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If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (March 10, 2011) is 4090 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Looks like a reference, but probably isn't: '12' on line 330 ** Obsolete normative reference: RFC 5246 (ref. 'TLS') (Obsoleted by RFC 8446) ** Obsolete normative reference: RFC 4366 (ref. 'TLS-EXT') (Obsoleted by RFC 5246, RFC 6066) -- Obsolete informational reference (is this intentional?): RFC 3588 (ref. 'Diameter') (Obsoleted by RFC 6733) -- Obsolete informational reference (is this intentional?): RFC 5996 (Obsoleted by RFC 7296) Summary: 2 errors (**), 0 flaws (~~), 1 warning (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 TLS Working Group Y. Nir 3 Internet-Draft Check Point 4 Intended status: Standards Track Y. Sheffer 5 Expires: September 11, 2011 Independent 6 H. Tschofenig 7 NSN 8 P. Gutmann 9 University of Auckland 10 March 10, 2011 12 TLS using EAP Authentication 13 draft-nir-tls-eap-11 15 Abstract 17 This document describes an extension to the TLS protocol to allow TLS 18 clients to authenticate with non-certificate credentials using the 19 Extensible Authentication Protocol (EAP). 21 This work follows the example of IKEv2, where EAP has been added to 22 the protocol to allow clients to use different credentials such as 23 passwords, token cards, and shared secrets. 25 Status of this Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on September 11, 2011. 42 Copyright Notice 44 Copyright (c) 2011 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 1.1. EAP Applicability . . . . . . . . . . . . . . . . . . . . 4 61 1.2. Comparison with Design Alternatives . . . . . . . . . . . 4 62 1.3. Conventions Used in This Document . . . . . . . . . . . . 4 63 2. Operating Environment . . . . . . . . . . . . . . . . . . . . 5 64 3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 6 65 3.1. The tee_supported Extension . . . . . . . . . . . . . . . 7 66 3.2. The InterimAuth Handshake Message . . . . . . . . . . . . 7 67 3.3. The EapMsg Handshake Message . . . . . . . . . . . . . . . 8 68 3.4. Calculating the Finished message . . . . . . . . . . . . . 8 69 4. Security Considerations . . . . . . . . . . . . . . . . . . . 10 70 4.1. InterimAuth vs. Finished . . . . . . . . . . . . . . . . . 10 71 4.2. Identity Protection . . . . . . . . . . . . . . . . . . . 10 72 4.3. Mutual Authentication . . . . . . . . . . . . . . . . . . 11 73 5. Performance Considerations . . . . . . . . . . . . . . . . . . 12 74 6. Operational Considerations . . . . . . . . . . . . . . . . . . 13 75 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 76 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 77 9. Changes from Previous Versions . . . . . . . . . . . . . . . . 16 78 9.1. Changes in version -02 . . . . . . . . . . . . . . . . . . 16 79 9.2. Changes in version -01 . . . . . . . . . . . . . . . . . . 16 80 9.3. Changes from the protocol model draft . . . . . . . . . . 16 81 10. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 17 82 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 83 11.1. Normative References . . . . . . . . . . . . . . . . . . . 18 84 11.2. Informative References . . . . . . . . . . . . . . . . . . 18 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20 87 1. Introduction 89 This document describes a new extension to [TLS]. This extension 90 allows a TLS client to authenticate using [EAP] instead of performing 91 the authentication at the application level. The extension follows 92 [TLS-EXT]. For the remainder of this document we will refer to this 93 extension as TEE (TLS with EAP Extension). 95 TEE extends the TLS handshake beyond the regular setup, to allow the 96 EAP protocol to run between the TLS server (called an "authenticator" 97 in EAP) and the TLS client (called either a "supplicant" or a 98 "peer"). This allows the TLS architecture to handle client 99 authentication before exposing the server application software to an 100 unauthenticated client. In doing this, we follow the approach taken 101 for IKEv2 in [RFC5996]. However, similar to regular TLS, we protect 102 the user identity by only sending the client identity after the 103 server has authenticated. In this our solution differs from that of 104 IKEv2. 106 Currently used applications that rely on non-certificate user 107 credentials use TLS to authenticate the server only. After that, the 108 application takes over, and presents a login screen where the user is 109 expected to present their credentials. 