RFC 2486].
	AUTN		AUTN
	Authentication value generated by the AuC which together with the		Authentication value generated by the AuC which together with the
	RAND authenticates the server to the client, 128 bits [1].		RAND authenticates the server to the peer, 128 bits [TS 33.102].
	AUTS		AUTS
	A value generated by the client upon experiencing a		A value generated by the peer upon experiencing a synchronization
	synchronization failure, 112 bits.		failure, 112 bits.
			Permanent Identity
			The permanent identity of the peer, including an NAI realm
			portion in environments where a realm is used. The permanent
			identity is usually based on the IMSI. Used on full
			authentication only.
			Permanent Username
			The username portion of permanent identity, ie. not including any
			realm portions.
			Pseudonym Identity
			A pseudonym identity of the peer, including an NAI realm portion
			in environments where a real is used. Used on full authentication
			only.
			Pseudonym Username
			The username portion of pseudonym identity, ie. not including any
			realm portions.
			EAP AKA Authentication 27 October, 2003
			Re-authentication Identity
			A re-authentication identity of the peer, including an NAI realm
			portion in environments where a real is used. Used on re-
			authentication only.
			Re-authentication Username
			The username portion of re-authentication identity, ie. not
			including any realm portions.
	RAND		RAND
	Random number generated by the AuC, 128 bits [1].		Random number generated by the AuC, 128 bits [TS 33.102].
	RES		RES
	Authentication result from the client, which together with the		Authentication result from the peer, which together with the RAND
	RAND authenticates the client to the server, 128 bits [1].		authenticates the peer to the server, 128 bits [TS 33.102].
	SQN		SQN
	Sequence number used in the authentication process, 48 bits [1].		Sequence number used in the authentication process, 48 bits [TS
			33.102].
	SIM		SIM
	Subscriber Identity Module. The SIM is an application		Subscriber Identity Module. The SIM is an application
	traditionally resident on smart cards distributed by GSM		traditionally resident on smart cards distributed by GSM
	operators.		operators.
	SRES		SRES
	The authentication result parameter in GSM, corresponds to the		The authentication result parameter in GSM, corresponds to the
	RES parameter in UMTS aka, 32 bits.		RES parameter in UMTS aka, 32 bits.
	USIM		USIM
	UMTS Subscriber Identity Module. USIM is an application that is		UMTS Subscriber Identity Module. USIM is an application that is
	resident e.g. on smart cards distributed by UMTS operators.		resident e.g. on smart cards distributed by UMTS operators.
	EAP AKA Authentication June 2003
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
	this document are to be interpreted as described in RFC 2119 [6]		this document are to be interpreted as described in [RFC 2119]
	3. Protocol Overview		3. Protocol Overview
	In this document, the term EAP Server refers to the network element
	that terminates the EAP protocol. Usually the EAP server is separate
	from the authenticator device, which is the network element closest
	to the client, such as a Network Access Server (NAS) or an IEEE
	802.1X bridge. Alternatively, the EAP server functionality may be
	co-located in the authenticator although typically, the EAP server
	functionality is implemented on a separate AAA server with whom the
	authenticator communicates using an AAA protocol. (The exact AAA
	communications are outside the scope of this document, however.)
	The message flow below shows the basic successful full		The message flow below shows the basic successful full
	authentication case with the EAP AKA. The EAP AKA uses two		authentication exchange in EAP AKA. At the minimum, EAP AKA uses two
	roundtrips to authorize the user and generate session keys. As in		roundtrips to authorize the user and generate session keys. As in
	other EAP schemes, first an identity request/response message pair		other EAP schemes, an identity request/response message pair is
	is exchanged. (As specified in [5], the initial identity request is		usually exchanged first. On full authentication, the peer's identity
	not required, and MAY be bypassed in cases where the authenticator		response includes either the user's International Mobile Subscriber
	can presume the identity, such as when using leased lines, dedicated
	dial-ups, etc. Please see also Section 4.2 for specification how to		EAP AKA Authentication 27 October, 2003
	obtain the identity via EAP AKA messages.)
			Identity (IMSI), or a temporary identity (pseudonym) if identity
			privacy is in effect, as specified in Section 4.1. (As specified in
			[EAP], the initial identity request is not required, and MAY be
			bypassed in cases where the network can presume the identity, such
			as when using leased lines, dedicated dial-ups, etc. Please see also
			Section 4.1.2 for specification how to obtain the identity via EAP
			AKA messages.)
	Next, the EAP server starts the actual AKA protocol by sending an		Next, the EAP server starts the actual AKA protocol by sending an
	EAP-Request/AKA-Challenge message. EAP AKA packets encapsulate		EAP-Request/AKA-Challenge message. EAP AKA packets encapsulate
	parameters in attributes, encoded in a Type, Length, Value format.		parameters in attributes, encoded in a Type, Length, Value format.
	The packet format and the use of attributes are specified in Section		The packet format and the use of attributes are specified in Section
	6. The EAP-Request/AKA-Challenge message contains a random number		5. The EAP-Request/AKA-Challenge message contains a random number
	(AT_RAND) and an authorization vector (AT_AUTN), and a message		(AT_RAND) and a network authentication token (AT_AUTN), and a
	authentication code AT_MAC. The EAP-Request/AKA-Challenge message		message authentication code AT_MAC. The EAP-Request/AKA-Challenge
	MAY optionally contain encrypted data, which is used for Identity		message MAY optionally contain encrypted data, which is used for
	privacy support, as described in Section 4.3. The AT_MAC attribute		identity privacy and re-authentication support, as described in
	contains a message authentication code covering the EAP packet. The		Section 4.1. The AT_MAC attribute contains a message authentication
	encrypted data is not shown in the figures of this section.		code covering the EAP packet. The encrypted data is not shown in the
			figures of this section.
	The client runs the AKA algorithm (perhaps inside an USIM) and		The peer runs the AKA algorithm (typically using a USIM) and
	verifies the AUTN. If this is successful, the client is talking to a		verifies the AUTN. If this is successful, the peer is talking to a
	legitimate EAP server and proceeds to send the EAP-Response/AKA-		legitimate EAP server and proceeds to send the EAP-Response/AKA-
	Challenge. This message contains a result parameter that allows the		Challenge. This message contains a result parameter that allows the
	EAP server in turn to authenticate the client, and the AT_MAC		EAP server in turn to authenticate the peer, and the AT_MAC
	attribute to integrity protect the EAP message.		attribute to integrity protect the EAP message.
	EAP AKA Authentication June 2003		EAP AKA Authentication 27 October, 2003
	Client Authenticator		Peer Authenticator
	| |		| |
	| EAP-Request/Identity |		| EAP-Request/Identity |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	| EAP-Response/Identity |		| EAP-Response/Identity |
	| (Includes user's NAI) |		| (Includes user's NAI) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	| +------------------------------+		| +------------------------------+
	| | Server runs UMTS algorithms, |		| | Server runs UMTS algorithms, |
	| | generates RAND and AUTN. |		| | generates RAND and AUTN. |
	| +------------------------------+		| +------------------------------+
	| |		| |
	| EAP-Request/AKA-Challenge |		| EAP-Request/AKA-Challenge |
	| (AT_RAND, AT_AUTN, AT_MAC) |		| (AT_RAND, AT_AUTN, AT_MAC) |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	+-------------------------------------+ |		+-------------------------------------+ |
	| Client runs UMTS algorithms on USIM,| |		| Peer runs UMTS algorithms on USIM, | |
	| verifies AUTN and MAC, derives RES | |		| verifies AUTN and MAC, derives RES | |
	| and session key | |		| and session key | |
	+-------------------------------------+ |		+-------------------------------------+ |
	| |		| |
	| EAP-Response/AKA-Challenge |		| EAP-Response/AKA-Challenge |
	| (AT_RES, AT_MAC) |		| (AT_RES, AT_MAC) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	| +--------------------------------+		| +--------------------------------+
	| | Server checks the given RES, |		| | Server checks the given RES, |
	| | and MAC and finds them correct.|		| | and MAC and finds them correct.|
	| +--------------------------------+		| +--------------------------------+
	| |		| |
	| EAP-Success |		| EAP-Success |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	The second message flow shows how the EAP server rejects the Client		The second message flow shows how the EAP server rejects the Peer
	due to a failed authentication. The same flow is also used in the		due to a failed authentication. The same flow is also used in the
	GSM compatible mode, except that the AT_AUTN attribute and AT_MAC		GSM compatible mode, except that the AT_AUTN attribute and AT_MAC
	attribute are not used in the messages.		attribute are not used in the messages.
	EAP AKA Authentication June 2003		EAP AKA Authentication 27 October, 2003
	Client Authenticator		Peer Authenticator
	| |		| |
	| EAP-Request/Identity |		| EAP-Request/Identity |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	| EAP-Response/Identity |		| EAP-Response/Identity |
	| (Includes user's NAI) |		| (Includes user's NAI) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	| +------------------------------+		| +------------------------------+
	| | Server runs UMTS algorithms, |		| | Server runs UMTS algorithms, |
	| | generates RAND and AUTN. |		| | generates RAND and AUTN. |
	| +------------------------------+		| +------------------------------+
	| |		| |
	| EAP-Request/AKA-Challenge |		| EAP-Request/AKA-Challenge |
	| (AT_RAND, AT_AUTN, AT_MAC) |		| (AT_RAND, AT_AUTN, AT_MAC) |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	+-------------------------------------+ |		+-------------------------------------+ |
	| Client runs UMTS algorithms on USIM,| |		| Peer runs UMTS algorithms on USIM, | |
	| possibly verifies AUTN, and sends an| |		| possibly verifies AUTN, and sends an| |
	| invalid response | |		| invalid response | |
	+-------------------------------------+ |		+-------------------------------------+ |
	| |		| |
	| EAP-Response/AKA-Challenge |		| EAP-Response/AKA-Challenge |
	| (AT_RES, AT_MAC) |		| (AT_RES, AT_MAC) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	| +------------------------------------------+		| +------------------------------------------+
	| | Server checks the given RES and the MAC, |		| | Server checks the given RES and the MAC, |
	| | and finds one of them incorrct. |		| | and finds one of them incorrct. |
	| +------------------------------------------+		| +------------------------------------------+
	| |		| |
	| EAP-Failure |		| EAP-Failure |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	The next message flow shows the client rejecting the AUTN of the EAP		The next message flow shows the peer rejecting the AUTN of the EAP
	server.		server.
	The client sends an explicit error message (EAP-Response/AKA-		The peer sends an explicit error message (EAP-Response/AKA-
	Authentication-Reject) to the Authenticator, as usual in AKA when		Authentication-Reject) to the EAP server, as usual in AKA when AUTN
	AUTN is incorrect. This allows the EAP server to produce the same		is incorrect. This allows the EAP server to produce the same error
	error statistics as AKA in general produces in UMTS. Please note		statistics as AKA in general produces in UMTS.
	that this behavior is different from other EAP/AKA error cases, such
	as when encountering an incorrect AT_MAC attribute, the client
	silently discards the EAP/AKA message.
	EAP AKA Authentication June 2003		EAP AKA Authentication 27 October, 2003
	Client Authenticator		Peer Authenticator
	| |		| |
	| EAP-Request/Identity |		| EAP-Request/Identity |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	| EAP-Response/Identity |		| EAP-Response/Identity |
	| (Includes user's NAI) |		| (Includes user's NAI) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	| +------------------------------+		| +------------------------------+
	| | Server runs UMTS algorithms, |		| | Server runs UMTS algorithms, |
	| | generates RAND and a bad AUTN|		| | generates RAND and a bad AUTN|
	| +------------------------------+		| +------------------------------+
	| |		| |
	| EAP-Request/AKA-Challenge |		| EAP-Request/AKA-Challenge |
	| (AT_RAND, AT_AUTN, AT_MAC) |		| (AT_RAND, AT_AUTN, AT_MAC) |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	+-------------------------------------+ |		+-------------------------------------+ |
	| Client runs UMTS algorithms on USIM | |		| Peer runs UMTS algorithms on USIM | |
	| and discovers AUTN that can not be | |		| and discovers AUTN that can not be | |
	| verified | |		| verified | |
	+-------------------------------------+ |		+-------------------------------------+ |
	| |		| |
	| EAP-Response/AKA-Authentication-Reject |		| EAP-Response/AKA-Authentication-Reject |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	| |		| |
	| EAP-Failure |		| EAP-Failure |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	The AKA uses shared secrets between the Client and the Client's home		The AKA uses shared secrets between the Peer and the Peer's home
	operator together with a sequence number to actually perform an		operator together with a sequence number to actually perform an
	authentication. In certain circumstances it is possible for the		authentication. In certain circumstances it is possible for the
	sequence numbers to get out of sequence. Here's what happens then:		sequence numbers to get out of sequence. Here's what happens then:
	EAP AKA Authentication June 2003		EAP AKA Authentication 27 October, 2003
	Client Authenticator		Peer Authenticator
	| |		| |
	| EAP-Request/Identity |		| EAP-Request/Identity |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	| EAP-Response/Identity |		| EAP-Response/Identity |
	| (Includes user's NAI) |		| (Includes user's NAI) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	| +------------------------------+		| +------------------------------+
	| | Server runs UMTS algorithms, |		| | Server runs UMTS algorithms, |
	| | generates RAND and AUTN. |		| | generates RAND and AUTN. |
	| +------------------------------+		| +------------------------------+
	| |		| |
	| EAP-Request/AKA-Challenge |		| EAP-Request/AKA-Challenge |
	| (AT_RAND, AT_AUTN, AT_MAC) |		| (AT_RAND, AT_AUTN, AT_MAC) |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	+-------------------------------------+ |		+-------------------------------------+ |
	| Client runs UMTS algorithms on USIM | |		| Peer runs UMTS algorithms on USIM | |
	| and discovers AUTN that contains an | |		| and discovers AUTN that contains an | |
	| inappropriate sequence number | |		| inappropriate sequence number | |
	+-------------------------------------+ |		+-------------------------------------+ |
	| |		| |
	| EAP-Response/AKA-Synchronization-Failure |		| EAP-Response/AKA-Synchronization-Failure |
	| (AT_AUTS) |		| (AT_AUTS) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	| +---------------------------+		| +---------------------------+
	| | Perform resynchronization |		| | Perform resynchronization |
	skipping to change at page 10, line 48 ¶		skipping to change at page 11, line 48 ¶
	| | the sent RAND |		| | the sent RAND |
	| +---------------------------+		| +---------------------------+
	| |		| |
	After the resynchronization process has taken place in the server		After the resynchronization process has taken place in the server
	and AAA side, the process continues by the server side sending a new		and AAA side, the process continues by the server side sending a new
	EAP-Request/AKA-Challenge message.		EAP-Request/AKA-Challenge message.
	In addition to the full authentication scenarios described above,		In addition to the full authentication scenarios described above,
	EAP AKA includes a re-authentication procedure, which is specified		EAP AKA includes a re-authentication procedure, which is specified
	in Section 5.		in Section 4.2. Re-authentication is based on keys derived on full
			authentication. If the peer has maintained state information for re-
			authentication and wants to use re-authentication, then the peer
			indicates this by using a specific re-authentication identity
			instead of the permanent identity or a pseudonym identity. The re-
			authentication procedure is described in Section 4.2.
	4. Identity Management		4. Operation
	This section specifies user identity management and identity privacy		4.1. Identity Management
	support.
	4.1. User Identity in EAP-Response/Identity		4.1.1. Format, Generation and Usage of Peer Identities
	In the beginning of an EAP authentication, the Authenticator issues		EAP AKA Authentication 27 October, 2003
	the EAP-Request/Identity packet to the client. The client responds
	with EAP-Response/Identity, which contains the user's identity. The
	formats of these packets are specified in [5].
	EAP AKA Authentication June 2003		General
			In the beginning of EAP authentication, the Authenticator or the EAP
			server usually issues the EAP-Request/Identity packet to the peer.
			The peer responds with EAP-Response/Identity, which contains the
			user's identity. The formats of these packets are specified in
			[EAP].
	UMTS subscribers are identified with the International Mobile		UMTS subscribers are identified with the International Mobile
	Subscriber Identity (IMSI) [7]. The IMSI is composed of a three		Subscriber Identity (IMSI) [TS 23.003]. The IMSI is composed of a
	digit Mobile Country Code (MCC), a two or three digit Mobile Network		three digit Mobile Country Code (MCC), a two or three digit Mobile
	Code (MNC) and a not more than 10 digit Mobile Subscriber		Network Code (MNC) and a not more than 10 digit Mobile Subscriber
	Identification Number (MSIN). In other words, the IMSI is a string		Identification Number (MSIN). In other words, the IMSI is a string
	of not more than 15 digits. MCC and MNC uniquely identify the		of not more than 15 digits. MCC and MNC uniquely identify the GSM
	operator.		operator and help identify the AuC from which the authentication
			vectors need to be retrieved for this subscriber.
	Internet AAA protocols identify users with the Network Access		Internet AAA protocols identify users with the Network Access
	Identifier (NAI) [4]. When used in a roaming environment, the NAI is		Identifier (NAI) [RFC 2486]. When used in a roaming environment, the
	composed of a username and a realm, separated with "@"		NAI is composed of a username and a realm, separated with "@"
	(username@realm). The username portion identifies the subscriber		(username@realm). The username portion identifies the subscriber
	within the realm. The AAA nodes use the realm portion of the NAI to		within the realm.
	route AAA requests to the correct AAA server. The realm name used in
	this protocol MAY be chosen by the operator and it MAY be a
	configurable parameter in the EAP/AKA client implementation. In this
	case, the client is typically configured with the NAI realm of the
	home operator. Operators MAY reserve a specific realm name for
	EAP/AKA users. This convention makes it easy to recognize that the
	NAI identifies a subscriber that uses EAP/AKA. Such a reserved NAI
	realm may be a useful hint to the first authentication method to use
	during method negotiation.
	There are three types of NAI username portions in EAP/AKA: non-		This section specifies the peer identity format used in EAP/AKA. In
	pseudonym permanent usernames, pseudonym usernames and re-		this document, the term identity or peer identity refers to the
	authentication usernames. The first two are only used on full		whole identity string that is used to identify the peer. The peer
	authentication and the last one only on re-authentication. When the		identity may include a realm portion. "Username" refers to the
	optional identity privacy support is not used, the non-pseudonym		portion of the peer identity that identifies the user, i.e. the
	permanent username is used.		username does not include the realm portion.
	The non-pseudonym permanent username MAY be derived from the IMSI.		Identity Privacy Support
	In this case, the permanent username MUST be of the format "0imsi".
	In other words, the first character of the username is the digit
	zero (ASCII value 0x30), followed by the IMSI. The IMSI is an ASCII
	string that consists of not more than 15 decimal digits (ASCII
	values between 0x30 and 0x39) as specified in [7]
	The EAP server MAY use the leading "0" as a hint to try EAP/AKA as		EAP/AKA includes optional identity privacy (anonymity) support that
	the first authentication method during method negotiation. The		can be used to hide the cleartext permanent identity and thereby to
	EAP/AKA server MAY propose EAP/AKA even if the leading character was		make the subscriber's EAP exchanges untraceable to eavesdroppers.
	not "0".		Because the permanent identity never changes, revealing it would
			help observers to track the user. The permanent identity is usually
			based on the IMSI, which may further help the tracking, because the
			same identifier may used in other contexts as well. Identity privacy
			is based on temporary identities, or pseudonyms, which are
			equivalent to but separate from the Temporary Mobile Subscriber
			Identities (TMSI) that are used on cellular networks. Please see
			Section 9.1 for security considerations regarding identity privacy.
	Alternatively, an implementation may choose a permanent username		Username Types in EAP/AKA Identities
	that is not based on the IMSI. In this case the selection of the
	username, its format, and its processing is a local matter. In this
	case, the client implementation MUST NOT prepend any leading
	characters to the username.
	When the optional identity privacy support is used on full		There are three types of usernames in EAP/AKA peer identities:
	authentication, the client MAY use the pseudonym received upon the
	previous full authentication sequence as the username portion of the
	NAI, as specified in Section 4.3. The client MUST NOT modify the
	EAP AKA Authentication June 2003		(1) Permanent usernames. For example,
			0123456789098765@myoperator.com might be a valid permanent identity.
			In this example, 0123456789098765 is the permanent username.
	pseudonym received in AT_NEXT_PSEUDONYM. For example, the client		EAP AKA Authentication 27 October, 2003
	MUST NOT prepend any leading characters in the pseudonym.
	On re-authentication, the client uses the re-authentication identity		(2) Pseudonym usernames. For example, 2s7ah6n9q@myoperator.com might
	received upon the previous authentication sequence as the NAI. A new		be a valid pseudonym identity. In this example, 2s7ah6n9q is the
	re-authentication identity may be delivered as part of both full		pseudonym username.
	authentication and re-authentication. The client MUST NOT modify the
	re-authentication identity received in AT_NEXT_REAUTH_ID but the
	client must use the re-authentication identity as it is. For
	example, the client MUST NOT prepend any leading characters in the
	re-authentication identity.
	If no configured realm name is available, the client MAY derive the		(3) Re-authentication usernames. For example,
			43953754a@myoperator.com might be a valid re-authentication
			identity. In this case, 43953754 is the re-authentication username.
			The first two types of identities are only used on full
			authentication and the last one only on re-authentication. When the
			optional identity privacy support is not used, the non-pseudonym
			permanent identity is used on full authentication. The re-
			authentication exchange is specified in Section 4.2.
			sername Decoration
			In some environments, the peer may need to decorate the identity by
			prepending or appending the username with a string, in order to
			indicate supplementary AAA routing information in addition to the
			NAI realm. (The usage of a NAI realm portion is not considered to be
			decoration.) Username decoration is out of the scope of this
			document. However, it should be noted that username decoration might
			prevent the server from recognizing a valid username. Hence,
			although the peer MAY use username decoration in the identities the
			peer includes in EAP-Response/Identity, and the EAP server MAY
			accept a decorated peer username in this message, the peer or the
			EAP server MUST NOT decorate any other peer identities that are used
			in various EAP/AKA attributes. Only the identity used in EAP-
			Response/Identity may be decorated.
			NAI Realm Portion
			The peer MAY include a realm portion in the peer identity, as per
			the NAI format. The use of a realm portion is not mandatory.
			If a realm is used, the realm MAY be chosen by the operator and it
			MAY a configurable parameter in the EAP/SIM peer implementation. In
			this case, the peer is typically configured with the NAI realm of
			the home operator. Operators MAY reserve a specific realm name for
			EAP/AKA users. This convention makes it easy to recognize that the
			NAI identifies a UMTS subscriber. Such reserved NAI realm may be
			useful as a hint as to the first authentication method to use during
			method negotiation. When the peer is using a pseudonym username
			instead of the permanent username, the peer selects the realm name
			portion similarly as it select the realm portion when using the
			permanent username.
			If no configured realm name is available, the peer MAY derive the
	realm name from the MCC and MNC portions of the IMSI. A recommended		realm name from the MCC and MNC portions of the IMSI. A recommended
	way to derive the realm from the IMSI will be specified in [8].		way to derive the realm from the IMSI using the realm
			3gppnetwork.org will be specified in [Draft 3GPP TS 23.234].
	Alternatively, the realm name may be obtained by concatenating		Alternatively, the realm name may be obtained by concatenating
	"mnc", the MNC digits of IMSI, ".mcc", the MCC digits of IMSI and		"mnc", the MNC digits of IMSI, ".mcc", the MCC digits of IMSI and
	".owlan.org". For example, if the IMSI is 123456789098765, and the		".owlan.org". For example, if the IMSI is 123456789098765, and the
			EAP AKA Authentication 27 October, 2003
	MNC is three digits long, then the derived realm name is		MNC is three digits long, then the derived realm name is
	"mnc456.mcc123.owlan.org".		"mnc456.mcc123.owlan.org".
