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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 224 == Missing Reference: 'IoT' is mentioned on line 339, but not defined == Missing Reference: 'IKEv2' is mentioned on line 370, but not defined ** Obsolete normative reference: RFC 4307 (Obsoleted by RFC 8247) Summary: 1 error (**), 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: October 7, 2016 INSIDE Secure 6 P. Wouters 7 Red Hat 8 D. Migault 9 Ericsson 10 April 5, 2016 12 Algorithm Implementation Requirements and Usage Guidance for IKEv2 13 draft-ietf-ipsecme-rfc4307bis-05 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 October 7, 2016. 46 Copyright Notice 48 Copyright (c) 2016 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 64 1.1. Updating Algorithm Implementation Requirements and Usage 65 Guidance . . . . . . . . . . . . . . . . . . . . . . . . 3 66 1.2. Updating Algorithm Requirement Levels . . . . . . . . . . 3 67 1.3. Document Audience . . . . . . . . . . . . . . . . . . . . 4 68 2. Conventions Used in This Document . . . . . . . . . . . . . . 4 69 3. Algorithm Selection . . . . . . . . . . . . . . . . . . . . . 5 70 3.1. Type 1 - IKEv2 Encryption Algorithm Transforms . . . . . 5 71 3.2. Type 2 - IKEv2 Pseudo-random Function Transforms . . . . 6 72 3.3. Type 3 - IKEv2 Integrity Algorithm Transforms . . . . . . 7 73 3.4. Type 4 - IKEv2 Diffie-Hellman Group Transforms . . . . . 8 74 4. IKEv2 Authentication . . . . . . . . . . . . . . . . . . . . 10 75 4.1. IKEv2 Authentication Method . . . . . . . . . . . . . . . 10 76 4.1.1. Recommendations for RSA key length . . . . . . . . . 11 77 4.2. Digital Signature Recommendations . . . . . . . . . . . . 11 78 5. Algorithms for Internet of Things . . . . . . . . . . . . . . 12 79 6. Security Considerations . . . . . . . . . . . . . . . . . . . 13 80 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 81 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 82 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 83 9.1. Normative References . . . . . . . . . . . . . . . . . . 14 84 9.2. Informative References . . . . . . . . . . . . . . . . . 14 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 87 1. Introduction 89 The Internet Key Exchange (IKE) protocol [RFC7296] is used to 90 negotiate the parameters of the IPsec SA, such as the encryption and 91 authentication algorithms and the keys for the protected 92 communications between the two endpoints. The IKE protocol itself is 93 also protected by cryptographic algorithms which are negotiated 94 between the two endpoints using IKE. Different implementations of 95 IKE may negotiate different algorithms based on their individual 96 local policy. To ensure interoperability, a set of "mandatory-to- 97 implement" IKE cryptograhic algorithms is defined. 99 This document describes the parameters of the IKE protocol. It does 100 not describe the cryptographic parameters of the AH or ESP protocols. 102 1.1. Updating Algorithm Implementation Requirements and Usage Guidance 104 The field of cryptography evolves continuously. New stronger 105 algorithms appear and existing algorithms are found to be less secure 106 then originally thought. Therefore, algorithm implementation 107 requirements and usage guidance need to be updated from time to time 108 to reflect the new reality. The choices for algorithms must be 109 conservative to minimize the risk of algorithm compromise. 110 Algorithms need to be suitable for a wide variety of CPU 111 architectures and device deployments ranging from high end bulk 112 encryption devices to small low-power IoT devices. 114 The algorithm implementation requirements and usage guidance may need 115 to change over time to adapt to the changing world. For this reason, 116 the selection of mandatory-to-implement algorithms was removed from 117 the main IKEv2 specification and placed in a separate document. 