111 This creates several problems. It allows a client to access the 112 application before authentication, thus creating a potential for 113 anonymous attacks on non-hardened applications. Additionally, web 114 pages are not particularly well suited for long shared secrets and 115 for interfacing with certain devices such as USB tokens. 117 TEE allows full mutual authentication to occur for all these 118 applications within the TLS exchange. The application receives 119 control only when the user is identified and authenticated. The 120 authentication can be built into the server infrastructure by 121 connecting to an AAA server. The client side can be integrated into 122 client software such as web browsers and mail clients. An EAP 123 infrastructure is already built into some operating systems providing 124 a user interface for each authentication method within EAP. 126 We intend TEE to be used for various protocols that use TLS such as 127 HTTPS, in cases where certificate based client authentication is not 128 practical. This includes web-based mail services, online banking, 129 premium content websites and mail clients. 131 Another class of applications that may see benefit from TEE are TLS 132 based VPN clients used as part of so-called "SSL VPN" products. No 133 such client protocols have so far been standardized. 135 1.1. EAP Applicability 137 Section 1.3 of [EAP] states that EAP is only applicable for network 138 access authentication, rather than for "bulk data transfer". It then 139 goes on to explain why the transport properties of EAP indeed make it 140 unsuitable for bulk data transfer, e.g. for large file transport. 141 Our proposed use of EAP falls squarely within the applicability as 142 defined, since we make no further use of EAP beyond access 143 authentication. 145 1.2. Comparison with Design Alternatives 147 It has been suggested to implement EAP authentication as part of the 148 protected application, rather than as part of the TLS handshake. A 149 BCP document could be used to describe a secure way of doing this. 150 The drawbacks we see in such an approach are listed below: 151 o EAP does not have a pre-defined transport method. Application 152 designers would need to specify an EAP transport for each 153 application. Making this a part of TLS has the benefit of a 154 single specification for all protected applications. 155 o The integration of EAP and TLS is security-sensitive and should be 156 standardized and interoperable. We do not believe that it should 157 be left to application designers to do this in a secure manner. 158 Specifically on the server-side, integration with AAA servers adds 159 complexity and is more naturally part of the underlying 160 infrastrcture. 161 o Our current proposal provides channel binding between TLS and EAP, 162 to counter the MITM attacks described in [MITM]. TLS does not 163 provide any standard way of extracting cryptographic material from 164 the TLS state, and in most implementations, the TLS state is not 165 exposed to the protected application. Because of this, it is 166 difficult for application designers to bind the user 167 authentication to the protected channel provided by TLS. 169 1.3. Conventions Used in This Document 171 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 172 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 173 document are to be interpreted as described in [RFC2119]. 175 2. Operating Environment 177 TEE will work between a client application and a server application, 178 performing either client authentication or mutual authentication 179 within the TLS exchange. 181 Client Server 182 +-------------------------+ +------------------------+ 183 | |GUI| | Client | |TLS+-+-----+-+TLS| |Server | | 184 | +-^-+ |Software| +-^-+ | +-+-^-+ |Application | | 185 | | +--------+ | | | | |Software | | 186 | | | | | | +------------+ | 187 | +-v----------------v-+ | | | | 188 | | EAP | | +---|--------------------+ 189 | | Infrastructure | | | 190 | +--------------------+ | | +--------+ 191 +-------------------------+ | | AAA | 192 | | Server | 193 +----- | 194 +--------+ 196 The above diagram shows the typical deployment. The client has 197 software that either includes a UI for some EAP methods, or else is 198 able to invoke some operating system EAP infrastructure that takes 199 care of the user interaction. The server is configured with the 200 address and protocol of the AAA server. Typically the AAA server 201 communicates using the RADIUS protocol with EAP ([RADIUS] and 202 [RAD-EAP]), or the Diameter protocol ([Diameter] and [Dia-EAP]). 204 As stated in the introduction, we expect TEE to be used in both 205 browsers and applications. Further uses may be authentication and 206 key generation for other protocols, and tunneling clients, which so 207 far have not been standardized. 