	If the client is not able to determine whether the MNC is two or		The IMSI is a string of digits without any explicit structure, so
	three digits long, the client MAY use a 3-digit MNC. If the correct		the peer may not be able to determine the length of the MNC portion.
	length of the MNC is two, then the MNC used in the realm name will		If the peer is not able to determine whether the MNC is two or three
	include the first digit of MSIN. Hence, when configuring AAA		digits long, the peer MAY use a 3-digit MNC. If the correct length
	networks for operators that have 2-digit MNCs, the network SHOULD		of the MNC is two, then the MNC used in the realm name includes the
	also be prepared for realm names with incorrect 3-digit MNCs.		first digit of MSIN. Hence, when configuring AAA networks for
			operators that have 2-digit MNC's, the network SHOULD also be
			prepared for realm names with incorrect 3-digit MNC's.
	4.2. Obtaining Subscriber Identity via EAP AKA Messages		Format of the Permanent Username
	It may be useful to obtain the identity of the subscriber through		The non-pseudonym permanent username SHOULD be derived from the
	means other than EAP Request/Identity. This can eliminate the need		IMSI. In this case, the permanent username MUST be of the format "0"
	for an identity request when using EAP method negotiation. If this		| IMSI, where the character "|" denotes concatenation. In other
	was not possible then it might not be possible to negotiate EAP/AKA		words, the first character of the username is the digit zero (ASCII
	as the second method since not all EAP implementations support		value 0x30), followed by the IMSI. The IMSI is an ASCII string that
	multiple EAP Identity requests.		consists of not more than 15 decimal digits (ASCII values between
			0x30 and 0x39) as specified in [TS 23.003].
	EAP-Request/AKA-Identity and EAP-Response/AKA-Identity packets may		The EAP server MAY use the leading "0" as a hint to try EAP/AKA as
	be used for obtaining the subscriber identity. The EAP-Request/AKA-		the first authentication method during method negotiation, rather
	Challenge, EAP-Response/AKA-Challenge, or the packets used on re-		than for example EAP/SIM. The EAP/AKA server MAY propose EAP/AKA
	authentication may optionally include the AT_CHECKCODE attribute,		even if the leading character was not "0".
	which enables the protocol peers to ensure the integrity of the AKA-
	Identity packets. AT_CHECKCODE is specified in Section 7.2.		Alternatively, an implementation MAY choose a permanent username
			that is not based on the IMSI. In this case the selection of the
			username, its format, and its processing is out of the scope of this
			document. In this case, the peer implementation MUST NOT prepend any
			leading characters to the username.
			Generating Pseudonyms and Re-authentication Identities by the Server
			Pseudonym usernames and re-authentication identities are generated
			by the EAP server. The EAP server produces pseudonym usernames and
			re-authentication identities in an implementation-dependent manner.
			Only the EAP server needs to be able to map the pseudonym username
			to the permanent identity, or to recognize a re-authentication
			identity. Regardless of construction method, the pseudonym username
			MUST conform to the grammar specified for the username portion of an
			NAI. The re-authentication identity also MUST conform to the NAI
			grammar. The EAP servers that the subscribers of an operator can use
			MUST ensure that the pseudonym usernames and the username portions
			used in re-authentication identities they generate are unique.
			In any case, it is necessary that permanent usernames, pseudonym
			usernames and re-authentication usernames are separate and
			recognizable from each other. It is also desirable that EAP SIM and
			EAP AKA user names be recognizable from each other as an aid for the
			server to which method to offer.
			EAP AKA Authentication 27 October, 2003
			In general, it is the task of the EAP server and the policies of its
			administrator to ensure sufficient separation in the usernames.
			Pseudonym usernames and re-authentication usernames are both
			produced and used by the EAP server. The EAP server MUST compose
			pseudonym usernames and re-authentication usernames so that it can
			recognize if a NAI username is an EAP AKA pseudonym username or an
			EAP AKA re-authentication username. For instance, when the usernames
			have been derived from the IMSI, the server could use different
			leading characters in the pseudonym usernames and re-authentication
			usernames (e.g. the pseudonym could begin with a leading "2"
			character). When mapping a re-authentication identity to a permanent
			identity, the server SHOULD only examine the username portion of the
			re-authentication identity and ignore the realm portion of the
			identity.
			Because the peer may fail to save a pseudonym username sent to in an
			EAP-Request/AKA-Challenge, for example due to malfunction, the EAP
			server SHOULD maintain at least one old pseudonym username in
			addition to the most recent pseudonym username.
			Transmitting Pseudonyms and Re-authentication Identities to the Peer
			The server transmits pseudonym usernames and re-authentication
			identities to the peer in cipher, using the AT_ENCR_DATA attribute.
			The EAP-Request/AKA-Challenge message MAY include an encrypted
			pseudonym username and/or an encrypted re-authentication identity in
			the value field of the AT_ENCR_DATA attribute. Because identity
			privacy support and re-authentication are optional to implement, the
			peer MAY ignore the AT_ENCR_DATA attribute and always use the
			permanent identity. On re-authentication (discussed in Section 4.2),
			the server MAY include a new encrypted re-authentication identity in
			the EAP-Request/AKA-Reauthentication message.
			On receipt of the EAP-Request/AKA-Challenge, the peer MAY decrypt
			the encrypted data in AT_ENCR_DATA and if a pseudonym username is
			included, the peer may use the obtained pseudonym username on the
			next full authentication. If a re-authentication identity is
			included, then the peer MAY save it and other re-authentication
			state information, as discussed in Section 4.2, for the next re-
			authentication.
			If the peer does not receive a new pseudonym username in the EAP-
			Request/AKA-Challenge message, the peer MAY use an old pseudonym
			username instead of the permanent username on next full
			authentication. The username portions of re-authentication
			identities are one-time usernames, which the peer MUST NOT re-use.
			Usage of the Pseudonym by the Peer
			When the optional identity privacy support is used on full
			authentication, the peer MAY use the pseudonym username received as
			part of the previous full authentication sequence as the username
			portion of the NAI. The peer MUST NOT modify the pseudonym username
			EAP AKA Authentication 27 October, 2003
			received in AT_NEXT_PSEUDONYM. However, as discussed above, the peer
			MAY need to decorate the username in some environments by appending
			or prepending the username with a string that indicates
			supplementary AAA routing information.
			When using a pseudonym username in an environment where a realm
			portion is used, the peer concatenates the received pseudonym
			username with the "@" character and a NAI realm portion. The
			selection of the NAI realm is discussed above.
			Usage of the Re-authentication Identity by the Peer
			On re-authentication, the peer uses the re-authentication identity,
			received as part of the previous authentication sequence. A new re-
			authentication identity may be delivered as part of both full
			authentication and re-authentication. The peer MUST NOT modify the
			username part of the re-authentication identity received in
			AT_NEXT_REAUTH_ID, except in cases when username decoration is
			required. Even in these cases, the "root" re-authentication username
			must not be modified, but it may be appended or prepended with
			another string.
			4.1.2. Communicating the Peer Identity to the Server
			General
			The peer identity MAY be communicated to the server with the EAP-
			Response/Identity message. This message MAY contain the permanent
			identity, a pseudonym identity, or a re-authentication identity. If
			the peer uses the permanent identity or a pseudonym identity, which
			the server is able to map to the permanent identity, then the
			authentication proceeds as discussed in the overview of Section 3.
			If the peer uses a re-authentication identity, and the server
			recognized the identity and agrees on using re-authentication, then
			a re-authentication exchange is performed, as described in Section
			4.2.
			The peer identity can also be transmitted from the peer to the
			server using EAP/AKA messages instead of EAP-Response/Identity. In
			this case, the server includes an identity requesting attribute
			(AT_ANY_ID_REQ, AT_FULLAUTH_ID_REQ or AT_PERMANENT_ID_REQ) in the
			EAP-Request/AKA-Identity message, and the peer includes the
			AT_IDENTITY attribute, which contains the peer's identity, in the
			EAP-Response/AKA-Identity message. The AT_ANY_ID_REQ attribute is a
			general identity requesting attribute, which the server uses if it
			does not specify which kind of an identity the peer should return in
			AT_IDENTITY. The server uses the AT_FULLAUTH_ID_REQ attribute to
			request either the permanent identity or a pseudonym identity. The
			server uses the AT_PERMANENT_ID_REQ attribute to request the peer to
			send its permanent identity. The EAP-Request/AKA-Challenge, EAP-
			Response/AKA-Challenge, or the packets used on re-authentication may
			optionally include the AT_CHECKCODE attribute, which enables the
			protocol peers to ensure the integrity of the AKA-Identity packets.
			AT_CHECKCODE is specified in Section 0.
			EAP AKA Authentication 27 October, 2003
			The identity format in the AT_IDENTITY attribute is the same as in
			the EAP-Response/Identity packet (except that identity decoration is
			not allowed). The AT_IDENTITY attribute contains a permanent
			identity, a pseudonym identity or a re-authentication identity.
			Obtaining the subscriber identity via EAP/AKA messages is useful if
			the server does not have any EAP/AKA peer identity at the beginning
			of the EAP/AKA exchange or does not recognize the identity the peer
			used in EAP-Response/Identity. This may happen if, for example, the
			EAP-Response/Identity has been issued by some EAP method other than
			EAP/AKA or if intermediate entities or software layers in the peer
			have modified the identity string in the EAP-Response/Identity
			packet. Also, some EAP layer implementations may cache the identity
			string from the first EAP authentication and do not obtain a new
			identity string from the EAP method implementation on subsequent
			authentication exchanges.
			As the identity string is used in key derivation, any of these cases
			will result in failed authentication unless the EAP server uses
			EAP/AKA attributes to obtain an unmodified copy of the identity
			string. Therefore, unless the EAP server can be certain that no
			intermediate element or software layer has modified the EAP-
			Response/Identity packet, the EAP server SHOULD always use the
			EAP/AKA attributes to obtain the identity, even if the identity
			received in EAP-Response/Identity was valid.
			Please note that the EAP/AKA peer and the EAP/AKA server only
			process the AT_IDENTITY attribute and entities that only pass
			through EAP packets do not process this attribute. Hence, if the EAP
			server is not co-located in the authenticator, then the
			authenticator and other intermediate AAA elements (such as possible
			AAA proxy servers) will continue to refer to the peer with the
			original identity from the EAP-Response/Identity packet regardless
			of whether the AT_IDENTITY attribute is used in EAP/AKA to transmit
			another identity.
			Choice of Identity for the EAP-Response/Identity
			If EAP/AKA peer is started upon receiving an EAP-Request/Identity
			message, then the peer performs the following steps.
			If the peer has maintained re-authentication state information and
			if the peer wants to use re-authentication, then the peer transmits
			the re-authentication identity in EAP-Response/Identity.
			Else, if the peer has a pseudonym username available, then the peer
			transmits the pseudonym identity in EAP-Response/Identity.
			In other cases, the peer transmits the permanent identity in EAP-
			Response/Identity.
			EAP AKA Authentication 27 October, 2003
			Server Operation in the Beginning of EAP/AKA Exchange
	If the EAP server has not received any identity (permanent identity,		If the EAP server has not received any identity (permanent identity,
	pseudonym or re-authentication identity) from the client when		pseudonym identity or re-authentication identity) from the peer when
	sending the first EAP/AKA request, then the EAP server SHOULD issue		sending the first EAP/AKA request, or if the EAP server has received
	the EAP-Request/AKA-Identity packet and includes the AT_ANY_ID_REQ		an EAP-Response/Identity packet but the contents do not appear to be
	attribute (specified in Section 8.5). This attribute does not		a valid permanent identity, pseudonym identity or a re-
	contain any data.		authentication identity, then the server MUST request an identity
			from the peer using one of the methods below.
	If the EAP server has received an EAP-Response/Identity packet but		The server sends the EAP-Request/AKA-Identity message with the
	the contents do not appear to be a valid permanent identity,		AT_PERMANENT_ID_REQ message to indicate that the server wants the
	pseudonym or a re-authentication identity, the EAP server SHOULD		peer to include the permanent identity in the AT_IDENTITY attribute
			of the EAP-Response/AKA-Identity message. This is done in the
			following cases:
	EAP AKA Authentication June 2003		- The server does not support re-authentication or identity privacy.
	issue an EAP-Request/AKA-Identity packet with the AT_ANY_ID_REQ		- The server received an identity that it recognizes as a pseudonym
	attribute.		identity but the server is not able to map the pseudonym identity to
			a permanent identity.
	In some environments the intermediate entities or software layers in		The server issues the EAP-Request/AKA-Identity packet with the
	the client may modify the identity string in the EAP-		AT_FULLAUTH_ID_REQ attribute to indicate that the server wants the
	Response/Identity packet. For example, some EAP layer		peer to include a full authentication identity (pseudonym identity
	implementations may cache the identity string from the first		or permanent identity) in the AT_IDENTITY attribute of the EAP-
	authentication and do not obtain a new identity string from the EAP		Response/AKA-Identity message. This is done in the following cases:
	method implementation on subsequent authentication exchanges.
	Because the identity string is used in key derivation, such
	modifications will result in failed authentication unless the EAP
	server uses the AT_ANY_ID_REQ attribute to obtain an unmodified copy
	of the identity string. Therefore, in cases when there is a
	possibility that an intermediate element or software layer may
	modify the EAP-Response/Identity packet, the EAP server SHOULD
	always use the EAP-Request/AKA-Identity packet with the
	AT_ANY_ID_REQ attribute, even if the identity received in EAP-
	Response/Identity was valid.
	The AT_ANY_ID_REQ attribute requests the client to include the		- The server does not support re-authentication and the server
	AT_IDENTITY attribute (specified in Section 8.6) in the EAP-		supports identity privacy
	Response/AKA-Identity packet. The identity format in the AT_IDENTITY
	attribute is the same as in the Type-Data field of the EAP-
	Response/Identity packet. The AT_IDENTITY attribute contains a
	permanent identity, a pseudonym identity or a re-authentication
	identity. If the server does not support re-authentication, it uses
	the AT_FULLAUTH_ID_REQ attribute instead of the AT_ANY_ID_REQ
	attribute to directly request for a full authentication identity
	(either the permanent identity or a pseudonym identity). If the
	server uses the AT_FULLAUTH_ID_REQ attribute, the client MUST NOT
	use a re-authentication identity in the AT_IDENTITY attribute.
	The use of pseudonyms for anonymity is specified in Section 4.3. The		- The server received an identity that it recognizes as a re-
	use of re-authentication identities is specified in Section 5.		authentication identity but the server is not able to map the re-
			authentication identity to a permanent identity
	The full authentication case is illustrated in the figure below. In		The server issues the EAP-Request/AKA-Identity packet with the
	this case, AT_IDENTITY contains either the permanent identity or a		AT_ANY_ID_REQ attribute to indicate that the server wants the peer
	pseudonym identity. The same sequence is also used in case the		to include an identity in the AT_IDENTITY attribute of the EAP-
	server uses the AT_FULLAUTH_ID_REQ in EAP-Request/AKA-Identity		Response/SIM/Start message, and the server does not indicate any
			preferred type for the identity. This is done in other cases, such
			as when the server does not have any identity, or the server does
			not recognize the format of a received identity.
	EAP AKA Authentication June 2003		Processing of EAP-Request/AKA-Identity by the Peer
	Client Authenticator		Upon receipt of an EAP-Request/AKA-Identity message, the peer MUST
			perform the following steps.
			If the EAP-Request/AKA-Identity includes AT_PERMANENT_ID_REQ the
			peer MUST either respond with EAP-Response/AKA-Identity and include
			the permanent identity in AT_IDENTITY or respond with EAP-
			Response/AKA-Client-Error packet with code "unable to process
			packet".
			EAP AKA Authentication 27 October, 2003
			If the EAP-Request/AKA-Identity includes AT_FULL_AUTH_ID_REQ, and if
			the peer has a pseudonym available, then the peer SHOULD respond
			with EAP-Response/AKA-Identity and includes the pseudonym identity
			in AT_IDENTITY. If the peer does not have a pseudonym when it
			receives this message, then the peer MUST either respond with EAP-
			Response/AKA-Identity and include the permanent identity in
			AT_IDENTITY or respond with EAP-Response/AKA-Client-Error packet
			with code "unable to process packet." The Peer MUST NOT use a re-
			authentication identity in the AT_IDENTITY attribute.
			If the EAP-Request/AKA-Identity includes AT_ANY_ID_REQ, and if the
			peer has maintained re-authentication state information and the peer
			wants to use re-authentication, then the peer responds with EAP-
			Response/AKA-Identity and includes the re-authentication identity in
			AT_IDENTITY. Else, if the peer has a pseudonym identity available,
			then the peer responds with EAP-Response/AKA-Identity and includes
			the pseudonym identity in AT_IDENTITY. Else, the peer responds with
			EAP-Response/AKA-Identity and includes the permanent identity in
			AT_IDENTITY.
			An EAP/AKA exchange may include several EAP/AKA-Identity rounds. The
			server may issue a second EAP-Request/AKA-Identity, if it was not
			able to recognize the identity the peer used in the previous
			AT_IDENTITY attribute. At most three EAP/AKA-Identity rounds can be
			used. AT_ANY_ID_REQ can only be used in the first EAP-Request/AKA-
			Identity, in other words AT_ANY_ID_REQ MUST NOT be used in the
			second or third EAP-Request/AKA-Identity. AT_FULLAUTH_ID_REQ MUST
			NOT be used if the previous EAP-Request/AKA-Identity included
			AT_PERMANENT_ID_REQ. The peer operation in cases when it receives an
			unexpected attribute is specified in Section 4.4.1.
			Attacks against Identity Privacy
			The section above specifies two possible ways the peer can operate
			upon receipt of AT_PERMANENT_ID_REQ. This is because a received
			AT_PERMANENT_ID_REQ does not necessarily originate from the valid
			network, but an active attacker may transmit an EAP-Request/AKA-
			Identity packet with an AT_PERMANENT_ID_REQ attribute to the peer,
			in an effort to find out the true identity of the user. If the peer
			does not want to reveal its permanent identity, then the peer sends
			the EAP-Response/AKA-Client-Error packet with the error code "unable
			to process packet", and the authentication exchange terminates.
			Basically, there are two different policies that the peer can employ
			with regard to AT_PERMANENT_ID_REQ. A "conservative" peer assumes
			that the network is able to maintain pseudonyms robustly. Therefore,
			if a conservative peer has a pseudonym username, the peer responds
			with EAP-Response/AKA-Client-Error to the EAP packet with
			AT_PERMANENT_ID_REQ, because the peer believes that the valid
			network is able to map the pseudonym identity to the peer's
			permanent identity. (Alternatively, the conservative peer may accept
			AT_PERMANENT_ID_REQ in certain circumstances, for example if the
			pseudonym was received a long time ago.) The benefit of this policy
			is that it protects the peer against active attacks on anonymity. On
			EAP AKA Authentication 27 October, 2003
			the other hand, a "liberal" peer always accepts the
			AT_PERMANENT_ID_REQ and responds with the permanent identity. The
			benefit of this policy is that it works even if the valid network
			sometimes loses pseudonyms and is not able to map them to the
			permanent identity.
			Processing of AT_IDENTITY by the Server
			When the server receives an EAP-Response/AKA-Identity message with
			the AT_IDENTITY (in response to the server's identity requesting
			attribute), the server MUST operate as follows.
			If the server used AT_PERMANENT_ID_REQ, and if the AT_IDENTITY does
			not contain a valid permanent identity, then the server sends EAP
			Failure and the EAP exchange terminates. If the server recognizes
			the permanent identity and is able to continue, then the server
			proceeds with full authentication by sending EAP-Request/AKA-
			Challenge.
			If the server used AT_FULLAUTH_ID_REQ, and if AT_IDENTITY contains a
			valid permanent identity or a pseudonym identity that the server can
			map to a valid permanent identity, then the server proceeds with
			full authentication by sending EAP-Request/AKA-Challenge. If
			AT_IDENTITY contains a pseudonym identity that the server is not
			able to map to a valid permanent identity, or an identity that the
			server is not able to recognize or classify, then the server sends
			EAP-Request/ AKA-Identity with AT_PERMANENT_ID_REQ.
			If the server used AT_ANY_ID_REQ, and if the AT_IDENTITY contains a
			valid permanent identity or a pseudonym identity that the server can
			map to a valid permanent identity, then the server proceeds with
			full authentication by sending EAP-Request/ AKA-Challenge.
			If the server used AT_ANY_ID_REQ, and if AT_IDENTITY contains a
			valid re-authentication identity and the server agrees on using re-
			authentication, then the server proceeds with re-authentication by
			sending EAP-Request/ AKA-Reauthentication (Section 4.2).
			If the server used AT_ANY_ID_REQ, and if the peer sent an EAP-
			Response/AKA-Identity with AT_IDENTITY that contains an identity
			that the server recognizes as a re-authentication identity, but the
			server is not able to map the identity to a permanent identity, then
			the server sends EAP-Request/AKA-Identity with AT_FULLAUTH_ID_REQ.
			If the server used AT_ANY_ID_REQ, and if AT_IDENTITY contains a
			valid re-authentication identity, which the server is able to map to
			a permanent identity, and if the server does not want to use re-
			authentication, then the server proceeds with full authentication by
			sending EAP-Request/AKA-Challenge.
			If the server used AT_ANY_ID_REQ, and AT_IDENTITY contains an
			identity that the server recognizes as a pseudonym identity but the
			server is not able to map the pseudonym identity to a permanent
			EAP AKA Authentication 27 October, 2003
			identity, then the server sends EAP-Request/AKA-Identity with
			AT_PERMANENT_ID_REQ.
			If the server used AT_ANY_ID_REQ, and AT_IDENTITY contains an
			identity that the server is not able to recognize or classify, then
			the server sends EAP-Request/AKA-Identity with AT_FULLAUTH_ID_REQ.
			4.1.3. Message Sequence Examples (Informative)
			This section contains non-normative message sequence examples to
			illustrate how the peer identity can be communicated to the server.
			sage of AT_ANY_ID_REQ
			Obtaining the peer identity with EAP/AKA attributes is illustrated
			in the figure below.
			Peer Authenticator
	| |		| |
	| +------------------------------+		| +------------------------------+
	| | Server does not have any |		| | Server does not have any |
	| | Subscriber identity available|		| | Subscriber identity available|
	| | When starting EAP/AKA |		| | When starting EAP/AKA |
	| +------------------------------+		| +------------------------------+
	| |		| |
	| EAP-Request/AKA-Identity |		| EAP-Request/AKA-Identity |
	| (AT_ANY_ID_REQ) |		| (AT_ANY_ID_REQ) |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	| |		| |
	| EAP-Response/AKA-Identity |		| EAP-Response/AKA-Identity |
	| (AT_IDENTITY) |		| (AT_IDENTITY) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	If the client wants to perform full authentication, it includes the		all Back on Full Authentication
	permanent identity or a pseudonym identity in the AT_IDENTITY
	attribute. The client may use these identities in response to either
	AT_ANY_ID_REQ or AT_FULLAUTH_ID_REQ. If the server uses the
	AT_ANY_ID_REQ and the client wants to perform re-authentication,
	then the client includes a re-authentication identity in the
	AT_IDENTITY attribute.
	If the client uses its full authentication identity and the
	AT_IDENTITY attribute contains a valid permanent identity or a valid
	pseudonym identity that the EAP server is able to decode to the
	permanent identity, then the full authentication sequence proceeds
	as usual with the EAP Server issuing the EAP-Request/AKA-Challenge
	message.
	On re-authentication, if the AT_IDENTITY attribute contains a valid		The figure below illustrates the case when the server does not
	re-authentication identity and the server agrees on using re-		recognize the re-authentication identity the peer used in
	authentication, then the server proceeds with the re-authentication		AT_IDENTITY.
	sequence and issues the EAP-Request/AKA-Reauthentication packet, as
	specified in Section 5. If the server does not recognize the re-
	authentication identity, then it issues a second EAP-Request/AKA-
	Identity message and includes the AT_FULLAUTH_ID_REQ attribute. In
	this case, a second EAP/AKA-Identity round trip is required. The
	messages used on the first roundtrip are ignored. (However all AKA-
	Identity round trips are included in the calculation of the
	AT_CHECKCODE attribute, as specified in Section 7.2). This is
	illustrated below.