119 1.2. Updating Algorithm Requirement Levels 121 The mandatory-to-implement algorithm of tomorrow should already be 122 available in most implementations of IKE by the time it is made 123 mandatory. This document attempts to identify and introduce those 124 algorithms for future mandatory-to-implement status. There is no 125 guarantee that the algorithms in use today may become mandatory in 126 the future. Published algorithms are continuously subjected to 127 cryptographic attack and may become too weak or could become 128 completely broken before this document is updated. 130 This document only provides recommendations for the mandatory-to- 131 implement algorithms or algorithms too weak that are recommended not 132 to be implemented. As a result, any algorithm listed at the IKEv2 133 IANA registry not mentioned in this document MAY be implemented. For 134 clarification and consistency with [RFC4307] an algorithm will be set 135 to MAY only when it has been downgraded. 137 Although this document updates the algorithms to keep the IKEv2 138 communication secure over time, it also aims at providing 139 recommendations so that IKEv2 implementations remain interoperable. 140 IKEv2 interoperability is addressed by an incremental introduction or 141 deprecation of algorithms. In addition, this document also considers 142 the new use cases for IKEv2 deployment, such as Internet of Things 143 (IoT). 145 It is expected that deprecation of an algorithm is performed 146 gradually. This provides time for various implementations to update 147 their implemented algorithms while remaining interoperable. Unless 148 there are strong security reasons, an algorithm is expected to be 149 downgraded from MUST to MUST- or SHOULD, instead of MUST NOT. 150 Similarly, an algorithm that has not been mentioned as mandatory-to- 151 implement is expected to be introduced with a SHOULD instead of a 152 MUST. 154 The current trend toward Internet of Things and its adoption of IKEv2 155 requires this specific use case to be taken into account as well. 156 IoT devices are resource constrained devices and their choice of 157 algorithms are motivated by minimizing the footprint of the code, the 158 computation effort and the size of the messages to send. This 159 document indicates "[IoT]" when a specified algorithm is specifically 160 listed for IoT devices. 162 1.3. Document Audience 164 The recommendations of this document mostly target IKEv2 implementers 165 as implementations need to meet both high security expectations as 166 well as high interoperability between various vendors and with 167 different versions. Interoperability requires a smooth move to more 168 secure cipher suites. This may differ from a user point of view that 169 may deploy and configure IKEv2 with only the safest cipher suite. On 170 the other hand, comments and recommendations from this document are 171 also expected to be useful for such users. 173 IKEv1 is out of scope of this document. IKEv1 is deprecated and the 174 recommendations of this document must not be considered for IKEv1, as 175 most IKEv1 implementations have been "frozen" and will not be able to 176 update the list of mandatory-to-implement algorithms. 178 2. Conventions Used in This Document 180 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 181 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 182 document are to be interpreted as described in [RFC2119]. 184 We define some additional terms here: 186 SHOULD+ This term means the same as SHOULD. However, it is likely 187 that an algorithm marked as SHOULD+ will be promoted at 188 some future time to be a MUST. 189 SHOULD- This term means the same as SHOULD. However, an algorithm 190 marked as SHOULD- may be deprecated to a MAY in a future 191 version of this document. 192 MUST- This term means the same as MUST. However, we expect at 193 some point that this algorithm will no longer be a MUST in 194 a future document. Although its status will be determined 195 at a later time, it is reasonable to expect that if a 196 future revision of a document alters the status of a MUST- 197 algorithm, it will remain at least a SHOULD or a SHOULD- 198 level. 