209 3. Protocol Overview 211 When TLS is used with EAP, additional records are sent after the 212 ChangeCipherSpec protocol message and before the Finished message, 213 effectively creating an extended handshake before the application 214 layer data can be sent. Each EapMsg handshake record contains 215 exactly one EAP message. Using EAP for client authentication allows 216 TLS to be used with various AAA back-end servers such as RADIUS or 217 Diameter. 219 TLS with EAP may be used for securing a data connection such as HTTP 220 or POP3. We believe it has three main benefits: 221 o The ability of EAP to work with backend servers can remove that 222 burden from the application layer. 223 o Moving the user authentication into the TLS handshake protects the 224 presumably less secure application layer from attacks by 225 unauthenticated parties. 226 o Using mutual authentication methods within EAP can help thwart 227 certain classes of phishing attacks. 229 The TEE extension defines the following: 230 o A new extension type called tee_supported, used to indicate that 231 the communicating application (either client or server) supports 232 this extension. 233 o A new message type for the handshake protocol, called InterimAuth, 234 which is used to sign previous messages. 235 o A new message type for the handshake protocol, called EapMsg, 236 which is used to carry a single EAP message. 238 The diagram below outlines the protocol structure. For illustration 239 purposes only, we use the GPSK EAP method [RFC5433]. 241 Client Server 242 ------ ------ 244 ClientHello(*) --------> 245 ServerHello(*) 246 (Certificate) 247 ServerKeyExchange 248 EapMsg(Identity-Request) 249 <-------- ServerHelloDone 250 ClientKeyExchange 251 (CertificateVerify) 252 ChangeCipherSpec 253 InterimAuth 254 EapMsg(Identity-Reply) --------> 255 ChangeCipherSpec 256 InterimAuth 257 EapMsg(GPSK-Request) 258 <-------- 259 EapMsg(GPSK-Reply) --------> 260 EapMsg(GPSK-Request) 261 <-------- 262 EapMsg(GPSK-Reply) --------> 263 EapMsg(Success) 264 <-------- Finished 265 Finished --------> 267 (*) The ClientHello and ServerHello include the tee_supported 268 extension to indicate support for TEE 270 The client indicates in the first message its support for TEE. The 271 server sends an EAP identity request in the reply. The client sends 272 the identity reply after the handshake completion. The EAP request- 273 response sequence continues until the client is either authenticated 274 or rejected. 276 3.1. The tee_supported Extension 278 The tee_supported extension is a ClientHello and ServerHello 279 extension as defined in section 2.3 of [TLS-EXT]. The extension_type 280 field is TBA by IANA. The extension_data is zero-length. 282 3.2. The InterimAuth Handshake Message 284 The InterimAuth message is identical in syntax to the Finished 285 message described in section 7.4.9 of [TLS]. It is calculated in 286 exactly the same way. 288 The semantics, however, are somewhat different. The "Finished" 289 message indicates that application data may now be sent. The 290 "InterimAuth" message does not indicate this. Instead, further 291 handshake messages are needed. 293 The HandshakeType value for the InterimAuth handshake message is TBA 294 by IANA. 296 3.3. The EapMsg Handshake Message 298 The EapMsg handshake message carries exactly one EAP message as 299 defined in [EAP]. 301 The HandshakeType value for the EapMsg handshake message is TBA by 302 IANA. 304 The EapMsg message is used to tunnel EAP messages between the 305 authentication server, which may be co-located with the TLS server, 306 or else may be a separate AAA server, and the supplicant, which is 307 co-located with the TLS client. TLS on either side receives the EAP 308 data from the EAP infrastructure, and treats it as opaque. TLS does 309 not make any changes to the EAP payload or make any decisions based 310 on the contents of an EapMsg handshake message. 312 Note that it is expected that the authentication server notifies the 313 TLS server about authentication success or failure, and so TLS need 314 not inspect the eap_payload within the EapMsg to detect success or 315 failure. 317 struct { 318 opaque eap_payload[4..65535]; 319 } EapMsg; 321 eap_payload is defined in section 4 of RFC 3748. It includes the 322 Code, Identifier, Length and Data fields of the EAP packet. 324 3.4. Calculating the Finished message 326 If the EAP method is key-generating (see [RFC5247]), the Finished 327 message is calculated as follows: 329 struct { 330 opaque verify_data[12]; 331 } Finished; 333 verify_data 334 PRF(MSK, finished_label, MD5(handshake_messages) + 335 SHA-1(handshake_messages)) [0..11]; 337 The finished_label and the PRF are as defined in section 7.4.9 of 338 [TLS]. 