	EAP AKA Authentication June 2003		EAP AKA Authentication 27 October, 2003
	Client Authenticator		Peer Authenticator
	| |		| |
	| +------------------------------+		| +------------------------------+
	| | Server does not have any |		| | Server does not have any |
	| | Subscriber identity available|		| | Subscriber identity available|
	| | When starting EAP/AKA |		| | When starting EAP/AKA |
	| +------------------------------+		| +------------------------------+
	| |		| |
	| EAP-Request/AKA-Identity |		| EAP-Request/AKA-Identity |
	| (AT_ANY_ID_REQ) |		| (AT_ANY_ID_REQ) |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	skipping to change at page 15, line 45 ¶		skipping to change at page 22, line 45 ¶
	| EAP-Response/AKA-Identity |		| EAP-Response/AKA-Identity |
	| (AT_IDENTITY with a full-auth. Identity) |		| (AT_IDENTITY with a full-auth. Identity) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	If the server recognizes the re-authentication identity, but still		If the server recognizes the re-authentication identity, but still
	wants to fall back on full authentication, the server may issue the		wants to fall back on full authentication, the server may issue the
	EAP-Request/AKA-Challenge packet. In this case, the full		EAP-Request/AKA-Challenge packet. In this case, the full
	authentication procedure proceeds as usual.		authentication procedure proceeds as usual.
	An extra EAP/AKA-Identity round trip is also required in cases when		Requesting the Permanent Identity 1
	the AT_IDENTITY attribute contains a pseudonym identity that the EAP
	server fails to decode. The operation in this case is specified in
	Section 4.3.
	4.3. Identity Privacy Support
	EAP/AKA includes optional identity privacy (anonymity) support that
	can be used to hide the cleartext permanent identity and to make the
	subscriber's connections unlinkable to eavesdroppers. Identity
	privacy is based on temporary identities, or pseudonyms, which are
	equivalent to but separate from the Temporary Mobile Subscriber
	Identities (TMSI) that are used on cellular networks. Please see
	Section 12.1 for security considerations concerning identity
	privacy.
	EAP AKA Authentication June 2003
	If identity privacy is not used or if the client does not have any
	pseudonyms or re-authentication identities available, the client
	transmits the permanent identity in the EAP-Response/Identity packet
	or in the AT_IDENTITY attribute.
	The EAP-Request/AKA-Challenge message MAY include an encrypted
	pseudonym in the value field of the AT_ENCR_DATA attribute. The
	AT_IV and AT_MAC attributes are also used to transport the pseudonym
	to the client, as described in Section 8.1. Because the identity
	privacy support is optional to implement, the client MAY ignore the
	AT_IV and AT_ENCR_DATA attributes and always transmit the permanent
	identity in the EAP-Response/Identity packet and in the AT_IDENTITY
	attribute.
	On receipt of the EAP-Request/AKA-Challenge, the client verifies the
	AT_MAC attribute before looking at the AT_ENCR_DATA attribute. If
	the AT_MAC is invalid, then the client MUST silently discard the EAP
	packet. If the AT_MAC attribute is valid, then the client MAY
	decrypt the encrypted data in AT_ENCR_DATA and use the obtained
	pseudonym on the next full authentication.
	If the client does not receive a new pseudonym in the EAP-
	Request/AKA-Challenge message, the client MAY use an old pseudonym
	instead of the permanent identity on next full authentication.
	The EAP server produces pseudonyms in an implementation-dependent
	manner. Only the EAP server needs to be able to map the pseudonym to
	the permanent identity. Regardless of construction method, the
	pseudonym MUST conform to the grammar specified for the username
	portion of an NAI.
	In any case, it is necessary that permanent usernames and pseudonyms
	are separate and recognizable from each other. It is also desirable
	that EAP SIM and EAP AKA usernames be recognizable from each other
	as an aid for the server to which method to offer.
	In general, it is the task of the EAP server and the policies of its
	administrator to ensure sufficient separation in the usernames.
	Pseudonyms, for instance, are both produced and used by the EAP
	server. The EAP server MUST compose pseudonyms so that it can
	recognize if a NAI username is an EAP AKA pseudonym. For instance,
	when the usernames have been derived from the IMSI, the pseudonym
	could begin with a leading "2" character.
	The client MAY transmit the received pseudonym in the first EAP-
	Response/Identity packet of the next full authentication with the
	EAP server. The client concatenates the received pseudonym with the
	"@" character and the NAI realm portion. The client selects the
	realm name portion similarly as it select the realm name portion
	when using the permanent identity. If the EAP server successfully
	decodes the pseudonym received in the EAP-Response/Identity packet
	to a known client permanent identity, the authentication proceeds
	with the EAP-Request/AKA-Challenge message as usual.
	EAP AKA Authentication June 2003
	Because the client may fail to save a pseudonym sent to in an EAP-
	Request/AKA-Challenge, for example due to malfunction, the EAP
	server SHOULD maintain at least one old pseudonym in addition to the
	most recent pseudonym.
	If the EAP server requests the client to include its identity in the
	EAP-Response/AKA-Identity packet, as specified in Section 4.2, the
	client MAY transmit the received pseudonym in the AT_IDENTITY
	attribute. If the EAP server successfully decodes the pseudonym to a
	known identity, then the authentication proceeds with the EAP-
	Request/AKA-Challenge packet as usual.
	If the EAP server fails to decode the pseudonym to a known identity,
	then the EAP server requests the permanent identity (non-pseudonym
	identity) by including the AT_PERMANENT_ID_REQ attribute (Section
	8.5) in the EAP-Request/AKA-Identity message. Because another EAP
	server may have generated the pseudonym using a different coding
	scheme, the EAP server SHOULD use AT_PERMANENT_ID_REQ also in cases
	when it does not recognize the format of the client identity.
	The EAP server issues the EAP-Request/AKA-Identity message also in
	the case when it received the undecodable pseudonym in AT_IDENTITY
	included in the EAP-Response/AKA-Identity packet. In this case, a
	second EAP/AKA-Identity round trip is required.
	A received AT_PERMANENT_ID_REQ does not necessarily originate from
	the valid network, but an active attacker may transmit an EAP-
	Request/AKA-Identity packet with an AT_PERMANENT_ID_REQ attribute to
	the client, in an effort to find out the true identity of the user.
	The client MAY silently discard any EAP-Request/AKA-Identity
	messages that include AT_PERMANENT_ID_REQ for a while in order to
	wait for an EAP-Request/AKA-Identity packet without
	AT_PERMANENT_ID_REQ. If the valid network sent the message, the
	message will be retransmitted, so the client can reconsider replying
	to the message when it receives a retransmission.
	Basically, there are two different policies that the client can
	employ with regard to AT_PERMANENT_ID_REQ. A "conservative" client
	assumes that the network is able to maintain pseudonyms robustly.
	Therefore, if a conservative client has a pseudonym, the client
	silently ignores the EAP packet with AT_PERMANENT_ID_REQ, because
	the client believes that the valid network is able to decode the
	pseudonym. (Alternatively, the conservative client may respond to
	AT_PERMANENT_ID_REQ in certain circumstances, for example if the
	pseudonym was received a long time ago.) The benefit of this policy
	is that it protects the client against active attacks on anonymity.
	On the other hand, a "liberal" client always accepts the
	AT_PERMANENT_ID_REQ and responds with the permanent identity. The
	benefit of this policy is that it works even if the valid network
	sometimes loses pseudonyms and is not able to decode them to the
	permanent identity.
	The value field of the AT_PERMANENT_ID_REQ does not contain any data
	but the attribute is included to request the client to include the
	AT_IDENTITY attribute (Section 8.6) with the permanent
	EAP AKA Authentication June 2003
	authentication identity in the EAP-Response/AKA-Identity message. In
	this case, the AT_IDENTITY attribute contains the client's permanent
	identity in the clear.
	Please note that the EAP/AKA client and the EAP/AKA server only
	process the AT_IDENTITY attribute. Entities that only pass EAP
	packets through do not process this attribute. Hence, if the EAP
	server is not co-located in the authenticator, then the
	authenticator and other intermediate AAA elements (such as possible
	AAA proxy servers) will continue to refer to the client with the
	original identity from the EAP-Response/Identity packet regardless
	if the decoding fails in the EAP server.
	The figure below illustrates the case when the EAP server fails to		The figure below illustrates the case when the EAP server fails to
	decode the pseudonym included in the EAP-Response/Identity packet.		decode a pseudonym identity included in the EAP-Response/Identity
			packet.
	Client Authenticator		EAP AKA Authentication 27 October, 2003
			Peer Authenticator
	| |		| |
	| EAP-Request/Identity |		| EAP-Request/Identity |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	| EAP-Response/Identity |		| EAP-Response/Identity |
	| (Includes a pseudonym) |		| (Includes a pseudonym) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	| +------------------------------+		| +------------------------------+
	| | Server fails to decode the |		| | Server fails to decode the |
	skipping to change at page 18, line 51 ¶		skipping to change at page 23, line 35 ¶
	| |		| |
	| EAP-Response/AKA-Identity |		| EAP-Response/AKA-Identity |
	| (AT_IDENTITY with permanent identity) |		| (AT_IDENTITY with permanent identity) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	If the server recognizes the permanent identity, then the		If the server recognizes the permanent identity, then the
	authentication sequence proceeds as usual with the EAP Server		authentication sequence proceeds as usual with the EAP Server
	issuing the EAP-Request/AKA-Challenge message.		issuing the EAP-Request/AKA-Challenge message.
	If the server does not recognize the permanent identity, or if the		Requesting the Permanent Identity 2
	server is not able to continue the authentication exchange with the
	client after receiving the permanent identity, then the server
	issues the EAP Failure packet and the authentication exchange
	terminates.
	The figure below illustrates the case when the EAP server fails to		The figure below illustrates the case when the EAP server fails to
	decode the pseudonym included in the AT_IDENTITY attribute.		decode the pseudonym included in the AT_IDENTITY attribute.
	EAP AKA Authentication June 2003		EAP AKA Authentication 27 October, 2003
	Client Authenticator		Peer Authenticator
	| |		| |
	| +------------------------------+		| +------------------------------+
	| | Server does not have any |		| | Server does not have any |
	| | Subscriber identity available|		| | Subscriber identity available|
	| | When starting EAP/AKA |		| | When starting EAP/AKA |
	| +------------------------------+		| +------------------------------+
	| |		| |
	| EAP-Request/AKA-Identity |		| EAP-Request/AKA-Identity |
	| (AT_ANY_ID_REQ) |		| (AT_ANY_ID_REQ) |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	skipping to change at page 19, line 40 ¶		skipping to change at page 24, line 40 ¶
	| EAP-Request/AKA-Identity |		| EAP-Request/AKA-Identity |
	| (AT_PERMANENT_ID_REQ) |		| (AT_PERMANENT_ID_REQ) |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	| |		| |
	| EAP-Response/AKA-Identity |		| EAP-Response/AKA-Identity |
	| (AT_IDENTITY with permanent identity) |		| (AT_IDENTITY with permanent identity) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	In the worst case, there are three EAP/AKA-Identity round trips		Three EAP/AKA-Identity Round Trips
	before the server has obtained an acceptable identity: on the first
	round, the client sends its re-authentication identity in
	AT_IDENTITY. The server fails to accept it and request a full
	authentication identity with a second EAP-Request/AKA-Identity. The
	client responds with a pseudonym identity in AT_IDENTITY. The server
	fails to decode the pseudonym and has to issue a third EAP-
	Request/AKA-Identity, including AT_PERMANENT_ID_REQ. Finally, the
	server accepts the client's EAP-Response/AKA-Identity with the
	AT_IDENTITY attribute and proceeds with full authentication. This is
	illustrated in the figure below.
	EAP AKA Authentication June 2003		The figure below illustrates the case with three EAP/AKA-Identity
			round trips.
	Client Authenticator		EAP AKA Authentication 27 October, 2003
			Peer Authenticator
	| |		| |
	| +------------------------------+		| +------------------------------+
	| | Server does not have any |		| | Server does not have any |
	| | Subscriber identity available|		| | Subscriber identity available|
	| | When starting EAP/AKA |		| | When starting EAP/AKA |
	| +------------------------------+		| +------------------------------+
	| |		| |
	| EAP-Request/AKA-Identity |		| EAP-Request/AKA-Identity |
	| (AT_ANY_ID_REQ) |		| (AT_ANY_ID_REQ) |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	skipping to change at page 20, line 53 ¶		skipping to change at page 25, line 53 ¶
	| (AT_PERMANENT_ID_REQ) |		| (AT_PERMANENT_ID_REQ) |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	| |		| |
	| EAP-Response/AKA-Identity |		| EAP-Response/AKA-Identity |
	| (AT_IDENTITY with permanent identity) |		| (AT_IDENTITY with permanent identity) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	After the last EAP-Response/AKA-Identity message, the full		After the last EAP-Response/AKA-Identity message, the full
	authentication sequence proceeds as usual. If the EAP Server		authentication sequence proceeds as usual.
	recognizes the permanent identity and is able to proceed, the server
	issues the EAP-Request/AKA-Challenge message. If the server does not
	recognize the permanent identity, or if the server is not able to
	continue the authentication exchange with the client after receiving
	the permanent identity, then the server issues the EAP Failure
	packet and the authentication exchange terminates.
	EAP AKA Authentication June 2003		4.2. Re-authentication
	5. Re-authentication		4.2.1. General
	In some environments, EAP authentication may be performed		In some environments, EAP authentication may be performed
	frequently. Because the EAP AKA full authentication procedure makes		frequently. Because the EAP AKA full authentication procedure makes
			EAP AKA Authentication 27 October, 2003
	use of the UMTS AKA algorithms, and it therefore requires fresh		use of the UMTS AKA algorithms, and it therefore requires fresh
	authentication vectors from the Authentication Centre, the full		authentication vectors from the Authentication Centre, the full
	authentication procedure may result in many network operations when		authentication procedure may result in many network operations when
	used very frequently. Therefore, EAP AKA includes a more inexpensive		used very frequently. Therefore, EAP AKA includes a more inexpensive
	re-authentication procedure that does not make use of the UMTS AKA		re-authentication procedure that does not make use of the UMTS AKA
	algorithms and does not need new vectors from the Authentication		algorithms and does not need new vectors from the Authentication
	Centre.		Centre.
	Re-authentication is optional to implement for both the EAP AKA		Re-authentication is optional to implement for both the EAP AKA
	server and client. On each EAP authentication, either one of the		server and peer. On each EAP authentication, either one of the
	entities may also fall back on full authentication if they do not		entities may also fall back on full authentication if they do not
	want to use re-authentication.		want to use re-authentication.
	Re-authentication is based on the keys derived on the preceding full		Re-authentication is based on the keys derived on the preceding full
	authentication. The same K_aut and K_encr keys as in full		authentication. The same K_aut and K_encr keys as in full
	authentication are used to protect EAP AKA packets and attributes,		authentication are used to protect EAP AKA packets and attributes,
	and the original Master Key from full authentication is used to		and the original Master Key from full authentication is used to
	generate a fresh Master Session Key, as specified in Section 10.		generate a fresh Master Session Key, as specified in Section 4.5.
	On re-authentication, the client protects against replays with an		On re-authentication, the peer protects against replays with an
	unsigned 16-bit counter, included in the AT_COUNTER attribute. On		unsigned 16-bit counter, included in the AT_COUNTER attribute. On
	full authentication, both the server and the client initialize the		full authentication, both the server and the peer initialize the
	counter to one. The counter value of at least one is used on the		counter to one. The counter value of at least one is used on the
	first re-authentication. On subsequent re-authentications, the		first re-authentication. On subsequent re-authentications, the
	counter MUST be greater than on any of the previous re-		counter MUST be greater than on any of the previous re-
	authentications. For example, on the second re-authentication,		authentications. For example, on the second re-authentication,
	counter value is two or greater etc. The AT_COUNTER attribute is		counter value is two or greater etc. The AT_COUNTER attribute is
	encrypted.		encrypted.
	The server includes an encrypted server nonce (AT_NONCE_S) in the		The server includes an encrypted server nonce (AT_NONCE_S) in the
	re-authentication request. The AT_MAC attribute in the client's		re-authentication request. The AT_MAC attribute in the peer's
	response is calculated over NONCE_S to provide a challenge/response		response is calculated over NONCE_S to provide a challenge/response
	authentication scheme. The NONCE_S also contributes to the new		authentication scheme. The NONCE_S also contributes to the new
	Master Session Key.		Master Session Key.
	As discussed in Section 4.3, in some environments the client may		Both the peer and the server SHOULD have an upper limit for the
	assume that the network can reliably store pseudonyms and therefore		number of subsequent re-authentications allowed before a full
	the client may fail to respond to the AT_PERMANENT_ID_REQ attribute.		authentication needs to be performed. Because a 16-bit counter is
	The network SHOULD store pseudonyms on a reliable database. Because		used in re-authentication, the theoretical maximum number of re-
	one of the objectives of the re-authentication procedure is to		authentications is reached when the counter value reaches 0xFFFF.
	reduce load on the network, the re-authentication procedure does not		In order to use re-authentication, the peer and the EAP server need
	require the EAP server to contact a reliable database. Therefore,		to store the following values: Master Key, latest counter value and
	the re-authentication procedure makes use of separate re-		the next re-authentication identity. K_aut, K_encr may either be
			stored or derived again from MK. The server may also need to store
			the permanent identity of the user.
			4.2.2. Re-authentication Identity
			The re-authentication procedure makes use of separate re-
	authentication user identities. Pseudonyms and the permanent		authentication user identities. Pseudonyms and the permanent
	identity are reserved for full authentication only. The network does		identity are reserved for full authentication only. If a re-
	not need to store re-authentication identities as carefully as		authentication identity is lost and the network does not recognize
	pseudonyms. If a re-authentication identity is lost and the network		it, the EAP server can fall back on full authentication.
	does not recognize it, the EAP server can fall back on full
	authentication.
	EAP AKA Authentication June 2003		EAP AKA Authentication 27 October, 2003
	If the EAP server supports re-authentication, it MAY include the		If the EAP server supports re-authentication, it MAY include the
	skippable AT_NEXT_REAUTH_ID attribute in the encrypted data of EAP-		skippable AT_NEXT_REAUTH_ID attribute in the encrypted data of EAP-
	Request/AKA-Challenge message. This attribute contains a new re-		Request/AKA-Challenge message. This attribute contains a new re-
	authentication identity for the next re-authentication. The client		authentication identity for the next re-authentication. The peer MAY
	MAY ignore this attribute, in which case it will use full		ignore this attribute, in which case it will use full authentication
	authentication next time. If the client wants to use re-		next time. If the peer wants to use re-authentication, it uses this
	authentication, it uses this re-authentication identity on next		re-authentication identity on next authentication. Even if the peer
	authentication. Even if the client has a re-authentication identity,		has a re-authentication identity, the peer MAY discard the re-
	the client MAY discard the re-authentication identity and use a		authentication identity and use a pseudonym or the permanent
	pseudonym or the permanent identity instead, in which case full		identity instead, in which case full authentication MUST be
	authentication will be performed.		performed.
	The re-authentication identity received in AT_NEXT_REAUTH_ID		In environments where a real portion is needed in the peer identity,
	contains both the username portion and the realm portion of the		the re-authentication identity received in AT_NEXT_REAUTH_ID MUST
	Network Access Identifier. The EAP Server can choose an appropriate		contain both a username portion and a realm portion, as per the NAI
	realm part in order to have the AAA infrastructure route subsequent		format. The EAP Server can choose an appropriate realm part in order
	re-authentication related requests to the same AAA server. For		to have the AAA infrastructure route subsequent re-authentication
	example, the realm part MAY include a portion that is specific to		related requests to the same AAA server. For example, the realm part
	the AAA server. Hence, it is sufficient to store the context		MAY include a portion that is specific to the AAA server. Hence, it
	required for re-authentication in the AAA server that performed the		is sufficient to store the context required for re-authentication in
	full authentication.		the AAA server that performed the full authentication.
	The client MAY use the re-authentication identity in the EAP-		The peer MAY use the re-authentication identity in the EAP-
	Response/Identity packet or, in response to server's AT_ANY_ID_REQ		Response/Identity packet or, in response to server's AT_ANY_ID_REQ
	attribute, the client MAY use the re-authentication identity in the		attribute, the peer MAY use the re-authentication identity in the
	AT_IDENTITY attribute of the EAP-Response/AKA-Identity packet.		AT_IDENTITY attribute of the EAP-Response/AKA-Identity packet. The
			peer MUST NOT modify the username portion of the re-authentication
			identity, but the peer MAY modify the realm portion or replace it
			with another realm portion.
	Even if the client uses a re-authentication identity, the server may		Even if the peer uses a re-authentication identity, the server may
	want to fall back on full authentication, for example because the		want to fall back on full authentication, for example because the
	server does not recognize the re-authentication identity or does not		server does not recognize the re-authentication identity or does not
	want to use re-authentication. If the server was able to decode the		want to use re-authentication. If the server was able to decode the
	re-authentication identity to the permanent identity, the server		re-authentication identity to the permanent identity, the server
	issues the EAP-Request/AKA-Challenge packet to initiate full		issues the EAP-Request/AKA-Challenge packet to initiate full
	authentication. If the server was not able to recover the client's		authentication. If the server was not able to recover the peer's
	identity from the re-authentication identity, the server starts the		identity from the re-authentication identity, the server starts the
	full authentication procedure by issuing an EAP-Request/AKA-Identity		full authentication procedure by issuing an EAP-Request/AKA-Identity
	packet. This packet always starts a full authentication sequence if		packet. This packet always starts a full authentication sequence if
	it does not include the AT_ANY_ID_REQ attribute. (As specified in		it does not include the AT_ANY_ID_REQ attribute.
	Sections 4.2 and 4.3, the server MAY use AT_ANY_ID_REQ,
	AT_FULLAUTH_ID_REQ or AT_PERMANENT_ID_REQ attributes if it does not
	know the client's identity.)
	Both the client and the server SHOULD have an upper limit for the
	number of subsequent re-authentications allowed before a full
	authentication needs to be performed. Because a 16-bit counter is
	used in re-authentication, the theoretical maximum number of re-
	authentications is reached when the counter value reaches 0xFFFF.
	In order to use re-authentication, the client and the server need to		4.2.3. Re-authentication Procedure
	store the following values: original Master Key, K_aut, K_encr,
	latest counter value and the next re-authentication identity.
	The following figure illustrates the re-authentication procedure.		The following figure illustrates the re-authentication procedure.
	Encrypted attributes are denoted with '*'. The client uses its re-		Encrypted attributes are denoted with '*'. The peer uses its re-
	EAP AKA Authentication June 2003
	authentication identity in the EAP-Response/Identity packet. As		authentication identity in the EAP-Response/Identity packet. As
	discussed above, an alternative way to communicate the re-		discussed above, an alternative way to communicate the re-
	authentication identity to the server is for the client to use the		authentication identity to the server is for the peer to use the
	AT_IDENTITY attribute in the EAP-Response/AKA-Identity message. This		AT_IDENTITY attribute in the EAP-Response/AKA-Identity message. This
	latter case is not illustrated in the figure below, and it is only		latter case is not illustrated in the figure below, and it is only
	possible when the server requests the client to send its identity by		possible when the server requests the peer to send its identity by
	including the AT_ANY_ID_REQ attribute in the EAP-Request/AKA-		including the AT_ANY_ID_REQ attribute in the EAP-Request/AKA-
	Identity packet.		Identity packet.
