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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) -- Looks like a reference, but probably isn't: '1' on line 223 == Missing Reference: 'IoT' is mentioned on line 342, but not defined == Missing Reference: 'IKEv2' is mentioned on line 374, but not defined ** Obsolete normative reference: RFC 4307 (Obsoleted by RFC 8247) Summary: 2 errors (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Y. Nir 3 Internet-Draft Check Point 4 Intended status: Standards Track T. Kivinen 5 Expires: September 17, 2016 INSIDE Secure 6 P. Wouters 7 Red Hat 8 D. Migault 9 Ericsson 10 March 16, 2016 12 Algorithm Implementation Requirements and Usage Guidance for IKEv2 13 draft-ietf-ipsecme-rfc4307bis-04 15 Abstract 17 The IPsec series of protocols makes use of various cryptographic 18 algorithms in order to provide security services. The Internet Key 19 Exchange (IKE) protocol is used to negotiate the IPsec Security 20 Association (IPsec SA) parameters, such as which algorithms should be 21 used. To ensure interoperability between different implementations, 22 it is necessary to specify a set of algorithm implementation 23 requirements and usage guidance to ensure that there is at least one 24 algorithm that all implementations support. This document defines 25 the current algorithm implementation requirements and usage guidance 26 for IKEv2. This document does not update the algorithms used for 27 packet encryption using IPsec Encapsulated Security Payload (ESP) 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at http://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on September 17, 2016. 46 Copyright Notice 47 Copyright (c) 2016 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (http://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 63 1.1. Updating Algorithm Implementation Requirements and Usage 64 Guidance . . . . . . . . . . . . . . . . . . . . . . . . 3 65 1.2. Updating Algorithm Requirement Levels . . . . . . . . . . 3 66 1.3. Document Audience . . . . . . . . . . . . . . . . . . . . 4 67 2. Conventions Used in This Document . . . . . . . . . . . . . . 4 68 3. Algorithm Selection . . . . . . . . . . . . . . . . . . . . . 5 69 3.1. Type 1 - IKEv2 Encryption Algorithm Transforms . . . . . 5 70 3.2. Type 2 - IKEv2 Pseudo-random Function Transforms . . . . 6 71 3.3. Type 3 - IKEv2 Integrity Algorithm Transforms . . . . . . 7 72 3.4. Type 4 - IKEv2 Diffie-Hellman Group Transforms . . . . . 8 73 4. IKEv2 Authentication . . . . . . . . . . . . . . . . . . . . 10 74 4.1. IKEv2 Authentication Method . . . . . . . . . . . . . . . 10 75 4.1.1. Recommendations for RSA key length . . . . . . . . . 11 76 4.2. Digital Signature Recommendations . . . . . . . . . . . . 11 77 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12 78 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 79 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 80 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 81 8.1. Normative References . . . . . . . . . . . . . . . . . . 13 82 8.2. Informative References . . . . . . . . . . . . . . . . . 14 84 1. Introduction 86 The Internet Key Exchange (IKE) protocol [RFC7296] is used to 87 negotiate the parameters of the IPsec SA, such as the encryption and 88 authentication algorithms and the keys for the protected 89 communications between the two endpoints. The IKE protocol itself is 90 also protected by encryption which is negotiated between the two 91 endpoints using IKE. Different implementations of IKE may negotiate 92 different algorithms based on their individual local policy. To 93 ensure interoperability, a set of "mandatory-to-implement" IKE 94 encryption algorithms is defined. 96 This document describes the parameters of the IKE protocol. It does 97 not describe the cryptographic parameters of the AH or ESP protocols. 99 1.1. Updating Algorithm Implementation Requirements and Usage Guidance 101 The field of cryptography evolves continuously. New stronger 102 algorithms appear and existing algorithms are found to be less secure 103 then originally thought. Therefore, algorithm implementation 104 requirements and usage guidance need to be updated from time to time 105 to reflect the new reality. The choices for algorithms must be 106 conservative to minimize the risk of algorithm compromise. 