340 The handshake_messages field, unlike regular TLS, does not sign all 341 the data in the handshake. Instead it signs all the data that has 342 not been signed by the previous InterimAuth message. The 343 handshake_messages field includes all of the octets beginning with 344 and including the InterimAuth message, up to but not including this 345 Finished message. This is the concatenation of all the Handshake 346 structures exchanged thus far, and not yet signed, as defined in 347 section 7.4 of [TLS]and in this document. 349 The Master Session Key (MSK) is derived by the AAA server and by the 350 client if the EAP method is key-generating. On the server-side, it 351 is typically received from the AAA server over the RADIUS or Diameter 352 protocol. On the client-side, it is passed to TLS by some other 353 method. 355 If the EAP method is not key-generating, then the master_secret is 356 used to sign the messages instead of the MSK. For a discussion on 357 the use of such methods, see Section 4.1. 359 4. Security Considerations 361 4.1. InterimAuth vs. Finished 363 In regular TLS, the Finished message provides two functions: it signs 364 all preceding messages, and it signals that application data can now 365 be sent. In TEE, it only signs those messages that have not yet been 366 signed. 368 Some EAP methods, such as EAP-TLS, EAP-IKEv2 and EAP-SIM generate 369 keys in addition to authenticating clients. Such methods are said to 370 be resistant to man-in-the-middle (MITM) attacks as discussed in 371 [MITM]. Such methods are called key-generating methods. 373 To realize the benefit of such methods, we need to verify the key 374 that was generated within the EAP method. This is referred to as the 375 MSK in EAP. In TEE, the InterimAuth message signs all previous 376 messages with the master_secret, just like the Finished message in 377 regular TLS. The Finished message signs the rest of the messages 378 using the MSK if such exists. If not, then the messages are signed 379 with the master_secret as in regular TLS. 381 The need for signing twice arises from the fact that we need to use 382 both the master_secret and the MSK. It was possible to use just one 383 Finished record and blend the MSK into the master_secret. However, 384 this would needlessly complicate the protocol and make security 385 analysis more difficult. Instead, we have decided to follow the 386 example of IKEv2, where two AUTH payloads are exchanged. 388 It should be noted that using non-key-generating methods may expose 389 the client to a MITM attack if the same method and credentials are 390 used in some other situation, in which the EAP is done outside of a 391 protected tunnel with an authenticated server. Unless it can be 392 determined that the EAP method is never used in such a situation, 393 non-key-generating methods SHOULD NOT be used. This issue is 394 discussed extensively in [Compound-Authentication]. 396 4.2. Identity Protection 398 Unlike [TLS-PSK], TEE provides identity protection for the client. 399 The client's identity is hidden from a passive eavesdropper using TLS 400 encryption. Active attacks are discussed in Section 4.3. 402 We could save one round-trip by having the client send its identity 403 within the Client Hello message. This is similar to TLS-PSK. 404 However, we believe that identity protection is a worthy enough goal, 405 so as to justify the extra round-trip. 407 4.3. Mutual Authentication 409 In order to achieve our security goals, we need to have both the 410 server and the client authenticate. Client authentication is 411 obviously done using the EAP method. The server authentication can 412 be done in either of two ways: 413 1. The client can verify the server certificate. This may work well 414 depending on the scenario, but implies that the client or its 415 user can recognize the right DN or alternate name, and 416 distinguish it from plausible alternatives. The introduction to 417 [I.D.Webauth-phishing] shows that at least in HTTPS, this is not 418 always the case. 419 2. The client can use a mutually authenticated (MA) EAP method such 420 as GPSK. In this case, server certificate verification does not 421 matter, and the TLS handshake may as well be anonymous. Note 422 that in this case, the client identity is sent to the server 423 before server authentication. 425 To summarize: 426 o Clients MUST NOT propose anonymous ciphersuites, unless they 427 support MA EAP methods. 428 o Clients MUST NOT accept non-MA methods if the ciphersuite is 429 anonymous. 