< draft-ietf-ipsecme-rfc4307bis-07.txt		draft-ietf-ipsecme-rfc4307bis-08.txt >
	Network Working Group Y. Nir		Network Working Group Y. Nir
	Internet-Draft Check Point		Internet-Draft Check Point
	Obsoletes: 4307 (if approved) T. Kivinen		Obsoletes: 4307 (if approved) T. Kivinen
	Updates: 7296 (if approved) INSIDE Secure		Updates: 7296 (if approved) INSIDE Secure
	Intended status: Standards Track P. Wouters		Intended status: Standards Track P. Wouters
	Expires: October 09, 2016 Red Hat		Expires: November 12, 2016 Red Hat
	D. Migault		D. Migault
	Ericsson		Ericsson
	April 07, 2016		May 11, 2016
	Algorithm Implementation Requirements and Usage Guidance for IKEv2		Algorithm Implementation Requirements and Usage Guidance for IKEv2
	draft-ietf-ipsecme-rfc4307bis-07		draft-ietf-ipsecme-rfc4307bis-08
	Abstract		Abstract
	The IPsec series of protocols makes use of various cryptographic		The IPsec series of protocols makes use of various cryptographic
	algorithms in order to provide security services. The Internet Key		algorithms in order to provide security services. The Internet Key
	Exchange (IKE) protocol is used to negotiate the IPsec Security		Exchange (IKE) protocol is used to negotiate the IPsec Security
	Association (IPsec SA) parameters, such as which algorithms should be		Association (IPsec SA) parameters, such as which algorithms should be
	used. To ensure interoperability between different implementations,		used. To ensure interoperability between different implementations,
	it is necessary to specify a set of algorithm implementation		it is necessary to specify a set of algorithm implementation
	requirements and usage guidance to ensure that there is at least one		requirements and usage guidance to ensure that there is at least one
	skipping to change at page 1, line 45 ¶		skipping to change at page 1, line 45 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on October 09, 2016.		This Internet-Draft will expire on November 12, 2016.
	Copyright Notice		Copyright Notice
	Copyright (c) 2016 IETF Trust and the persons identified as the		Copyright (c) 2016 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	skipping to change at page 2, line 27 ¶		skipping to change at page 2, line 30 ¶
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	1.1. Updating Algorithm Implementation Requirements and Usage		1.1. Updating Algorithm Implementation Requirements and Usage
	Guidance . . . . . . . . . . . . . . . . . . . . . . . . 3		Guidance . . . . . . . . . . . . . . . . . . . . . . . . 3
	1.2. Updating Algorithm Requirement Levels . . . . . . . . . . 3		1.2. Updating Algorithm Requirement Levels . . . . . . . . . . 3
	1.3. Document Audience . . . . . . . . . . . . . . . . . . . . 4		1.3. Document Audience . . . . . . . . . . . . . . . . . . . . 4
	2. Conventions Used in This Document . . . . . . . . . . . . . . 4		2. Conventions Used in This Document . . . . . . . . . . . . . . 4
	3. Algorithm Selection . . . . . . . . . . . . . . . . . . . . . 5		3. Algorithm Selection . . . . . . . . . . . . . . . . . . . . . 5
	3.1. Type 1 - IKEv2 Encryption Algorithm Transforms . . . . . 5		3.1. Type 1 - IKEv2 Encryption Algorithm Transforms . . . . . 5
	3.2. Type 2 - IKEv2 Pseudo-random Function Transforms . . . . 7		3.2. Type 2 - IKEv2 Pseudo-random Function Transforms . . . . 6
	3.3. Type 3 - IKEv2 Integrity Algorithm Transforms . . . . . . 8		3.3. Type 3 - IKEv2 Integrity Algorithm Transforms . . . . . . 7
	3.4. Type 4 - IKEv2 Diffie-Hellman Group Transforms . . . . . 9		3.4. Type 4 - IKEv2 Diffie-Hellman Group Transforms . . . . . 8
	4. IKEv2 Authentication . . . . . . . . . . . . . . . . . . . . 10		4. IKEv2 Authentication . . . . . . . . . . . . . . . . . . . . 10
	4.1. IKEv2 Authentication Method . . . . . . . . . . . . . . . 10		4.1. IKEv2 Authentication Method . . . . . . . . . . . . . . . 10
	4.1.1. Recommendations for RSA key length . . . . . . . . . 11		4.1.1. Recommendations for RSA key length . . . . . . . . . 11
	4.2. Digital Signature Recommendations . . . . . . . . . . . . 11		4.2. Digital Signature Recommendations . . . . . . . . . . . . 11
	5. Algorithms for Internet of Things . . . . . . . . . . . . . . 12		5. Algorithms for Internet of Things . . . . . . . . . . . . . . 12
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 13		6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
	8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14		8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
	9.1. Normative References . . . . . . . . . . . . . . . . . . 14		9.1. Normative References . . . . . . . . . . . . . . . . . . 14
	9.2. Informative References . . . . . . . . . . . . . . . . . 14		9.2. Informative References . . . . . . . . . . . . . . . . . 14
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
	1. Introduction		1. Introduction
	The Internet Key Exchange (IKE) protocol [RFC7296] is used to		The Internet Key Exchange (IKE) protocol [RFC7296] is used to
	negotiate the parameters of the IPsec SA, such as the encryption and		negotiate the parameters of the IPsec SA, such as the encryption and
	authentication algorithms and the keys for the protected		authentication algorithms and the keys for the protected
	communications between the two endpoints. The IKE protocol itself is		communications between the two endpoints. The IKE protocol itself is
	also protected by cryptographic algorithms which are negotiated		also protected by cryptographic algorithms which are negotiated
	between the two endpoints using IKE. Different implementations of		between the two endpoints using IKE. Different implementations of
	IKE may negotiate different algorithms based on their individual		IKE may negotiate different algorithms based on their individual
	local policy. To ensure interoperability, a set of "mandatory-to-		local policy. To ensure interoperability, a set of "mandatory-to-
	implement" IKE cryptographic algorithms is defined.		implement" IKE cryptographic algorithms is defined.
