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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 5296 (Obsoleted by RFC 6696) ** Obsolete normative reference: RFC 5226 (ref. 'IANA') (Obsoleted by RFC 8126) == Outdated reference: A later version (-12) exists of draft-ietf-radext-radsec-04 Summary: 3 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group K. Hoeper, Ed. 3 Internet-Draft Motorola 4 Intended status: Standards Track Y. Ohba, Ed. 5 Expires: October 5, 2009 Toshiba 6 April 3, 2009 8 Distribution of EAP based keys for handover and re-authentication 9 draft-ietf-hokey-key-mgm-06 11 Status of this Memo 13 This Internet-Draft is submitted to IETF in full conformance with the 14 provisions of BCP 78 and BCP 79. This document may contain material 15 from IETF Documents or IETF Contributions published or made publicly 16 available before November 10, 2008. The person(s) controlling the 17 copyright in some of this material may not have granted the IETF 18 Trust the right to allow modifications of such material outside the 19 IETF Standards Process. Without obtaining an adequate license from 20 the person(s) controlling the copyright in such materials, this 21 document may not be modified outside the IETF Standards Process, and 22 derivative works of it may not be created outside the IETF Standards 23 Process, except to format it for publication as an RFC or to 24 translate it into languages other than English. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF), its areas, and its working groups. Note that 28 other groups may also distribute working documents as Internet- 29 Drafts. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 The list of current Internet-Drafts can be accessed at 37 http://www.ietf.org/ietf/1id-abstracts.txt. 39 The list of Internet-Draft Shadow Directories can be accessed at 40 http://www.ietf.org/shadow.html. 42 This Internet-Draft will expire on October 5, 2009. 44 Copyright Notice 46 Copyright (c) 2009 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents in effect on the date of 51 publication of this document (http://trustee.ietf.org/license-info). 52 Please review these documents carefully, as they describe your rights 53 and restrictions with respect to this document. 55 Abstract 57 This document describes a mechanism for delivering root keys from an 58 Extensible Authentication Protocol (EAP) server to another network 59 server that requires the keys for offering security protected 60 services, such as re-authentication, to an EAP peer. The distributed 61 root key can be either a usage-specific root key (USRK), a domain- 62 specific root key (DSRK) or a domain-specific usage-specific root key 63 (DSUSRK) that has been derived from an Extended Master Session Key 64 (EMSK) hierarchy previously established between the EAP server and an 65 EAP peer. The document defines a key distribution exchange (KDE) 66 protocol using Remote Authentication Dial In User Service (RADIUS) 67 that can distribute these different types of root keys and discusses 68 its security requirements. 70 Table of Contents 72 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 73 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 74 3. Key Delivery Architecture . . . . . . . . . . . . . . . . . . 5 75 4. Key Distribution Exchange (KDE) . . . . . . . . . . . . . . . 7 76 4.1. Context and Scope for Distributed Keys . . . . . . . . . . 8 77 4.2. Key Distribution Exchange Scenarios . . . . . . . . . . . 8 78 5. RADIUS KDE Attribute . . . . . . . . . . . . . . . . . . . . . 9 79 6. KDE used in the EAP Re-authentication Protocol (ERP) . . . . . 10 80 7. Conflicting Messages . . . . . . . . . . . . . . . . . . . . . 11 81 8. Security Considerations . . . . . . . . . . . . . . . . . . . 11 82 8.1. Requirements on RADIUS Key Transport . . . . . . . . . . . 11 83 8.2. Distributing RK without Peer Consent . . . . . . . . . . . 12 84 9. IANA consideration . . . . . . . . . . . . . . . . . . . . . . 