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6 Network Working Group P. Hoffman\r
7 Request for Comments: 4109 VPN Consortium\r
8 Updates: 2409 May 2005\r
9 Category: Standards Track\r
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11 \r
12 Algorithms for Internet Key Exchange version 1 (IKEv1)\r
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14 Status of This Memo\r
15 \r
16 This document specifies an Internet standards track protocol for the\r
17 Internet community, and requests discussion and suggestions for\r
18 improvements. Please refer to the current edition of the "Internet\r
19 Official Protocol Standards" (STD 1) for the standardization state\r
20 and status of this protocol. Distribution of this memo is unlimited.\r
21 \r
22 Copyright Notice\r
23 \r
24 Copyright (C) The Internet Society (2005).\r
25 \r
26 Abstract\r
27 \r
28 The required and suggested algorithms in the original Internet Key\r
29 Exchange version 1 (IKEv1) specification do not reflect the current\r
30 reality of the IPsec market requirements. The original specification\r
31 allows weak security and suggests algorithms that are thinly\r
32 implemented. This document updates RFC 2409, the original\r
33 specification, and is intended for all IKEv1 implementations deployed\r
34 today.\r
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57 Hoffman Standards Track [Page 1]\r
59 RFC 4109 Algorithms for IKEv1 May 2005\r
60 \r
61 \r
62 1. Introduction\r
63 \r
64 The original IKEv1 definition, [RFC2409], has a set of MUST-level and\r
65 SHOULD-level requirements that do not match the needs of IPsec users.\r
66 This document updates RFC 2409 by changing the algorithm requirements\r
67 defined there.\r
68 \r
69 The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,\r
70 SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this\r
71 document, are to be interpreted as described in [RFC2119].\r
72 \r
73 2. Old Algorithm Requirements\r
74 \r
75 RFC 2409 has the following MUST-level and SHOULD-level requirements:\r
76 \r
77 o DES for encryption MUST be supported.\r
78 o MD5 and SHA-1 for hashing and HMAC functions MUST be supported.\r
79 o Pre-shared secrets for authentication MUST be supported.\r
80 o Diffie-Hellman MODP group 1 (discrete log 768 bits) MUST be\r
81 supported.\r
82 o TripleDES for encryption SHOULD be supported.\r
83 o Tiger for hashing SHOULD be supported.\r
84 o DSA and RSA for authentication with signatures SHOULD be\r
85 supported.\r
86 o RSA for authentication with encryption SHOULD be supported.\r
87 o Diffie-Hellman MODP group 2 (discrete log 1024 bits) SHOULD be\r
88 supported.\r
89 \r
90 RFC 2409 gives two conflicting requirement levels for Diffie-Hellman\r
91 MODP groups with elliptic curves. Section 4 of that specification\r
92 says that "IKE implementations ... MAY support ECP and EC2N groups",\r
93 but Sections 6.3 and 6.4 say that MODP groups 3 and 4 for EC2N groups\r
94 SHOULD be supported.\r
95 \r
96 3. New Algorithm Requirements\r
97 \r
98 The new requirements for IKEv1 are listed here. Note that some of\r
99 the requirements are the same as those in RFC 2409, whereas others\r
100 are changed.\r
101 \r
102 o TripleDES for encryption MUST be supported.\r
103 o AES-128 in CBC mode [RFC3602] for encryption SHOULD be supported.\r
104 o SHA-1 for hashing and HMAC functions MUST be supported.\r
105 o Pre-shared secrets for authentication MUST be supported.\r
106 o AES-128 in XCBC mode for PRF functions ([RFC3566] and [RFC3664])\r
107 SHOULD be supported.\r
108 o Diffie-Hellman MODP group 2 (discrete log 1024 bits) MUST be\r
109 supported.\r
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113 Hoffman Standards Track [Page 2]\r
115 RFC 4109 Algorithms for IKEv1 May 2005\r
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117 \r
118 o Diffie-Hellman MODP group 14 (discrete log 2048 bits) [RFC3526]\r
119 SHOULD be supported.\r
120 o RSA for authentication with signatures SHOULD be supported.\r
121 \r
122 If additional updates are made to IKEv1 in the future, then it is\r
123 very likely that implementation of AES-128 in CBC mode for encryption\r
124 will become mandatory.\r
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126 The other algorithms that were listed at MUST-level and SHOULD-level\r
127 in RFC 2409 are now MAY-level. This includes DES for encryption, MD5\r
128 and Tiger for hashing, Diffie-Hellman MODP group 1, Diffie-Hellman\r
129 MODP groups with elliptic curves, DSA for authentication with\r
130 signatures, and RSA for authentication with encryption.\r
131 \r
132 DES for encryption, MD5 for hashing, and Diffie-Hellman MODP group 1\r
133 are dropped to MAY due to cryptographic weakness.\r
134 \r
135 Tiger for hashing, Diffie-Hellman MODP groups with elliptic curves,\r
136 DSA for authentication with signatures, and RSA for authentication\r
137 with encryption are dropped due to lack of any significant deployment\r