	skipping to change at page 4, line 4 ¶		skipping to change at page 3, line 47 ¶
	algorithms for future mandatory-to-implement status. There is no		algorithms for future mandatory-to-implement status. There is no
	guarantee that the algorithms in use today may become mandatory in		guarantee that the algorithms in use today may become mandatory in
	the future. Published algorithms are continuously subjected to		the future. Published algorithms are continuously subjected to
	cryptographic attack and may become too weak or could become		cryptographic attack and may become too weak or could become
	completely broken before this document is updated.		completely broken before this document is updated.
	This document only provides recommendations for the mandatory-to-		This document only provides recommendations for the mandatory-to-
	implement algorithms or algorithms too weak that are recommended not		implement algorithms or algorithms too weak that are recommended not
	to be implemented. As a result, any algorithm listed at the IKEv2		to be implemented. As a result, any algorithm listed at the IKEv2
	IANA registry not mentioned in this document MAY be implemented. For		IANA registry not mentioned in this document MAY be implemented. For
	clarification and consistency with [RFC4307] an algorithm will be set		clarification and consistency with [RFC4307] an algorithm will be
	to MAY only when it has been downgraded.		denoted here as MAY only when it has been downgraded.
	Although this document updates the algorithms to keep the IKEv2		Although this document updates the algorithms to keep the IKEv2
	communication secure over time, it also aims at providing		communication secure over time, it also aims at providing
	recommendations so that IKEv2 implementations remain interoperable.		recommendations so that IKEv2 implementations remain interoperable.
	IKEv2 interoperability is addressed by an incremental introduction or		IKEv2 interoperability is addressed by an incremental introduction or
	deprecation of algorithms. In addition, this document also considers		deprecation of algorithms. In addition, this document also considers
	the new use cases for IKEv2 deployment, such as Internet of Things		the new use cases for IKEv2 deployment, such as Internet of Things
	(IoT).		(IoT).
	It is expected that deprecation of an algorithm is performed		It is expected that deprecation of an algorithm is performed
	skipping to change at page 4, line 30 ¶		skipping to change at page 4, line 25 ¶
	Similarly, an algorithm that has not been mentioned as mandatory-to-		Similarly, an algorithm that has not been mentioned as mandatory-to-
	implement is expected to be introduced with a SHOULD instead of a		implement is expected to be introduced with a SHOULD instead of a
	MUST.		MUST.
	The current trend toward Internet of Things and its adoption of IKEv2		The current trend toward Internet of Things and its adoption of IKEv2
	requires this specific use case to be taken into account as well.		requires this specific use case to be taken into account as well.
	IoT devices are resource constrained devices and their choice of		IoT devices are resource constrained devices and their choice of
	algorithms are motivated by minimizing the footprint of the code, the		algorithms are motivated by minimizing the footprint of the code, the
	computation effort and the size of the messages to send. This		computation effort and the size of the messages to send. This
	document indicates "[IoT]" when a specified algorithm is specifically		document indicates "[IoT]" when a specified algorithm is specifically
	listed for IoT devices.		listed for IoT devices. Requirement levels that are marked as "IoT"
			apply to IoT devices and to server-side implementations that might
			presumably need to interoperate with them, including any general-
			purpose VPN gateways.
	1.3. Document Audience		1.3. Document Audience
	The recommendations of this document mostly target IKEv2 implementers		The recommendations of this document mostly target IKEv2 implementers
	as implementations need to meet both high security expectations as		as implementations need to meet both high security expectations as
	well as high interoperability between various vendors and with		well as high interoperability between various vendors and with
	different versions. Interoperability requires a smooth move to more		different versions. Interoperability requires a smooth move to more
	secure cipher suites. This may differ from a user point of view that		secure cipher suites. This may differ from a user point of view that
	may deploy and configure IKEv2 with only the safest cipher suite. On		may deploy and configure IKEv2 with only the safest cipher suite. On
	the other hand, comments and recommendations from this document are		the other hand, comments from this document are also expected to be
	also expected to be useful for such users.		useful for such users.