			EAP AKA Authentication 27 October, 2003
	If the server recognizes the re-authentication identity and agrees		If the server recognizes the re-authentication identity and agrees
	on using re-authentication, then the server sends the EAP-		on using re-authentication, then the server sends the EAP-
	Request/AKA-Reauthentication packet to the client. This packet MUST		Request/AKA-Reauthentication packet to the peer. This packet MUST
	include the encrypted AT_COUNTER attribute, with a fresh counter		include the encrypted AT_COUNTER attribute, with a fresh counter
	value, the encrypted AT_NONCE_S attribute that contains a random		value, the encrypted AT_NONCE_S attribute that contains a random
	number chosen by the server, the AT_ENCR_DATA and the AT_IV		number chosen by the server, the AT_ENCR_DATA and the AT_IV
	attributes used for encryption, and the AT_MAC attribute that		attributes used for encryption, and the AT_MAC attribute that
	contains a message authentication code over the packet. The packet		contains a message authentication code over the packet. The packet
	MAY also include an encrypted AT_NEXT_REAUTH_ID attribute that		MAY also include an encrypted AT_NEXT_REAUTH_ID attribute that
	contains the next re-authentication identity.		contains the next re-authentication identity.
	Re-authentication identities are one-time identities. If the client		Re-authentication identities are one-time identities. If the peer
	does not receive a new re-authentication identity, it MUST use		does not receive a new re-authentication identity, it MUST use
	either the permanent identity or a pseudonym identity on the next		either the permanent identity or a pseudonym identity on the next
	authentication to initiate full authentication.		authentication to initiate full authentication.
	The client verifies that the counter value is fresh (greater than		The peer verifies that the counter value is fresh (greater than any
	any previously used value). The client also verifies that AT_MAC is		previously used value). The peer also verifies that AT_MAC is
	correct. The client MAY save the next re-authentication identity		correct. The peer MAY save the next re-authentication identity from
	from the encrypted AT_NEXT_REAUTH_ID for next time. If all checks		the encrypted AT_NEXT_REAUTH_ID for next time. If all checks are
	are successful, the client responds with the EAP-Response/AKA-		successful, the peer responds with the EAP-Response/AKA-
	Reauthentication packet, including the AT_COUNTER attribute with the		Reauthentication packet, including the AT_COUNTER attribute with the
	same counter value and the AT_MAC attribute.		same counter value and the AT_MAC attribute.
	The server verifies the AT_MAC attribute and also verifies that the		The server verifies the AT_MAC attribute and also verifies that the
	counter value is the same that it used in the EAP-Request/AKA-		counter value is the same that it used in the EAP-Request/AKA-
	Reauthentication packet. If these checks are successful, the re-		Reauthentication packet. If these checks are successful, the re-
	authentication has succeeded and the server sends the EAP-Success		authentication has succeeded and the server sends the EAP-Success
	packet to the client.		packet to the peer.
	EAP AKA Authentication June 2003		EAP AKA Authentication 27 October, 2003
	Client Authenticator		Peer Authenticator
	| |		| |
	| EAP-Request/Identity |		| EAP-Request/Identity |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	| EAP-Response/Identity |		| EAP-Response/Identity |
	| (Includes a re-authentication identity) |		| (Includes a re-authentication identity) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	| +--------------------------------+		| +--------------------------------+
	| | Server recognizes the identity |		| | Server recognizes the identity |
	skipping to change at page 24, line 29 ¶		skipping to change at page 29, line 29 ¶
	| | re-authentication |		| | re-authentication |
	| +--------------------------------+		| +--------------------------------+
	| |		| |
	| EAP-Request/AKA-Reauthentication |		| EAP-Request/AKA-Reauthentication |
	| (AT_IV, AT_ENCR_DATA, *AT_COUNTER, |		| (AT_IV, AT_ENCR_DATA, *AT_COUNTER, |
	| *AT_NONCE_S, *AT_NEXT_REAUTH_ID, AT_MAC) |		| *AT_NONCE_S, *AT_NEXT_REAUTH_ID, AT_MAC) |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	| |		| |
	+-----------------------------------------------+ |		+-----------------------------------------------+ |
	| Client verifies AT_MAC and the freshness of | |		| Peer verifies AT_MAC and the freshness of | |
	| the counter. Client MAY store the new re- | |		| the counter. Peer MAY store the new re- | |
	| authentication identity for next re-auth. | |		| authentication identity for next re-auth. | |
	+-----------------------------------------------+ |		+-----------------------------------------------+ |
	| |		| |
	| EAP-Response/AKA-Reauthentication |		| EAP-Response/AKA-Reauthentication |
	| (AT_IV, AT_ENCR_DATA, *AT_COUNTER with same value, |		| (AT_IV, AT_ENCR_DATA, *AT_COUNTER with same value, |
	| AT_MAC) |		| AT_MAC) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	| +--------------------------------+		| +--------------------------------+
	| | Server verifies AT_MAC and |		| | Server verifies AT_MAC and |
	| | the counter |		| | the counter |
	| +--------------------------------+		| +--------------------------------+
	| |		| |
	| EAP-Success |		| EAP-Success |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	If the client does not accept the counter value of EAP-Request/AKA-		4.2.4. Re-authentication Procedure when Counter is Too Small
			If the peer does not accept the counter value of EAP-Request/AKA-
	Reauthentication, it indicates the counter synchronization problem		Reauthentication, it indicates the counter synchronization problem
	by including the encrypted AT_COUNTER_TOO_SMALL in EAP-Response/AKA-		by including the encrypted AT_COUNTER_TOO_SMALL in EAP-Response/AKA-
	Reauthentication. The server responds with EAP-Request/AKA-Challenge		Reauthentication. The server responds with EAP-Request/AKA-Challenge
	to initiate a normal full authentication procedure. This is		to initiate a normal full authentication procedure. This is
	illustrated in the following figure. Encrypted attributes are		illustrated in the following figure. Encrypted attributes are
	denoted with '*'.		denoted with '*'.
	EAP AKA Authentication June 2003		EAP AKA Authentication 27 October, 2003
	Client Authenticator		Peer Authenticator
	| |		| |
	| EAP-Request/Identity |		| EAP-Request/Identity |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	| EAP-Response/Identity |		| EAP-Response/Identity |
	| (Includes a re-authentication identity) |		| (Includes a re-authentication identity) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	| EAP-Request/AKA-Reauthentication |		| EAP-Request/AKA-Reauthentication |
	| (AT_IV, AT_ENCR_DATA, *AT_COUNTER, |		| (AT_IV, AT_ENCR_DATA, *AT_COUNTER, |
	skipping to change at page 25, line 32 ¶		skipping to change at page 30, line 32 ¶
	| AT_MAC is valid but the counter is not fresh. | |		| AT_MAC is valid but the counter is not fresh. | |
	+-----------------------------------------------+ |		+-----------------------------------------------+ |
	| |		| |
	| EAP-Response/AKA-Reauthentication |		| EAP-Response/AKA-Reauthentication |
	| (AT_IV, AT_ENCR_DATA, *AT_COUNTER_TOO_SMALL, |		| (AT_IV, AT_ENCR_DATA, *AT_COUNTER_TOO_SMALL, |
	| *AT_COUNTER, AT_MAC) |		| *AT_COUNTER, AT_MAC) |
	|------------------------------------------------------>|		|------------------------------------------------------>|
	| |		| |
	| +----------------------------------------------+		| +----------------------------------------------+
	| | Server verifies AT_MAC but detects |		| | Server verifies AT_MAC but detects |
	| | That client has included AT_COUNTER_TOO_SMALL|		| | That peer has included AT_COUNTER_TOO_SMALL|
	| +----------------------------------------------+		| +----------------------------------------------+
	| |		| |
	| EAP-Request/AKA-Challenge |		| EAP-Request/AKA-Challenge |
	|<------------------------------------------------------|		|<------------------------------------------------------|
	| |		| |
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	| Normal full authentication follows. |		| Normal full authentication follows. |
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	| |		| |
	In the figure above, the first three messages are similar to the		In the figure above, the first three messages are similar to the
	basic re-authentication case. When the client detects that the		basic re-authentication case. When the peer detects that the counter
	counter value is not fresh, it includes the AT_COUNTER_TOO_SMALL		value is not fresh, it includes the AT_COUNTER_TOO_SMALL attribute
	attribute in EAP-Response/AKA-Reauthentication. This attribute		in EAP-Response/AKA-Reauthentication. This attribute doesn't contain
	doesn't contain any data but it is a request for the server to		any data but it is a request for the server to initiate full
	initiate full authentication. In this case, the client MUST ignore		authentication. In this case, the peer MUST ignore the contents of
	the contents of the server's AT_NEXT_REAUTH_ID attribute.		the server's AT_NEXT_REAUTH_ID attribute.
	On receipt of AT_COUNTER_TOO_SMALL, the server verifies AT_MAC and		On receipt of AT_COUNTER_TOO_SMALL, the server verifies AT_MAC and
	verifies that AT_COUNTER contains the same as in the EAP-		verifies that AT_COUNTER contains the same as in the EAP-
	Request/AKA-Reauthentication packet. If not, the server silently		Request/AKA-Reauthentication packet. If not, the server silently
	discards the EAP-Response/AKA-Reauthentication packet. If all checks		discards the EAP-Response/AKA-Reauthentication packet. If all checks
	on the packet are successful, the server transmits a EAP-		on the packet are successful, the server transmits a EAP-
	Request/AKA-Challenge packet and the full authentication procedure		Request/AKA-Challenge packet and the full authentication procedure
	is performed as usual. Since the server already knows the subscriber		is performed as usual. Since the server already knows the subscriber
	identity, it MUST NOT use the EAP-Request/AKA-Identity packet to		identity, it MUST NOT use the EAP-Request/AKA-Identity packet to
	request the identity.		request the identity.
	EAP AKA Authentication June 2003		EAP AKA Authentication 27 October, 2003
	6. Message Format
	The Type-Data of the EAP AKA packets begins with a 1-octet Subtype		4.3. EAP/AKA Notifications
	field, which is followed by a 2-octet reserved field. The rest of
	the Type-Data consists of attributes that are encoded in Type,
	Length, Value format. The figure below shows the generic format of
	an attribute.
	0 1 2 3		The EAP-Request/Notification, specified in [EAP], can be used to
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		convey a displayable message from the EAP server to the peer.
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		Because these messages are textual messages, it may be hard for the
	|Attribute Type | Length | Value...		peer to present them in the user's preferred language. Therefore,
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		EAP/AKA uses a separate EAP/AKA message subtype to transmit
			localizable notification codes instead of the EAP-
			Request/Notification packet.
	Attribute Type		The EAP server MAY issue an EAP-Request/AKA-Notification packet to
			the peer. The peer MAY show a notification message to the user and
			the peer MUST respond to the EAP server with an EAP-Response/AKA-
			Notification packet, even if the peer did not recognize the
			notification code.
	Indicates the particular type of attribute. The attribute type		The notification code is a 16-bit number. The most significant bit
	values are listed in Section 11.		is called the Failure bit (F bit). The F bit specifies whether the
			notification implies failure. The code values with the F bit set to
			zero (code values 0...32767) are used on unsuccessful cases. The
			receipt of a notification code from this range implies failed
			authentication, so the peer can use the notification as a failure
			indication. After receiving the EAP-Response/AKA-Notification for
			these notification codes, the server MUST send the EAP-Failure
			packet.
	Length		The receipt of a notification code with the F bit set to one (values
			32768...65536) does not imply failure, so the peer MUST NOT change
			its state when it receives such a notification. (This version of the
			protocol does not specify any notification codes with the F bit set
			to one.)
	Indicates the length of this attribute in multiples of 4 bytes.		The second most significant bit of the notification code is called
	The maximum length of an attribute is 1024 bytes. The length		the Phase bit (P bit). It specifies at which phase of the EAP/AKA
	includes the Attribute Type and Length bytes.		exchange the notification can be used. If the P bit is set to zero,
			the notification can only be used after the EAP/AKA-Challenge round
			in full authentication or the EAP/AKA-Reauthentication round in
			reautentication. For these notifications, the AT_MAC attribute MUST
			be included in both EAP-Request/AKA-Notification and EAP-
			Response/AKA-Notification.
	Value		If the P bit is set to one, the notification can only by used before
			the EAP/AKA-Challenge round in full authentication or the EAP/AKA-
			Reauthentication round in reauthentication. For these notifications,
			the AT_MAC attribute MUST NOT be included in either EAP-Request/AKA-
			Notification or EAP-Response/AKA-Notification. (This version of the
			protocol does not specify any notification codes with the P bit set
			to one.)
	The particular data associated with this attribute. This field is		Some of the notification codes are authorization related and hence
	always included and it is two or more bytes in length. The type		not usually considered as part of the responsibility of an EAP
	and length fields determine the format and length of the value		method. However, they are included as part of EAP/AKA because there
	field.		are currently no other ways to convey this information to the user
	When an attribute numbered within the range 0 through 127 is		EAP AKA Authentication 27 October, 2003
	encountered but not recognized, the EAP/AKA message containing that
	attribute MUST be silently discarded. These attributes are called
	non-skippable attributes.
	When an attribute numbered in the range 128 through 255 is		in a localizable way, and the information is potentially useful for
	encountered but not recognized that particular attribute is ignored,		the user. An EAP/AKA server implementation may decide never to send
	but the rest of the attributes and message data MUST still be		these EAP/AKA notifications.
	processed. The Length field of the attribute is used to skip the
	attribute value when searching for the next attribute. These
	attributes are called skippable attributes.
	EAP/AKA packets do not include a version field. However, should		4.4. Error Cases
	there be a reason to revise this protocol in the future, new non-
	skippable or skippable attributes could be specified in order to
	implement revised EAP/AKA versions in a backward-compatible manner.
	Unless otherwise specified, the order of the attributes in an EAP		This section specifies the operation of the peer and the server in
	AKA message is insignificant, and an EAP AKA implementation should		error cases. The subsections below require the EAP/AKA peer and
	not assume a certain order to be used.		server to send an error packet (EAP-Response/AKA-Client-Error or EAP
			Failure) in error cases. However, implementations SHOULD NOT rely
			upon the correct error reporting behavior of the peer,
			authenticator, or the server. It is possible for error and other
			messages to be lost in transit or for a malicious participant to
			attempt to consume resources by not issuing error messages. Both
			the peer and the EAP server SHOULD have a mechanism to clean up
			state even if an error message or EAP Success is not received after
			a timeout period.
	EAP AKA Authentication June 2003		4.4.1. Peer Operation
	Attributes can be encapsulated within other attributes. In other		Two special error messages have been specified for error cases that
	words, the value field of an attribute type can be specified to		are related to the processing of the UMTS AKA AUTN parameter, as
	contain other attributes.		described in Section 3: (1) if the peer does not accept AUTN, the
			peer responds with EAP-Response/AKA-Authentication-Reject (Section
			6.5), and the server issues EAP Failure, and (2) if the peer detects
			that the sequence number in AUTN is not correct, the peer responds
			with EAP-Response/AKA-Synchronization-Failure (Section 6.6), and the
			server proceeds with a new EAP-Request/AKA-Challenge.
	7. Message Authentication and Encryption		In other error cases, when an EAP/AKA peer detects an error in a
			received EAP/AKA packet, the EAP/AKA peer responds with the EAP-
			Response/AKA-Client-Error packet. In response to the EAP-
			Response/AKA-Client-Error, the EAP server MUST issue the EAP Failure
			packet and the authentication exchange terminates.
	This section specifies EAP/AKA attributes for attribute encryption		By default, the peer uses the client error code 0, "unable to
	and EAP/AKA message authentication.		process packet". This error code is used in the following cases:
	Encryption and integrity protection are based on the AKA session		- the peer is not able to parse the EAP request, i.e. the EAP
	keys CK and IK. Because the CK and IK keys are derived from the RAND		request is malformed
	challenge, these attributes can only be used in the EAP-Request/AKA-
	Challenge message and any EAP/AKA messages sent after it. For
	example, these attributes cannot be used in EAP-Request/AKA-
	Identity, because the RAND challenge has not yet been transmitted at
	that point. Integrity protection with AT_MAC MUST be used in all
	messages when keys have been derived.
	7.1. AT_MAC Attribute		- the peer encountered a malformed attribute
	The AT_MAC attribute can be used for EAP/AKA message integrity		- wrong attribute types or duplicate attributes have been included
	protection. Whenever AT_ENCR_DATA (Section 7.3) is included in an		in the EAP request
	EAP message, it MUST be followed (not necessarily immediately) by an
	AT_MAC attribute. Messages that do not meet this condition MUST be
	silently discarded.
	The value field of the AT_MAC attribute contains two reserved bytes		- a mandatory attribute is missing
	followed by a message authentication code (MAC). The MAC is
	calculated over the whole EAP packet, concatenated with optional
	message-specific data, with the exception that the value field of
	the MAC attribute is set to zero when calculating the MAC. The
	reserved bytes are set to zero when sending and ignored on
	reception.
	The contents of the message-specific data, if present, are specified		- unrecognized non-skippable attribute
	separately for each EAP/AKA message. The message-specific data is
	included in order to protect data that is not transmitted with the
	EAP packet.
	The format of the AT_MAC attribute is shown below.		- unrecognized or unexpected EAP/AKA Subtype in the EAP request
	0 1 2 3		- invalid AT_MAC
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_MAC | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| MAC |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The MAC algorithm is HMAC-SHA1-128 [9] keyed hash value. (The HMAC-		EAP AKA Authentication 27 October, 2003
	SHA1-128 value is obtained from the 20-byte HMAC-SHA1 value by
	EAP AKA Authentication June 2003		- invalid AT_CHECKCODE
	truncating the output to 16 bytes. Hence, the length of the MAC is		- invalid pad bytes in AT_PADDING
	16 bytes.) The message authentication key (K_aut) used in the
	calculation of the MAC is derived from the AKA integrity key (IK)
	and cipher key (CK), as specified in Section 10.
	7.2. AT_CHECKCODE Attribute		- the peer does not want to process AT_PERMANENT_ID_REQ
	The AT_MAC attribute is not used in the very first EAP/AKA messages,		4.4.2. Server Operation
	because keying material has not been derived yet. The client and the
	server may exchange one or more pairs of EAP/AKA messages of the
	Subtype AKA-Identity before keys are derived and before the AT_MAC
	attribute can be applied. The EAP/AKA-Identity messages may also be
	used upon re-authentication.
	The AT_CHECKCODE attribute MAY be used to protect the EAP/AKA-		If an EAP/AKA server detects an error in a received EAP/AKA
	Identity messages. AT_CHECKCODE is included in EAP-Request/AKA-		response, the server MUST issue the EAP Failure packet and the
	Challenge and/or EAP-Response/AKA-Challenge upon full		authentication exchange terminates. The errors cases when the server
	authentication. In re-authentication, AT_CHECKCODE can be included		issues an EAP Failure include the following:
	in EAP-Request/AKA-Reauthentication and/or EAP-Response/AKA-
	Reauthentication. Because the AT_MAC attribute is used in these
	messages, AT_CHECKCODE will be integrity protected with AT_MAC.
	The format of the AT_CHECKCODE attribute is shown below.
	0 1 2 3		- the server is not able to parse the peer's EAP response
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_CHECKCODE | Length | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| Checkcode (0 or 20 bytes) |
	| |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The value field of AT_CHECKCODE begins with two reserved bytes,		- the server encounters a malformed attribute, a non-recognized non-
	which may be followed by a 20-byte checkcode. If the checkcode is		skippable attribute, or a duplicate attribute
	not included in AT_CHECKCODE, then the attribute indicates that no
	EAP/AKA-Identity messages were exchanged. This may occur in both
	full authentication and re-authentication. The reserved bytes are
	set to zero when sending and ignored on reception.
	The checkcode is a hash value, calculated with SHA1 [10], over all		- a mandatory attribute is missing or an invalid attribute was
	EAP-Request/AKA-Identity and EAP-Response/ AKA-Identity packets		included
	exchanged in this authentication exchange. The packets are included
	in the order that they were transmitted, that is, starting with the
	first EAP-Request/ AKA-Identity message, followed by the
	corresponding EAP-Response/ AKA-Identity, followed by the second
	EAP-Request/ AKA-Identity (if used) etc.
	EAP packets are included in the hash calculation "as-is", as they		- unrecognized or unexpected EAP/AKA Subtype in the EAP Response
	were transmitted or received. All reserved bytes, padding bytes etc.
	that are specified for various attributes are included as such, and
	the receiver must not reset them to zero. No delimiter bytes,
	EAP AKA Authentication June 2003		- invalid AT_MAC
	padding or any other framing are included between the EAP packets		- invalid AT_CHECKCODE
	when calculating the checkcode.
	Messages are included in request/response pairs; in other words only		- invalid AT_COUNTER
	full "round trips" are included. Packets that are silently discarded
	are not included. The EAP server must only include an EAP-
	Request/AKA-Identity in the calculation once it has received a
	corresponding response, with the same Identifier value.
	Retransmissions or requests to which the server does not receive
	response are not included.
	The client must include the EAP-Request/AKA-Identity and the		4.4.3. Failure
	corresponding response in the calculation only if the client
	receives a subsequent EAP-Request/AKA-Challenge, or a follow-up EAP-
	Request/AKA-Identity with different attributes (attribute types)
	than in the first EAP-Request/AKA-Identity. After sending EAP-
	Response/AKA-Identity, if the client receives another EAP-
	Request/AKA-Identity with the same attributes as in the previous
	request, then the client's response to the first request must have
	been lost. In this case the client must not include the first
	request and its response in the calculation of the checkcode.
	The AT_CHECKCODE attribute is optional to implement. It is specified		As normally in EAP, the EAP server sends the EAP-Failure packet to
	in order to allow protecting the EAP/ AKA-Identity messages and any		the peer when the authentication procedure fails on the EAP Server.
	future extensions to them. The implementation of AT_CHECKCODE is		In EAP/AKA, this may occur for example if the EAP server does not
	recommended.		recognize the peer identity, or if the EAP server is not able to
			obtain the authentication vectors for the subscriber or the
			authentication exchange times out. The server may also send EAP
			Failure if there is an error in the received EAP/AKA response, as
			discussed in Section 4.4.2.
	If the receiver of AT_CHECKCODE implements this attribute, then the		The server can send EAP-Failure at any time in the EAP exchange. The
	receiver MUST check that the checkcode is correct. If the checkcode		peer MUST process EAP-Failure.
	is invalid, the receiver must terminate the authentication exchange.
	If the EAP/AKA-Identity messages are extended with new attributes		4.4.4. EAP Success
	then AT_CHECKCODE must be implemented and used. More specifically,
	if the server includes any other attributes than
	AT_PERMANENT_ID_REQ, AT_FULLAUTH_ID_REQ or AT_ANY_ID_REQ in the EAP-
	Request/AKA-Identity packet, then the server MUST include
	AT_CHECKCODE in EAP-Request/AKA-Challenge or EAP-Request/AKA-
	Reauthentication. If the client includes any other attributes than
	AT_IDENTITY in the EAP-Response/AKA-Identity message, then the
	client MUST include AT_CHECKCODE in EAP-Response/AKA-Challenge or
	EAP-Response/AKA-Reauthentication.
	If the server implements the processing of any other attribute than		On full authentication, the server can only send EAP-Success after
	AT_IDENTITY for the EAP-Response/AKA-Identity message, then the		the EAP/AKA-Challenge round. The peer MUST silently discard any EAP-
	server MUST implement AT_CHECKCODE. In this case, if the server		Success packets if they are received before the peer has
	receives any other attribute than AT_IDENTITY in the EAP-		successfully authenticated the server and sent the EAP-Response/AKA-
	Response/AKA-Identity message, then the server MUST check that		Challenge packet.
	AT_CHECKCODE is present in EAP-Response/AKA-Challenge or EAP-
	Response/AKA-Reauthentication. If AT_CHECKCODE is not included, the
	server must terminate the authentication exchange.
