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4 TLS Working Group J. Salowey\r
5 Internet-Draft A. Choudhury\r
6 Intended status: Standards Track D. McGrew\r
7 Expires: October 16, 2008 Cisco Systems, Inc.\r
8 April 14, 2008\r
9 \r
10 \r
11 AES-GCM Cipher Suites for TLS\r
12 draft-ietf-tls-rsa-aes-gcm-03\r
13 \r
14 Status of this Memo\r
15 \r
16 By submitting this Internet-Draft, each author represents that any\r
17 applicable patent or other IPR claims of which he or she is aware\r
18 have been or will be disclosed, and any of which he or she becomes\r
19 aware will be disclosed, in accordance with Section 6 of BCP 79.\r
20 \r
21 Internet-Drafts are working documents of the Internet Engineering\r
22 Task Force (IETF), its areas, and its working groups. Note that\r
23 other groups may also distribute working documents as Internet-\r
24 Drafts.\r
25 \r
26 Internet-Drafts are draft documents valid for a maximum of six months\r
27 and may be updated, replaced, or obsoleted by other documents at any\r
28 time. It is inappropriate to use Internet-Drafts as reference\r
29 material or to cite them other than as "work in progress."\r
30 \r
31 The list of current Internet-Drafts can be accessed at\r
32 http://www.ietf.org/ietf/1id-abstracts.txt.\r
33 \r
34 The list of Internet-Draft Shadow Directories can be accessed at\r
35 http://www.ietf.org/shadow.html.\r
36 \r
37 This Internet-Draft will expire on October 16, 2008.\r
38 \r
39 Copyright Notice\r
40 \r
41 Copyright (C) The IETF Trust (2008).\r
42 \r
43 Abstract\r
44 \r
45 This memo describes the use of the Advanced Encryption Standard (AES)\r
46 in Galois/Counter Mode (GCM) as a Transport Layer Security (TLS)\r
47 authenticated encryption operation. GCM provides both\r
48 confidentiality and data origin authentication, can be efficiently\r
49 implemented in hardware for speeds of 10 gigabits per second and\r
50 above, and is also well-suited to software implementations. This\r
51 memo defines TLS cipher suites that use AES-GCM with RSA, DSS and\r
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53 \r
54 \r
55 Salowey, et al. Expires October 16, 2008 [Page 1]\r
57 Internet-Draft AES-GCM Cipher suites April 2008\r
58 \r
59 \r
60 Diffie-Hellman based key exchange mechanisms.\r
61 \r
62 \r
63 Table of Contents\r
64 \r
65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3\r
66 \r
67 2. Conventions Used In This Document . . . . . . . . . . . . . . . 3\r
68 \r
69 3. AES-GCM Cipher Suites . . . . . . . . . . . . . . . . . . . . . 3\r
70 \r
71 4. TLS Versions . . . . . . . . . . . . . . . . . . . . . . . . . 4\r
72 \r
73 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5\r
74 \r
75 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5\r
76 6.1. Counter Reuse . . . . . . . . . . . . . . . . . . . . . . . 5\r
77 6.2. Recommendations for Multiple Encryption Processors . . . . 5\r
78 \r
79 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6\r
80 \r
81 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7\r
82 8.1. Normative References . . . . . . . . . . . . . . . . . . . 7\r
83 8.2. Informative References . . . . . . . . . . . . . . . . . . 7\r
84 \r
85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7\r
86 Intellectual Property and Copyright Statements . . . . . . . . . . 9\r
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111 Salowey, et al. Expires October 16, 2008 [Page 2]\r
113 Internet-Draft AES-GCM Cipher suites April 2008\r
114 \r
115 \r
116 1. Introduction\r
117 \r
118 This document describes the use of AES [AES] in Galois Counter Mode\r
119 (GCM) [GCM] (AES-GCM) with various key exchange mechanisms as a\r
120 cipher suite for TLS. AES-GCM is an authenticated encryption with\r
121 associated data (AEAD) cipher (as defined in TLS 1.2\r
122 [I-D.ietf-tls-rfc4346-bis]) providing both confidentiality and data\r
123 origin authentication. The following sections define cipher suites\r
124 based on RSA, DSS and Diffie-Hellman key exchanges; ECC based cipher\r