107 Algorithms need to be suitable for a wide variety of CPU 108 architectures and device deployments ranging from high end bulk 109 encryption devices to small low-power IoT devices. 111 The algorithm implementation requirements and usage guidance may need 112 to change over time to adapt to the changing world. For this reason, 113 the selection of mandatory-to-implement algorithms was removed from 114 the main IKEv2 specification and placed in this document. 116 1.2. Updating Algorithm Requirement Levels 118 The mandatory-to-implement algorithm of tomorrow should already be 119 available in most implementations of IKE by the time it is made 120 mandatory. This document attempts to identify and introduce those 121 algorithms for future mandatory-to-implement status. There is no 122 guarantee that the algorithms in use today may become mandatory in 123 the future. Published algorithms are continuously subjected to 124 cryptographic attack and may become too weak or could become 125 completely broken before this document is updated. 127 This document only provides recommendations for the mandatory-to- 128 implement algorithms or algorithms too weak that are recommended not 129 to be implemented. As a result, any algorithm listed at the IKEv2 130 IANA registry not mentioned in this document MAY be implemented. For 131 clarification and consistency with [RFC4307] an algorithm will be set 132 to MAY only when it has been downgraded. 134 Although this document updates the algorithms to keep the IKEv2 135 communication secure over time, it also aims at providing 136 recommendations so that IKEv2 implementations remain interoperable. 137 IKEv2 interoperability is addressed by an incremental introduction or 138 deprecation of algorithms. In addition, this document also considers 139 the new use cases for IKEv2 deployment, such as Internet of Things 140 (IoT). 142 It is expected that deprecation of an algorithm is performed 143 gradually. This provides time for various implementations to update 144 their implemented algorithms while remaining interoperable. Unless 145 there are strong security reasons, an algorithm is expected to be 146 downgraded from MUST to MUST- or SHOULD, instead of MUST NOT. 147 Similarly, an algorithm that has not been mentioned as mandatory-to- 148 implement is expected to be introduced with a SHOULD instead of a 149 MUST. 151 The current trend toward Internet of Things and its adoption of IKEv2 152 requires this specific use case to be taken into account as well. 153 IoT devices are resource constrained devices and their choice of 154 algorithms are motivated by minimizing the footprint of the code, the 155 computation effort and the size of the messages to send. This 156 document indicates "[IoT]" when a specified algorithm is specifically 157 listed for IoT devices. 159 1.3. Document Audience 161 The recommendations of this document mostly target IKEv2 implementers 162 as implementations need to meet both high security expectations as 163 well as high interoperability between various vendors and with 164 different versions. Interoperability requires a smooth move to more 165 secure cipher suites. This may differ from a user point of view that 166 may deploy and configure IKEv2 with only the safest cipher suite. On 167 the other hand, comments and recommendations from this document are 168 also expected to be useful for such users. 170 IKEv1 is out of scope of this document. IKEv1 is deprecated and the 171 recommendations of this document must not be considered for IKEv1, as 172 most IKEv1 implementations have been "frozen" and will not be able to 173 update the list of mandatory-to-implement algorithms. 175 2. Conventions Used in This Document 177 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 178 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 179 document are to be interpreted as described in [RFC2119]. 