199 IoT stands for Internet of Things. 201 3. Algorithm Selection 203 3.1. Type 1 - IKEv2 Encryption Algorithm Transforms 205 The algorithms in the below table are negotiated in the SA payload 206 and used for the Encrypted Payload. References to the specification 207 defining these algorithms and the ones in the following subsections 208 are in the IANA registry [IKEV2-IANA]. Some of these algorithms are 209 Authenticated Encryption with Associated Data (AEAD - [RFC5282]). 210 Algorithms that are not AEAD MUST be used in conjunction with an 211 integrity algorithms in Section 3.3. 213 +-----------------------------+----------+-------+----------+ 214 | Name | Status | AEAD? | Comment | 215 +-----------------------------+----------+-------+----------+ 216 | ENCR_AES_CBC | MUST- | No | [1] | 217 | ENCR_CHACHA20_POLY1305 | SHOULD | Yes | | 218 | AES-GCM with a 16 octet ICV | SHOULD | Yes | [1] | 219 | ENCR_AES_CCM_8 | SHOULD | Yes | [1][IoT] | 220 | ENCR_3DES | MAY | No | | 221 | ENCR_DES | MUST NOT | No | | 222 +-----------------------------+----------+-------+----------+ 224 [1] - This requirement level is for 128-bit keys. 256-bit keys are at 225 MAY. 192-bit keys can safely be ignored. [IoT] - This requirement is 226 for interoperability with IoT. 228 ENCR_AES_CBC is raised from SHOULD+ in [RFC4307] to MUST. It is the 229 only shared mandatory-to-implement algorithm with RFC4307 and as a 230 result it is necessary for interoperability with IKEv2 implementation 231 compatible with RFC4307. 233 ENCR_CHACHA20_POLY1305 was not ready to be considered at the time of 234 RFC4307. It has been recommended by the CRFG and others as an 235 alternative to AES-CBC and AES-GCM. It is also being standardized 236 for IPsec for the same reasons. At the time of writing, there were 237 not enough IKEv2 implementations supporting ENCR_CHACHA20_POLY1305 to 238 be able to introduce it at the SHOULD+ level. 240 AES-GCM with a 16 octet ICV was not considered in RFC4307. At the 241 time RFC4307 was written, AES-GCM was not defined in an IETF 242 document. AES-GCM was defined for ESP in [RFC4106] and later for 243 IKEv2 in [RFC5282]. The main motivation for adopting AES-GCM for ESP 244 is encryption performance and key longevity compared to AES-CBC. 245 This resulted in AES-GCM being widely implemented for ESP. As the 246 computation load of IKEv2 is relatively small compared to ESP, many 247 IKEv2 implementations have not implemented AES-GCM. For this reason, 248 AES-GCM is not promoted to a greater status than SHOULD. The reason 249 for promotion from MAY to SHOULD is to promote the slightly more 250 secure AEAD method over the traditional encrypt+auth method. Its 251 status is expected to be raised once widely implemented. As the 252 advantage of the shorter (and weaker) ICVs is minimal, the 8 and 12 253 octet ICV's remain at the MAY level. 255 ENCR_AES_CCM_8 was not considered in RFC4307. This document 256 considers it as SHOULD be implemented in order to be able to interact 257 with Internet of Things devices. As this case is not a general use 258 case for non-IoT VPNs, its status is expected to remain as SHOULD. 259 The 8 octet size of the ICV is expected to be sufficient for most use 260 cases of IKEv2, as far less packets are exchanged on those cases, and 261 IoT devices want to make packets as small as possible. When 262 implemented, ENCR_AES_CCM_8 MUST be implemented for key length 128 263 and MAY be implemented for key length 256. 265 ENCR_3DES has been downgraded from RFC4307 MUST- to SHOULD NOT. All 266 IKEv2 implementation already implement ENCR_AES_CBC, so there is no 267 need to keep support for the much slower ENCR_3DES. In addition, 268 ENCR_CHACHA20_POLY1305 provides a more modern alternative to AES. 270 ENCR_DES can be brute-forced using of-the-shelves hardware. It 271 provides no meaningful security whatsoever and therefor MUST NOT be 272 implemented. 