125 suites are defined in a separate document [I-D.ietf-tls-ecc-new-mac].\r
126 \r
127 AES-GCM is not only efficient and secure, but hardware\r
128 implementations can achieve high speeds with low cost and low\r
129 latency, because the mode can be pipelined. Applications that\r
130 require high data throughput can benefit from these high-speed\r
131 implementations. AES-GCM has been specified as a mode that can be\r
132 used with IPsec ESP [RFC4106] and 802.1AE MAC Security [IEEE8021AE].\r
133 \r
134 \r
135 2. Conventions Used In This Document\r
136 \r
137 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",\r
138 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this\r
139 document are to be interpreted as described in [RFC2119].\r
140 \r
141 \r
142 3. AES-GCM Cipher Suites\r
143 \r
144 The following cipher suites use the new authenticated encryption\r
145 modes defined in TLS 1.2 with AES in Galois Counter Mode (GCM) [GCM]:\r
146 \r
147 CipherSuite TLS_RSA_WITH_AES_128_GCM_SHA256 = {TBD,TBD}\r
148 CipherSuite TLS_RSA_WITH_AES_256_GCM_SHA384 = {TBD,TBD}\r
149 CipherSuite TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 = {TBD,TBD}\r
150 CipherSuite TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 = {TBD,TBD}\r
151 CipherSuite TLS_DH_RSA_WITH_AES_128_GCM_SHA256 = {TBD,TBD}\r
152 CipherSuite TLS_DH_RSA_WITH_AES_256_GCM_SHA384 = {TBD,TBD}\r
153 CipherSuite TLS_DHE_DSS_WITH_AES_128_GCM_SHA256 = {TBD,TBD}\r
154 CipherSuite TLS_DHE_DSS_WITH_AES_256_GCM_SHA384 = {TBD,TBD}\r
155 CipherSuite TLS_DH_DSS_WITH_AES_128_GCM_SHA256 = {TBD,TBD}\r
156 CipherSuite TLS_DH_DSS_WITH_AES_256_GCM_SHA384 = {TBD,TBD}\r
157 CipherSuite TLS_DH_anon_WITH_AES_128_GCM_SHA256 = {TBD,TBD}\r
158 CipherSuite TLS_DH_anon_WITH_AES_256_GCM_SHA384 = {TBD,TBD}\r
159 \r
160 These cipher suites use the AES-GCM authenticated encryption with\r
161 associated data (AEAD) algorithms AEAD_AES_128_GCM and\r
162 AEAD_AES_256_GCM described in [RFC5116]. Note that each of these\r
163 AEAD algorithms uses a 128-bit authentication tag with GCM. The\r
164 \r
165 \r
166 \r
167 Salowey, et al. Expires October 16, 2008 [Page 3]\r
169 Internet-Draft AES-GCM Cipher suites April 2008\r
170 \r
171 \r
172 "nonce" SHALL be 12 bytes long consisting of two parts as follows:\r
173 (this is an example of a "partially explicit" nonce; see section\r
174 3.2.1 in [RFC5116]).\r
175 \r
176 struct{\r
177 opaque salt[4];\r
178 opaque nonce_explicit[8];\r
179 } GCMNonce;\r
180 \r
181 The salt is the "implicit" part of the nonce and is not sent in the\r
182 packet. Instead the salt is generated as part of the handshake\r
183 process: it is either the client_write_IV (when the client is\r
184 sending) or the server_write_IV (when the server is sending). The\r
185 salt length (SecurityParameters.fixed_iv_length) is 4 octets.\r
186 \r
187 The nonce_explicit is the "explicit" part of the nonce. It is chosen\r
188 by the sender and is carried in each TLS record in the\r
189 GenericAEADCipher.nonce_explicit field. The nonce_explicit length\r
190 (SecurityParameters.record_iv_length) is 8 octets.\r
191 \r
192 Each value of the nonce_explicit MUST be distinct for each distinct\r
193 invocation of GCM encrypt function for any fixed key. Failure to\r
194 meet this uniqueness requirement can significantly degrade security.\r
195 The nonce_explicit MAY be the 64-bit sequence number.\r
196 \r
197 The RSA, DHE_RSA, DH_RSA, DHE_DSS, DH_DSS, and DH_anon key exchanges\r
198 are performed as defined in [I-D.ietf-tls-rfc4346-bis].\r
199 \r
200 The PRF algorithms SHALL be as follows:\r
201 \r
202 For cipher suites ending with _SHA256, the PRF is the TLS PRF\r
203 [I-D.ietf-tls-rfc4346-bis] with SHA-256 as the hash function.\r
204 \r
205 For cipher suites ending with _SHA384, the PRF is the TLS PRF\r
206 [I-D.ietf-tls-rfc4346-bis] with SHA-384 as the hash function.\r
207 \r
208 Implementations MUST send TLS Alert bad_record_mac for all types of\r