181 We define some additional terms here: 183 SHOULD+ This term means the same as SHOULD. However, it is likely 184 that an algorithm marked as SHOULD+ will be promoted at some 185 future time to be a MUST. 186 SHOULD- This term means the same as SHOULD. However, an algorithm 187 marked as SHOULD- may be deprecated to a MAY in a future 188 version of this document. 189 MUST- This term means the same as MUST. However, we expect at some 190 point that this algorithm will no longer be a MUST in a 191 future document. Although its status will be determined at a 192 later time, it is reasonable to expect that if a future 193 revision of a document alters the status of a MUST- 194 algorithm, it will remain at least a SHOULD or a SHOULD- 195 level. 196 IoT stands for Internet of Things. 198 Table 1 200 3. Algorithm Selection 202 3.1. Type 1 - IKEv2 Encryption Algorithm Transforms 204 The algorithms in the below table are negotiated in the SA payload 205 and used for the Encrypted Payload. References to the specification 206 defining these algorithms and the ones in the following subsections 207 are in the IANA registry [IKEV2-IANA]. Some of these algorithms are 208 Authenticated Encryption with Associated Data (AEAD - [RFC5282]). 209 Algorithms that are not AEAD MUST be used in conjunction with an 210 integrity algorithms in Section 3.3. 212 +-----------------------------+----------+-------+----------+ 213 | Name | Status | AEAD? | Comment | 214 +-----------------------------+----------+-------+----------+ 215 | ENCR_AES_CBC | MUST- | No | [1] | 216 | ENCR_CHACHA20_POLY1305 | SHOULD | Yes | | 217 | AES-GCM with a 16 octet ICV | SHOULD | Yes | [1] | 218 | ENCR_AES_CCM_8 | SHOULD | Yes | [1][IoT] | 219 | ENCR_3DES | MAY | No | | 220 | ENCR_DES | MUST NOT | No | | 221 +-----------------------------+----------+-------+----------+ 223 [1] - This requirement level is for 128-bit keys. 256-bit keys are at 224 MAY. 192-bit keys can safely be ignored. [IoT] - This requirement is 225 for interoperability with IoT. 227 Table 2 229 ENCR_AES_CBC is raised from SHOULD+ in [RFC4307] to MUST. It is the 230 only shared mandatory-to-implement algorithm with RFC4307 and as a 231 result it is necessary for interoperability with IKEv2 implementation 232 compatible with RFC4307. 234 ENCR_CHACHA20_POLY1305 was not ready to be considered at the time of 235 RFC4307. It has been recommended by the CRFG and others as an 236 alternative to AES-CBC and AES-GCM. It is also being standardized 237 for IPsec for the same reasons. At the time of writing, there were 238 not enough IKEv2 implementations supporting ENCR_CHACHA20_POLY1305 to 239 be able to introduce it at the SHOULD+ level. 241 AES-GCM with a 16 octet ICV was not considered as in RFC4307. At the 242 time RFC4307 was written, AES-GCM was not defined in an IETF 243 document. AES-GCM was defined for ESP in [RFC4106] and later for 244 IKEv2 in [RFC5282]. The main motivation for adopting AES-GCM for ESP 245 is encryption performance and key longevity compared to AES-CBC. 246 This resulted in AES-GCM being widely implemented for ESP. As the 247 computation load of IKEv2 is relatively small compared to ESP, many 248 IKEv2 implementations have not implemented AES-GCM. For this reason, 249 AES-GCM is not promoted to a greater status than SHOULD. The reason 250 for promotion from MAY to SHOULD is to promote the slightly more 251 secure AEAD method over the traditional encrypt+auth method. Its 252 status is expected to be raised once widely implemented. As the 253 advantage of the shorter (and weaker) ICVs is minimal, the 8 and 12 254 octet ICV's remain at the MAY level. 256 ENCR_AES_CCM_8 was not considered in RFC4307. This document 257 considers it as SHOULD be implemented in order to be able to interact 258 with Internet of Things devices. As this case is not a general use 259 case for non-IoT VPNs, its status is expected to remain as SHOULD. 260 The 8 octet size of the ICV is expected to be sufficient for most use 261 cases of IKEv2, as far less packets are exchanged on the IKE SA 262 compared to the IPsec SA. When implemented, ENCR_AES_CCM_8 MUST be 263 implemented for key length 128 and MAY be implemented for key length 264 256. 