	Similarly, if the client implements the processing of any other		On re-authentication, EAP-Success can only be sent after the
	attribute than AT_PERMANENT_ID_REQ, AT_FULLAUTH_ID_REQ or		EAP/AKA-Reauthentication round. The peer MUST silently discard any
	AT_ANY_ID_REQ for the EAP-Request/AKA-Identity packet, then the		EAP-Success packets if they are received before the peer has
	EAP AKA Authentication June 2003		EAP AKA Authentication 27 October, 2003
	client MUST implement AT_CHECKCODE. In this case, if the client		successfully authenticated the server and sent the EAP-Response/AKA-
	receives any other attribute than AT_PERMANENT_ID_REQ,		Reauthentication packet.
	AT_FULLAUTH_ID_REQ or AT_ANY_ID_REQ in the EAP-Request/AKA-Identity
	packet, then the client MUST check that AT_CHECKCODE is present in
	EAP-Request/AKA-Challenge or EAP-Request/AKA-Reauthentication. If
	the attribute was not included, the client must terminate the
	authentication exchange.
	7.3. AT_IV, AT_ENCR_DATA and AT_PADDING Attributes		If the peer receives an EAP/AKA notification (section 4.3) that
			indicates failure, then the peer MUST no longer accept the EAP-
			Success packet even if the server authentication was successfully
			completed.
	AT_IV and AT_ENCR_DATA attributes can be optionally used to transmit		4.5. Key Generation
	encrypted information between the EAP/AKA client and server.
	The value field of AT_IV contains two reserved bytes followed by a		This section specifies how keying material is generated.
	16-byte initialization vector required by the AT_ENCR_DATA
	attribute. The reserved bytes are set to zero when sending and
	ignored on reception. The AT_IV attribute MUST be included if and
	only if the AT_ENCR_DATA is included. Messages that do not meet this
	condition MUST be silently discarded.
	The sender of the AT_IV attribute chooses the initialization vector		On EAP AKA full authentication, a Master Key (MK) is derived from
	by random. The sender MUST NOT reuse the initialization vector value		the underlying UMTS AKA values (CK and IK keys), and the identity as
	from previous EAP AKA packets but the sender MUST choose it freshly		follows.
	for each AT_IV attribute. The sends SHOULD use a good source of
	randomness to generate the initialization vector. The format of
	AT_IV is shown below.
	0 1 2 3		MK = SHA1(Identity|IK|CK)
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_IV | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| Initialization Vector |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The value field of the AT_ENCR_DATA attribute consists of two		In the formula above, the "|" character denotes concatenation.
	reserved bytes followed by bytes encrypted using the Advanced		Identity denotes the peer identity string without any terminating
	Encryption Standard (AES) [11] in the Cipher Block Chaining (CBC)		null characters. It is the identity from the AT_IDENTITY attribute
	mode of operation, using the initialization vector from the AT_IV		from the last EAP-Response/AKA-Identity packet, or, if AT_IDENTITY
	attribute. The reserved bytes are set to zero when sending and		was not used, the identity from the EAP-Response/Identity packet.
	ignored on reception. Please see [12] for a description of the CBC		The identity string is included as-is, without any changes and
	mode. The format of the AT_ENCR_DATA attribute is shown below.		including the possible identity decoration. The hash function SHA-1
			is specified in [SHA-1].
	EAP AKA Authentication June 2003		The Master Key is fed into a Pseudo-Random number Function (PRF),
			which generates separate Transient EAP Keys (TEKs) for protecting
			EAP AKA packets, as well as a Master Session Key (MSK) for link
			layer security and an Extended Master Session Key (EMSK) for other
			purposes. On re-authentication, the same TEKs MUST be used for
			protecting EAP packets, but a new MSK and a new EMSK MUST be derived
			from the original MK and new values exchanged in the re-
			authentication.
	0 1 2 3		EAP AKA requires two TEKs for its own purposes, the authentication
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		key K_aut to be used with the AT_MAC attribute, and the encryption
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		key K_encr, to be used with the AT_ENCR_DATA attribute. The same
	| AT_ENCR_DATA | Length | Reserved |		K_aut and K_encr keys are used in full authentication and subsequent
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		re-authentications.
	| |
	. Encrypted Data .
	. .
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The encryption key (K_encr) is derived is derived from the AKA		Key derivation is based on the random number generation specified in
	integrity key (IK) and cipher key (CK), as specified in Section10.		NIST Federal Information Processing Standards (FIPS) Publication
	The plaintext consists of nested EAP/AKA attributes.		186-2 [PRF]. The pseudo-random number generator is specified in the
			change notice 1 (2001 October 5) of [PRF] (Algorithm 1). As
			specified in the change notice (page 74), when Algorithm 1 is used
			as a general-purpose pseudo-random number generator, the "mod q"
			term in step 3.3 is omitted. The function G used in the algorithm is
			constructed via Secure Hash Standard as specified in Appendix 3.3 of
			the standard. It should be noted that the function G is very similar
			to SHA-1, but the message padding is different. Please refer to
			[PRF] for full details. For convenience, the random number algorithm
			with the correct modification is cited in Annex A.
	The encryption algorithm requires the length of the plaintext to be		EAP AKA Authentication 27 October, 2003
	a multiple of 16 bytes. The sender may need to include the
	AT_PADDING attribute as the last attribute within AT_ENCR_DATA. The
	AT_PADDING attribute is not included if the total length of other
	nested attributes within the AT_ENCR_DATA attribute is a multiple of
	16 bytes. As usual, the Length of the Padding attribute includes the
	Attribute Type and Attribute Length fields. The Length of the
	Padding attribute is 4, 8 or 12 bytes. It is chosen so that the
	length of the value field of the AT_ENCR_DATA attribute becomes a
	multiple of 16 bytes. The actual pad bytes in the value field are
	set to zero (0x00) on sending. The recipient of the message MUST
	verify that the pad bytes are set to zero, and silently drop the
	message if this verification fails. The format of the AT_PADDING
	attribute is shown below.
	0 1 2 3		160-bit XKEY and XVAL values are used, so b = 160. On each full
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		authentication, the Master Key is used as the initial secret seed-
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		key XKEY. The optional user input values (XSEED_j) in step 3.1 are
	| AT_PADDING | Length | Padding... |		set to zero.
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	8. Messages		The resulting 320-bit random numbers x_0, x_1, ..., x_m-1 are
			concatenated and partitioned into suitable-sized chunks and used as
			keys in the following order: K_encr (128 bits), K_aut (128 bits),
			Master Session Key (64 bytes), Extended Master Session Key (64
			bytes).
	8.1. EAP-Request/AKA-Challenge		On re-authentication, the same pseudo-random number generator can be
			used to generate a new Master Session Key and new Initialization
			Vectors. The seed value XKEY' is calculated as follows:
			XKEY' = SHA1(Identity|counter|NONCE_S| MK)
	The format of the EAP-Request/AKA-Challenge packet is shown below.		In the formula above, the Identity denotes the re-authentication
			identity, without any terminating null characters, from the
			AT_IDENTITY attribute of the EAP-Response/AKA-Identity packet, or,
			if EAP-Response/AKA-Identity was not used on re-authentication, the
			identity string from the EAP-Response/Identity packet. The counter
			denotes the counter value from AT_COUNTER attribute used in the EAP-
			Response/AKA-Reauthentication packet. The counter is used in network
			byte order. NONCE_S denotes the 16-byte NONCE_S value from the
			AT_NONCE_S attribute used in the EAP-Request/AKA-Reauthentication
			packet. The MK is the Master Key derived on the preceding full
			authentication. The pseudo-random number generator is run with the
			new seed value XKEY', and the resulting 320-bit random numbers x_0,
			x_1, ..., x_m-1 are concatenated and partitioned into 64-byte chunks
			and used as the new 64-byte Master Session Key and the new 64-byte
			Extended Master Session Key.
	EAP AKA Authentication June 2003		The first 32 bytes of the MSK can be used as the Pairwise Master Key
			(PMK) for IEEE 802.11i.
	0 1 2 3		When the RADIUS attributes specified in [RFC 2548] are used to
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		transport keying material, then the first 32 bytes of the MSK
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		correspond to MS-MPPE-RECV-KEY and the second 32 bytes to MS-MPPE-
	| Code | Identifier | Length |		SEND-KEY. In this case, only 64 bytes of keying material (the MSK)
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		are used.
	| Type | Subtype | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_RAND | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| RAND |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_AUTN | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| AUTN |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_IV | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| Initialization Vector (optional) |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_ENCR_DATA | Length | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| Encrypted Data (optional) |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_CHECKCODE | Length | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| Checkcode (optional) |
	| |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_MAC | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| MAC |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The semantics of the fields is described below:		5. Message Format and Protocol Extensibility
	EAP AKA Authentication June 2003		5.1. Message Format
	Code		As specified in [EAP], EAP packets begin with the Code, Identifiers,
			Length, and Type fields, which are followed by EAP method specific
			Type-Data. The Code field in the EAP header is set to 1 for EAP
			requests, and to 2 for EAP Responses. The usage of the Length and
			Identifier fields in the EAP header is also specified in [EAP]. In
			EAP/AKA, the Type field is set to 23.
	1 for Request		EAP AKA Authentication 27 October, 2003
	Identifier		In EAP/AKA, the Type-Data begins with an EAP/AKA header that
			consists of a 1-octet Subtype field, and a 2-octet reserved field.
			The Subtype values used in EAP/AKA are defined in Section 8. The
			formats of the EAP header and the EAP/AKA header are shown below.
	See [5]		0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Code | Identifier | Length |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Type | Subtype | Reserved |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Length		The rest of the Type-Data, immediately following the EAP/AKA header,
			consists of attributes that are encoded in Type, Length, Value
			format. The figure below shows the generic format of an attribute.
	The length of the EAP Request packet.		0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			|Attribute Type | Length | Value...
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type		Attribute Type
	23		Indicates the particular type of attribute. The attribute type
			values are listed in Section 8.
	Subtype		Length
	1 for AKA-Challenge		Indicates the length of this attribute in multiples of 4 bytes.
			The maximum length of an attribute is 1024 bytes. The length
			includes the Attribute Type and Length bytes.
	Reserved		Value
	Set to zero when sending, ignored on reception.		The particular data associated with this attribute. This field is
			always included and it is two or more bytes in length. The type
			and length fields determine the format and length of the value
			field.
	AT_RAND		Attributes numbered within the range 0 through 127 are called non-
			skippable attributes. When an EAP/AKA peer encounters a non-
			skippable attribute type that the peer does not recognize, the peer
			MUST send the EAP-Response/AKA-Client-Error packet, and the
			authentication exchange terminates. If an EAP/AKA server encounters
			a non-skippable attribute that the server does not recognize, then
			the server sends the EAP Failure packet and the authentication
			exchange terminates.
	The value field of this attribute contains two reserved bytes		When an attribute numbered in the range 128 through 255 is
	followed by the AKA RAND parameter, 16 bytes (128 bits). The		encountered but not recognized that particular attribute is ignored,
	reserved bytes are set to zero when sending and ignored on
	reception. The AT_RAND attribute MUST be present in EAP-
	Request/AKA-Challenge.
	AT_AUTN		EAP AKA Authentication 27 October, 2003
	The value field of this attribute contains two reserved bytes		but the rest of the attributes and message data MUST still be
	followed by the AKA AUTN parameter, 16 bytes (128 bits). The		processed. The Length field of the attribute is used to skip the
	reserved bytes are set to zero when sending and ignored on		attribute value when searching for the next attribute. These
	reception. The AT_AUTN attribute MUST be included.		attributes are called skippable attributes.
	AT_IV		Unless otherwise specified, the order of the attributes in an EAP
			AKA message is insignificant, and an EAP AKA implementation should
			not assume a certain order to be used.
	See Section 7.3.		Attributes can be encapsulated within other attributes. In other
			words, the value field of an attribute type can be specified to
			contain other attributes.
	AT_ENCR_DATA		5.2. Protocol Extensibility
	See Section 7.3. The nested attributes that are included in the		EAP/AKA can be extended by specifying new attribute types. If
	plaintext of AT_ENCR_DATA are described below.		skippable attributes are used, it is possible to extend the protocol
			without breaking old implementations. As specified in Section 7.4,
			if new attributes are specified for EAP-Request/AKA-Identity or EAP-
			Response/AKA-Identity, then the AT_CHECKCODE MUST be used to
			integrity protect the new attributes.
	AT_CHECKCODE		When specifying new attributes, it should be noted that EAP/AKA does
			not support message fragmentation. Hence, the sizes of the new
			extensions MUST be limited so that the maximum transfer unit (MTU)
			of the underlying lower layer is not exceeded. According to [EAP],
			lower layers must provide an EAP MTU of 1020 bytes or greater, so
			any extensions to EAP/AKA SHOULD NOT exceed the EAP MTU of 1020
			bytes.
	The AT_CHECKCODE attribute is optional to include. See section		EAP/AKA packets do not include a version field. However, should
	7.2		there be a reason to revise this protocol in the future, new non-
			skippable or skippable attributes could be specified in order to
			implement revised EAP/AKA versions in a backward-compatible manner.
			It is possible to introduce version negotiation in the EAP-
			Request/AKA-Identity and EAP-Response/AKA-Identity messages by
			specifying new skippable attributes.
	EAP AKA Authentication June 2003		6. Messages
	AT_MAC		This section specifies the messages used in EAP/AKA. It specifies
			when a message may be transmitted or accepted, which attributes are
			allowed in a message, which attributes are required in a message,
			and other message specific details. Message format is specified in
			Section 5.1.
	AT_MAC MUST be included. In EAP-Request/AKA-Challenge, there is		6.1. EAP-Request/AKA-Identity
	no message-specific data covered by the MAC. See Section 7.1.
	In the EAP-Request/AKA-Challege message, the AT_IV, AT_ENCR_DATA and		The EAP/AKA-Identity roundtrip MAY used for obtaining the peer
	AT_MAC attributes are used for Identity privacy and for		identity to the server. As discussed in Section 4.1, several AKA-
	communicating the next re-authentication identity. The plaintext of		Identity rounds may be required in order to obtain a valid peer
	the AT_ENCR_DATA value field consists of nested attributes, which		identity.
	are shown below. Later versions of this protocol MAY specify
	additional attributes to be included within the encrypted data.
	0 1 2 3		EAP AKA Authentication 27 October, 2003
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_NEXT_PS... | Length | Actual Pseudonym Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	. Next Pseudonym .
	. .
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_NEXT_REAU..| Length | Actual Re-Auth Identity Length|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	. Next Re-authentication Username .
	. .
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_PADDING | Length | Padding... |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	AT_NEXT_PSEUDONYM		The server MUST include one of the following identity requesting
			attributes: AT_PERMANENT_ID_REQ, AT_FULLAUTH_ID_REQ, AT_ANY_ID_REQ.
			These three attributes are mutually exclusive, so the server MUST
			NOT include more than one of the attributes.
	This attribute is optional. The value field of this attribute		If the server has previously issued an EAP-Request/AKA-Identity
	begins with a 2-byte actual pseudonym length, which specifies the		message with the AT_PERMANENT_ID_REQ attribute, and if the server
	length of the pseudonym in bytes. This field is followed by a		has received a response from the peer, then the server MUST NOT
	pseudonym user name, of the indicated actual length, that the		issue a new EAP-Request/AKA-Identity packet.
	client can use in the next authentication, as described in
	Section 4.3. The user name does not include any terminating null
	characters. Because the length of the attribute must be a
	multiple of 4 bytes, the sender pads the pseudonym with zero
	bytes when necessary.
	AT_NEXT_REAUTH_ID		If the server has previously issued an EAP-Request/AKA-Identity
			message with the AT_FULLAUTH_ID_REQ attribute, and if the server has
			received a response from the peer, then the server MUST NOT issue a
			new EAP-Request/AKA-Identity packet with the AT_ANY_ID_REQ or
			AT_FULLAUTH_ID_REQ attributes.
	The AT_NEXT_REAUTH_ID attribute is optional to include. The value		If the server has previously issued an EAP-Request/AKA-Identity
	field of this attribute begins with a 2-byte actual re-		message with the AT_ANY_ID_REQ attribute, and if the server has
	authentication identity length, which specifies the length of the		received a response from the peer, then the server MUST NOT issue a
	re-authentication identity in bytes. This field is followed by a		new EAP-Request/AKA-Identity packet with the AT_ANY_ID_REQ.
	re-authentication identity, of the indicated actual length, that
	EAP AKA Authentication June 2003		This message MUST NOT include AT_MAC, AT_IV, or AT_ENCR_DATA.
	the client can use in the next re-authentication, as described in		6.2. EAP-Response/AKA-Identity
	Section 5. The re-authentication identity includes both a
	username portion and a realm name portion. The re-authentication
	identity does not include any terminating null characters.
	Because the length of the attribute must be a multiple of 4
	bytes, the sender pads the re-authentication identity with zero
	bytes when necessary.
	AT_PADDING		The peer sends EAP-Response/AKA-Identity in response to a valid EAP-
			Request/AKA-Identity from the server.
	AT_PADDING is optional to include. See Section 7.3.		The peer MUST include the AT_IDENTITY attribute. The usage of
			AT_IDENITY is defined in Section 4.1.
	8.2. EAP-Response/AKA-Challenge		This message MUST NOT include AT_MAC, AT_IV, or AT_ENCR_DATA.
	The format of the EAP-Response/AKA-Challenge packet is shown below.		6.3. EAP-Request/AKA-Challenge
	Later versions of this protocol MAY make use of the AT_ENCR_DATA and		The server sends the EAP-Request/AKA-Challenge on full
	AT_IV attributes in this message to include encrypted (skippable)		authentication after successfully obtaining the subscriber identity.
	attributes. AT_MAC, AT_ENCR_DATA and AT_IV attributes are not shown
	in the figure below. If present, they are processed as in EAP-
	Request/AKA-Challenge packet. The EAP server MUST process EAP-
	Response/AKA-Challenge messages that include these attributes even
	if the server did not implement these optional attributes.
	0 1 2 3		The AT_RAND attribute MUST be included.
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Code | Identifier | Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Subtype | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_RES | Length | RES Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
	| |
	| RES |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_CHECKCODE | Length | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| Checkcode (optional) |
	| |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_MAC | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| MAC |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	EAP AKA Authentication June 2003		AT_MAC MUST be included. In EAP-Request/AKA-Challenge, there is no
			message-specific data covered by the MAC, see Section 7.2.
	The semantics of the fields is described below:		The AT_CHECKCODE attribute MAY be included, and in certain cases
			specified in Section 7.4, it MUST be included.
	Code		The EAP-Request/AKA-Challenge packet MAY include encrypted
			attributes for identity privacy and for communicating the next re-
			authentication identity. In this case, the AT_IV and AT_ENCR_DATA
			attributes are included (Section 7.3).
	2 for Response		The plaintext of the AT_ENCR_DATA value field consist of nested
			attributes. The nested attributes MAY include AT_PADDING (as
			specified in Section 7.3). If the server supports identity privacy
	Identifier		EAP AKA Authentication 27 October, 2003
	See [5]		and wants to communicate a pseudonym to the peer for the next full
			authentication, then the nested encrypted attributes include the
			AT_NEXT_PSEUDONYM attribute. If the server supports re-
			authentication and wants to communicate a re-authentication identity
			to the peer, then the nested encrypted attributes include the
			AT_NEXT_REAUTH_ID attribute. Later versions of this protocol MAY
			specify additional attributes to be included within the encrypted
			data.
	Length		6.4. EAP-Response/AKA-Challenge
	The length of the EAP Response packet.		The peer sends EAP-Response/AKA-Challenge in response to a valid
			EAP-Request/AKA-Challenge.
	Type		The AT_MAC attribute MUST be included. In EAP-Response/AKA-
			Challenge, there is no message-specific data covered by the MAC, see
			Section 7.2.
	23		The AT_RES attribute MUST be included.
	Subtype		The AT_CHECKCODE attribute MAY be included, and in certain cases
			specified in Section 7.4, it MUST be included.
	1 for AKA-Challenge		Later versions of this protocol MAY make use of the AT_ENCR_DATA and
			AT_IV attributes in this message to include encrypted (skippable)
			attributes. The EAP server MUST process EAP-Response/AKA-Challenge
			messages that include these attributes even if the server did not
			implement these optional attributes.
	Reserved		6.5. EAP-Response/AKA-Authentication-Reject
	Set to zero when sending, ignored on reception.		The peer sends the EAP-Response/AKA-Authentication-Reject packet if
			it does not accept the AUTN parameter. This version of the protocol
			does not specify any attributes for this message. Future versions of
			the protocol MAY specify attributes for this message.
	AT_RES		The AT_MAC, AT_ENCR_DATA, or AT_IV attributes MUST NOT be used in
			this message.
	This attribute MUST be included in EAP-Response/AKA-Challenge.		6.6. EAP-Response/AKA-Synchronization-Failure
	The value field of this attribute begins with the 2-byte RES
	Length, which is identifies the exact length of the RES in bits.
	The RES length is followed by the UMTS AKA RES parameter.
	According to the specification [13] the length of the AKA RES can
	vary between 32 and 128 bits. Because the length of the AT_RES
	attribute must be a multiple of 4 bytes, the sender pads the RES
	with zero bits where necessary.
	AT_CHECKCODE		The peer sends the EAP-Response/AKA-Synchronization-Failure, when
			the sequence number in the AUTN parameter is incorrect.
	The AT_CHECKCODE attribute is optional to include. See section		The peer MUST include the AT_AUTS attribute. Future versions of the
	7.2		protocol MAY specify other additional attributes for this message.
	AT_MAC		The AT_MAC, AT_ENCR_DATA, or AT_IV attributes MUST NOT be used in
			this message.
	AT_MAC MUST be included. In EAP-Response/AKA-Challenge, there is		6.7. EAP-Request/AKA-Reauthentication
	no message-specific data covered by the MAC. See Section 7.1.
	8.3. EAP-Response/AKA-Authentication-Reject		EAP AKA Authentication 27 October, 2003
	The format of the EAP-Response/AKA-Authentication-Reject packet is		The server sends the EAP-Request/AKA-Reauthentication message if it
	shown below.		wants to use re-authentication, and if it has received a valid re-
			authentication identity in EAP-Response/Identity or EAP-
			Response/AKA-Identity.
	EAP AKA Authentication June 2003		The AT_MAC attribute MUST be included. No message-specific data is
			included in the MAC calculation, see Section 7.2.
	0 1 2 3		The AT_CHECKCODE attribute MAY be included, and in certain cases
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		specified in Section 7.4, it MUST be included.
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Code | Identifier | Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Subtype | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The semantics of the fields is described below:		The AT_IV and AT_ENCR_DATA attributes MUST be included. The
			plaintext consists of the following nested encrypted attributes,
			which MUST be included: AT_COUNTER and AT_NONCE_S. In addition, the
			nested encrypted attributes MAY include the following attributes:
			AT_NEXT_REAUTH_ID and AT_PADDING.
	Code		6.8. EAP-Response/AKA-Reauthentication
	2 for Response		The client sends the EAP-Response/AKA-Reauthentication packet in
			response to a valid EAP-Request/AKA-Reauthentication.
	Identifier		The AT_MAC attribute MUST be included. For EAP-Response/AKA-
			Reauthentication, the MAC code is calculated over the following
			data: EAP packet| NONCE_S. The EAP packet is represented as
			specified in Section 5.1. It is followed by the 16-byte NONCE_S
			value from the server's AT_NONCE_S attribute.
	See [5]		The AT_CHECKCODE attribute MAY be included, and in certain cases
			specified in Section 7.4, it MUST be included.
	Length		The AT_IV and AT_ENCR_DATA attributes MUST be included. The nested
			encrypted attributes MUST include the AT_COUNTER attribute. The
			AT_COUNTER_TOO_SMALL attribute MAY be included in the nested
			encrypted attributes, and it is included in cases specified in
			Section 4.2. The AT_PADDING attribute MAY be included.