12 85 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 86 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 12 87 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 88 12.1. Normative References . . . . . . . . . . . . . . . . . . . 13 89 12.2. Informative references . . . . . . . . . . . . . . . . . . 13 90 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 92 1. Introduction 94 The Extensible Authentication Protocol (EAP) [RFC3748] is an 95 authentication framework supporting authentication methods that are 96 specified in EAP methods. By definition, any key-generating EAP 97 method derives an Master Session Key (MSK) and an Extended Master 98 Session Key (EMSK). [RFC5295] reserves the EMSK for the sole purpose 99 of deriving root keys that can be used for specific purposes called 100 usages. In particular, [RFC5295] defines how to create a usage- 101 specific root key (USRK) for bootstrapping security in a specific 102 application, a domain-specific root key (DSRK) for bootstrapping 103 security of a set of services within a domain, and a usage-specific 104 DSRK (DSUSRK) for a specific application within a domain. 106 MSK and EMSK may be used to derive further keying material for a 107 variety of security mechanisms [RFC5247]. For example, the MSK has 108 been widely used for bootstrapping the wireless link security 109 associations between the peer and the network attachment points. 110 However, performance as well as security issues arise when using the 111 MSK and the current bootstrapping methods in mobile scenarios that 112 require handovers, as described in [RFC5169]. To address handover 113 latencies and other shortcomings, [RFC5296] specifies an EAP re- 114 authentication protocol (ERP) that uses keys derived from EMSK or 115 DSRK to enable efficient re-authentications in handover scenarios. 116 [RFC5295] and [RFC5296] both do not specify how root keys are 117 delivered to the network server requiring the key. Such a key 118 delivery mechanism is essential because the EMSK cannot leave the EAP 119 server ([RFC5295]) but root keys are needed by other network servers 120 disjoint with the EAP server. For example, in order to enable an EAP 121 peer to re-authenticate to a network during a handover, certain root 122 keys need to be made available by the EAP server to the server 123 carrying out the re-authentication. 125 This document specifies a mechanism for the delivery of EMSK child 126 keys from the server holding the EMSK or a root key to another 127 network server that requests a root key for providing protected 128 services (such as re-authentication and other usage and domain- 129 specific services) to EAP peers. In the remainder of this document, 130 a server delivering root keys is referred to as Key Delivering Server 131 (KDS) and a server authorized to request and receive root keys from a 132 KDS is referred to as Key Requesting Server (KRS). The Key 133 Distribution Exchange (KDE) protocol defined in this document uses 134 RADIUS [RFC2865], [RFC3579] and has several variants depending on the 135 type of key that is requested and delivered (i.e. DRSK, USRK, and 136 DSUSRK). The document also describes security requirements for the 137 secure key delivery over RADIUS. 139 2. Terminology 141 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 142 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 143 document are to be interpreted as described in [RFC2119]. 145 USRK: Usage-Specific Root Key. A root key that is derived from the 146 EMSK, see [RFC5295]. 148 USR-KH: USRK Holder. A network server that is authorized to request 149 and receive a USRK from the EAP server. The USR-KH can be an AAA 150 server or dedicated service server. 152 DSRK: Domain-Specific Root Key. A root key that is derived from the 153 EMSK, see [RFC5295]. 155 DSR-KH: DSRK Holder. A network server that is authorized to request 156 and receive a DSRK from the EAP server. The most likely 157 implementation of a DSR-KH is an AAA server in a domain, enforcing 158 the policies for the usage of the DSRK within this domain. 160 DSUSRK: Domain-Specific Usage-Specific Root Key. A root key that is 161 derived from the DSRK, see [RFC5295]. 