266 ENCR_3DES has been downgraded from RFC4307 MUST- to SHOULD NOT. All 267 IKEv2 implementation already implement ENCR_AES_CBC, so there is no 268 need to keep support for the much slower ENCR_3DES. In addition, 269 ENCR_CHACHA20_POLY1305 provides a more modern alternative to AES. 271 ENCR_DES can be brute-forced using of-the-shelves hardware. It 272 provides no meaningful security whatsoever and therefor MUST NOT be 273 implemented. 275 3.2. Type 2 - IKEv2 Pseudo-random Function Transforms 277 Transform Type 2 Algorithms are pseudo-random functions used to 278 generate random values when needed. 280 If an algorithm is selected as the integrity algorithm, it SHOULD 281 also be used as the PRF. When using an AEAD cipher, a choice of PRF 282 needs to be made. The table below lists the recommended algorithms. 284 +-------------------+----------+---------+ 285 | Name | Status | Comment | 286 +-------------------+----------+---------+ 287 | PRF_HMAC_SHA2_256 | MUST | | 288 | PRF_HMAC_SHA2_512 | SHOULD+ | | 289 | PRF_HMAC_SHA1 | MUST- | | 290 | PRF_AES128_CBC | SHOULD | [IoT] | 291 | PRF_HMAC_MD5 | MUST NOT | | 292 +-------------------+----------+---------+ 294 [IoT] - This requirement is for interoperability with IoT 296 Table 3 298 PRF_HMAC_SHA2_256 was not mentioned in RFC4307, as no SHA2 based 299 authentication was mentioned. PRF_HMAC_SHA2_256 MUST be implemented 300 in order to replace SHA1 and PRF_HMAC_SHA1. 302 PRF_HMAC_SHA2_512 SHOULD be implemented as a future replacement for 303 PRF_HMAC_SHA2_256 or for when stronger security is required. 304 PRF_HMAC_SHA2_512 is preferred over PRF_HMAC_SHA2_384, as the 305 additional overhead of PRF_HMAC_SHA2_512 is negligible. 307 PRF_HMAC_SHA1 has been downgraded from MUST in RFC4307 to MUST- as 308 their is an industry-wide trend to deprecate its usage. 310 PRF_AES128_CBC is only recommended in the scope of IoT, as Internet 311 of Things deployments tend to prefer AES based pseudo-random 312 functions in order to avoid implementing SHA2. For the non-IoT VPN 313 deployment it has been downgraded from SHOULD in RFC4307 to MAY as it 314 has not seen wide adoption. 316 PRF_HMAC_MD5 has been downgraded from MAY in RFC4307 to MUST NOT. 317 There is an industry-wide trend to deprecate its usage as MD5 support 318 is being removed from cryptographic libraries in general because its 319 non-HMAC use is known to be subject to collision attacks, for example 320 as mentioned in [TRANSCRIPTION]. 322 3.3. Type 3 - IKEv2 Integrity Algorithm Transforms 324 The algorithms in the below table are negotiated in the SA payload 325 and used for the Encrypted Payload. References to the specification 326 defining these algorithms are in the IANA registry. When an AEAD 327 algorithm (see Section 3.1) is proposed, this algorithm transform 328 type is not in use. 330 +------------------------+----------+---------+ 331 | Name | Status | Comment | 332 +------------------------+----------+---------+ 333 | AUTH_HMAC_SHA2_256_128 | MUST | | 334 | AUTH_HMAC_SHA2_512_256 | SHOULD | | 335 | AUTH_HMAC_SHA1_96 | MUST- | | 336 | AUTH_AES_XCBC_96 | SHOULD | [IoT] | 337 | AUTH_HMAC_MD5_96 | MUST NOT | | 338 | AUTH_DES_MAC | MUST NOT | | 339 | AUTH_KPDK_MD5 | MUST NOT | | 340 +------------------------+----------+---------+ 342 [IoT] - This requirement is for interoperability with IoT 344 Table 4 346 AUTH_HMAC_SHA2_256_128 was not mentioned in RFC4307, as no SHA2 based 347 authentication was mentioned. AUTH_HMAC_SHA2_256_128 MUST be 348 implemented in order to replace AUTH_HMAC_SHA1_96. 350 AUTH_HMAC_SHA2_512_256 SHOULD be implemented as a future replacement 351 of AUTH_HMAC_SHA2_256_128 or for when stronger security is required. 352 This value has been preferred over AUTH_HMAC_SHA2_384, as the 353 additional overhead of AUTH_HMAC_SHA2_512 is negligible. 355 AUTH_HMAC_SHA1_96 has been downgraded from MUST in RFC4307 to MUST- 356 as there is an industry-wide trend to deprecate its usage. 