274 3.2. Type 2 - IKEv2 Pseudo-random Function Transforms 276 Transform Type 2 algorithms are pseudo-random functions used to 277 generate pseudorandom values when needed. 279 If an algorithm is selected as the integrity algorithm, it SHOULD 280 also be used as the PRF. When using an AEAD cipher, a choice of PRF 281 needs to be made. The table below lists the recommended algorithms. 283 +-------------------+----------+---------+ 284 | Name | Status | Comment | 285 +-------------------+----------+---------+ 286 | PRF_HMAC_SHA2_256 | MUST | | 287 | PRF_HMAC_SHA2_512 | SHOULD+ | | 288 | PRF_HMAC_SHA1 | MUST- | | 289 | PRF_AES128_XCBC | SHOULD | [IoT] | 290 | PRF_HMAC_MD5 | MUST NOT | | 291 +-------------------+----------+---------+ 293 [IoT] - This requirement is for interoperability with IoT 295 PRF_HMAC_SHA2_256 was not mentioned in RFC4307, as no SHA2 based 296 transforms were mentioned. PRF_HMAC_SHA2_256 MUST be implemented in 297 order to replace SHA1 and PRF_HMAC_SHA1. 299 PRF_HMAC_SHA2_512 SHOULD be implemented as a future replacement for 300 PRF_HMAC_SHA2_256 or when stronger security is required. 301 PRF_HMAC_SHA2_512 is preferred over PRF_HMAC_SHA2_384, as the 302 additional overhead of PRF_HMAC_SHA2_512 is negligible. 304 PRF_HMAC_SHA1 has been downgraded from MUST in RFC4307 to MUST- as 305 their is an industry-wide trend to deprecate its usage. 307 PRF_AES128_XCBC is only recommended in the scope of IoT, as Internet 308 of Things deployments tend to prefer AES based pseudo-random 309 functions in order to avoid implementing SHA2. For the non-IoT VPN 310 deployment it has been downgraded from SHOULD in RFC4307 to MAY as it 311 has not seen wide adoption. 313 PRF_HMAC_MD5 has been downgraded from MAY in RFC4307 to MUST NOT. 314 There is an industry-wide trend to deprecate its usage as MD5 support 315 is being removed from cryptographic libraries in general because its 316 non-HMAC use is known to be subject to collision attacks, for example 317 as mentioned in [TRANSCRIPTION]. 319 3.3. Type 3 - IKEv2 Integrity Algorithm Transforms 321 The algorithms in the below table are negotiated in the SA payload 322 and used for the Encrypted Payload. References to the specification 323 defining these algorithms are in the IANA registry. When an AEAD 324 algorithm (see Section 3.1) is proposed, this algorithm transform 325 type is not in use. 327 +------------------------+----------+---------+ 328 | Name | Status | Comment | 329 +------------------------+----------+---------+ 330 | AUTH_HMAC_SHA2_256_128 | MUST | | 331 | AUTH_HMAC_SHA2_512_256 | SHOULD | | 332 | AUTH_HMAC_SHA1_96 | MUST- | | 333 | AUTH_AES_XCBC_96 | SHOULD | [IoT] | 334 | AUTH_HMAC_MD5_96 | MUST NOT | | 335 | AUTH_DES_MAC | MUST NOT | | 336 | AUTH_KPDK_MD5 | MUST NOT | | 337 +------------------------+----------+---------+ 339 [IoT] - This requirement is for interoperability with IoT 341 AUTH_HMAC_SHA2_256_128 was not mentioned in RFC4307, as no SHA2 based 342 transforms were mentioned. AUTH_HMAC_SHA2_256_128 MUST be 343 implemented in order to replace AUTH_HMAC_SHA1_96. 345 AUTH_HMAC_SHA2_512_256 SHOULD be implemented as a future replacement 346 of AUTH_HMAC_SHA2_256_128 or when stronger security is required. 347 This value has been preferred over AUTH_HMAC_SHA2_384, as the 348 additional overhead of AUTH_HMAC_SHA2_512 is negligible. 350 AUTH_HMAC_SHA1_96 has been downgraded from MUST in RFC4307 to MUST- 351 as there is an industry-wide trend to deprecate its usage. 353 AUTH_AES-XCBC is only recommended in the scope of IoT, as Internet of 354 Things deployments tend to prefer AES based pseudo-random functions 355 in order to avoid implementing SHA2. For the non-IoT VPN deployment, 356 it has been downgraded from SHOULD in RFC4307 to MAY as it has not 357 been widely adopted. 359 AUTH_HMAC_MD5_96, AUTH_DES_MAC and AUTH_KPDK_MD5 were not mentioned 360 in RFC4307 so its default status was MAY. It has been downgraded to 361 MUST NOT. There is an industry-wide trend to deprecate its usage. 