	The length of the EAP Response packet.		6.9. EAP-Response/AKA-Client-Error
	Type		The peer sends EAP-Response/AKA-Client-Error in error cases, as
			specified in Section 4.4.1.
	23		The AT_CLIENT_ERROR_CODE attribute MUST be included.
			The AT_MAC, AT_IV, or AT_ENCR_DATA attributes MUST NOT be used with
			this packet.
	Subtype		6.10. EAP-Request/AKA-Notification
	2 for AKA-Authentication-Reject		The usage of this message is specified in Section 4.3.
	Reserved		The AT_NOTIFICATION attribute MUST be included.
	Set to zero on sending, ignored on reception.		EAP AKA Authentication 27 October, 2003
	8.4. EAP-Response/AKA-Synchronization-Failure		The AT_MAC attribute is included in cases discussed in Section 4.3.
			No message-specific data is included in the MAC calculation. See
			Section 7.2.
	The format of the EAP-Response/AKA-Synchronization-Failure packet is		Later versions of this protocol MAY make use of the AT_ENCR_DATA and
	shown below.		AT_IV attributes in this message to include encrypted (skippable)
			attributes. These attributes MAY be included only if the P bit of
			the notification code in AT_NOTIFICATION is set to zero.
	0 1 2 3		6.11. EAP-Response/AKA-Notification
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Code | Identifier | Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Subtype | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|
	| AT_AUTS | Length = 4 | |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
	| |
	| AUTS |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	EAP AKA Authentication June 2003		The usage of this message is specified in Section 4.3. Because this
			packet is only an acknowledgement of EAP-Request/AKA-Notification,
			it does not contain any mandatory attributes.
	The semantics of the fields is described below:		The AT_MAC attribute is included in cases described in Section 4.3.
			No message-specific data is included in the MAC calculation. See
			Section 7.2.
	Code		Later versions of this protocol MAY make use of the AT_ENCR_DATA and
			AT_IV attributes in this message to include encrypted (skippable)
			attributes. These attributes MAY be included only if the P bit of
			the notification code in the AT_NOTIFICATION attribute of the
			server's EAP-Request/AKA-Notification packet is set to zero.
	2 for Response		7. Attributes
	Identifier		This section specifies the format of message attributes. The
			attribute type numbers are specified in Section 8.
	See [5]		7.1. Table of Attributes
	Length		The following table provides a guide to which attributes may be
			found in which kinds of messages, and in what quantity. Messages are
			denoted with numbers in parentheses as follows: (1) EAP-Request/AKA-
			Identity, (2) EAP-Response/AKA-Identity, (3) EAP-Request/AKA-
			Challenge, (4) EAP-Response/AKA-Challenge, (5) EAP-Request/AKA-
			Notification, (6) EAP-Response/AKA-Notification, (7) EAP-
			Response/AKA-Client-Error (8) EAP-Request/AKA-Reauthentication, (9)
			EAP-Response/AKA-Re-authentication, (10) EAP-Response/AKA-
			Authentication-Reject, and (11) EAP-Response/AKA-Synchronization-
			Failure. The column denoted with "E" indicates whether the attribute
			is a nested attribute that MUST be included within AT_ENCR_DATA.
	The length of the EAP Response packet, 20.		"0" indicates that the attribute MUST NOT be included in the
			message, "1" indicates that the attribute MUST be included in the
			message, "0-1" indicates that the attribute is sometimes included in
			the message, and "0*" indicates that the attribute is not included
			in the message in cases specified in this document, but MAY be
			included in the future versions of the protocol.
	Type		EAP AKA Authentication 27 October, 2003
	23		Attribute (1) (2) (3) (4) (5) (6) (7) (8) (9) (10)(11) E
			AT_MAC 0 0 1 1 0-1 0-1 0 1 1 0 0 N
			AT_IV 0 0 0-1 0* 0* 0* 0 1 1 0 0 N
			AT_ENCR_DATA 0 0 0-1 0* 0* 0* 0 1 1 0 0 N
			AT_PADDING 0 0 0-1 0* 0* 0* 0 0-1 0-1 0 0 Y
			AT_CHECKCODE 0 0 0-1 0-1 0 0 0 0-1 0-1 0 0 N
			AT_PERMANENT_ID_REQ 0-1 0 0 0 0 0 0 0 0 0 0 N
			AT_ANY_ID_REQ 0-1 0 0 0 0 0 0 0 0 0 0 N
			AT_FULLAUTH_ID_REQ 0-1 0 0 0 0 0 0 0 0 0 0 N
			AT_IDENTITY 0 0-1 0 0 0 0 0 0 0 0 0 N
			AT_RAND 0 0 1 0 0 0 0 0 0 0 0 N
			AT_AUTN 0 0 1 0 0 0 0 0 0 0 0 N
			AT_RES 0 0 0 1 0 0 0 0 0 0 0 N
			AT_AUTS 0 0 0 0 0 0 0 0 0 0 1 N
			AT_NEXT_PSEUDONYM 0 0 0-1 0 0 0 0 0 0 0 0 Y
			AT_NEXT_REAUTH_ID 0 0 0-1 0 0 0 0 0-1 0 0 0 Y
			AT_COUNTER 0 0 0 0 0 0 0 1 1 0 0 Y
			AT_COUNTER_TOO_SMALL 0 0 0 0 0 0 0 0 0-1 0 0 Y
			AT_NONCE_S 0 0 0 0 0 0 0 1 0 0 0 Y
			AT_NOTIFICATION 0 0 0 0 1 0 0 0 0 0 0 N
			AT_CLIENT_ERROR_CODE 0 0 0 0 0 0 1 0 0 0 0 N
	Subtype		It should be noted that attributes AT_PERMANENT_ID_REQ,
			AT_ANY_ID_REQ and AT_FULLAUTH_ID_REQ are mutually exclusive, so that
			only one of them can be included at the same time. If one of the
			attributes AT_IV and AT_ENCR_DATA is included, then both of the
			attributes MUST be included.
	4 for AKA-Synchronization-Failure		7.2. AT_MAC
	AT_AUTS		The AT_MAC attribute is used for EAP/AKA message authentication.
			Section 6 specifies which messages AT_MAC MUST be included.
	This attribute MUST be included in EAP-Response/AKA-		The value field of the AT_MAC attribute contains two reserved bytes
	Synchronization-Failure. The value field of this attribute		followed by a keyed message authentication code (MAC). The MAC is
	contains the AKA AUTS parameter, 112 bits (14 bytes).		calculated over the whole EAP packet, concatenated with optional
			message-specific data, with the exception that the value field of
			the MAC attribute is set to zero when calculating the MAC. The EAP
			packet includes the EAP header that begins with the Code field, the
			EAP/AKA header that begins with the Subtype field, and all the
			attributes, as specified in Section 5.1. The reserved bytes in
			AT_MAC are set to zero when sending and ignored on reception. The
			contents of the message-specific data that may be included in the
			MAC calculation are specified separately for each EAP/AKA message in
			Section 6.
	8.5. EAP-Request/AKA-Identity		The format of the AT_MAC attribute is shown below.
	The format of the EAP-Request/AKA-Identity packet is shown below.		EAP AKA Authentication 27 October, 2003
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Code | Identifier | Length |		| AT_MAC | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Subtype | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|AT_PERM..._REQ | Length = 1 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|AT_FULL..._REQ | Length = 1 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|AT_ANY_ID_REQ | Length = 1 | Reserved |		| |
			| MAC |
			| |
			| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The semantics of the fields is described below:		The MAC algorithm is HMAC-SHA1-128 [RFC 2104] keyed hash value. (The
			HMAC-SHA1-128 value is obtained from the 20-byte HMAC-SHA1 value by
	Code		truncating the output to 16 bytes. Hence, the length of the MAC is
			16 bytes.) The derivation of the authentication key (K_aut) used in
	1 for Request		the calculation of the MAC is specified in Section 4.5.
	EAP AKA Authentication June 2003
	Identifier
	See [5]
	Length
	The length of the EAP Request packet.
	Type
	23
	Subtype
	5 for AKA-Identity
	Reserved
	Set to zero on sending, ignored on reception.
	AT_PERMANENT_ID_REQ
	The AT_PERMANENT_ID_REQ attribute is optional to include and it
	is included in the cases defined in Section 4.3. It MUST NOT be
	included if AT_ANY_ID_REQ or AT_FULLAUTH_ID_REQ is included. The
	value field only contains two reserved bytes, which are set to
	zero on sending and ignored on reception.
	AT_FULLAUTH_ID_REQ
	The AT_FULLAUTH_ID_REQ attribute is optional to include and it is		When the AT_MAC attribute is included in an EAP/AKA message, the
	included in the cases defined in Section 4.2. It MUST NOT be		recipient MUST process the AT_MAC attribute before looking at any
	included if AT_ANY_ID_REQ or AT_PERMANENT_ID_REQ is included. The		other attributes. If the message authentication code is invalid,
	value field only contains two reserved bytes, which are set to		then the recipient MUST ignore all other attributes in the message
	zero on sending and ignored on reception.		and operate as specified in Section 4.4.
	AT_ANY_ID_REQ		7.3. AT_IV, AT_ENCR_DATA and AT_PADDING
	The AT_ANY_ID_REQ attribute is optional and it is included in the		AT_IV and AT_ENCR_DATA attributes can be used to transmit encrypted
	cases defined in Section 4.2. It MUST NOT be included if		information between the EAP/SIM peer and server.
	AT_PERMANENT_ID_REQ or AT_FULLAUTH_ID_REQ is included. The value
	field only contains two reserved bytes, which are set to zero on
	sending and ignored on reception.
	8.6. EAP-Response/AKA-Identity		The value field of AT_IV contains two reserved bytes followed by a
			16-byte initialization vector required by the AT_ENCR_DATA
			attribute. The reserved bytes are set to zero when sending and
			ignored on reception. The AT_IV attribute MUST be included if and
			only if the AT_ENCR_DATA is included. Section 4.4 specifies the
			operation if a packet that does not meet this condition is
			encountered.
	The format of the EAP-Response/AKA-Identity packet is shown below.		The sender of the AT_IV attribute chooses the initialization vector
			by random. The sender MUST NOT reuse the initialization vector value
			from previous EAP AKA packets and the sender MUST choose it freshly
			for each AT_IV attribute. The sender SHOULD use a good source of
			randomness to generate the initialization vector. Please see [RFC
			1750] for more information about generating random numbers for
			security applications. The format of AT_IV is shown below.
	EAP AKA Authentication June 2003		EAP AKA Authentication 27 October, 2003
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Code | Identifier | Length |		| AT_IV | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Subtype | Reserved |		| |
			| Initialization Vector |
			| |
			| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_IDENTITY | Length | Actual Identity Length |
			The value field of the AT_ENCR_DATA attribute consists of two
			reserved bytes followed by cipher text bytes encrypted using the
			Advanced Encryption Standard (AES) [AES] in the Cipher Block
			Chaining (CBC) mode of operation using the initialization vector
			from the AT_IV attribute. The reserved bytes are set to zero when
			sending and ignored on reception. Please see [CBC] for a description
			of the CBC mode. The format of the AT_ENCR_DATA attribute is shown
			below.
			0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| AT_ENCR_DATA | Length | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |		| |
	. Current Identity .		. Encrypted Data .
	. .		. .
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The semantics of the fields is described below:		The derivation of the encryption key (K_encr) is specified in
			Section 4.5.
	Code
	2 for Response		The plaintext consists of nested EAP/AKA attributes.
	Identifier		The encryption algorithm requires the length of the plaintext to be
			a multiple of 16 bytes. The sender may need to include the
			AT_PADDING attribute as the last attribute within AT_ENCR_DATA. The
			AT_PADDING attribute is not included if the total length of other
			nested attributes within the AT_ENCR_DATA attribute is a multiple of
			16 bytes. As usual, the Length of the Padding attribute includes the
			Attribute Type and Attribute Length fields. The length of the
			Padding attribute is 4, 8 or 12 bytes. It is chosen so that the
			length of the value field of the AT_ENCR_DATA attribute becomes a
			multiple of 16 bytes. The actual pad bytes in the value field are
			set to zero (0x00) on sending. The recipient of the message MUST
			verify that the pad bytes are set to zero. If this verification
			fails on the peer, then it MUST send the EAP-Response/AKA-Client-
			Error packet with the error code "unable to process packet" to
			terminate the authentication exchange. If this verification fails on
			the server, then the server sends EAP Failure, and the
			authentication exchange terminates. The format of the AT_PADDING
			attribute is shown below.
	See [5]		EAP AKA Authentication 27 October, 2003
	Length		0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| AT_PADDING | Length | Padding... |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
			| |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The length of the EAP Response packet.		7.4. AT_CHECKCODE
	Type		The AT_MAC attribute is not used in the very first EAP/AKA messages
			during the AKA-Identity round, because keying material has not been
			derived yet. The peer and the server may exchange one or more pairs
			of EAP/AKA messages of the Subtype AKA-Identity before keys are
			derived and before the AT_MAC attribute can be applied. The EAP/AKA-
			Identity messages may also be used upon re-authentication.
	23		The AT_CHECKCODE attribute MAY be used to protect the EAP/AKA-
			Identity messages. AT_CHECKCODE is included in EAP-Request/AKA-
			Challenge and/or EAP-Response/AKA-Challenge upon full
			authentication. In re-authentication, AT_CHECKCODE MAY be included
			in EAP-Request/AKA-Reauthentication and/or EAP-Response/AKA-
			Reauthentication. Because the AT_MAC attribute is used in these
			messages, AT_CHECKCODE will be integrity protected with AT_MAC.
			The format of the AT_CHECKCODE attribute is shown below.
	Subtype		0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| AT_CHECKCODE | Length | Reserved |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| |
			| Checkcode (0 or 20 bytes) |
			| |
			| |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	5 for AKA-Identity		The value field of AT_CHECKCODE begins with two reserved bytes,
			which may be followed by a 20-byte checkcode. If the checkcode is
			not included in AT_CHECKCODE, then the attribute indicates that no
			EAP/AKA-Identity messages were exchanged. This may occur in both
			full authentication and re-authentication. The reserved bytes are
			set to zero when sending and ignored on reception.
	Reserved		The checkcode is a hash value, calculated with SHA1 [SHA-1], over
			all EAP-Request/AKA-Identity and EAP-Response/ AKA-Identity packets
			exchanged in this authentication exchange. The packets are included
			in the order that they were transmitted, that is, starting with the
			first EAP-Request/ AKA-Identity message, followed by the
	Set to zero on sending, ignored on reception.		EAP AKA Authentication 27 October, 2003
	AT_IDENTITY		corresponding EAP-Response/ AKA-Identity, followed by the second
			EAP-Request/ AKA-Identity (if used) etc.
	The AT_IDENTITY attribute is optional to include and it is		EAP packets are included in the hash calculation "as-is", as they
	included in cases defined in Section 4.2 and 4.3. The value field		were transmitted or received. All reserved bytes, padding bytes etc.
	of this attribute begins with 2-byte actual identity length,		that are specified for various attributes are included as such, and
	which specifies the length of the identity in bytes. This field		the receiver must not reset them to zero. No delimiter bytes,
	is followed by the subscriber identity of the indicated actual		padding or any other framing are included between the EAP packets
	length, in the same Network Access Identifier format that is used		when calculating the checkcode.
	in EAP-Response/Identity, i.e. including the NAI realm portion.
	The identity is the permanent identity, a pseudonym identity or a
	re-authentication identity. The identity format is specified in
	Section 4.1. The identity does not include any terminating null
	characters. Because the length of the attribute must be a
	EAP AKA Authentication June 2003		Messages are included in request/response pairs; in other words only
			full "round trips" are included. Packets that are silently discarded
			are not included. The EAP server must only include an EAP-
			Request/AKA-Identity in the calculation once it has received a
			corresponding response, with the same Identifier value.
			Retransmissions or requests to which the server does not receive
			response are not included.
	multiple of 4 bytes, the sender pads the identity with zero bytes		The peer must include the EAP-Request/AKA-Identity and the
	when necessary.		corresponding response in the calculation only if the peer receives
			a subsequent EAP-Request/AKA-Challenge, or a follow-up EAP-
			Request/AKA-Identity with different attributes (attribute types)
			than in the first EAP-Request/AKA-Identity. After sending EAP-
			Response/AKA-Identity, if the peer receives another EAP-Request/AKA-
			Identity with the same attributes as in the previous request, then
			the peer's response to the first request must have been lost. In
			this case the peer must not include the first request and its
			response in the calculation of the checkcode.
	8.7. EAP-Request/AKA-Reauthentication		The AT_CHECKCODE attribute is optional to implement. It is specified
			in order to allow protecting the EAP/ AKA-Identity messages and any
			future extensions to them. The implementation of AT_CHECKCODE is
			RECOMMENDED.
	The format of the EAP-Request/AKA-Reauthentication packet is shown		If the receiver of AT_CHECKCODE implements this attribute, then the
	below.		receiver MUST check that the checkcode is correct. If the checkcode
			is invalid, the receiver must operate as specified in Section 4.4.
	0 1 2 3		If the EAP/AKA-Identity messages are extended with new attributes
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		then AT_CHECKCODE MUST be implemented and used. More specifically,
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		if the server includes any other attributes than
	| Code | Identifier | Length |		AT_PERMANENT_ID_REQ, AT_FULLAUTH_ID_REQ or AT_ANY_ID_REQ in the EAP-
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		Request/AKA-Identity packet, then the server MUST include
	| Type | Subtype | Reserved |		AT_CHECKCODE in EAP-Request/AKA-Challenge or EAP-Request/AKA-
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		Reauthentication. If the peer includes any other attributes than
	| AT_IV | Length = 5 | Reserved |		AT_IDENTITY in the EAP-Response/AKA-Identity message, then the peer
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		MUST include AT_CHECKCODE in EAP-Response/AKA-Challenge or EAP-
	| |		Response/AKA-Reauthentication.
	| Initialization Vector |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_ENCR_DATA | Length | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	. Encrypted Data .
	. .
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_CHECKCODE | Length | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| Checkcode (optional) |
	| |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_MAC | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| |
	| MAC |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Code		If the server implements the processing of any other attribute than
			AT_IDENTITY for the EAP-Response/AKA-Identity message, then the
			server MUST implement AT_CHECKCODE. In this case, if the server
			receives any other attribute than AT_IDENTITY in the EAP-
			Response/AKA-Identity message, then the server MUST check that
	1 for Request		EAP AKA Authentication 27 October, 2003
	Identifier		AT_CHECKCODE is present in EAP-Response/AKA-Challenge or EAP-
			Response/AKA-Reauthentication. The operation when a mandatory
			attribute is missing is specified in Section 4.4.
	See [5].		Similarly, if the peer implements the processing of any other
			attribute than AT_PERMANENT_ID_REQ, AT_FULLAUTH_ID_REQ or
			AT_ANY_ID_REQ for the EAP-Request/AKA-Identity packet, then the peer
			MUST implement AT_CHECKCODE. In this case, if the peer receives any
			other attribute than AT_PERMANENT_ID_REQ, AT_FULLAUTH_ID_REQ or
			AT_ANY_ID_REQ in the EAP-Request/AKA-Identity packet, then the peer
			MUST check that AT_CHECKCODE is present in EAP-Request/AKA-Challenge
			or EAP-Request/AKA-Reauthentication. The operation when a mandatory
			attribute is missing is specified in Section 4.4.
	EAP AKA Authentication June 2003		7.5. AT_PERMANENT_ID_REQ
	Length		The format of the AT_PERMANENT_ID_REQ attribute is shown below.
	The length of the EAP packet.		0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			|AT_PERM..._REQ | Length = 1 | Reserved |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type		The use of the AT_PERMANENT_ID_REQ is defined in Section 4.1. The
			value field only contains two reserved bytes, which are set to zero
			on sending and ignored on reception.
	23		7.6. AT_ANY_ID_REQ
	Subtype		The format of the AT_ANY_ID_REQ attribute is shown below.
	13		0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			|AT_ANY_ID_REQ | Length = 1 | Reserved |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Reserved		The use of the AT_ANY_ID_REQ is defined in Section 4.1. The value
			field only contains two reserved bytes, which are set to zero on
			sending and ignored on reception.
	Set to zero when sending, ignored on reception.		7.7. AT_FULLAUTH_ID_REQ
	AT_IV		The format of the AT_FULLAUTH_ID_REQ attribute is shown below.
	The AT_IV attribute is MUST be included. See Section 7.3.		0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			|AT_ANY_ID_REQ | Length = 1 | Reserved |
			+---------------+---------------+-------------------------------+
	AT_ENCR_DATA		EAP AKA Authentication 27 October, 2003
	The AT_ENCR_DATA attribute MUST be included. See Section 7.3. The		The use of the AT_FULLAUTH_ID_REQ is defined in Section 4.1. The
	plaintext consists of nested attributes as described below.		value field only contains two reserved bytes, which are set to zero
			on sending and ignored on reception.
	AT_CHECKCODE		7.8. AT_IDENTITY
	The AT_CHECKCODE attribute is optional to include. See section		The format of the AT_IDENTITY attribute is shown below.
	7.2
	AT_MAC		0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| AT_IDENTITY | Length | Actual Identity Length |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| |
			. Identity .
			. .
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	AT_MAC MUST be included. No message-specific data is included in		The use of the AT_IDENTITY is defined in Section 4.1. The value
	the MAC calculation. See Section 7.1.		field of this attribute begins with 2-byte actual identity length,
			which specifies the length of the identity in bytes. This field is
			followed by the subscriber identity of the indicated actual length.
			The identity is the permanent identity, a pseudonym identity or a
			re-authentication identity. The identity format is specified in
			Section 4.1.1. The same identity format is used in the AT_IDENTITY
			attribute and the EAP-Response/Identity packet, with the exception
			that the peer MUST NOT decorate the identity it includes in
			AT_IDENTITY. The identity does not include any terminating null
			characters. Because the length of the attribute must be a multiple
			of 4 bytes, the sender pads the identity with zero bytes when
			necessary.
	The AT_IV and AT_ENCR_DATA attributes are used for communicating		7.9. AT_RAND
	encrypted attributes. The plaintext of the AT_ENCR_DATA value field
	consists of nested attributes, which are shown below.
	EAP AKA Authentication June 2003		The format of the AT_RAND attribute is shown below.
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_COUNTER | Length = 1 | Counter |		| AT_RAND | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_NONCE_S | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| |
	| NONCE_S |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_NEXT_REAU..| Length | Actual Re-Auth Identity Length|
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |		| |
	. Next Re-authentication Username .		| RAND |
	. .
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_PADDING | Length | Padding... |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
	| |		| |
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	AT_COUNTER		The value field of this attribute contains two reserved bytes
			followed by the AKA RAND parameter, 16 bytes (128 bits). The
	The AT_COUNTER attribute MUST be included. The value field		reserved bytes are set to zero when sending and ignored on
	consists of a 16-bit unsigned integer counter value, represented		reception.
	in network byte order.
	AT_NONCE_S		EAP AKA Authentication 27 October, 2003
	The AT_NONCE_S attribute MUST be included. The value field		7.10. AT_AUTN
	contains two reserved bytes followed by a random number generated
	by the server (16 bytes) freshly for this EAP/AKA re-
	authentication. The random number is used as challenge for the
	client and also a seed value for the new keying material. The
	reserved bytes are set to zero upon sending and ignored upon
	reception.
	AT_NEXT_REAUTH_ID		The format of the AT_AUTN attribute is shown below.
	The AT_NEXT_REAUTH_ID attribute is optional to include. The		0 1 2 3
	attribute is described in Section 8.1.		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| AT_AUTN | Length = 5 | Reserved |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| |
			| AUTN |
			| |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	AT_PADDING		The value field of this attribute contains two reserved bytes
			followed by the AKA AUTN parameter, 16 bytes (128 bits). The
			reserved bytes are set to zero when sending and ignored on
			reception.