358 AUTH_AES-XCBC is only recommended in the scope of IoT, as Internet of 359 Things deployments tend to prefer AES based pseudo-random functions 360 in order to avoid implementing SHA2. For the non-IoT VPN deployment, 361 it has been downgraded from SHOULD in RFC4307 to MAY as it has not 362 been widely adopted. 364 AUTH_HMAC_MD5_96, AUTH_DES_MAC and AUTH_KPDK_MD5 were not mentioned 365 in RFC4307 so its default status was MAY. It has been downgraded to 366 MUST NOT. There is an industry-wide trend to deprecate its usage. 367 MD5 support is being removed from cryptographic libraries in general 368 because its non-HMAC use is known to be subject to collision attacks, 369 for example as mentioned in [TRANSCRIPTION]. 371 3.4. Type 4 - IKEv2 Diffie-Hellman Group Transforms 372 There are several Modular Exponential (MODP) groups and several 373 Elliptic Curve groups (ECC) that are defined for use in IKEv2. These 374 groups are defined in both the [IKEv2] base document and in 375 extensions documents and are identified by group number. Note that 376 it is critical to enforce a secure Diffie Hellman exchange as this 377 exchange provides encryption for the session. If an attacker can 378 retrieve the private numbers (for example a, b) (and? or?) the public 379 values (for example g**a, g**b), then the attacker can compute the 380 secret and the keys used and decrypt the exchange. Such an attack 381 can be performed off-line on a previously recorded communication, 382 years after the communication happened. This differs from attacks 383 that need to be executed during the authentication which must be 384 performed online and in near real-time. 386 +------------+----------------------------------------+-------------+ 387 | Number | Description | Status | 388 +------------+----------------------------------------+-------------+ 389 | 14 | 2048-bit MODP Group | MUST | 390 | 19 | 256-bit random ECP group | SHOULD | 391 | 5 | 1536-bit MODP Group | SHOULD NOT | 392 | 2 | 1024-bit MODP Group | SHOULD NOT | 393 | 1 | 768-bit MODP Group | MUST NOT | 394 | 22 | 1024-bit MODP Group with 160-bit Prime | SHOULD NOT | 395 | | Order Subgroup | | 396 | 23 | 2048-bit MODP Group with 224-bit Prime | SHOULD NOT | 397 | | Order Subgroup | | 398 | 24 | 2048-bit MODP Group with 256-bit Prime | SHOULD NOT | 399 | | Order Subgroup | | 400 +------------+----------------------------------------+-------------+ 402 Table 5 404 Group 14 or 2048-bit MODP Group is raised from SHOULD+ in RFC4307 as 405 a replacement for 1024-bit MODP Group. Group 14 is widely 406 implemented and considered secure. 408 Group 19 or 256-bit random ECP group was not specified in RFC4307, as 409 this group were not specified at that time. Group 19 is widely 410 implemented and considered secure. 412 Group 5 or 1536-bit MODP Group has been downgraded from MAY in 413 RFC4307 to SHOULD NOT. It was specified earlier, but is now 414 considered to be vulnerable to be broken within the next few years by 415 a nation state level attack, so its security margin is considered too 416 narrow. 418 Group 2 or 1024-bit MODP Group has been downgraded from MUST- in 419 RFC4307 to SHOULD NOT. It is known to be weak against sufficiently 420 funded attackers using commercially available mass-computing 421 resources, so its security margin is considered too narrow. It is 422 expected in the near future to be downgraded to MUST NOT. 424 Group 1 or 768-bit MODP Group was not mentioned in RFC4307 and so its 425 status was MAY. It can be broken within hours using cheap of-the- 426 shelves hardware. It provides no security whatsoever. 428 Group 22, 23 and 24 or 1024-bit MODP Group with 160-bit, and 2048-bit 429 MODP Group with 224-bit and 256-bit Prime Order Subgroup have small 430 subgroups, which means that checks specified in the "Additional 431 Diffie-Hellman Test for the IKEv2" [RFC6989] section 2.2 first bullet 432 point MUST be done when these groups are used. These groups are also 433 not safe-primes. The seeds for these groups have not been publicly 434 released, resulting in reduced trust in these groups. These groups 435 were proposed as alternatives for group 2 and 14 but never saw wide 436 deployment. It is expected in the near future to be further 437 downgraded to MUST NOT. 439 4. IKEv2 Authentication 441 IKEv2 authentication may involve a signatures verification. 