163 DSUSR-KH: DSUSRK holder. A network server authorized to request and 164 receive a DSUSRK from the DSR-KH. The most likely implementation 165 of a DSUSR-KH is an AAA server in a domain, responsible for a 166 particular service offered within this domain. 168 RK: Root Key. An EMSK child key, i.e. a USRK, DSRK, or DSUSRK. 170 KDS: Key Delivering Server. A network server that holds an EMSK or 171 DSRK and delivers root keys to KRS requesting root keys. The EAP 172 server and DSR-KH can act as KDS. 174 KRS: Key Requesting Server. A network server that shares an 175 interface with a KDS and is authorized to request root keys from 176 the KDS. USR-KH, DSR-KH, and DSUSR-KH can all act as KRS. 178 3. Key Delivery Architecture 180 An EAP server carries out the EAP authentications with EAP peers but 181 is typically not making any, potentially future, service 182 authorization decisions involving peers. Authorizations as well as 183 the service provisioning are handled by the respective network server 184 offering the requested service. These servers can be AAA servers or 185 other service servers. Whenever EAP-based keying material is used to 186 protect a requested service, a network server needs to request the 187 root key associated with the offered service from the respective KDS. 188 This kind of key requests and distributions are necessary because an 189 EMSK cannot leave the EAP server ([RFC5295]). Hence, any root key 190 that is directly derived from an EMSK must be derived and delivered 191 by the EAP server itself, whereas root keys derived from EMSK child 192 keys, such as a DSUSRK, can be requested from the respective root key 193 holder. Hence, a KDS can be either the EAP server or a DSRK holder 194 (DSR-KH), whereas a KRS can be either a USRK holder (USR-KH), a 195 DSR-KH or a DSUSRK holder (DSUSR-KH). 197 The KRS needs to share an interface with the KDS to be able to send 198 all necessary input data to derive the requested key and to receive 199 the requested key. The provided data includes the Key Derivation 200 Function (KDF) that should be used to derive the requested key. The 201 KRS uses the received root key to derive further keying material in 202 order to secure its offered services. Every KDS is responsible for 203 storing and protecting the received root key as well as the 204 derivation and distribution of any child key derived from the root 205 key. An example of a key delivery architecture is illustrated in 206 Figure 1 showing the different types of KRS and their interfaces to 207 the KDS. 209 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 210 | EAP server | 211 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 212 / | | \ 213 / | | \ 214 / | | \ 215 +-+-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+ +-+-+-+-+-+ 216 | USR-KH1 | | USR-KH2 | | DSR-KH1 | | DSR-KH2 | 217 | HOKEY server| | XYZ server| |Domain 1 | | Domain 2| 218 +-+-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+ +-+-+-+-+-+ 219 / | 220 / | 221 / | 222 +-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ 223 | DSUSR-KH | | DSUSR-KH2 | 224 | Domain 1 | | Domain 2 | 225 |Home domain | |Visited domain | 226 |HOKEY server | |HOKEY server | 227 +-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ 229 Figure 1: Example Key Delivery Architecture for the Different KRS and 230 KDS 232 4. Key Distribution Exchange (KDE) 234 In this section, a generic mechanism for a key distribution exchange 235 (KDE)over RADIUS is described in which a root key (RK) is distributed 236 from a KDS to a KRS. It is required that the communication path 237 between the KDS and the KRS is protected by the use of an appropriate 238 RADIUS transport security mechanism (see Section 8). Here, it is 239 assumed that the KRS and the KDS are separate entities, logically if 240 not physically, and the delivery of the requested RK is specified 241 accordingly. 243 The key distribution exchange consists of one roundtrip, i.e. two 244 messages between the KRS and the KDS, as illustrated in Figure 2. 