362 MD5 support is being removed from cryptographic libraries in general 363 because its non-HMAC use is known to be subject to collision attacks, 364 for example as mentioned in [TRANSCRIPTION]. 366 3.4. Type 4 - IKEv2 Diffie-Hellman Group Transforms 368 There are several Modular Exponential (MODP) groups and several 369 Elliptic Curve groups (ECC) that are defined for use in IKEv2. These 370 groups are defined in both the [IKEv2] base document and in 371 extensions documents and are identified by group number. Note that 372 it is critical to enforce a secure Diffie-Hellman exchange as this 373 exchange provides keys for the session. If an attacker can retrieve 374 the private numbers (a, or b) and the public values (g**a, and g**b), 375 then the attacker can compute the secret and the keys used and 376 decrypt the exchange and IPsec SA created inside the IKEv2 SA. Such 377 an attack can be performed off-line on a previously recorded 378 communication, years after the communication happened. This differs 379 from attacks that need to be executed during the authentication which 380 must be performed online and in near real-time. 382 +--------+---------------------------------------------+------------+ 383 | Number | Description | Status | 384 +--------+---------------------------------------------+------------+ 385 | 14 | 2048-bit MODP Group | MUST | 386 | 19 | 256-bit random ECP group | SHOULD | 387 | 5 | 1536-bit MODP Group | SHOULD NOT | 388 | 2 | 1024-bit MODP Group | SHOULD NOT | 389 | 1 | 768-bit MODP Group | MUST NOT | 390 | 22 | 1024-bit MODP Group with 160-bit Prime | SHOULD NOT | 391 | | Order Subgroup | | 392 | 23 | 2048-bit MODP Group with 224-bit Prime | SHOULD NOT | 393 | | Order Subgroup | | 394 | 24 | 2048-bit MODP Group with 256-bit Prime | SHOULD NOT | 395 | | Order Subgroup | | 396 +--------+---------------------------------------------+------------+ 398 Group 14 or 2048-bit MODP Group is raised from SHOULD+ in RFC4307 as 399 a replacement for 1024-bit MODP Group. Group 14 is widely 400 implemented and considered secure. 402 Group 19 or 256-bit random ECP group was not specified in RFC4307, as 403 this group were not specified at that time. Group 19 is widely 404 implemented and considered secure. 406 Group 5 or 1536-bit MODP Group has been downgraded from MAY in 407 RFC4307 to SHOULD NOT. It was specified earlier, but is now 408 considered to be vulnerable to be broken within the next few years by 409 a nation state level attack, so its security margin is considered too 410 narrow. 412 Group 2 or 1024-bit MODP Group has been downgraded from MUST- in 413 RFC4307 to SHOULD NOT. It is known to be weak against sufficiently 414 funded attackers using commercially available mass-computing 415 resources, so its security margin is considered too narrow. It is 416 expected in the near future to be downgraded to MUST NOT. 418 Group 1 or 768-bit MODP Group was not mentioned in RFC4307 and so its 419 status was MAY. It can be broken within hours using cheap of-the- 420 shelves hardware. It provides no security whatsoever. 422 Group 22, 23 and 24 or 1024-bit MODP Group with 160-bit, and 2048-bit 423 MODP Group with 224-bit and 256-bit Prime Order Subgroup have small 424 subgroups, which means that checks specified in the "Additional 425 Diffie-Hellman Test for the IKEv2" [RFC6989] section 2.2 first bullet 426 point MUST be done when these groups are used. These groups are also 427 not safe-primes. The seeds for these groups have not been publicly 428 released, resulting in reduced trust in these groups. These groups 429 were proposed as alternatives for group 2 and 14 but never saw wide 430 deployment. It is expected in the near future to be further 431 downgraded to MUST NOT. 433 4. IKEv2 Authentication 435 IKEv2 authentication may involve a signatures verification. 436 Signatures may be used to validate a certificate or to check the 437 signature of the AUTH value. Cryptographic recommendations regarding 438 certificate validation are out of scope of this document. What is 439 mandatory to implement is provided by the PKIX Community. This 440 document is mostly concerned on signature verification and generation 441 for the authentication. 