209 failures encountered in processing the AES-GCM algorithm.\r
210 \r
211 \r
212 4. TLS Versions\r
213 \r
214 These cipher suites make use of the authenticated encryption with\r
215 additional data defined in TLS 1.2 [I-D.ietf-tls-rfc4346-bis]. They\r
216 MUST NOT be negotiated in older versions of TLS. Clients MUST NOT\r
217 offer these cipher suites if they do not offer TLS 1.2 or later.\r
218 Servers which select an earlier version of TLS MUST NOT select one of\r
219 these cipher suites. Because TLS has no way for the client to\r
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223 Salowey, et al. Expires October 16, 2008 [Page 4]\r
225 Internet-Draft AES-GCM Cipher suites April 2008\r
226 \r
227 \r
228 indicate that it supports TLS 1.2 but not earlier, a non-compliant\r
229 server might potentially negotiate TLS 1.1 or earlier and select one\r
230 of the cipher suites in this document. Clients MUST check the TLS\r
231 version and generate a fatal "illegal_parameter" alert if they detect\r
232 an incorrect version.\r
233 \r
234 \r
235 5. IANA Considerations\r
236 \r
237 IANA has assigned the following values for the cipher suites defined\r
238 in this draft:\r
239 \r
240 CipherSuite TLS_RSA_WITH_AES_128_GCM_SHA256 = {TBD,TBD}\r
241 CipherSuite TLS_RSA_WITH_AES_256_GCM_SHA384 = {TBD,TBD}\r
242 CipherSuite TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 = {TBD,TBD}\r
243 CipherSuite TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 = {TBD,TBD}\r
244 CipherSuite TLS_DH_RSA_WITH_AES_128_GCM_SHA256 = {TBD,TBD}\r
245 CipherSuite TLS_DH_RSA_WITH_AES_256_GCM_SHA384 = {TBD,TBD}\r
246 CipherSuite TLS_DHE_DSS_WITH_AES_128_GCM_SHA256 = {TBD,TBD}\r
247 CipherSuite TLS_DHE_DSS_WITH_AES_256_GCM_SHA384 = {TBD,TBD}\r
248 CipherSuite TLS_DH_DSS_WITH_AES_128_GCM_SHA256 = {TBD,TBD}\r
249 CipherSuite TLS_DH_DSS_WITH_AES_256_GCM_SHA384 = {TBD,TBD}\r
250 CipherSuite TLS_DH_anon_WITH_AES_128_GCM_SHA256 = {TBD,TBD}\r
251 CipherSuite TLS_DH_anon_WITH_AES_256_GCM_SHA384 = {TBD,TBD}\r
252 \r
253 \r
254 6. Security Considerations\r
255 \r
256 The security considerations in [I-D.ietf-tls-rfc4346-bis] apply to\r
257 this document as well. The remainder of this section describes\r
258 security considerations specific to the cipher suites described in\r
259 this document.\r
260 \r
261 6.1. Counter Reuse\r
262 \r
263 AES-GCM security requires that the counter is never reused. The IV\r
264 construction in Section 3 is designed to prevent counter reuse.\r
265 \r
266 6.2. Recommendations for Multiple Encryption Processors\r
267 \r
268 If multiple cryptographic processors are in use by the sender, then\r
269 the sender MUST ensure that, for a particular key, each value of the\r
270 nonce_explicit used with that key is distinct. In this case each\r
271 encryption processor SHOULD include in the nonce_explicit a fixed\r
272 value that is distinct for each processor. The recommended format is\r
273 \r
274 nonce_explicit = FixedDistinct || Variable\r
275 \r
276 \r
277 \r
278 \r
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282 \r
283 \r
284 where the FixedDistinct field is distinct for each encryption\r
285 processor, but is fixed for a given processor, and the Variable field\r
286 is distinct for each distinct nonce used by a particular encryption\r
287 processor. When this method is used, the FixedDistinct fields used\r
288 by the different processors MUST have the same length.\r
289 \r
290 In the terms of Figure 2 in [RFC5116], the Salt is the Fixed-Common\r
291 part of the nonce (it is fixed, and it is common across all\r
292 encryption processors), the FixedDistinct field exactly corresponds\r
293 to the Fixed-Distinct field, and the Variable field corresponds to\r
294 the Counter field, and the explicit part exactly corresponds to the\r
295 nonce_explicit.\r
296 \r
297 For clarity, we provide an example for TLS in which there are two\r
298 distinct encryption processors, each of which uses a one-byte\r
299 FixedDistinct field:\r
300 \r