430 o Clients MUST NOT accept non-MA methods if they are not able to 431 verify the server credentials. Note that this document does not 432 define what verification involves. If the server DN is known and 433 stored on the client, verifying certificate signature and checking 434 revocation may be enough. For web browsers, the case is not as 435 clear cut, and MA methods SHOULD be used. 437 5. Performance Considerations 439 Regular TLS adds two round-trips to a TCP connection. However, 440 because of the stream nature of TCP, the client does not really need 441 to wait for the server's Finished message, and can begin sending 442 application data immediately after its own Finished message. In 443 practice, many clients do so, and TLS only adds one round-trip of 444 delay. 446 TEE adds as many round-trips as the EAP method requires. For 447 example, EAP-MD5 requires 1 round-trip, while EAP-GPSK requires 2 448 round-trips. Additionally, the client MUST wait for the EAP-Success 449 message before sending its own Finished message, so we need at least 450 3 round-trips for the entire handshake. The best a client can do is 451 two round-trips plus however many round-trips the EAP method 452 requires. 454 It should be noted, though, that these extra round-trips save 455 processing time at the application level. Two extra round-trips take 456 a lot less time than presenting a log-in web page and processing the 457 user's input. 459 It should also be noted, that TEE reverses the order of the Finished 460 messages. In regular TLS the client sends the Finished message 461 first. In TEE it is the server that sends the Finished message 462 first. This should not affect performance, and it is clear that the 463 client may send application data immediately after the Finished 464 message. 466 6. Operational Considerations 468 Section 4.3 defines a dependency between the TLS state and the EAP 469 state in that it mandates that certain EAP methods should not be used 470 with certain TLS ciphersuites. To avoid such dependencies, there are 471 two approaches that implementations can take. They can either not 472 use any anonymous ciphersuites, or else they can use only MA EAP 473 methods. 475 Where certificate validation is problematic, such as in browser-based 476 HTTPS, we recommend the latter approach. 478 In cases where the use of EAP within TLS is not known before opening 479 the connection, it is necessary to consider the implications of 480 requiring the user to type in credentials after the connection has 481 already started. TCP sessions may time out, because of security 482 considerations, and this may lead to session setup failure. 484 7. IANA Considerations 486 IANA is asked to assign an extension type value from the 487 "ExtensionType Values" registry for the tee_supported extension. 489 IANA is asked to assign two handshake message types from the "TLS 490 HandshakeType Registry", one for "EapMsg" and one for "InterimAuth". 492 8. Acknowledgments 494 The authors would like to thank Josh Howlett for his comments. 496 The TLS Inner Application Extension work ([TLS/IA]) has inspired the 497 authors to create this simplified work. TLS/IA provides a somewhat 498 different approach to integrating non-certificate credentials into 499 the TLS protocol, in addition to several other features available 500 from the RADIUS namespace. 502 The authors would also like to thank the various contributors to 503 [RFC5996] whose work inspired this one. 505 9. Changes from Previous Versions 507 9.1. Changes in version -02 509 o Added discussion of alternative designs. 511 9.2. Changes in version -01 513 o Changed the construction of the Finished message 514 o Replaced MS-CHAPv2 with GPSK in examples. 515 o Added open issues section. 516 o Added reference to [Compound-Authentication] 517 o Fixed reference to MITM attack 519 9.3. Changes from the protocol model draft 521 o Added diagram for EapMsg 522 o Added discussion of EAP applicability 523 o Added discussion of mutually-authenticated EAP methods vs other 524 methods in the security considerations. 525 o Added operational considerations. 526 o Other minor nits. 528 10. Open Issues 530 Some have suggested that since the protocol is identical to regular 531 TLS up to the InterimAuth message, we should call that the Finished 532 message, and call the last message in the extended handshake 533 something like "EapFinished". This has the advantage that the 534 construction of Finished is already well defined and will not change. 535 However, the Finished message has a specific meaning as indicated by 536 its name. It means that the handshake is over and that application 537 data can now be sent. This is not true of what is in this draft 538 called InterimAuth. We'd like the opinions of reviewrs about this 539 issue. 