245 First, the KRS sends a KDE-Request consisting of a RADIUS Access- 246 Request message with a KDE attribute in which the K-flag is cleared. 247 As a response, the KDS sends a KDE-Response consisting of a RADIUS 248 Access-Accept message with a KDE attribute in which the K-flag set. 249 The RADIUS KDE attribute used in this exchange is defined in 250 Section 5. 252 KRS KDS 253 -------- ------- 254 | | 255 | | 256 | KDE-Request (KRT) | 257 | (i.e., RADIUS Access-Request{KDE(K=0)}) | 258 |----------------------------------------->| 259 | KDE-Response(KDT) | 260 | (i.e., RADIUS Access-Accept{KDE(K=1)}) | 261 |<-----------------------------------------| 263 Figure 2: KDE Message Flow 265 KDE-Request: The KRS sends a Key Request Token (KRT) to the KDS. 266 The contents of KRT are detailed below. 268 KDE-Response: As a response, the KDS sends the requested RK to the 269 KRS wrapped inside a token called Key Delivery Token (KDT). The 270 contents of KDT are detailed below. 272 KRT : (PID, KT, KL) 274 KRT carries the identifiers of the peer (PID), the key type (KT) 275 and the key label (KL). See [RFC5295] for the specification of 276 key labels. 278 KDT : (KT, KL, RK, KN_RK, LT_RK) 280 KDT carries the root key (RK) to be distributed to the KRS, as 281 well as the key type (KT), the key label (KL), the key name 282 (KN_RK) and the lifetime of RK (LT_RK). 284 4.1. Context and Scope for Distributed Keys 286 The key lifetime of each distributed key MUST NOT be greater than 287 that of its parent key. 289 The key context of each distributed key is determined by the sequence 290 of KTs in the key hierarchy. When a DSRK is being delivered and the 291 DSRK applies to only a specific set of services, the service types 292 may need to be carried as part of context for the key. Carrying such 293 a specific set of services is outside the scope of this document. 295 The key scope of each distributed key is determined by the sequence 296 of (PID, KT, KL)-tuples in the key hierarchy. The KDF used to 297 generate the requested keys includes context and scope information, 298 thus, binding the key to the specific channel [RFC5295]. 300 4.2. Key Distribution Exchange Scenarios 302 Given the three types of KRS, there are three scenarios for the 303 distribution of EMSK child keys. For all scenarios, the trigger and 304 mechanism for key delivery may involve a specific request from an EAP 305 peer and/or another intermediary (such as an authenticator). For 306 simplicity, it is assumed that USR-KHs reside in the same domain as 307 the EAP server. 309 Scenario 1: EAP server to USR-KH: In this scenario, the EAP server 310 delivers a USRK to a USR-KH. 312 Scenario 2: EAP server to DSR-KH: In this scenario, the EAP server 313 delivers a DSRK to a DSR-KH. 315 Scenario 3: DSR-KH to DSUSR-KH: In this scenario, a DSR-KH in a 316 specific domain delivers keying material to a DSUSR-KH in the same 317 domain. 319 The key distribution exchanges for Scenario 3 can be combined with 320 the key distribution exchanges for Scenario 2 into a single roundtrip 321 exchange as shown in Figure 3. Here, KDE-Request and KDE-Response 322 are messages for Scenarios 2, whereas KDE-Request' and KDE-Response' 323 are messages for Scenarios 3. 325 DSUSR-KH DSR-KH EAP Server 326 -------- ------- ----- 327 | KDE-Request'(KRT') | KDE-Request(KRT) | 328 |------------------------>|-------------------------->| 329 | KDE-Response'(KDT') | KDE-Response(KDT) | 330 |<----------------------- |<--------------------------| 331 | | | 333 Figure 3: Combined Message Exchange 335 5. RADIUS KDE Attribute 337 This section defines the format of the RADIUS KDE attribute. See 338 Section 8 for security requirements on transporting this RADIUS 339 attribute. 341 0 1 2 3 342 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 1 343 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 344 | Type | Length |K| Reserved | Key Type | 345 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 346 | Key Label | 347 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 348 | Key Name (included only when K=1) | 349 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 350 | Key (included only when K=1) | 351 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 352 | Key Lifetime (included only when K=1) | 353 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 355 Type 357 = X (KDE) [X to be assigned by IANA]. 