301 Salt = eedc68dc\r
302 FixedDistinct = 01 (for the first encryption processor)\r
303 FixedDistinct = 02 (for the second encryption processor)\r
304 \r
305 The GCMnonces generated by the first encryption processor, and their\r
306 corresponding nonce_explicit, are:\r
307 \r
308 GCMNonce nonce_explicit\r
309 ------------------------ ----------------------------\r
310 eedc68dc0100000000000000 0100000000000000\r
311 eedc68dc0100000000000001 0100000000000001\r
312 eedc68dc0100000000000002 0100000000000002\r
313 ...\r
314 \r
315 The GCMnonces generated by the second encryption processor, and their\r
316 corresponding nonce_explicit, are\r
317 \r
318 GCMNonce nonce_explicit\r
319 ------------------------ ----------------------------\r
320 eedc68dc0200000000000000 0200000000000000\r
321 eedc68dc0200000000000001 0200000000000001\r
322 eedc68dc0200000000000002 0200000000000002\r
323 ...\r
324 \r
325 \r
326 \r
327 7. Acknowledgements\r
328 \r
329 This draft borrows heavily from [I-D.ietf-tls-ecc-new-mac]. The\r
330 authors would like to thank Alex Lam, Simon Josefsson and Pasi Eronen\r
331 for providing useful comments during the review of this draft.\r
332 \r
333 \r
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338 \r
339 \r
340 8. References\r
341 \r
342 8.1. Normative References\r
343 \r
344 [AES] National Institute of Standards and Technology, "Advanced\r
345 Encryption Standard (AES)", FIPS 197, November 2001.\r
346 \r
347 [GCM] Dworkin, M., "Recommendation for Block Cipher Modes of\r
348 Operation: Galois/Counter Mode (GCM) and GMAC", National\r
349 Institute of Standards and Technology SP 800-38D,\r
350 November 2007.\r
351 \r
352 [I-D.ietf-tls-rfc4346-bis]\r
353 Dierks, T. and E. Rescorla, "The Transport Layer Security\r
354 (TLS) Protocol Version 1.2", draft-ietf-tls-rfc4346-bis-10\r
355 (work in progress), March 2008.\r
356 \r
357 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate\r
358 Requirement Levels", BCP 14, RFC 2119, March 1997.\r
359 \r
360 [RFC5116] McGrew, D., "An Interface and Algorithms for Authenticated\r
361 Encryption", RFC 5116, January 2008.\r
362 \r
363 8.2. Informative References\r
364 \r
365 [I-D.ietf-tls-ecc-new-mac]\r
366 Rescorla, E., "TLS Elliptic Curve Cipher Suites with SHA-\r
367 256/384 and AES Galois Counter Mode",\r
368 draft-ietf-tls-ecc-new-mac-05 (work in progress),\r
369 April 2008.\r
370 \r
371 [IEEE8021AE]\r
372 Institute of Electrical and Electronics Engineers, "Media\r
373 Access Control Security", IEEE Standard 802.1AE,\r
374 August 2006.\r
375 \r
376 [RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode\r
377 (GCM) in IPsec Encapsulating Security Payload (ESP)",\r
378 RFC 4106, June 2005.\r
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391 Salowey, et al. Expires October 16, 2008 [Page 7]\r
393 Internet-Draft AES-GCM Cipher suites April 2008\r
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395 \r
396 Authors' Addresses\r
397 \r
398 Joseph Salowey\r
399 Cisco Systems, Inc.\r
400 2901 3rd. Ave\r
401 Seattle, WA 98121\r
402 USA\r
403 \r
404 Email: jsalowey@cisco.com\r
405 \r
406 \r
407 Abhijit Choudhury\r
408 Cisco Systems, Inc.\r
409 3625 Cisco Way\r
410 San Jose, CA 95134\r
411 USA\r
412 \r
413 Email: abhijitc@cisco.com\r
414 \r
415 \r
416 David McGrew\r
417 Cisco Systems, Inc.\r
418 170 W Tasman Drive\r
419 San Jose, CA 95134\r
420 USA\r
421 \r
422 Email: mcgrew@cisco.com\r
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447 Salowey, et al. Expires October 16, 2008 [Page 8]\r
449 Internet-Draft AES-GCM Cipher suites April 2008\r
450 \r
451 \r
452 Full Copyright Statement\r
453 \r
454 Copyright (C) The IETF Trust (2008).\r
455 \r
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492 \r
493 \r
494 Acknowledgment\r
495 \r
496 Funding for the RFC Editor function is provided by the IETF\r
497 Administrative Support Activity (IASA).\r
498 \r
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503 Salowey, et al. Expires October 16, 2008 [Page 9]\r