	IKEv1 is out of scope of this document. IKEv1 is deprecated and the		IKEv1 is out of scope of this document. IKEv1 is deprecated and the
	recommendations of this document must not be considered for IKEv1, as		recommendations of this document must not be considered for IKEv1, as
	most IKEv1 implementations have been "frozen" and will not be able to		most IKEv1 implementations have been "frozen" and will not be able to
	update the list of mandatory-to-implement algorithms.		update the list of mandatory-to-implement algorithms.
	2. Conventions Used in This Document		2. Conventions Used in This Document
	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 this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	We define some additional terms here:		We define some additional terms here:
	SHOULD+ This term means the same as SHOULD. However, it is likely		SHOULD+ This term means the same as SHOULD. However, it is likely
	that an algorithm marked as SHOULD+ will be promoted at some		that an algorithm marked as SHOULD+ will be promoted at
	future time to be a MUST.		some future time to be a MUST.
	SHOULD- This term means the same as SHOULD. However, an algorithm		SHOULD- This term means the same as SHOULD. However, an algorithm
	marked as SHOULD- may be deprecated to a MAY in a future		marked as SHOULD- may be deprecated to a MAY in a future
	version of this document.		version of this document.
	MUST- This term means the same as MUST. However, we expect at some		MUST- This term means the same as MUST. However, we expect at
	point that this algorithm will no longer be a MUST in a		some point that this algorithm will no longer be a MUST in
	future document. Although its status will be determined at a		a future document. Although its status will be determined
	later time, it is reasonable to expect that if a future		at a later time, it is reasonable to expect that if a
	revision of a document alters the status of a MUST-		future revision of a document alters the status of a MUST-
	algorithm, it will remain at least a SHOULD or a SHOULD-		algorithm, it will remain at least a SHOULD or a SHOULD-
	level.		level.
	IoT stands for Internet of Things.		IoT stands for Internet of Things.
	Table 1
	3. Algorithm Selection		3. Algorithm Selection
	3.1. Type 1 - IKEv2 Encryption Algorithm Transforms		3.1. Type 1 - IKEv2 Encryption Algorithm Transforms
	The algorithms in the below table are negotiated in the SA payload		The algorithms in the below table are negotiated in the SA payload
	and used for the Encrypted Payload. References to the specification		and used for the Encrypted Payload. References to the specification
	defining these algorithms and the ones in the following subsections		defining these algorithms and the ones in the following subsections
	are in the IANA registry [IKEV2-IANA]. Some of these algorithms are		are in the IANA registry [IKEV2-IANA]. Some of these algorithms are
	Authenticated Encryption with Associated Data (AEAD - [RFC5282]).		Authenticated Encryption with Associated Data (AEAD - [RFC5282]).
	Algorithms that are not AEAD MUST be used in conjunction with an		Algorithms that are not AEAD MUST be used in conjunction with an
	skipping to change at page 6, line 9 ¶		skipping to change at page 5, line 49 ¶
	| AES-GCM with a 16 octet ICV | SHOULD | Yes | [1] |		| AES-GCM with a 16 octet ICV | SHOULD | Yes | [1] |
	| ENCR_AES_CCM_8 | SHOULD | Yes | [1][IoT] |		| ENCR_AES_CCM_8 | SHOULD | Yes | [1][IoT] |
	| ENCR_3DES | MAY | No | |		| ENCR_3DES | MAY | No | |
	| ENCR_DES | MUST NOT | No | |		| ENCR_DES | MUST NOT | No | |
	+-----------------------------+----------+-------+----------+		+-----------------------------+----------+-------+----------+
	[1] - This requirement level is for 128-bit keys. 256-bit keys are at		[1] - This requirement level is for 128-bit keys. 256-bit keys are at
	SHOULD. 192-bit keys can safely be ignored. [IoT] - This requirement		SHOULD. 192-bit keys can safely be ignored. [IoT] - This requirement
	is for interoperability with IoT.		is for interoperability with IoT.
	Table 2
	ENCR_AES_CBC is raised from SHOULD+ in [RFC4307] to MUST. It is the		ENCR_AES_CBC is raised from SHOULD+ in [RFC4307] to MUST. It is the
	only shared mandatory-to-implement algorithm with RFC4307 and as a		only shared mandatory-to-implement algorithm with RFC4307 and as a
	result it is necessary for interoperability with IKEv2 implementation		result it is necessary for interoperability with IKEv2 implementation
	compatible with RFC4307.		compatible with RFC4307.