359 Length 361 >4 363 K (Key included) 365 A flag to indicate whether this attribute contains a Key field. 366 This flag is set for a KDE-Response. This flag is cleared for a 367 KDE-Request. 369 Reserved 371 Reserved bits. All reserved bits MUST be set to 0 by the sender 372 and ignored by the recipient. 374 Key Type 376 A field to contain a KT. The following KT values are defined: 0 377 (DSRK), 1 (USRK) and 2 (DSUSRK). 379 Key Label 381 A field to contain a key label (KL). The first octet contains the 382 length of the rest of this field in octets. 384 Key Name 386 A field to contain a KN_RK. The first octet contains the length 387 of the rest of this field in octets. This field is contained if 388 and only if K-flag is set. 390 Key 392 A field to contain a RK. The first octet contains the length of 393 the rest of this field in octets. This field is contained if and 394 only if K-flag is set. 396 Key Lifetime 398 A 4-octet unsigned integer to indicate a LT_RK. This field is 399 contained if and only if K-flag is set. 401 6. KDE used in the EAP Re-authentication Protocol (ERP) 403 This section describes how the presented KDE should be used to 404 request and deliver the root keys used for re-authentication in the 405 EAP Re-authentication Protocol (ERP) defined in [RFC5296]. ERP 406 supports two forms of bootstrapping, implicit as well as explicit 407 bootstrapping, and KDE is discussed for both cases in the remainder 408 of this section. 410 In implicit bootstrapping the local EAP Re-authentication (ER) server 411 requests the DSRK from the home AAA server during the initial EAP 412 exchange. Here, the local ER server acts as the KRS and the home AAA 413 server as the KDS. In this case, the local ER server requesting the 414 DSRK MUST include a KDE attribute with the K-flag cleared in the 415 RADIUS Access-Request message that carries the first EAP-Response 416 message from the peer. A value of the RADIUS User-Name attribute is 417 used as the PID. Upon receiving a valid KDE-Request, the home AAA 418 server includes a KDE attribute with K-flag set in the RADIUS Access- 419 Accept message that carries the EAP-Success message. 421 Explicit bootstrapping is initiated by a peer if it doesn't know the 422 domain. Here, EAP-Initiate and EAP-Finish messages are exchanged 423 between the peer and the home AAA server, with the bootstrapping flag 424 in the EAP-Initiate message set. In this case, the local ER server 425 (acting as KRS) MUST include a KDE attribute with the K-bit cleared 426 in a RADIUS Access-Request message that carries an EAP-Initiate 427 message with the bootstrapping flag turned on. A value of the RADIUS 428 User-Name attribute is used as the PID. In its response, the home 429 AAA server (acting as KDS) MUST include a KDE attribute with K-flag 430 set in a RADIUS Access-Accept message that carries an EAP-Finish 431 message for which the bootstrapping flag is set. 433 7. Conflicting Messages 435 In addition to the rules specified in Section 2.6.3. of [RFC3579], 436 the following combinations SHOULD NOT be sent by a RADIUS Server: 438 Access-Accept/EAP-Message/EAP-Finish with 'R' flag set to 1 439 Access-Reject/EAP-Message/EAP-Finish with 'R' flag set to 0 440 Access-Reject/Keying-Material 441 Access-Reject/KDE 442 Access-Challenge/EAP-Message/EAP-Initiate 443 Access-Challenge/EAP-Message/EAP-Finish 444 Access-Challenge/KDE 446 8. Security Considerations 448 This section provides security requirements and an analysis on 449 transporting EAP keying material using RADIUS. 