443 4.1. IKEv2 Authentication Method 445 +--------+---------------------------------------+------------+ 446 | Number | Description | Status | 447 +--------+---------------------------------------+------------+ 448 | 1 | RSA Digital Signature | MUST | 449 | 3 | DSS Digital Signature | SHOULD NOT | 450 | 9 | ECDSA with SHA-256 on the P-256 curve | SHOULD | 451 | 10 | ECDSA with SHA-384 on the P-384 curve | SHOULD | 452 | 11 | ECDSA with SHA-512 on the P-521 curve | SHOULD | 453 | 14 | Digital Signature | SHOULD | 454 +--------+---------------------------------------+------------+ 456 RSA Digital Signature is widely deployed and therefore kept for 457 interoperability. It is expected to be downgraded in the future as 458 its signatures are based on the older RSASSA-PKCS1-v1.5 which is no 459 longer recommended. RSA authentication, as well as other specific 460 Authentication Methods, are expected to be replaced with the generic 461 Digital Signature method of [RFC7427]. RSA Digital Signature is not 462 recommended for keys smaller then 2048, but since these signatures 463 only have value in real-time, and need no future protection, smaller 464 keys was kept at SHOULD NOT instead of MUST NOT. 466 ECDSA based Authentication Methods are also expected to be downgraded 467 as it does not provide hash function agility. Instead, ECDSA (like 468 RSA) is expected to be performed using the generic Digital Signature 469 method. 471 DSS Digital Signature is bound to SHA-1 and has the same level of 472 security as 1024-bit RSA. It is expected to be downgraded to MUST 473 NOT in the future. 475 Digital Signature [RFC7427] is expected to be promoted as it provides 476 hash function, signature format and algorithm agility. 478 4.1.1. Recommendations for RSA key length 480 +-------------------------------------------+------------+ 481 | Description | Status | 482 +-------------------------------------------+------------+ 483 | RSA with key length 2048 | MUST | 484 | RSA with key length 3072 and 4096 | SHOULD | 485 | RSA with key length between 2049 and 4095 | MAY | 486 | RSA with key length smaler than 2048 | SHOULD NOT | 487 +-------------------------------------------+------------+ 489 4.2. Digital Signature Recommendations 491 Recommendations for when a hash function is involved in a signature: 493 +--------+-------------+------------+---------+ 494 | Number | Description | Status | Comment | 495 +--------+-------------+------------+---------+ 496 | 1 | SHA1 | SHOULD NOT | | 497 | 2 | SHA2-256 | MUST | | 498 | 3 | SHA2-384 | MAY | | 499 | 4 | SHA2-512 | SHOULD | | 500 +--------+-------------+------------+---------+ 502 With the use of Digital Signature, RSASSA-PKCS1-v1.5 MAY be 503 implemented. RSASSA-PSS MUST be implemented. 505 Recommendation of Authentication Method described in [RFC7427] 506 notation: 508 +------------------------------------+------------+---------+ 509 | Description | Status | Comment | 510 +------------------------------------+------------+---------+ 511 | RSASSA-PSS with SHA-256 | SHOULD | | 512 | ecdsa-with-sha256 | SHOULD | | 513 | sha1WithRSAEncryption | SHOULD NOT | | 514 | dsa-with-sha1 | SHOULD NOT | | 515 | ecdsa-with-sha1 | SHOULD NOT | | 516 | RSASSA-PSS with Empty Parameters | SHOULD NOT | | 517 | RSASSA-PSS with Default Parameters | SHOULD NOT | | 518 | sha256WithRSAEncryption | MAY | | 519 | sha384WithRSAEncryption | MAY | | 520 | sha512WithRSAEncryption | MAY | | 521 | sha512WithRSAEncryption | MAY | | 522 | dsa-with-sha256 | MAY | | 523 | ecdsa-with-sha384 | MAY | | 524 | ecdsa-with-sha512 | MAY | ?SHOULD | 525 +------------------------------------+------------+---------+ 527 5. Algorithms for Internet of Things 529 Some algorithms in this document are marked for the Internet of 530 Things (IoT). There are several reasons why the IoT devices want 531 have different set of algorithms than other users of IKEv2. Those 532 devices are usually very constrained, meaning the memory size and cpu 533 power is so limited, that they want to implement just minimal set of 534 algorithms. This means they quite often only implement one algorithm 535 and pick it so that the same algorithm is already implemented in 536 software or hardware for other users. 