	ENCR_CHACHA20_POLY1305 was not ready to be considered at the time of		ENCR_CHACHA20_POLY1305 was not ready to be considered at the time of
	RFC4307. It has been recommended by the CRFG and others as an		RFC4307. It has been recommended by the CRFG and others as an
	alternative to AES-CBC and AES-GCM. It is also being standardized		alternative to AES-CBC and AES-GCM. It is also being standardized
	for IPsec for the same reasons. At the time of writing, there were		for IPsec for the same reasons. At the time of writing, there were
	not enough IKEv2 implementations supporting ENCR_CHACHA20_POLY1305 to		not enough IKEv2 implementations supporting ENCR_CHACHA20_POLY1305 to
	skipping to change at page 7, line 30 ¶		skipping to change at page 7, line 21 ¶
	+-------------------+----------+---------+		+-------------------+----------+---------+
	| PRF_HMAC_SHA2_256 | MUST | |		| PRF_HMAC_SHA2_256 | MUST | |
	| PRF_HMAC_SHA2_512 | SHOULD+ | |		| PRF_HMAC_SHA2_512 | SHOULD+ | |
	| PRF_HMAC_SHA1 | MUST- | |		| PRF_HMAC_SHA1 | MUST- | |
	| PRF_AES128_XCBC | SHOULD | [IoT] |		| PRF_AES128_XCBC | SHOULD | [IoT] |
	| PRF_HMAC_MD5 | MUST NOT | |		| PRF_HMAC_MD5 | MUST NOT | |
	+-------------------+----------+---------+		+-------------------+----------+---------+
	[IoT] - This requirement is for interoperability with IoT		[IoT] - This requirement is for interoperability with IoT
	Table 3
	PRF_HMAC_SHA2_256 was not mentioned in RFC4307, as no SHA2 based		PRF_HMAC_SHA2_256 was not mentioned in RFC4307, as no SHA2 based
	transforms were mentioned. PRF_HMAC_SHA2_256 MUST be implemented in		transforms were mentioned. PRF_HMAC_SHA2_256 MUST be implemented in
	order to replace SHA1 and PRF_HMAC_SHA1.		order to replace SHA1 and PRF_HMAC_SHA1.
	PRF_HMAC_SHA2_512 SHOULD be implemented as a future replacement for		PRF_HMAC_SHA2_512 SHOULD be implemented as a future replacement for
	PRF_HMAC_SHA2_256 or when stronger security is required.		PRF_HMAC_SHA2_256 or when stronger security is required.
	PRF_HMAC_SHA2_512 is preferred over PRF_HMAC_SHA2_384, as the		PRF_HMAC_SHA2_512 is preferred over PRF_HMAC_SHA2_384, as the
	additional overhead of PRF_HMAC_SHA2_512 is negligible.		additional overhead of PRF_HMAC_SHA2_512 is negligible.
	PRF_HMAC_SHA1 has been downgraded from MUST in RFC4307 to MUST- as		PRF_HMAC_SHA1 has been downgraded from MUST in RFC4307 to MUST- as
	skipping to change at page 8, line 29 ¶		skipping to change at page 8, line 19 ¶
	| AUTH_HMAC_SHA2_512_256 | SHOULD | |		| AUTH_HMAC_SHA2_512_256 | SHOULD | |
	| AUTH_HMAC_SHA1_96 | MUST- | |		| AUTH_HMAC_SHA1_96 | MUST- | |
	| AUTH_AES_XCBC_96 | SHOULD | [IoT] |		| AUTH_AES_XCBC_96 | SHOULD | [IoT] |
	| AUTH_HMAC_MD5_96 | MUST NOT | |		| AUTH_HMAC_MD5_96 | MUST NOT | |
	| AUTH_DES_MAC | MUST NOT | |		| AUTH_DES_MAC | MUST NOT | |
	| AUTH_KPDK_MD5 | MUST NOT | |		| AUTH_KPDK_MD5 | MUST NOT | |
	+------------------------+----------+---------+		+------------------------+----------+---------+
	[IoT] - This requirement is for interoperability with IoT		[IoT] - This requirement is for interoperability with IoT
	Table 4
	AUTH_HMAC_SHA2_256_128 was not mentioned in RFC4307, as no SHA2 based		AUTH_HMAC_SHA2_256_128 was not mentioned in RFC4307, as no SHA2 based
	transforms were mentioned. AUTH_HMAC_SHA2_256_128 MUST be		transforms were mentioned. AUTH_HMAC_SHA2_256_128 MUST be
	implemented in order to replace AUTH_HMAC_SHA1_96.		implemented in order to replace AUTH_HMAC_SHA1_96.
	AUTH_HMAC_SHA2_512_256 SHOULD be implemented as a future replacement		AUTH_HMAC_SHA2_512_256 SHOULD be implemented as a future replacement
	of AUTH_HMAC_SHA2_256_128 or when stronger security is required.		of AUTH_HMAC_SHA2_256_128 or when stronger security is required.
	This value has been preferred over AUTH_HMAC_SHA2_384, as the		This value has been preferred over AUTH_HMAC_SHA2_384, as the
	additional overhead of AUTH_HMAC_SHA2_512 is negligible.		additional overhead of AUTH_HMAC_SHA2_512 is negligible.
	AUTH_HMAC_SHA1_96 has been downgraded from MUST in RFC4307 to MUST-		AUTH_HMAC_SHA1_96 has been downgraded from MUST in RFC4307 to MUST-
	as there is an industry-wide trend to deprecate its usage.		as there is an industry-wide trend to deprecate its usage.