	The AT_PADDING attribute is optional to include. See section 7.3		7.11. AT_RES
	8.8. EAP-Response/AKA-Reauthentication		The format of the AT_RES attribute is shown below.
	EAP AKA Authentication June 2003		0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| AT_RES | Length | RES Length |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
			| |
			| RES |
			| |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The format of the EAP-Response/AKA-Reauthentication packet is shown		The value field of this attribute begins with the 2-byte RES Length,
	below.		which is identifies the exact length of the RES in bits. The RES
			length is followed by the UMTS AKA RES parameter. According to [TS
			33.105] the length of the AKA RES can vary between 32 and 128 bits.
			Because the length of the AT_RES attribute must be a multiple of 4
			bytes, the sender pads the RES with zero bits where necessary.
	0 1 2 3		7.12. AT_AUTS
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Code | Identifier | Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Subtype | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_IV | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| Initialization Vector |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_ENCR_DATA | Length | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	. Encrypted Data .
	. .
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_CHECKCODE | Length | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| Checkcode (optional) |
	| |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_MAC | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| |
	| MAC |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Code		The format of the AT_AUTS attribute is shown below.
	2 for Response		EAP AKA Authentication 27 October, 2003
	Identifier		0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+|
			| AT_AUTS | Length = 4 | |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
			| |
			| AUTS |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	See [5].		The value field of this attribute contains the AKA AUTS parameter,
			112 bits (14 bytes).
	Length		7.13. AT_NEXT_PSEUDONYM
	The length of the EAP packet.		The format of the AT_NEXT_PSEUDONYM attribute is shown below.
	EAP AKA Authentication June 2003		0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| AT_NEXT_PSEU..| Length | Actual Pseudonym Length |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| |
			. Next Pseudonym .
			. .
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type		The value field of this attribute begins with 2-byte actual
			pseudonym length which specifies the length of the following
			pseudonym in bytes. This field is followed by a pseudonym username
			that the peer can use in the next authentication. The username MUST
			NOT include any realm portion. The username does not include any
			terminating null characters. Because the length of the attribute
			must be a multiple of 4 bytes, the sender pads the pseudonym with
			zero bytes when necessary. The username encoding MUST follow the
			UTF-8 transformation format [RFC2279].
	23		7.14. AT_NEXT_REAUTH_ID
	Subtype		The format of the AT_NEXT_REAUTH_ID attribute is shown below.
	13		0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| AT_NEXT_REAU..| Length | Actual Re-Auth Identity Length|
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| |
			. Next Re-authentication Username .
			. .
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Reserved		EAP AKA Authentication 27 October, 2003
	Set to zero when sending, ignored on reception.		The value field of this attribute begins with 2-byte actual re-
			authentication identity length which specifies the length of the
			following re-authentication identity in bytes. This field is
			followed by a re-authentication identity that the peer can use in
			the next re-authentication, as described in Section 4.2. In
			environments where a realm portion is required, the re-
			authentication identity includes both a username portion and a realm
			name portion. The re-authentication identity does not include any
			terminating null characters. Because the length of the attribute
			must be a multiple of 4 bytes, the sender pads the re-authentication
			identity with zero bytes when necessary. The identity encoding MUST
			follow the UTF-8 transformation format [RFC2279].
	AT_IV		7.15. AT_COUNTER
	The AT_IV attribute is MUST be included. See Section 7.3.		The format of the AT_COUNTER attribute is shown below.
	AT_ENCR_DATA		0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| AT_COUNTER | Length = 1 | Counter |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The AT_ENCR_DATA attribute MUST be included. See Section 7.3. The		The value field of the AT_COUNTER attribute consists of a 16-bit
	plaintext consists of nested attributes as described below.		unsigned integer counter value, represented in network byte order.
	AT_CHECKCODE		7.16. AT_COUNTER_TOO_SMALL
	The AT_CHECKCODE attribute is optional to include. See section		The format of the AT_COUNTER_TOO_SMALL attribute is shown below.
	7.2
	AT_MAC		0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| AT_COUNTER...| Length = 1 | Reserved |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	For EAP-Response/AKA-Reauthentication, the MAC code is calculated		The value field of this attribute consists of two reserved bytes,
	over the following data:		which are set to zero upon sending and ignored upon reception.
	EAP packet| NONCE_S		7.17. AT_NONCE_S
	The EAP packet is represented as specified in Section 7.1. It is		The format of the AT_NONCE_S attribute is shown below.
	followed by the 16-byte NONCE_S value from the server's
	AT_NONCE_S attribute.
	The AT_IV and AT_ENCR_DATA attributes are used for communicating		EAP AKA Authentication 27 October, 2003
	encrypted attributes. The plaintext of the AT_ENCR_DATA value field
	consists of nested attributes, which are shown below.
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_COUNTER | Length = 1 | Counter |		| AT_COUNTER | Length = 1 | Counter |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_COUNTER...| Length = 1 | Reserved |		| AT_NONCE_S | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_PADDING | Length | Padding... |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |		| |
			| NONCE_S |
	| |		| |
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	EAP AKA Authentication June 2003		The value field of the AT_NONCE_S attribute contains two reserved
			bytes followed by a random number generated by the server (16 bytes)
	AT_COUNTER		freshly for this EAP/AKA re-authentication. The random number is
			used as challenge for the peer and also a seed value for the new
	The AT_COUNTER attribute MUST be included. The format of this		keying material. The reserved bytes are set to zero upon sending and
	attribute is specified in Section 8.7.		ignored upon reception.
	AT_COUNTER_TOO_SMALL
	The AT_COUNTER_TOO_SMALL attribute is optional to include, and it
	is included in cases specified in Section 5.
	AT_PADDING
	The AT_PADDING attribute is optional to include. See section 7.3
	8.9. EAP/AKA Notifications
	The EAP-Request/Notification, specified in [5], can be used to
	convey a displayable message from the authenticator to the client.
	Because these messages are textual messages, it may be hard for the
	client to present them in the user's preferred language. Therefore,
	EAP/AKA uses a separate EAP/AKA message subtype to transmit
	localizable notification codes instead of the EAP-
	Request/Notification packet.
	The EAP server MAY issue an EAP-Request/AKA-Notification packet to
	the client. The client MAY show a notification message to the user
	and the client MUST respond to the EAP server with an EAP-
	Response/AKA-Notification packet, even if the client did not
	recognize the notification code.
	The notification code is a 16-bit number. The most significant bit
	is called the Failure bit (F bit). The F bit specifies whether the
	notification implies failure. The code values with the F bit set to
	zero (code values 0...32767) are used on unsuccessful cases. The
	receipt of a notification code from this range implies failed
	authentication, so the client can use the notification as a failure
	indication. After receiving the EAP-Response/AKA-Notification for
	these notification codes, the server MUST send the EAP-Failure
	packet.
	The receipt of a notification code with the F bit set to one (values
	32768...65536) does not imply failure, so the client MUST NOT change
	its state when it receives such a notification.
	The second most significant bit of the notification code is called
	the Phase bit (P bit). It specifies at which phase of the EAP/AKA
	exchange the notification can be used. If the P bit is set to zero,
	the notification can only be used after the EAP/AKA-Challenge round
	in full authentication or the EAP/AKA-Reauthentication round in re-
	autentication. For these notifications, the AT_MAC attribute MUST be
	included in both EAP-Request/AKA-Notification and EAP-Response/AKA-
	Notification.
	EAP AKA Authentication June 2003
	If the P bit of the notification code is set to one, the		The server MUST choose the NONCE_S value freshly for each EAP/AKA
	notification can only by used before the EAP/AKA-Challenge round in		re-authentication exchange. The server SHOULD use a good source of
	full authentication or the EAP/AKA-Reauthentication round in		randomness to generate NONCE_S. Please see [RFC 1750] for more
	reauthentication. For these notifications, the AT_MAC attribute MUST		information about generating random numbers for security
	NOT be included in either EAP-Request/AKA-Notification or EAP-		applications.
	Response/AKA-Notification.
	Some of the notification codes are authorization related and hence		7.18. AT_NOTIFICATION
	not usually considered as part of the responsibility of an EAP
	method. However, they are included as part of EAP/AKA because there
	are currently no other ways to convey this information to the user
	in a localizable way, and the information is potentially useful for
	the user. An EAP/AKA server implementation may decide never to send
	these EAP/AKA notifications.
	The format of the EAP-Request/AKA-Notification packet is shown		The format of the AT_NOTIFICATION attribute is shown below.
	below.
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Code | Identifier | Length |		|AT_NOTIFICATION| Length = 1 |F|P| Notification Code |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Subtype | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|AT_NOTIFICATION| Length = 1 |F|P| Notification Code |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_MAC | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| |
	| MAC |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Code		The value field of this attribute contains a two-byte notification
			code. The first and second bit (F and P) of the notification code
	1 for Request		are interpreted as described in Section 4.3.
	Identifier
	See [5].
	Length
	The length of the EAP packet.
	Type
	23
	EAP AKA Authentication June 2003
	Subtype
	12
	Reserved
	Set to zero when sending, ignored on reception.
	AT_NOTIFICATION
	The AT_NOTIFICATION attribute MUST be included. The value field
	of this attribute contains a two-byte notification code. The
	first and second bit (F and P) of the notification code are
	interpreted as described above.
	The following code values have been reserved. The descriptions		The notification code values listed below have been reserved. The
	below illustrate the semantics of the notifications. The client		descriptions below illustrate the semantics of the notifications.
	implementation MAY use different wordings when presenting the		The peer implementation MAY use different wordings when presenting
	notifications to the user. The "requested service" depends on the		the notifications to the user. The "requested service" depends on
	environment where EAP/AKA is applied.		the environment where EAP/AKA is applied.
	1026 - User has been temporarily denied access to the requested		1026 - User has been temporarily denied access to the requested
	service (Implies failure, used after the challenge round)		service. (Implies failure, used after the challenge round)
	1031 - User has not subscribed to the requested service (Implies		1031 - User has not subscribed to the requested service (implies
	failure, used after the challenge round)		failure, used after the challenge round)
	AT_MAC		EAP AKA Authentication 27 October, 2003
	AT_MAC is included in cases described above. No message-specific		7.19. AT_CLIENT_ERROR_CODE
	data is included in the MAC calculation. See Section 7.1.
	The format of the EAP-Response/AKA-Notification packet is shown		The format of the AT_CLIENT_ERROR_CODE attribute is shown below.
	below. Because this packet is only an acknowledgement of EAP-
	Request/AKA-Notification, it does not contain any mandatory
	attributes.
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Code | Identifier | Length |		|AT_CLIENT_ERR..| Length = 1 | Client Error Code |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Subtype | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| AT_MAC | Length = 5 | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |
	| |
	| MAC |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	EAP AKA Authentication June 2003		The value field of this attribute contains a two-byte client error
			code. The following error code values have been reserved.
	Code
	2 for Response
	Identifier
	See [5].
	Length
	The length of the EAP packet.
	Type
	23
	Subtype
	12
	Reserved
	Set to zero when sending, ignored on reception.
	AT_MAC
	AT_MAC is included in cases described above. No message-specific
	data is included in the MAC calculation. See Section 7.1.
	9. Error Cases and the Usage of EAP-Failure and EAP-Success
	9.1. Processing Erroneous Packets
	In general, if an EAP/AKA client or server implementation detects an
	error in a received EAP/AKA packet, the EAP/AKA implementation
	silently ignores the EAP packet, does not change its state and does
	not send any EAP messages to its peer. Examples of such errors,
	specified in detail elsewhere in this document, are an invalid
	AT_MAC value, a mandatory attribute is missing, illegal attributes
	included and an unrecognized non-skippable attribute. If no valid
	packets are received, the authentication exchange will eventually
	time out.
	If the EAP/AKA client receives an EAP/AKA Request of an unrecognized
	subtype, the EAP/AKA client MUST silently discard the EAP request.
	9.2. EAP-Failure
	As normally in EAP, the EAP server sends the EAP-Failure packet to
	the client when the authentication procedure fails on the EAP
	Server. In EAP/AKA, this may occur for example if the EAP server
	does not recognize the user identity, or if the EAP server is not
	EAP AKA Authentication June 2003
	able to obtain authentication vectors for the subscriber or the
	authentication exchange times out.
	The server can send EAP-Failure at any time in the EAP exchange. The
	client MUST process EAP-Failure.
	9.3. EAP-Success
	On full authentication, the server can only send EAP-Success after
	the EAP/AKA-Challenge round. The client MUST silently discard any
	EAP-Success packets if they are received before the client has
	successfully authenticated the server and sent the EAP-Response/AKA-
	Challenge packet.
	On re-authentication, EAP-Success can only be sent after the
	EAP/AKA-Reauthentication round. The client MUST silently discard any
	EAP-Success packets if they are received before the client has
	successfully authenticated the server and sent the EAP-Response/AKA-
	Reauthentication packet.
	If the client receives an EAP/AKA notification (section 8.9) that
	indicates failure, then the client MUST no longer accept the EAP-
	Success packet even if the server authentication was successfully
	completed.
	10. Key Derivation
	This section specifies how EAP AKA keying material is derived.
	On EAP AKA full authentication, a Master Key (MK) is derived from
	the underlying UMTS AKA values (IK and CK keys) and the Identity as
	follows.
	MK = SHA1(Identity|IK|CK)
	The hash function SHA1 is specified in [10]. In the formula above,
	the "|" character denotes concatenation. Identity denotes the user
	identity string without any terminating null characters. It is the
	identity from the AT_IDENTITY attribute from the last EAP-
	Response/AKA-Identity packet, or, if AT_IDENTITY was not used, the
	identity from the EAP-Response/Identity packet.
	The Master Key is fed into a Pseudo-Random number Function (PRF),
	which generates separate Transient EAP Keys (TEKs) for protecting
	EAP AKA packets, as well as a Master Session Key (MSK) for link
	layer security and an Extended Master Session Key (EMSK) for other
	purposes. On re-authentication, the same TEKs will be used for
	protecting EAP packets, but a new MSK and a new EMSK will be derived
	from the original MK and new values exchanged in the re-
	authentication.
	EAP AKA requires two TEKs for its own purposes, a message
	authentication key K_aut and an encryption key K_encr, to be used
	EAP AKA Authentication June 2003
	with the AT_MAC and AT_ENCR_DATA attributes. The same K_aut and
	K_encr keys are used in full authentication and subsequent re-
	authentications.
	Key derivation is based on the pseudo-random number generator
	specified in NIST Federal Information Processing Standards
	Publication 186-2 [14]. The pseudo-random number generator is
	specified in the change notice 1 (2001 October 5)of [14] (Algorithm
	1). As specified in the change notice (page 74), when Algorithm 1 is
	used as a general-purpose random number generator, the "mod q" term
	in step 3.2 is omitted. The function G used in the algorithm is
	constructed via Secure Hash Standard as specified in Appendix 3.3 of
	the standard. For convenience, the pseudo-random number algorithm
	with the correct modification is cited in Annex A.
	160-bit XKEY and XVAL values are used, so b = 160. On full
	authentication, the Master Key is used as the initial secret seed
	value XKEY
	The optional user input values (XSEED_j) in Step 3.1 are set to
	zero.
	The resulting 320-bit random numbers x_0, x_1, ..., x_m-1 are
	concatenated and partitioned into suitable-sized chunks and used as
	keys in the following order: K_encr (128 bits), K_aut (128 bits),
	Master Session Key (64 bytes), Extended Master Session Key (64
	bytes).
	On re-authentication, the same pseudo-random number generator can be
	used to generate a new Master Session Key and a new Extended Master
	Session Key. The seed value XKEY' is calculated as follows:
	XKEY' = SHA1(Identity|counter|NONCE_S|MK)
	In the formula above, the Identity denotes the re-authentication
	user identity, without any terminating null characters, from the
	AT_IDENTITY attribute of the EAP-Response/AKA-Identity packet, or,
	if EAP-Response/AKA-Identity was not used on re-authentication, the
	identity string from the EAP-Response/Identity packet. The counter
	denotes the counter value from AT_COUNTER attribute used in the EAP-
	Response/AKA-Reauthentication packet. The counter is used in network
	byte order. NONCE_S denotes the 16-byte NONCE_S value from the
	AT_NONCE_S attribute used in the EAP-Request/AKA-Reauthentication
	packet. The MK is the Master Key from the preceding full
	authentication. The pseudo-random number generator is run with the
	new seed value XKEY', and the resulting 320-bit random numbers x_0,
	x_1, ..., x_m-1 are concatenated and partitioned into 64-byte chunks
	and used as the new Master Session Key and the new Extended Master
	Session Key.
	The first 32 bytes of the MSK can be used as the Pairwise Master Key
	(PMK) for IEEE 802.11i.
	EAP AKA Authentication June 2003
	When the RADIUS attributes specified in [16] are used to transport		0 "unable to process packet": a general error code
	keying material, then the first 32 bytes of the MSK correspond to
	MS-MPPE-RECV-KEY and the second 32 bytes to MS-MPPE-SEND-KEY. In
	this case, only 64 bytes of keying material are used.
	11. IANA and Protocol Numbering Considerations		8. IANA and Protocol Numbering Considerations
	The realm name "owlan.org" has been reserved for NAI realm names		The realm name "owlan.org" has been reserved for NAI realm names
	generated from the IMSI.		generated from the IMSI.
	IANA has assigned the number 23 for EAP AKA authentication.		IANA has assigned the number 23 for EAP AKA authentication.
	EAP AKA messages include a Subtype field. The following Subtypes are		EAP AKA messages include a Subtype field. The following Subtypes are
	specified:		specified:
	AKA-Challenge...................................1		AKA-Challenge...................................1
	AKA-Authentication-Reject.......................2		AKA-Authentication-Reject.......................2
	AKA-Synchronization-Failure.....................4		AKA-Synchronization-Failure.....................4
	AKA-Identity....................................5		AKA-Identity....................................5
	AKA-Notification...............................12		AKA-Notification...............................12
	AKA-Reauthentication...........................13		AKA-Reauthentication...........................13
			AKA-Client-Error...............................14
			EAP AKA Authentication 27 October, 2003
	The Subtype-specific data is composed of attributes, which have		The Subtype-specific data is composed of attributes, which have
	attribute type numbers. The following attribute types are specified:		attribute type numbers. The following attribute types are specified:
	AT_RAND.........................................1		AT_RAND.........................................1
	AT_AUTN.........................................2		AT_AUTN.........................................2
	AT_RES..........................................3		AT_RES..........................................3
	AT_AUTS.........................................4		AT_AUTS.........................................4
	AT_PADDING......................................6		AT_PADDING......................................6
	AT_PERMANENT_ID_REQ............................10		AT_PERMANENT_ID_REQ............................10
	AT_MAC.........................................11		AT_MAC.........................................11
			AT_NOTIFICATION................................12
	AT_ANY_ID_REQ..................................13		AT_ANY_ID_REQ..................................13
	AT_IDENTITY....................................14		AT_IDENTITY....................................14
	AT_FULLAUTH_ID_REQ.............................17		AT_FULLAUTH_ID_REQ.............................17
	AT_COUNTER.....................................19		AT_COUNTER.....................................19
	AT_COUNTER_TOO_SMALL...........................20		AT_COUNTER_TOO_SMALL...........................20
	AT_NONCE_S.....................................21		AT_NONCE_S.....................................21
			AT_CLIENT_ERROR_CODE...........................22
	AT_IV.........................................129		AT_IV.........................................129
	AT_ENCR_DATA..................................130		AT_ENCR_DATA..................................130
	AT_NEXT_PSEUDONYM.............................132		AT_NEXT_PSEUDONYM.............................132
	AT_NEXT_REAUTH_ID.............................133		AT_NEXT_REAUTH_ID.............................133
	AT_CHECKCODE..................................134		AT_CHECKCODE..................................134
			The AT_NOTIFICATION attribute contains a notification code value.
			Values 1024, 1026 and 1031 have been specified in Section 7.18 of
			this document.
			The AT_CLIENT_ERROR_CODE attribute contains a client error code.
			Value 0 has been specified in Section 7.19 of this document.
	All requests for value assignment from the various number spaces		All requests for value assignment from the various number spaces
	described in this document require proper documentation, according		described in this document require proper documentation, according
	to the "Specification Required" policy described in [17]. Requests		to the "Specification Required" policy described in [RFC 2434].
	must be specified in sufficient detail so that interoperability		Requests must be specified in sufficient detail so that
	between independent implementations is possible. Possible forms of		interoperability between independent implementations is possible.
	documentation include, but are not limited to, RFCs, the products of		Possible forms of documentation include, but are not limited to,
			RFCs, the products of another standards body (e.g. 3GPP), or
			permanently and readily available vendor design notes.
	EAP AKA Authentication June 2003		EAP AKA and EAP SIM [EAP SIM] are "sister" protocols with similar
			message structure and protocol numbering spaces. Many attributes and
			message Subtypes have the same protocol numbers in these two
			protocols. Hence, it is recommended that the same protocol number
			value SHOULD NOT be allocated for two different purposes in EAP AKA
			and EAP SIM.
	another standards body (e.g. 3GPP), or permanently and readily		9. Security Considerations
	available vendor design notes.
	12. Security Considerations		The EAP base protocol specification [EAP] highlights several attacks
			that are possible against the EAP protocol. This section discusses
	The revised EAP base protocol [18] highlights several attacks that		EAP AKA Authentication 27 October, 2003
	are possible against the EAP protocol. This section discusses the
	claimed security properties of EAP AKA as well as vulnerabilities
	and security recommendations.
	12.1. Identity Protection		the claimed security properties of EAP AKA as well as
			vulnerabilities and security recommendations.
			9.1. Identity Protection
	EAP/AKA includes optional Identity privacy support that protects the		EAP/AKA includes optional Identity privacy support that protects the
	privacy of the subscriber identity against passive eavesdropping.		privacy of the subscriber identity against passive eavesdropping.
	The mechanism cannot be used on the first connection with a given		The mechanism cannot be used on the first exchange with a given
	server, when the IMSI will have to be sent in the clear. The		server, when the IMSI will have to be sent in the clear. The
	terminal SHOULD store the pseudonym in a non-volatile memory so that		terminal SHOULD store the pseudonym in a non-volatile memory so that
	it can be maintained across reboots. An active attacker that		it can be maintained across reboots. An active attacker that
	impersonates the network may use the AT_PERMANENT_ID_REQ attribute		impersonates the network may use the AT_PERMANENT_ID_REQ attribute
	(Section 4.3) to learn the subscriber's IMSI. However, as discussed		(Section 1.1) to learn the subscriber's IMSI. However, as discussed
	in Section 4.3, the terminal can refuse to send the cleartext IMSI		in Section 1.1, the terminal can refuse to send the cleartext IMSI
	if it believes that the network should be able to recognize the		if it believes that the network should be able to recognize the
	pseudonym.		pseudonym.
	If the client and server cannot guarantee that the pseudonym will be		If the peer and server cannot guarantee that the pseudonym will be
	maintained reliably and Identity privacy is required then additional		maintained reliably and Identity privacy is required then additional
	protection from an external security mechanism such as Protected		protection from an external security mechanism such as Protected
	Extensible Authentication Protocol (PEAP) [19] may be used. The		Extensible Authentication Protocol (PEAP) [PEAP] may be used. The
	benefits and the security considerations of using an external		benefits and the security considerations of using an external
	security mechanism with EAP/AKA are beyond the scope of this		security mechanism with EAP/AKA are beyond the scope of this
	document.		document.
	12.2. Mutual Authentication		9.2. Mutual Authentication
	EAP/AKA provides mutual authentication via the UMTS AKA mechanisms.		EAP/AKA provides mutual authentication via the UMTS AKA mechanisms.