442 Signatures may be used to validate a certificate or to check the 443 signature of the AUTH value. Cryptographic recommendations regarding 444 certificate validation are out of scope of this document. What is 445 mandatory to implement is provided by the PKIX Community. This 446 document is mostly concerned on signature verification and generation 447 for the authentication. 449 4.1. IKEv2 Authentication Method 451 +--------+---------------------------------------+------------+ 452 | Number | Description | Status | 453 +--------+---------------------------------------+------------+ 454 | 1 | RSA Digital Signature | MUST | 455 | 3 | DSS Digital Signature | SHOULD NOT | 456 | 9 | ECDSA with SHA-256 on the P-256 curve | SHOULD | 457 | 10 | ECDSA with SHA-384 on the P-384 curve | SHOULD | 458 | 11 | ECDSA with SHA-512 on the P-521 curve | SHOULD | 459 | 14 | Digital Signature | SHOULD | 460 +--------+---------------------------------------+------------+ 462 Table 6 464 RSA Digital Signature is widely deployed and therefor kept for 465 interoperability. It is expected to be downgraded in the future as 466 its signatures are based on the older RSASSA-PKCS1-v1.5 which is no 467 longer recommended. RSA authentication, as well as other specific 468 Authentication Methods, are expected to be replaced with the generic 469 Digital Signature method of [RFC7427]. RSA Digital Signature is not 470 recommended for keys smaller then 2048, but since these signatures 471 only have value in real-time, and need no future protection, smaller 472 keys was kept at SHOULD NOT instead of MUST NOT. 474 ECDSA based Authentication Methods are also expected to be downgraded 475 as it does not provide hash function agility. Instead, ECDSA (like 476 RSA) is expected to be performed using the generic Digital Signature 477 method. 479 DSS Digital Signature is bound to SHA-1 and has the same level of 480 security as 1024-bit RSA. It is expected to be downgraded to MUST 481 NOT in the future. 483 Digital Signature [RFC7427] is expected to be promoted as it provides 484 hash function, signature format and algorithm agility. 486 4.1.1. Recommendations for RSA key length 488 +-------------------------------------------+------------+ 489 | Description | Status | 490 +-------------------------------------------+------------+ 491 | RSA with key length 2048 | MUST | 492 | RSA with key length 3072 and 4096 | SHOULD | 493 | RSA with key length between 2049 and 4095 | MAY | 494 | RSA with key length smaler than 2048 | SHOULD NOT | 495 +-------------------------------------------+------------+ 497 Table 7 499 4.2. Digital Signature Recommendations 501 Recommendations for when a hash function is involved in a signature: 503 +--------+-------------+------------+---------+ 504 | Number | Description | Status | Comment | 505 +--------+-------------+------------+---------+ 506 | 1 | SHA1 | SHOULD NOT | | 507 | 2 | SHA2-256 | MUST | | 508 | 3 | SHA2-384 | MAY | | 509 | 4 | SHA2-512 | SHOULD | | 510 +--------+-------------+------------+---------+ 512 Table 8 514 With the use of Digital Signature, RSASSA-PKCS1-v1.5 MAY be 515 implemented. RSASSA-PSS MUST be implemented. 517 Recommendation of Authentication Method described in [RFC7427] 518 notation: 520 +------------------------------------+------------+---------+ 521 | Description | Status | Comment | 522 +------------------------------------+------------+---------+ 523 | RSASSA-PSS with SHA-256 | SHOULD | | 524 | ecdsa-with-sha256 | SHOULD | | 525 | sha1WithRSAEncryption | SHOULD NOT | | 526 | dsa-with-sha1 | SHOULD NOT | | 527 | ecdsa-with-sha1 | SHOULD NOT | | 528 | RSASSA-PSS with Empty Parameters | SHOULD NOT | | 529 | RSASSA-PSS with Default Parameters | SHOULD NOT | | 530 | sha256WithRSAEncryption | MAY | | 531 | sha384WithRSAEncryption | MAY | | 532 | sha512WithRSAEncryption | MAY | | 533 | sha512WithRSAEncryption | MAY | | 534 | dsa-with-sha256 | MAY | | 535 | ecdsa-with-sha384 | MAY | | 536 | ecdsa-with-sha512 | MAY | ?SHOULD | 537 +------------------------------------+------------+---------+ 539 Table 9 541 5. Security Considerations 543 The security of cryptographic-based systems depends on both the 544 strength of the cryptographic algorithms chosen and the strength of 545 the keys used with those algorithms. The security also depends on 546 the engineering of the protocol used by the system to ensure that 547 there are no non-cryptographic ways to bypass the security of the 548 overall system. 