	AUTH_AES-XCBC is only recommended in the scope of IoT, as Internet of		AUTH_AES-XCBC is only recommended in the scope of IoT, as Internet of
	Things deployments tend to prefer AES based pseudo-random functions		Things deployments tend to prefer AES based pseudo-random functions
	in order to avoid implementing SHA2. For the non-IoT VPN deployment,		in order to avoid implementing SHA2. For the non-IoT VPN deployment,
	it has been downgraded from SHOULD in RFC4307 to MAY as it has not		it has been downgraded from SHOULD in RFC4307 to MAY as it has not
	been widely adopted.		been widely adopted.
	AUTH_HMAC_MD5_96, AUTH_DES_MAC and AUTH_KPDK_MD5 were not mentioned		AUTH_DES_MAC, AUTH_HMAC_MD5_96, and AUTH_KPDK_MD5 were not mentioned
	in RFC4307 so its default status was MAY. It has been downgraded to		in RFC4307 so their default status ware MAY. They have been
	MUST NOT. There is an industry-wide trend to deprecate its usage.		downgraded to MUST NOT. There is an industry-wide trend to deprecate
			DES and MD5. MD5 support is being removed from cryptographic
	MD5 support is being removed from cryptographic libraries in general		libraries in general because its non-HMAC use is known to be subject
	because its non-HMAC use is known to be subject to collision attacks,		to collision attacks, for example as mentioned in [TRANSCRIPTION].
	for example as mentioned in [TRANSCRIPTION].
	3.4. Type 4 - IKEv2 Diffie-Hellman Group Transforms		3.4. Type 4 - IKEv2 Diffie-Hellman Group Transforms
	There are several Modular Exponential (MODP) groups and several		There are several Modular Exponential (MODP) groups and several
	Elliptic Curve groups (ECC) that are defined for use in IKEv2. These		Elliptic Curve groups (ECC) that are defined for use in IKEv2. These
	groups are defined in both the [IKEv2] base document and in		groups are defined in both the [IKEv2] base document and in
	extensions documents and are identified by group number. Note that		extensions documents and are identified by group number. Note that
	it is critical to enforce a secure Diffie-Hellman exchange as this		it is critical to enforce a secure Diffie-Hellman exchange as this
	exchange provides keys for the session. If an attacker can retrieve		exchange provides keys for the session. If an attacker can retrieve
	the private numbers (a, or b) and the public values (g**a, and g**b),		the private numbers (a, or b) and the public values (g**a, and g**b),
	then the attacker can compute the secret and the keys used and		then the attacker can compute the secret and the keys used and
	decrypt the exchange and IPsec SA created inside the IKEv2 SA. Such		decrypt the exchange and IPsec SA created inside the IKEv2 SA. Such
	an attack can be performed off-line on a previously recorded		an attack can be performed off-line on a previously recorded
	communication, years after the communication happened. This differs		communication, years after the communication happened. This differs
	from attacks that need to be executed during the authentication which		from attacks that need to be executed during the authentication which
	must be performed online and in near real-time.		must be performed online and in near real-time.
	+------------+----------------------------------------+-------------+		+--------+---------------------------------------------+------------+
	| Number | Description | Status |		| Number | Description | Status |
	+------------+----------------------------------------+-------------+		+--------+---------------------------------------------+------------+
	| 14 | 2048-bit MODP Group | MUST |		| 14 | 2048-bit MODP Group | MUST |
	| 19 | 256-bit random ECP group | SHOULD |		| 19 | 256-bit random ECP group | SHOULD |
	| 5 | 1536-bit MODP Group | SHOULD NOT |		| 5 | 1536-bit MODP Group | SHOULD NOT |
	| 2 | 1024-bit MODP Group | SHOULD NOT |		| 2 | 1024-bit MODP Group | SHOULD NOT |
	| 1 | 768-bit MODP Group | MUST NOT |		| 1 | 768-bit MODP Group | MUST NOT |
	| 22 | 1024-bit MODP Group with 160-bit Prime | SHOULD NOT |		| 22 | 1024-bit MODP Group with 160-bit Prime | SHOULD NOT |
	| | Order Subgroup | |		| | Order Subgroup | |
	| 23 | 2048-bit MODP Group with 224-bit Prime | SHOULD NOT |		| 23 | 2048-bit MODP Group with 224-bit Prime | SHOULD NOT |
	| | Order Subgroup | |		| | Order Subgroup | |
	| 24 | 2048-bit MODP Group with 256-bit Prime | SHOULD NOT |		| 24 | 2048-bit MODP Group with 256-bit Prime | SHOULD NOT |
	| | Order Subgroup | |		| | Order Subgroup | |
	+------------+----------------------------------------+-------------+		+--------+---------------------------------------------+------------+
	Table 5
	Group 14 or 2048-bit MODP Group is raised from SHOULD+ in RFC4307 as		Group 14 or 2048-bit MODP Group is raised from SHOULD+ in RFC4307 as
	a replacement for 1024-bit MODP Group. Group 14 is widely		a replacement for 1024-bit MODP Group. Group 14 is widely
	implemented and considered secure.		implemented and considered secure.