	12.3. Key Derivation		9.3. Key Derivation
	EAP/AKA supports key derivation with 128-bit effective key strength.		EAP/AKA supports key derivation with 128-bit effective key strength.
	The key hierarchy is specified in Section 10.		The key hierarchy is specified in Section 0.
	The Transient EAP Keys used to protect EAP AKA packets (K_encr,		The Transient EAP Keys used to protect EAP AKA packets (K_encr,
	K_aut) and the Master Session Keys are cryptographically separate.		K_aut) and the Master Session Keys are cryptographically separate.
	An attacker cannot derive any non-trivial information from K_encr or		An attacker cannot derive any non-trivial information from K_encr or
	K_aut based on the Master Session Key or vice versa. An attacker		K_aut based on the Master Session Key or vice versa. An attacker
	also cannot calculate the pre-shared secret from the UMTS AKA IK,		also cannot calculate the pre-shared secret from the UMTS AKA IK,
	UMTS AKA CK, EAP AKA K_encr, EAP AKA K_aut or from the Master		UMTS AKA CK, EAP AKA K_encr, EAP AKA K_aut or from the Master
	Session Key.		Session Key.
	12.4. Brute-Force and Dictionary Attacks		9.4. Brute-Force and Dictionary Attacks
	The effective strength of EAP/AKA values is 128 bits, and there are		The effective strength of EAP/AKA values is 128 bits, and there are
	no known computationally feasible brute-force attacks. Because UMTS		no known computationally feasible brute-force attacks. Because UMTS
	EAP AKA Authentication June 2003
	AKA is not a password protocol (the pre-shared secret must not be a		AKA is not a password protocol (the pre-shared secret must not be a
	weak password), EAP/AKA is not vulnerable to dictionary attacks.		weak password), EAP/AKA is not vulnerable to dictionary attacks.
	12.5. Integrity Protection, Replay Protection and Confidentiality		9.5. Integrity Protection, Replay Protection and Confidentiality
	AT_MAC, AT_IV and AT_ENCR_DATA attributes are used to provide		AT_MAC, AT_IV and AT_ENCR_DATA attributes are used to provide
	integrity, replay and confidentiality protection for EAP/AKA		integrity, replay and confidentiality protection for EAP/AKA
	Requests and Responses. Integrity protection includes the EAP		Requests and Responses. Integrity protection includes the EAP
			EAP AKA Authentication 27 October, 2003
	header. Integrity protection (AT_MAC) is based on a keyed message		header. Integrity protection (AT_MAC) is based on a keyed message
	authentication code. Confidentiality (AT_ENCR_DATA and AT_IV) is		authentication code. Confidentiality (AT_ENCR_DATA and AT_IV) is
	based on a block cipher.		based on a block cipher.
	Because keys are not available in the beginning of the EAP methods,		Because keys are not available in the beginning of the EAP methods,
	the AT_MAC attribute cannot be used for protecting EAP/AKA-Identity		the AT_MAC attribute cannot be used for protecting EAP/AKA-Identity
	messages. However, the AT_CHECKCODE attribute can optionally be used		messages. However, the AT_CHECKCODE attribute can optionally be used
	to protect the integrity of the EAP/AKA-Identity roundtrip.		to protect the integrity of the EAP/AKA-Identity roundtrip.
	On full authentication, replay protection is provided by the		On full authentication, replay protection is provided by RAND and
	underlying UMTS AKA scheme, which makes use of the RAND and AUTN		AUTN values from the underlying UMTS AKA scheme. On re-
	values. On re-authentication, a counter and a server nonce is used		authentication, a counter and a server nonce is used to provide
	to provide replay protection.		replay protection.
	The contents of the EAP-Response/Identity packet are implicitly		The contents of the EAP-Response/Identity packet are implicitly
	integrity protected by including them in key derivation.		integrity protected by including them in key derivation.
	Because EAP/AKA is not a tunneling method, EAP Notification, EAP		Because EAP/AKA is not a tunneling method, EAP Notification, EAP
	Success or EAP Failure packets are not confidential, integrity		Success or EAP Failure packets are not confidential, integrity
	protected or replay protected. On physically insecure networks, this		protected or replay protected. On physically insecure networks, this
	may enable an attacker to mount denial of service attacks by sending		may enable an attacker to mount denial of service attacks by sending
	false EAP Notification, EAP Success or EAP Failure packets. However,		false EAP Notification, EAP Success or EAP Failure packets. However,
	the attacker cannot force the peers to believe successful		the attacker cannot force the peers to believe successful
	authentication has occurred when mutual authentication failed or has		authentication has occurred when mutual authentication failed or has
	not happened yet.		not happened yet.
	An eavesdropper will see the EAP Notification, EAP Success and EAP		An eavesdropper will see the EAP Notification, EAP Success and EAP
	Failure packets sent in the clear. With EAP AKA, confidential		Failure packets sent in the clear. With EAP AKA, confidential
	information MUST NOT be transmitted in EAP Notification packets.		information MUST NOT be transmitted in EAP Notification packets.
	12.6. Negotiation Attacks		9.6. Negotiation Attacks
	EAP/AKA does not protect the EAP-Response/Nak packet. Because		EAP/AKA does not protect the EAP-Response/Nak packet. Because
	EAP/AKA does not protect the EAP method negotiation, EAP method		EAP/AKA does not protect the EAP method negotiation, EAP method
	downgrading attacks may be possible, especially if the user uses the		downgrading attacks may be possible, especially if the user uses the
	same identity with EAP/AKA and other EAP methods.		same identity with EAP/AKA and other EAP methods.
	As described in Section 6, EAP/AKA allows the protocol to be		As described in Section 5, EAP/AKA allows the protocol to be
	extended by defining new attribute types. When defining such		extended by defining new attribute types. When defining such
	attributes, it should be noted that any extra attributes included in		attributes, it should be noted that any extra attributes included in
	EAP-Request/AKA-Identity or EAP-Response/AKA-Identity packets are		EAP-Request/AKA-Identity or EAP-Response/AKA-Identity packets are
	not included in the MACs later on, and thus some other precautions		not included in the MACs later on, and thus some other precautions
	must be taken to avoid modifications to them.		must be taken to avoid modifications to them.
	EAP/AKA does not support ciphersuite negotiation or EAP/AKA protocol		EAP/AKA does not support ciphersuite negotiation or EAP/AKA protocol
	version negotiation.		version negotiation.
	EAP AKA Authentication June 2003		9.7. Fast Reconnect
	12.7. Fast Reconnect
	EAP/AKA includes an optional re-authentication ("fast reconnect")		EAP/AKA includes an optional re-authentication ("fast reconnect")
	procedure, as recommended in [18] for EAP types that are intended		procedure, as recommended in [EAP] for EAP types that are intended
	for physically insecure networks.		for physically insecure networks.
	12.8. Acknowledged Result Indications		9.8. Acknowledged Result Indications
			EAP AKA Authentication 27 October, 2003
	EAP/AKA does not provide acknowledged or integrity protected Success		EAP/AKA does not provide acknowledged or integrity protected Success
	or Failure indications.		or Failure indications.
	If an EAP Success or an EAP Failure packet is lost when using		If an EAP Success or an EAP Failure packet is lost when using
	EAP/AKA over an unreliable medium, and if the protocol over which		EAP/AKA over an unreliable medium, and if the protocol over which
	EAP/AKA is transported does not address the possible loss of Success		EAP/AKA is transported does not address the possible loss of Success
	or Failure, then the peer and authenticator may end up having a		or Failure, then the peer and EAP server may end up having a
	different interpretation of the state of the authentication		different interpretation of the state of the authentication
	conversation.		conversation.
	On physically insecure networks, an attacker may mount denial of		On physically insecure networks, an attacker may mount denial of
	service attacks by sending false EAP Success or EAP Failure		service attacks by sending false EAP Success or EAP Failure
	indications. However, the attacker cannot force the client or the		indications. However, the attacker cannot force the peer or the EAP
	authenticator to believe successful authentication has occurred when		server to believe successful authentication has occurred when mutual
	mutual authentication failed or has not happened yet.		authentication failed or has not happened yet.
	12.9. Man-in-the-middle Attacks		9.9. Man-in-the-middle Attacks
	In order to avoid man-in-the-middle attacks and session hijacking,		In order to avoid man-in-the-middle attacks and session hijacking,
	user data SHOULD be integrity protected on physically insecure		user data SHOULD be integrity protected on physically insecure
	networks. The EAP/AKA Master Session Key or keys derived from it MAY		networks. The EAP/AKA Master Session Key or keys derived from it MAY
	be used as the integrity protection keys, or, if an external		be used as the integrity protection keys, or, if an external
	security mechanism such as PEAP is used, then the link integrity		security mechanism such as PEAP is used, then the link integrity
	protection keys MAY be derived by the external security mechanism.		protection keys MAY be derived by the external security mechanism.
	There are man-in-the-middle attacks associated with the use of any		There are man-in-the-middle attacks associated with the use of any
	EAP method within a tunneled protocol such as PEAP, or within a		EAP method within a tunneled protocol such as PEAP, or within a
	sequence of EAP methods followed by each other. This specification		sequence of EAP methods followed by each other. This specification
	does not address these attacks. If EAP/AKA is used with a tunneling		does not address these attacks. If EAP/AKA is used with a tunneling
	protocol or as part of a sequence of methods, there should be		protocol or as part of a sequence of methods, there should be
	cryptographic binding provided between the protocols and EAP/AKA to		cryptographic binding provided between the protocols and EAP/AKA to
	prevent man-in-the-middle attacks through rogue authenticators being		prevent man-in-the-middle attacks through rogue authenticators being
	able to setup one-way authenticated tunnels. EAP/AKA Master Session		able to setup one-way authenticated tunnels. EAP/AKA Master Session
	Key MAY be used to provide the cryptographic binding. However the		Key MAY be used to provide the cryptographic binding. However the
	mechanism how the binding is provided depends on the tunneling or		mechanism how the binding is provided depends on the tunneling or
	sequencing protocol, and it is beyond the scope of this document.		sequencing protocol, and it is beyond the scope of this document.
	12.10. Generating Random Numbers		9.10. Generating Random Numbers
	An EAP/AKA implementation SHOULD use a good source of randomness to		An EAP/AKA implementation SHOULD use a good source of randomness to
	generate the random numbers required in the protocol. Please see		generate the random numbers required in the protocol. Please see
	[20] for more information on generating random numbers for security		[RFC 1750] for more information on generating random numbers for
	applications.		security applications.
	13. Security Claims
	EAP AKA Authentication June 2003		10. Security Claims
	This section provides the security claims required by [18].		This section provides the security claims required by [EAP].
	[a] Intended use. EAP AKA is intended for use over both physically		[a] Intended use. EAP AKA is intended for use over both physically
	insecure networks and physically or otherwise secure networks.		insecure networks and physically or otherwise secure networks.
	Applicable media include but are not limited to PPP, IEEE 802 wired		Applicable media include but are not limited to PPP, IEEE 802 wired
	networks and IEEE 802.11.		networks and IEEE 802.11.
			EAP AKA Authentication 27 October, 2003
	[b] Mechanism. EAP AKA is based on the UMTS AKA mechanism, which is		[b] Mechanism. EAP AKA is based on the UMTS AKA mechanism, which is
	an authentication and key agreement mechanism based on a symmetric		an authentication and key agreement mechanism based on a symmetric
	128-bit pre-shared secret.		128-bit pre-shared secret.
	[c] Security claims. The security properties of the method are		[c] Security claims. The security properties of the method are
	discussed in Section 12.		discussed in Section 9.
	[d] Key strength. EAP/AKA supports key derivation with 128-bit		[d] Key strength. EAP/AKA supports key derivation with 128-bit
	effective key strength.		effective key strength.
	[e] Description of key hierarchy. Please see Section 10.		[e] Description of key hierarchy. Please see Section 0.
	[f] Indication of vulnerabilities. Vulnerabilities are discussed in		[f] Indication of vulnerabilities. Vulnerabilities are discussed in
	Section 12.		Section 9.
	14. Intellectual Property Right Notices		11. Intellectual Property Right Notices
	On IPR related issues, Nokia and Ericsson refer to the their		On IPR related issues, Nokia and Ericsson refer to the their
	respective statements on patent licensing. Please see		respective statements on patent licensing. Please see
	http://www.ietf.org/ietf/IPR/NOKIA and		http://www.ietf.org/ietf/IPR/NOKIA and
	http://www.ietf.org/ietf/IPR/ERICSSON-General		http://www.ietf.org/ietf/IPR/ERICSSON-General
	Acknowledgements and Contributions		Acknowledgements and Contributions
	The authors wish to thank Rolf Blom of Ericsson, Bernard Aboba of		The authors wish to thank Rolf Blom of Ericsson, Bernard Aboba of
	Microsoft, Arne Norefors of Ericsson, N.Asokan of Nokia, Valtteri		Microsoft, Arne Norefors of Ericsson, N.Asokan of Nokia, Valtteri
	Niemi of Nokia, Kaisa Nyberg of Nokia, Jukka-Pekka Honkanen of		Niemi of Nokia, Kaisa Nyberg of Nokia, Jukka-Pekka Honkanen of
	Nokia, Pasi Eronen of Nokia, Olivier Paridaens of Alcatel and Ilkka		Nokia, Pasi Eronen of Nokia, Olivier Paridaens of Alcatel and Ilkka
	Uusitalo of Ericsson for interesting discussions in this problem		Uusitalo of Ericsson for interesting discussions in this problem
	space.		space.
	The attribute format is based on the extension format of Mobile IPv4		The attribute format is based on the extension format of Mobile IPv4
	[21].		[RFC 3344].
	Authors' Addresses		Authors' Addresses
	Jari Arkko		Jari Arkko
	Ericsson		Ericsson
	02420 Jorvas Phone: +358 40 5079256		02420 Jorvas Phone: +358 40 5079256
	Finland Email: jari.arkko@ericsson.com		Finland Email: jari.arkko@ericsson.com
	Henry Haverinen		Henry Haverinen
	Nokia Mobile Phones		Nokia Mobile Phones
	P.O. Box 88		P.O. Box 88
	33721 Tampere Phone: +358 50 594 4899		33721 Tampere Phone: +358 50 594 4899
	Finland E-mail: henry.haverinen@nokia.com		Finland E-mail: henry.haverinen@nokia.com
	EAP AKA Authentication June 2003		EAP AKA Authentication 27 October, 2003
	Annex A. Pseudo-Random Number Generator		Annex A. Pseudo-Random Number Generator
	The "|" character denotes concatenation, and "^" denotes involution.		The "|" character denotes concatenation, and "^" denotes involution.
	Step 1: Choose a new, secret value for the seed-key, XKEY		Step 1: Choose a new, secret value for the seed-key, XKEY
	Step 2: In hexadecimal notation let		Step 2: In hexadecimal notation let
	t = 67452301 EFCDAB89 98BADCFE 10325476 C3D2E1F0		t = 67452301 EFCDAB89 98BADCFE 10325476 C3D2E1F0
	This is the initial value for H0|H1|H2|H3|H4		This is the initial value for H0|H1|H2|H3|H4
	in the FIPS SHS [10]		in the FIPS SHS [SHA-1]
	Step 3: For j = 0 to m - 1 do		Step 3: For j = 0 to m - 1 do
	3.1 XSEED_j = optional user input		3.1 XSEED_j = 0 /* no optional user input */
	3.2 For i = 0 to 1 do		3.2 For i = 0 to 1 do
	a. XVAL = (XKEY + XSEED_j) mod 2^b		a. XVAL = (XKEY + XSEED_j) mod 2^b
	b. w_i = G(t, XVAL)		b. w_i = G(t, XVAL)
	c. XKEY = (1 + XKEY + w_i) mod 2^b		c. XKEY = (1 + XKEY + w_i) mod 2^b
	3.3 x_j = w_0|w_1		3.3 x_j = w_0|w_1
	EAP AKA Authentication June 2003		EAP AKA Authentication 27 October, 2003
	References
	[1] 3GPP Technical Specification 3GPP TS 33.102 V5.1.0: "Technical
	Specification Group Services and System Aspects; 3G Security;
	Security Architecture (Release 5)", 3rd Generation Partnership
	Project, December 2002. (NORMATIVE)
	[2] IEEE P802.1X/D11, "Standards for Local Area and Metropolitan
	Area Networks: Standard for Port Based Network Access
	Control", March 2001. (INFORMATIVE)
	[3] IEEE Draft 802.11eS/D1, "Draft Supplement to STANDARD FOR		Normative References
	Telecommunications and Information Exchange between Systems -
	LAN/MAN Specific Requirements - Part 11: Wireless Medium
	Access Control (MAC) and physical layer (PHY) specifications:
	Specification for Enhanced Security", March 2001.
	(INFORMATIVE)
	[4] Aboba, B. and M. Beadles, "The Network Access Identifier", RFC		[TS 33.102] 3GPP Technical Specification 3GPP TS 33.102 V5.1.0:
	2486, January 1999. (NORMATIVE)		"Technical Specification Group Services and System Aspects; 3G
			Security; Security Architecture (Release 5)", 3rd Generation
			Partnership Project, December 2002.
	[5] L. Blunk, J. Vollbrecht, "PPP Extensible Authentication		[RFC 2486] Aboba, B. and M. Beadles, "The Network Access
	Protocol (EAP)", RFC 2284, March 1998. (NORMATIVE)		Identifier", RFC 2486, January 1999.
	[6] S. Bradner, "Key words for use in RFCs to indicate Requirement		[EAP] L. Blunk et al., "Extensible Authentication Protocol (EAP)",
	Levels", RFC 2119, March 1997. (NORMATIVE)		draft-ietf-eap-rfc2284bis-05.txt, work-in-progress, September 2003.
	[7] 3GPP Technical Specification 3GPP TS 23.003 V5.5.1: "3rd		[RFC 2119] S. Bradner, "Key words for use in RFCs to indicate
	Generation Parnership Project; Technical Specification Group		Requirement Levels", RFC 2119, March 1997.
	Core Network; Numbering, addressing and identification
	(Release 5)", 3rd Generation Parnership Project, January 2003
	(NORMATIVE)
	[8] Draft 3GPP Technical Specification 3GPP TS 23.234 V 1.4.0:		[TS 23.003] 3GPP Technical Specification 3GPP TS 23.003 V5.5.1: "3rd
	"Technical Specification Group Services and System Aspects;		Generation Parnership Project; Technical Specification Group Core
	3GPP system to Wireless Local Area Network (WLAN)		Network; Numbering, addressing and identification (Release 5)", 3rd
	Interworking; System Description", 3rd Generation Partnership		Generation Partnership Project, January 2003
	Project, work in progress, January 2003. (INFORMATIVE)
	[9] H. Krawczyk, M. Bellare, R. Canetti, "HMAC: Keyed-Hashing for		[RFC 2104] H. Krawczyk, M. Bellare, R. Canetti, "HMAC: Keyed-Hashing
	Message Authentication", RFC2104, February 1997. (NORMATIVE)		for Message Authentication", RFC2104, February 1997.
	[10] Federal Information Processing Standard (FIPS) Publication		[SHA-1] Federal Information Processing Standard (FIPS) Publication
	180-1, "Secure Hash Standard," National Institute of Standards		180-1, "Secure Hash Standard," National Institute of Standards and
	and Technology, U.S. Department of Commerce, April 17, 1995.		Technology, U.S. Department of Commerce, April 17, 1995.
	(NORMATIVE)
	[11] Federal Information Processing Standard (FIPS) draft standard,		[AES] Federal Information Processing Standards (FIPS) Publication
	"Advanced Encryption Standard (AES)",		197, "Advanced Encryption Standard (AES)", National Institute of
			Standards and Technology, November 26, 2001.
			http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf
	EAP AKA Authentication June 2003		[CBC] NIST Special Publication 800-38A, "Recommendation for Block
			Cipher Modes of Operation - Methods and Techniques", National
			Institute of Standards and Technology, December 2001.
			http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf
	http://csrc.nist.gov/publications/drafts/dfips-AES.pdf,		[TS 33.105] 3GPP Technical Specification 3GPP TS 33.105 4.1.0:
	September 2001. (NORMATIVE)		"Technical Specification Group Services and System Aspects; 3G
			Security; Cryptographic Algorithm Requirements (Release 4)", 3rd
			Generation Partnership Project, June 2001
	[12] US National Bureau of Standards, "DES Modes of Operation",		[PRF] Federal Information Processing Standards (FIPS) Publication
	Federal Information Processing Standard (FIPS) Publication 81,		186-2 (with change notice), "Digital Signature Standard (DSS)",
	December 1980. (NORMATIVE)		National Institute of Standards and Technology, January 27, 2000
			Available on-line at:
			http://csrc.nist.gov/publications/fips/fips186-2/fips186-2-
			change1.pdf
	[13] 3GPP Technical Specification 3GPP TS 33.105 4.1.0: "Technical		EAP AKA Authentication 27 October, 2003
	Specification Group Services and System Aspects; 3G Security;
	Cryptographic Algorithm Requirements (Release 4)", 3rd
	Generation Partnership Project, June 2001 (NORMATIVE)
	[14] Federal Information Processing Standards (FIPS) Publication		[RFC 2434] T. Narten, H. Alvestrand, "Guidelines for Writing an IANA
	186-2 (with change notice), "Digital Signature Standard		Considerations Section in RFCs", RFC 2434, October 1998.
	(DSS)", National Institute of Standards and Technology,
	January 27, 2000, (NORMATIVE)
	Available on-line at:
	http://csrc.nist.gov/publications/fips/fips186-2/
	fips186-2-change1.pdf
	[15] B. Aboba, D. Simon, "PPP EAP TLS Authentication Protocol", RFC		Informative References
	2716, October 1999 (INFORMATIVE)
	[16] G. Zorn, "Microsoft Vendor-specific RADIUS Attributes", RFC		[RFC 2548] G. Zorn, "Microsoft Vendor-specific RADIUS Attributes",
	2548, March 1999 (INFORMATIVE)		RFC 2548, March 1999
	[17] T. Narten, H. Alvestrand, "Guidelines for Writing an IANA		[PEAP] H. Andersson, S. Josefsson, G. Zorn, D. Simon, A. Palekar,
	Considerations Section in RFCs", RFC 2434, October 1998.		"Protected EAP Protocol (PEAP)", draft-josefsson-pppext-eap-tls-eap-
	(NORMATIVE)		05.txt, work-in-progress, September 2002.
	[18] L. Blunk, J. Vollbrecht, B. Aboba, "Extensible Authentication		[RFC 1750] D. Eastlake, 3rd, S. Crocker, J. Schiller, "Randomness
	Protocol (EAP)", draft-ietf-pppext-rfc2284bis-07.txt, work-in-		Recommendations for Security", RFC 1750 (Informational), December
	progress, October 2002. (NORMATIVE)		1994.
	[19] H. Andersson, S. Josefsson, G. Zorn, D. Simon, A. Palekar,		[RFC 3344] C. Perkins (editor), "IP Mobility Support", RFC 3344,
	"Protected EAP Protocol (PEAP)", draft-josefsson-pppext-eap-		August 2002.
	tls-eap-05.txt, work-in-progress, September 2002.
	(IMFORMATIVE)
	[20] D. Eastlake, 3rd, S. Crocker, J. Schiller, "Randomness		[EAP SIM] H. Haverinen, J. Salowey, "EAP SIM Authentication", draft-
	Recommendations for Security", RFC 1750 (Informational),		haverinen-pppext-eap-sim-12.txt, October 2003, work in progress
	December 1994. (INFORMATIVE)
	[21] C. Perkins (editor), "IP Mobility Support", RFC 3344, August		[TS 23.234] Draft 3GPP Technical Specification 3GPP TS 23.234 V
	2002. (INFORMATIVE)		1.4.0: "Technical Specification Group Services and System Aspects;
			3GPP system to Wireless Local Area Network (WLAN) Interworking;
			System Description", 3rd Generation Partnership Project, work in
			progress, January 2003.
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