550 The Diffie-Hellman Group parameter is the most important one to 551 choose conservatively. Any party capturing all IKE and ESP traffic 552 that (even years later) can break the selected DH group in IKE, can 553 gain access to the symmetric keys used to encrypt all the ESP 554 traffic. Therefore, these groups must be chosen very conservatively. 555 However, specifying an extremely large DH group also puts a 556 considerable load on the device, especially when this is a large VPN 557 gateway or an IoT constrained device. 559 This document concerns itself with the selection of cryptographic 560 algorithms for the use of IKEv2, specifically with the selection of 561 "mandatory-to-implement" algorithms. The algorithms identified in 562 this document as "MUST implement" or "SHOULD implement" are not known 563 to be broken at the current time, and cryptographic research so far 564 leads us to believe that they will likely remain secure into the 565 foreseeable future. However, this isn't necessarily forever and it 566 is expected that new revisions of this document will be issued from 567 time to time to reflect the current best practice in this area. 569 6. IANA Considerations 571 This document makes no requests of IANA. 573 7. Acknowledgements 575 The first version of this document was RFC 4307 by Jeffrey I. 576 Schiller of the Massachusetts Institute of Technology (MIT). Much of 577 the original text has been copied verbatim. 579 We would like to thank Paul Hoffman, Yaron Sheffer, John Mattsson and 580 Tommy Pauly for their valuable feedback. 582 8. References 584 8.1. Normative References 586 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 587 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ 588 RFC2119, March 1997, 589 . 591 [RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode 592 (GCM) in IPsec Encapsulating Security Payload (ESP)", RFC 593 4106, DOI 10.17487/RFC4106, June 2005, 594 . 596 [RFC4307] Schiller, J., "Cryptographic Algorithms for Use in the 597 Internet Key Exchange Version 2 (IKEv2)", RFC 4307, DOI 598 10.17487/RFC4307, December 2005, 599 . 601 [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. 602 Kivinen, "Internet Key Exchange Protocol Version 2 603 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 604 2014, . 606 [RFC5282] Black, D. and D. McGrew, "Using Authenticated Encryption 607 Algorithms with the Encrypted Payload of the Internet Key 608 Exchange version 2 (IKEv2) Protocol", RFC 5282, DOI 609 10.17487/RFC5282, August 2008, 610 . 612 8.2. Informative References 614 [RFC7427] Kivinen, T. and J. Snyder, "Signature Authentication in 615 the Internet Key Exchange Version 2 (IKEv2)", RFC 7427, 616 DOI 10.17487/RFC7427, January 2015, 617 . 619 [RFC6989] Sheffer, Y. and S. Fluhrer, "Additional Diffie-Hellman 620 Tests for the Internet Key Exchange Protocol Version 2 621 (IKEv2)", RFC 6989, DOI 10.17487/RFC6989, July 2013, 622 . 624 [IKEV2-IANA] 625 , "Internet Key Exchange Version 2 (IKEv2) Parameters", , 626 . 628 [TRANSCRIPTION] 629 Bhargavan, K. and G. Leurent, "Transcript Collision 630 Attacks: Breaking Authentication in TLS, IKE, and SSH", 631 NDSS , feb 2016. 633 Authors' Addresses 635 Yoav Nir 636 Check Point Software Technologies Ltd. 637 5 Hasolelim st. 638 Tel Aviv 6789735 639 Israel 641 EMail: ynir.ietf@gmail.com 643 Tero Kivinen 644 INSIDE Secure 645 Eerikinkatu 28 646 HELSINKI FI-00180 647 FI 649 EMail: kivinen@iki.fi 651 Paul Wouters 652 Red Hat 654 EMail: pwouters@redhat.com 655 Daniel Migault 656 Ericsson 657 8400 boulevard Decarie 658 Montreal, QC H4P 2N2 659 Canada 661 Phone: +1 514-452-2160 662 EMail: daniel.migault@ericsson.com