138 and interoperability.\r
139 \r
140 4. Summary\r
141 \r
142 Algorithm RFC 2409 This document\r
143 ------------------------------------------------------------------\r
144 DES for encryption MUST MAY (crypto weakness)\r
145 TripleDES for encryption SHOULD MUST\r
146 AES-128 for encryption N/A SHOULD\r
147 MD5 for hashing and HMAC MUST MAY (crypto weakness)\r
148 SHA1 for hashing and HMAC MUST MUST\r
149 Tiger for hashing SHOULD MAY (lack of deployment)\r
150 AES-XCBC-MAC-96 for PRF N/A SHOULD\r
151 Pre-shared secrets MUST MUST\r
152 RSA with signatures SHOULD SHOULD\r
153 DSA with signatures SHOULD MAY (lack of deployment)\r
154 RSA with encryption SHOULD MAY (lack of deployment)\r
155 D-H Group 1 (768) MUST MAY (crypto weakness)\r
156 D-H Group 2 (1024) SHOULD MUST\r
157 D-H Group 14 (2048) N/A SHOULD\r
158 D-H elliptic curves SHOULD MAY (lack of deployment)\r
159 \r
160 5. Security Considerations\r
161 \r
162 This document is all about security. All the algorithms that are\r
163 either MUST-level or SHOULD-level in the "new algorithm requirements"\r
164 section of this document are believed to be robust and secure at the\r
165 time of this writing.\r
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169 Hoffman Standards Track [Page 3]\r
171 RFC 4109 Algorithms for IKEv1 May 2005\r
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173 \r
174 6. Normative References\r
175 \r
176 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate\r
177 Requirement Levels", BCP 14, RFC 2119, March 1997.\r
178 \r
179 [RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange\r
180 (IKE)", RFC 2409, November 1998.\r
181 \r
182 [RFC3526] Kivinen, T. and M. Kojo, "More Modular Exponential (MODP)\r
183 Diffie-Hellman groups for Internet Key Exchange (IKE)",\r
184 RFC 3526, May 2003.\r
185 \r
186 [RFC3566] Frankel, S. and H. Herbert, "The AES-XCBC-MAC-96 Algorithm\r
187 and Its Use With IPsec", RFC 3566, September 2003.\r
188 \r
189 [RFC3602] Frankel, S., Glenn, R., and S. Kelly, "The AES-CBC Cipher\r
190 Algorithm and Its Use with IPsec", RFC 3602, September\r
191 2003.\r
192 \r
193 [RFC3664] Hoffman, P., "The AES-XCBC-PRF-128 Algorithm for the\r
194 Internet Key Exchange Protocol (IKE)", RFC 3664, January\r
195 2004.\r
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197 Author's Address\r
198 \r
199 Paul Hoffman\r
200 VPN Consortium\r
201 127 Segre Place\r
202 Santa Cruz, CA 95060\r
203 US\r
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205 EMail: paul.hoffman@vpnc.org\r
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225 Hoffman Standards Track [Page 4]\r
227 RFC 4109 Algorithms for IKEv1 May 2005\r
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229 \r
230 Full Copyright Statement\r
231 \r
232 Copyright (C) The Internet Society (2005).\r
233 \r
234 This document is subject to the rights, licenses and restrictions\r
235 contained in BCP 78, and except as set forth therein, the authors\r
236 retain all their rights.\r
237 \r
238 This document and the information contained herein are provided on an\r
239 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS\r
240 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET\r
241 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,\r
242 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE\r
243 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED\r
244 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.\r
245 \r
246 Intellectual Property\r
247 \r
248 The IETF takes no position regarding the validity or scope of any\r
249 Intellectual Property Rights or other rights that might be claimed to\r
250 pertain to the implementation or use of the technology described in\r
251 this document or the extent to which any license under such rights\r
252 might or might not be available; nor does it represent that it has\r
253 made any independent effort to identify any such rights. Information\r
254 on the procedures with respect to rights in RFC documents can be\r
255 found in BCP 78 and BCP 79.\r
256 \r
257 Copies of IPR disclosures made to the IETF Secretariat and any\r
258 assurances of licenses to be made available, or the result of an\r
259 attempt made to obtain a general license or permission for the use of\r
260 such proprietary rights by implementers or users of this\r
261 specification can be obtained from the IETF on-line IPR repository at\r
262 http://www.ietf.org/ipr.\r
263 \r
264 The IETF invites any interested party to bring to its attention any\r
265 copyrights, patents or patent applications, or other proprietary\r
266 rights that may cover technology that may be required to implement\r
267 this standard. Please address the information to the IETF at ietf-\r
268 ipr@ietf.org.\r
269 \r
270 Acknowledgement\r
271 \r
272 Funding for the RFC Editor function is currently provided by the\r
273 Internet Society.\r
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281 Hoffman Standards Track [Page 5]\r