summaryrefslogtreecommitdiff
path: root/doc/protocol/draft-rescorla-tls-suiteb-01.txt
blob: e6644fbd59160aa6573a891561ffe25087c8b8fc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449



Network Working Group                                          M. Salter
Internet-Draft                                  National Security Agency
Intended status:  Informational                              E. Rescorla
Expires:  December 4, 2007                             Network Resonance
                                                            June 2, 2007


                     Suite B Cipher Suites for TLS
                    draft-rescorla-tls-suiteb-01.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on December 4, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   The United States Government has published guidelines for "NSA Suite
   B Cryptography" dated July, 2005, which defines cryptographic
   algorithm polcy for national security applications.  This document
   defines a profile of TLS which is conformant with Suite B.






Salter & Rescorla       Expires December 4, 2007                [Page 1]

Internet-Draft               Suite B for TLS                   June 2007


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Conventions Used In This Document . . . . . . . . . . . . . . . 3
   3.  Suite B Requirements  . . . . . . . . . . . . . . . . . . . . . 3
   4.  Suite B Compliance Requirements . . . . . . . . . . . . . . . . 4
     4.1.  Security Levels . . . . . . . . . . . . . . . . . . . . . . 4
     4.2.  Acceptable Curves . . . . . . . . . . . . . . . . . . . . . 5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6
   Intellectual Property and Copyright Statements  . . . . . . . . . . 8



































Salter & Rescorla       Expires December 4, 2007                [Page 2]

Internet-Draft               Suite B for TLS                   June 2007


1.  Introduction

   In July, 2005 the National Security Agency posted "Fact Sheet, NSA
   Suite B Cryptography" which stated:

       To complement the existing policy for the use of the Advanced
       Encryption Standard (AES) to protect national security systems
       and information as specified in The National Policy on the use of
       the Advanced Encryption Standard (AES) to Protect National
       Security Systems and National Security Information (CNSSP-15),
       the National Security Agency (NSA) announced Suite B Cryptography
       at the 2005 RSA Conference.  In addition to the AES, Suite B
       includes cryptographic algorithms for hashing, digital
       signatures, and key exchange.

       Suite B only specifies the cryptographic algorithms to be
       used. Many other factors need to be addressed in determining
       whether a particular device implementing a particular set of
       cryptographic algorithms should be used to satisfy a particular
       requirement.

   Among those factors are "requirements for interoperability both
   domestically and internationally".

   This document is a profile of of TLS 1.2 [I-D.ietf-tls-rfc4346-bis]
   and of the cipher suites defined in [I-D.ietf-tls-ecc-new-mac], but
   does not itself define any new cipher suites.  This profile requires
   TLS 1.2.


2.  Conventions Used In This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].


3.  Suite B Requirements

   The "Suite B Fact Sheet" requires that key establishment and
   authentication algorithms be based on Elliptic Curve Cryptography,
   that the encryption algorithm be AES [AES], and that the function
   used for key derivation and data integrity be SHA [SHS].  It defines
   two security levels, of 128 and 192 bits.

   In particular it states:





Salter & Rescorla       Expires December 4, 2007                [Page 3]

Internet-Draft               Suite B for TLS                   June 2007


      SUITE B includes:

       Encryption:          Advanced Encryption Standard (AES)  -
                            FIPS 197 (with keys sizes of 128 and 256
                            bits)

       Digital Signature:   Elliptic Curve Digital Signature Algorithm -
                            FIPS 186-2 (using the curves with 256 and
                            384-bit prime moduli)

       Key Exchange:        Elliptic Curve Diffie-Hellman or Elliptic
                            Curve MQV Draft NIST Special Publication
                            800-56 (using the curves with 256 and
                            384-bit prime moduli)

       Hashing:             Secure Hash Algorithm - FIPS 180-2
                            (using SHA-256 and SHA-384)

      All implementations of Suite B must, at a minimum, include AES
      with 128-bit keys, the 256-bit prime modulus elliptic curve and
      SHA-256 as a common mode for widespread interoperability.

   The 128-bit security level corresponds to an elliptic curve size of
   256 bits, AES-128, and SHA-256.  The 192-bit security level
   corresponds to an elliptic curve size of 384 bits, AES-256, and SHA-
   384.


4.  Suite B Compliance Requirements

   To be considered "Suite B compatible" at least one of the Galois
   Counter Mode (GCM) CipherSuites defined in [I-D.ietf-tls-ecc-new-mac]
   MUST be negotiated.  In compliance with the guidance in the Suite B
   Fact Sheet every TLS implementation of Suite B SHOULD implement
   TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256.