	Group 19 or 256-bit random ECP group was not specified in RFC4307, as		Group 19 or 256-bit random ECP group was not specified in RFC4307, as
	this group were not specified at that time. Group 19 is widely		this group were not specified at that time. Group 19 is widely
	implemented and considered secure.		implemented and considered secure.
	Group 5 or 1536-bit MODP Group has been downgraded from MAY in		Group 5 or 1536-bit MODP Group has been downgraded from MAY in
	skipping to change at page 11, line 4 ¶		skipping to change at page 10, line 39 ¶
	| Number | Description | Status |		| Number | Description | Status |
	+--------+---------------------------------------+------------+		+--------+---------------------------------------+------------+
	| 1 | RSA Digital Signature | MUST |		| 1 | RSA Digital Signature | MUST |
	| 2 | Shared Key Message Integrity Code | MUST |		| 2 | Shared Key Message Integrity Code | MUST |
	| 3 | DSS Digital Signature | SHOULD NOT |		| 3 | DSS Digital Signature | SHOULD NOT |
	| 9 | ECDSA with SHA-256 on the P-256 curve | SHOULD |		| 9 | ECDSA with SHA-256 on the P-256 curve | SHOULD |
	| 10 | ECDSA with SHA-384 on the P-384 curve | SHOULD |		| 10 | ECDSA with SHA-384 on the P-384 curve | SHOULD |
	| 11 | ECDSA with SHA-512 on the P-521 curve | SHOULD |		| 11 | ECDSA with SHA-512 on the P-521 curve | SHOULD |
	| 14 | Digital Signature | SHOULD |		| 14 | Digital Signature | SHOULD |
	+--------+---------------------------------------+------------+		+--------+---------------------------------------+------------+
	Table 6
	RSA Digital Signature is widely deployed and therefore kept for		RSA Digital Signature is widely deployed and therefore kept for
	interoperability. It is expected to be downgraded in the future as		interoperability. It is expected to be downgraded in the future as
	its signatures are based on the older RSASSA-PKCS1-v1.5 which is no		its signatures are based on the older RSASSA-PKCS1-v1.5 which is no
	longer recommended. RSA authentication, as well as other specific		longer recommended. RSA authentication, as well as other specific
	Authentication Methods, are expected to be replaced with the generic		Authentication Methods, are expected to be replaced with the generic
	Digital Signature method of [RFC7427]. RSA Digital Signature is not		Digital Signature method of [RFC7427]. RSA Digital Signature is not
	recommended for keys smaller then 2048, but since these signatures		recommended for keys smaller then 2048, but since these signatures
	only have value in real-time, and need no future protection, smaller		only have value in real-time, and need no future protection, smaller
	keys was kept at SHOULD NOT instead of MUST NOT.		keys was kept at SHOULD NOT instead of MUST NOT.
	skipping to change at page 11, line 42 ¶		skipping to change at page 11, line 28 ¶
	+-------------------------------------------+------------+		+-------------------------------------------+------------+
	| Description | Status |		| Description | Status |
	+-------------------------------------------+------------+		+-------------------------------------------+------------+
	| RSA with key length 2048 | MUST |		| RSA with key length 2048 | MUST |
	| RSA with key length 3072 and 4096 | SHOULD |		| RSA with key length 3072 and 4096 | SHOULD |
	| RSA with key length between 2049 and 4095 | MAY |		| RSA with key length between 2049 and 4095 | MAY |
	| RSA with key length smaller than 2048 | SHOULD NOT |		| RSA with key length smaller than 2048 | SHOULD NOT |
	+-------------------------------------------+------------+		+-------------------------------------------+------------+
	Table 7
	The IKEv2 RFC7296 mandates support for the RSA keys of size 1024 or		The IKEv2 RFC7296 mandates support for the RSA keys of size 1024 or
	2048 bits, but here we make key sizes less than 2048 SHOULD NOT as		2048 bits, but here we make key sizes less than 2048 SHOULD NOT as
	there is industry-wide trend to deprecate key lengths less than 2048		there is industry-wide trend to deprecate key lengths less than 2048
	bits.		bits.
	4.2. Digital Signature Recommendations		4.2. Digital Signature Recommendations
	Recommendations for when a hash function is involved in a signature:		When Digital Signature authentication method is implemented, then the
			following recommendations are applied for hash functions:
	+--------+-------------+------------+---------+		+--------+-------------+------------+---------+
	| Number | Description | Status | Comment |		| Number | Description | Status | Comment |
	+--------+-------------+------------+---------+		+--------+-------------+------------+---------+
	| 1 | SHA1 | SHOULD NOT | |		| 1 | SHA1 | SHOULD NOT | |
	| 2 | SHA2-256 | MUST | |		| 2 | SHA2-256 | MUST | |
	| 3 | SHA2-384 | MAY | |		| 3 | SHA2-384 | MAY | |
	| 4 | SHA2-512 | SHOULD | |		| 4 | SHA2-512 | SHOULD | |
	+--------+-------------+------------+---------+		+--------+-------------+------------+---------+
	Table 8		When Digital Signature authentication method is used with RSA
			signature algorithm, then RSASSA-PSS MUST be supported and RSASSA-
	With the use of Digital Signature, RSASSA-PKCS1-v1.5 MAY be		PKCS1-v1.5 MAY be supported.
	implemented. RSASSA-PSS MUST be implemented.