451 8.1. Requirements on RADIUS Key Transport 453 RADIUS messages that carry a KDE attribute MUST be encrypted, 454 integrity-protected and replay-protected with a security association 455 created by a RADIUS transport protocol such as TLS 456 [I-D.ietf-radext-radsec]. When there is an intermediary such as a 457 RADIUS proxy on the path between the KRS and the KDS, there will be a 458 series of hop-by-hop security associations along the path. The use 459 of hop-by-hop security associations implies that the intermediary on 460 each hop can access the distributed keying material. Hence the use 461 of hop-by-hop security SHOULD be limited to an environment where an 462 intermediary is trusted not to abuse the distributed key material. 464 8.2. Distributing RK without Peer Consent 466 When a KDE-Request message is sent as a result of explicit ERP 467 bootstrapping [RFC5296], cryptographic verification of peer consent 468 on distributing a RK is provided by the integrity checksum of the 469 EAP-Initiate message with the bootstrapping flag turned on. 471 When a KDE-Request message is sent as a result of implicit ERP 472 bootstrapping [RFC5296], cryptographic verification of peer consent 473 on distributing a RK is not provided. As a result, it is possible 474 for a KRS to request a RK from the home server and obtain the RK even 475 if the peer does not support ERP, which can lead to an unintended use 476 of a RK and failed authentication attempts. 478 9. IANA consideration 480 This document defines a new namespace for maintaining Key Type used 481 to identify the type of the root key RK. The range of values 0 - 255 482 are for permanent, standard message types, allocated by IETF Review 483 [IANA]. This document defines the values 0 (DSRK), 1 (USRK) and 2 484 (DSUSRK). 486 This document defines a new RADIUS Attribute Type for KDE in 487 Section 5. 489 10. Acknowledgements 491 The author would like to thank Dan Harkins, Chunqiang Li, Rafael 492 Marin Lopez and Charles Clancy for their valuable comments. 494 11. Contributors 496 The following people contributed to this document. 498 Madjid Nakhjiri (madjid.nakhjiri@motorola.com) 500 Kedar Gaonkar (kgaonkar3@gatech.edu) 502 Lakshminath Dondeti (ldondeti@qualcomm.com) 504 Vidya Narayanan (vidyan@qualcomm.com) 506 Glen Zorn (glenzorn@comcast.net) 508 12. References 510 12.1. Normative References 512 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 513 Requirement Levels", BCP 14, RFC 2119, March 1997. 515 [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, 516 "Remote Authentication Dial In User Service (RADIUS)", 517 RFC 2865, June 2000. 519 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 520 Levkowetz, "Extensible Authentication Protocol (EAP)", 521 RFC 3748, June 2004. 523 [RFC5295] Salowey, J., Dondeti, L., Narayanan, V., and M. Nakhjiri, 524 "Specification for the Derivation of Root Keys from an 525 Extended Master Session Key (EMSK)", RFC 5295, 526 August 2008. 528 [RFC5296] Narayanan, V. and L. Dondeti, "EAP Extensions for EAP Re- 529 authentication Protocol (ERP)", RFC 5296, August 2008. 531 [IANA] Narten, T. and H. Alvestrand, "Guidelines for Writing an 532 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 533 May 2008. 535 12.2. Informative references 537 [RFC3579] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication 538 Dial In User Service) Support For Extensible 539 Authentication Protocol (EAP)", RFC 3579, September 2003. 541 [RFC5247] Aboba, B., Simon, D., and P. Eronen, "Extensible 542 Authentication Protocol (EAP) Key Management Framework", 543 RFC 5247, August 2008. 545 [RFC5169] Clancy, T., Nakhjiri, M., Narayanan, V., and L. Dondeti, 546 "Handover Key Management and Re-Authentication Problem 547 Statement", RFC 5169, March 2008. 549 [I-D.ietf-radext-radsec] 550 Winter, S., McCauley, M., Venaas, S., and K. Wierenga, 551 "TLS encryption for RADIUS over TCP (RadSec)", 552 draft-ietf-radext-radsec-04 (work in progress), 553 March 2009. 555 Authors' Addresses 557 Katrin Hoeper (editor) 558 Motorola 559 1301 E Algonquin Road 560 Schaumburg, IL 60196 561 USA 563 Phone: +1 847 576 4714 564 Email: khoeper@motorola.com 566 Yoshihiro Ohba (editor) 567 Toshiba America Research, Inc. 568 1 Telcordia Drive 569 Piscataway, NJ 08854 570 USA 572 Phone: +1 732 699 5305 573 Email: yohba@tari.toshiba.com