4.1.  Security Levels

   As described in Section 1, Suite B specifies two security levels, 128
   and 192 bit.  The following table lists the security levels for each
   cipher suite:










Salter & Rescorla       Expires December 4, 2007                [Page 4]

Internet-Draft               Suite B for TLS                   June 2007


       +-----------------------------------------+----------------+
       | Cipher Suite                            | Security Level |
       +-----------------------------------------+----------------+
       | TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 | 128            |
       | TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256  | 128            |
       | TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 | 192            |
       | TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384  | 192            |
       +-----------------------------------------+----------------+

4.2.  Acceptable Curves

   RFC 4492 defines a variety of elliptic curves.  For cipher suites
   defined in this specification, only secp256r1 (23) or secp384r1 (24)
   may be used.  (These are the same curves that appear in FIPS 186-2 as
   P-256 and P-384, respectively.)  For cipher suites at the 128-bit
   security level, secp256r1 MUST be used.  For cipher suites at the
   192-bit security level, secp384r1 MUST be used.  RFC 4492 requires
   that uncompressed (0) form be supported. ansiX962_compressed_prime(1)
   point formats MAY be supported.

   Clients desiring to negotiate only a Suite B-compliant connection
   MUST generate a "Supported Elliptic Curves Extension" containing only
   the allowed curves.  These curves MUST match the cipher suite
   security levels being offered.  Clients which are willing to do both
   Suite B-compliant and non-Suite B-compliant connections MAY omit the
   extension or send the extension but offer other curves as well as the
   appropriate Suite B ones.

   Servers desiring to negotiate a Suite B-compliant connection SHOULD
   check for the presence of the extension, but MUST NOT negotiate
   inappropriate curves even if they are offered by the client.  This
   allows a Client which is willing to do either Suite B-compliant or
   non-Suite B-compliant modes to interoperate with a server which will
   only do Suite B-compliant modes.  If the client does not advertise an
   acceptable curve, the server MUST generate a fatal
   "handshake_failure" alert and terminate the connection.  Clients MUST
   check the chosen curve to make sure it is acceptable.


5.  Security Considerations

   Most of the security considerations for this document are described
   in TLS 1.2 [I-D.ietf-tls-rfc4346-bis], RFC 4492 [RFC4492], and
   [I-D.ietf-tls-ecc-new-mac].  Readers should consult those documents.

   In order to meet the goal of a consistent security level for the
   entire cipher suite, in Suite B mode TLS implementations MUST ONLY
   use the curves defined in Section 4.2.  Otherwise, it is possible to



Salter & Rescorla       Expires December 4, 2007                [Page 5]

Internet-Draft               Suite B for TLS                   June 2007


   have a set of symmetric algorithms with much weaker or stronger
   security properties than the asymmetric (ECC) algorithms.


6.  IANA Considerations

   This document defines no actions for IANA.


7.  Acknowledgements

   This work was supported by the US Department of Defense.


8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4492]  Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
              Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
              for Transport Layer Security (TLS)", RFC 4492, May 2006.

   [I-D.ietf-tls-rfc4346-bis]
              Dierks, T. and E. Rescorla, "The TLS Protocol Version
              1.2", draft-ietf-tls-rfc4346-bis-03 (work in progress),
              March 2007.

   [AES]      National Institute of Standards and Technology,
              "Specification for the Advanced Encryption Standard
              (AES)", FIPS 197, November 2001.

   [SHS]      National Institute of Standards and Technology, "Secure
              Hash Standard", FIPS 180-2, August 2002.

   [I-D.ietf-tls-ecc-new-mac]
              Rescorla, E., "TLS Elliptic Curve Cipher Suites with SHA-
              256/384 and AES Galois Counter Mode", April 2007.

8.2.  Informative References









Salter & Rescorla       Expires December 4, 2007                [Page 6]

Internet-Draft               Suite B for TLS                   June 2007


Authors' Addresses

   Margaret Salter
   National Security Agency
   9800 Savage Rd.
   Fort Meade  20755-6709
   USA

   Email:  msalter@restarea.ncsc.mil


   Eric Rescorla
   Network Resonance
   2483 E. Bayshore #212
   Palo Alto  94303
   USA

   Email:  ekr@networkresonance.com

































Salter & Rescorla       Expires December 4, 2007                [Page 7]

Internet-Draft               Suite B for TLS                   June 2007


Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.


Acknowledgment

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).





Salter & Rescorla       Expires December 4, 2007                [Page 8]