	Recommendation of Authentication Method described in [RFC7427]		The following table lists recommendations for authentication methods
	notation:		in RFC7427 [RFC7427] notation. These recommendations are applied
			only if Digital Signature authentication method is implemented.
	+------------------------------------+------------+---------+		+------------------------------------+------------+---------+
	| Description | Status | Comment |		| Description | Status | Comment |
	+------------------------------------+------------+---------+		+------------------------------------+------------+---------+
	| RSASSA-PSS with SHA-256 | SHOULD | |		| RSASSA-PSS with SHA-256 | MUST | |
	| ecdsa-with-sha256 | SHOULD | |		| ecdsa-with-sha256 | SHOULD | |
	| sha1WithRSAEncryption | SHOULD NOT | |		| sha1WithRSAEncryption | SHOULD NOT | |
	| dsa-with-sha1 | SHOULD NOT | |		| dsa-with-sha1 | SHOULD NOT | |
	| ecdsa-with-sha1 | SHOULD NOT | |		| ecdsa-with-sha1 | SHOULD NOT | |
	| RSASSA-PSS with Empty Parameters | SHOULD NOT | |		| RSASSA-PSS with Empty Parameters | SHOULD NOT | |
	| RSASSA-PSS with Default Parameters | SHOULD NOT | |		| RSASSA-PSS with Default Parameters | SHOULD NOT | |
	+------------------------------------+------------+---------+		+------------------------------------+------------+---------+
	Table 9
	5. Algorithms for Internet of Things		5. Algorithms for Internet of Things
	Some algorithms in this document are marked for use with the Internet		Some algorithms in this document are marked for use with the Internet
	of Things (IoT). There are several reasons why IoT devices prefer a		of Things (IoT). There are several reasons why IoT devices prefer a
	different set of algorithms from regular IKEv2 clients. IoT devices		different set of algorithms from regular IKEv2 clients. IoT devices
	are usually very constrained, meaning the memory size and CPU power		are usually very constrained, meaning the memory size and CPU power
	is so limited, that these clients only have resources to implement		is so limited, that these clients only have resources to implement
	and run one set of algorithms. For example, instead of implementing		and run one set of algorithms. For example, instead of implementing
	AES and SHA, these devices typically use AES_XCBC as integrity		AES and SHA, these devices typically use AES_XCBC as integrity
	algorithm so SHA does not need to be implemented.		algorithm so SHA does not need to be implemented.
	skipping to change at page 14, line 4 ¶		skipping to change at page 13, line 38 ¶
	algorithms for the use of IKEv2, specifically with the selection of		algorithms for the use of IKEv2, specifically with the selection of
	"mandatory-to-implement" algorithms. The algorithms identified in		"mandatory-to-implement" algorithms. The algorithms identified in
	this document as "MUST implement" or "SHOULD implement" are not known		this document as "MUST implement" or "SHOULD implement" are not known
	to be broken at the current time, and cryptographic research so far		to be broken at the current time, and cryptographic research so far
	leads us to believe that they will likely remain secure into the		leads us to believe that they will likely remain secure into the
	foreseeable future. However, this isn't necessarily forever and it		foreseeable future. However, this isn't necessarily forever and it
	is expected that new revisions of this document will be issued from		is expected that new revisions of this document will be issued from
	time to time to reflect the current best practice in this area.		time to time to reflect the current best practice in this area.
	7. IANA Considerations		7. IANA Considerations
	This document makes no requests of IANA.		This document makes no requests of IANA.
	8. Acknowledgements		8. Acknowledgements
	The first version of this document was RFC 4307 by Jeffrey I.		The first version of this document was RFC 4307 by Jeffrey I.
	Schiller of the Massachusetts Institute of Technology (MIT). Much of		Schiller of the Massachusetts Institute of Technology (MIT). Much of
	the original text has been copied verbatim.		the original text has been copied verbatim.
	We would like to thank Paul Hoffman, Yaron Sheffer, John Mattsson and		We would like to thank Paul Hoffman, Yaron Sheffer, John Mattsson and
	Tommy Pauly for their valuable feedback.		Tommy Pauly for their valuable feedback.
	9. References		9. References
	9.1. Normative References		9.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/		Requirement Levels", BCP 14, RFC 2119,
	RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<http://www.rfc-editor.org/info/rfc2119>.		<http://www.rfc-editor.org/info/rfc2119>.
	[RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode		[RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode
	(GCM) in IPsec Encapsulating Security Payload (ESP)", RFC		(GCM) in IPsec Encapsulating Security Payload (ESP)",
	4106, DOI 10.17487/RFC4106, June 2005,		RFC 4106, DOI 10.17487/RFC4106, June 2005,
	<http://www.rfc-editor.org/info/rfc4106>.		<http://www.rfc-editor.org/info/rfc4106>.