541 The MSK from the EAP exchange is only used to sign the Finished 542 message. It is not used again in the data encryption. In this we 543 followed the example of IKEv2. The reason is that TLS already has 544 perfectly good ways of exchanging keys, and we do not need this 545 capability from EAP methods. Also, using the MSK in keys would 546 require an additional ChangeCipherSpec and would complicate the 547 protocol. We'd like the opinions of reviewrs about this issue. 549 Another response we got was that we should have a MUST requirement 550 that only mutually authenticated and key-generating methods be used 551 in TEE. This would simplify the security considerations section. 552 While we agree that this is a good idea, most EAP methods in common 553 use are not compliant. Additionally, such requirements assume that 554 EAP packets are visible to a passive attacker. As EAP is used in 555 protected tunnels such as in L2TP, in IKEv2 and here, this assumption 556 may not be required. If we consider the server authenticated by its 557 certificate, it may be acceptable to use a non-MA method. 559 It has been suggested that identity protection is not important 560 enough to add a roundtrip, and so we should have the client send the 561 username in the ClientHello. We are not sure about how others feel 562 about this, and would like to solicit the reviewers opinion. Note 563 that if this is done, the client sends the user name before ever 564 receiving any indication that the server actually supports TEE. This 565 might be acceptable in an email client, where the server is 566 preconfigured, but it may be unacceptable in other uses, such as web 567 browsers. 569 11. References 571 11.1. Normative References 573 [EAP] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 574 Levkowetz, "Extensible Authentication Protocol (EAP)", 575 RFC 3748, June 2004. 577 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 578 Requirement Levels", BCP 14, RFC 2119, March 1997. 580 [TLS] Dierks, T. and E. Rescorla, "The Transport Layer Security 581 (TLS) Protocol Version 1.2", RFC 5246, August 2008. 583 [TLS-EXT] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., 584 and T. Wright, "Transport Layer Security (TLS) 585 Extensions", RFC 4366, April 2006. 587 11.2. Informative References 589 [Compound-Authentication] 590 Puthenkulam, J., Lortz, V., Palekar, A., and D. Simon, 591 "The Compound Authentication Binding Problem", 592 draft-puthenkulam-eap-binding-04 (work in progress), 593 October 2003. 595 [Dia-EAP] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible 596 Authentication Protocol (EAP) Application", RFC 4072, 597 August 2005. 599 [Diameter] 600 Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. 601 Arkko, "Diameter Base Protocol", RFC 3588, September 2003. 603 [I.D.Webauth-phishing] 604 Hartman, S., "Requirements for Web Authentication 605 Resistant to Phishing", draft-hartman-webauth-phishing-09 606 (work in progress), August 2008. 608 [MITM] Asokan, N., Niemi, V., and K. Nyberg, "Man-in-the-Middle 609 in Tunneled Authentication Protocols", IACR ePrint 610 Archive , October 2002. 612 [RAD-EAP] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication 613 Dial In User Service) Support For Extensible 614 Authentication Protocol (EAP)", RFC 3579, September 2003. 616 [RADIUS] Rigney, C., Willens, S., Rubens, A., and W. Simpson, 617 "Remote Authentication Dial In User Service (RADIUS)", 618 RFC 2865, June 2000. 620 [RFC5247] Aboba, B., Simon, D., and P. Eronen, "Extensible 621 Authentication Protocol (EAP) Key Management Framework", 622 RFC 5247, August 2008. 624 [RFC5433] Clancy, T. and H. Tschofenig, "EAP Generalized Pre-Shared 625 Key (EAP-GPSK)", RFC 5433, February 2009. 627 [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, 628 "Internet Key Exchange Protocol: IKEv2", RFC 5996, 629 September 2010. 631 [TLS-PSK] Eronen, P. and H. Tschofenig, "Pre-Shared Key Ciphersuites 632 for Transport Layer Security (TLS)", RFC 4279, 633 December 2005. 635 [TLS/IA] Funk, P., Blake-Wilson, S., Smith, H., Tschofenig, N., and 636 T. Hardjono, "TLS Inner Application Extension (TLS/IA)", 637 draft-funk-tls-inner-application-extension-03 (work in 638 progress), June 2006. 640 Authors' Addresses 642 Yoav Nir 643 Check Point Software Technologies Ltd. 644 5 Hasolelim st. 645 Tel Aviv 67897 646 Israel 648 Email: ynir@checkpoint.com 650 Yaron Sheffer 651 Independent 653 Email: yaronf.ietf@gmail.com 655 Hannes Tschofenig 656 Nokia Siemens Networks 657 Linnoitustie 6 658 Espoo 02600 659 Finland 661 Phone: +358 (50) 4871445 662 Email: Hannes.Tschofenig@gmx.net 663 URI: http://www.tschofenig.priv.at 665 Peter Gutmann 666 University of Auckland 667 Department of Computer Science 668 New Zealand 670 Email: pgut001@cs.auckland.ac.nz