	[RFC4307] Schiller, J., "Cryptographic Algorithms for Use in the		[RFC4307] Schiller, J., "Cryptographic Algorithms for Use in the
	Internet Key Exchange Version 2 (IKEv2)", RFC 4307, DOI		Internet Key Exchange Version 2 (IKEv2)", RFC 4307,
	10.17487/RFC4307, December 2005,		DOI 10.17487/RFC4307, December 2005,
	<http://www.rfc-editor.org/info/rfc4307>.		<http://www.rfc-editor.org/info/rfc4307>.
	[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.		[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
	Kivinen, "Internet Key Exchange Protocol Version 2		Kivinen, "Internet Key Exchange Protocol Version 2
	(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October		(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
	2014, <http://www.rfc-editor.org/info/rfc7296>.		2014, <http://www.rfc-editor.org/info/rfc7296>.
	[RFC5282] Black, D. and D. McGrew, "Using Authenticated Encryption		[RFC5282] Black, D. and D. McGrew, "Using Authenticated Encryption
	Algorithms with the Encrypted Payload of the Internet Key		Algorithms with the Encrypted Payload of the Internet Key
	Exchange version 2 (IKEv2) Protocol", RFC 5282, DOI		Exchange version 2 (IKEv2) Protocol", RFC 5282,
	10.17487/RFC5282, August 2008,		DOI 10.17487/RFC5282, August 2008,
	<http://www.rfc-editor.org/info/rfc5282>.		<http://www.rfc-editor.org/info/rfc5282>.
	9.2. Informative References		9.2. Informative References
	[RFC7427] Kivinen, T. and J. Snyder, "Signature Authentication in		[RFC7427] Kivinen, T. and J. Snyder, "Signature Authentication in
	the Internet Key Exchange Version 2 (IKEv2)", RFC 7427,		the Internet Key Exchange Version 2 (IKEv2)", RFC 7427,
	DOI 10.17487/RFC7427, January 2015,		DOI 10.17487/RFC7427, January 2015,
	<http://www.rfc-editor.org/info/rfc7427>.		<http://www.rfc-editor.org/info/rfc7427>.
	[RFC6989] Sheffer, Y. and S. Fluhrer, "Additional Diffie-Hellman		[RFC6989] Sheffer, Y. and S. Fluhrer, "Additional Diffie-Hellman
	Tests for the Internet Key Exchange Protocol Version 2		Tests for the Internet Key Exchange Protocol Version 2
	(IKEv2)", RFC 6989, DOI 10.17487/RFC6989, July 2013,		(IKEv2)", RFC 6989, DOI 10.17487/RFC6989, July 2013,
	<http://www.rfc-editor.org/info/rfc6989>.		<http://www.rfc-editor.org/info/rfc6989>.
	[RFC7815] Kivinen, T., "Minimal Internet Key Exchange Version 2		[RFC7815] Kivinen, T., "Minimal Internet Key Exchange Version 2
	(IKEv2) Initiator Implementation", RFC 7815, DOI 10.17487/		(IKEv2) Initiator Implementation", RFC 7815,
	RFC7815, March 2016,		DOI 10.17487/RFC7815, March 2016,
	<http://www.rfc-editor.org/info/rfc7815>.		<http://www.rfc-editor.org/info/rfc7815>.
	[IKEV2-IANA]		[IKEV2-IANA]
	, "Internet Key Exchange Version 2 (IKEv2) Parameters", ,		"Internet Key Exchange Version 2 (IKEv2) Parameters",
	<http://www.iana.org/assignments/ikev2-parameters>.		<http://www.iana.org/assignments/ikev2-parameters>.
	[TRANSCRIPTION]		[TRANSCRIPTION]
	Bhargavan, K. and G. Leurent, "Transcript Collision		Bhargavan, K. and G. Leurent, "Transcript Collision
	Attacks: Breaking Authentication in TLS, IKE, and SSH",		Attacks: Breaking Authentication in TLS, IKE, and SSH",
	NDSS , feb 2016.		NDSS , feb 2016.
	[IEEE-802-15-4]		[IEEE-802-15-4]
	, "IEEE Standard for Low-Rate Wireless Personal Area		"IEEE Standard for Low-Rate Wireless Personal Area
	Networks (WPANs)", IEEE Standard 802.15.4, 2015.		Networks (WPANs)", IEEE Standard 802.15.4, 2015.
	[IEEE-802-15-9]		[IEEE-802-15-9]
	, "IEEE Recommended Practice for Transport of Key		"IEEE Recommended Practice for Transport of Key Management
	Management Protocol (KMP) Datagrams", IEEE Standard		Protocol (KMP) Datagrams", IEEE Standard 802.15.9, 2016.
	802.15.9, 2016.
	Authors' Addresses		Authors' Addresses
	Yoav Nir		Yoav Nir
	Check Point Software Technologies Ltd.		Check Point Software Technologies Ltd.
	5 Hasolelim st.		5 Hasolelim st.
	Tel Aviv 6789735		Tel Aviv 6789735
	Israel		Israel
	EMail: ynir.ietf@gmail.com		EMail: ynir.ietf@gmail.com
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