538 For example IEEE Std 802.15.4 [IEEE-802-15-4] devices has mandatory 539 to implement link level security using AES-CCM with 128 bit keys. 540 The IEEE Recommended Practice for Transport of Key Management 541 Protocol (KMP) Datagrams [IEEE-802-15-9] already provides a way to 542 use Minimal IKEv2 [RFC7815] over 802.15.4 to provide link keys for 543 the 802.15.4. 545 Those devices might want to use AES-CCM as their IKEv2 algorithm, so 546 they can reuse the hardware implementing it. They cannot use the 547 AES-CBC, as the hardware quite often do not include support for AES 548 decryption needed for it. So even when AES-CCM algorithm support 549 requires support for the AEAD [RFC5282] support for IKEv2, the 550 benefit of reusing crypto hardware makes it worthwhile. 552 Other important aspects of the IoT devices, that their transfer rates 553 are usually quite low (in order of tens of kbits/s), and each bit 554 they transmit costs a lot in energy consumption (shortening the 555 battery life). Because of this they usually want to use options 556 which support shorter packets. I.e., using 8 octet ICV instead of 557 16. 559 Also as each of those IoT devices have different constraints, we 560 cannot specify one exact profile for them. This document points out 561 some algorithms commonly used in the IoT devices, but there might be 562 devices using different set of algorithms, because of requirements 563 for the environment. 565 6. Security Considerations 567 The security of cryptographic-based systems depends on both the 568 strength of the cryptographic algorithms chosen and the strength of 569 the keys used with those algorithms. The security also depends on 570 the engineering of the protocol used by the system to ensure that 571 there are no non-cryptographic ways to bypass the security of the 572 overall system. 574 The Diffie-Hellman Group parameter is the most important one to 575 choose conservatively. Any party capturing all IKE and ESP traffic 576 that (even years later) can break the selected DH group in IKE, can 577 gain access to the symmetric keys used to encrypt all the ESP 578 traffic. Therefore, these groups must be chosen very conservatively. 579 However, specifying an extremely large DH group also puts a 580 considerable load on the device, especially when this is a large VPN 581 gateway or an IoT constrained device. 583 This document concerns itself with the selection of cryptographic 584 algorithms for the use of IKEv2, specifically with the selection of 585 "mandatory-to-implement" algorithms. The algorithms identified in 586 this document as "MUST implement" or "SHOULD implement" are not known 587 to be broken at the current time, and cryptographic research so far 588 leads us to believe that they will likely remain secure into the 589 foreseeable future. However, this isn't necessarily forever and it 590 is expected that new revisions of this document will be issued from 591 time to time to reflect the current best practice in this area. 593 7. IANA Considerations 595 This document makes no requests of IANA. 597 8. Acknowledgements 599 The first version of this document was RFC 4307 by Jeffrey I. 600 Schiller of the Massachusetts Institute of Technology (MIT). Much of 601 the original text has been copied verbatim. 603 We would like to thank Paul Hoffman, Yaron Sheffer, John Mattsson and 604 Tommy Pauly for their valuable feedback. 606 9. References 608 9.1. Normative References 610 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 611 Requirement Levels", BCP 14, RFC 2119, 612 DOI 10.17487/RFC2119, March 1997, 613 . 615 [RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode 616 (GCM) in IPsec Encapsulating Security Payload (ESP)", 617 RFC 4106, DOI 10.17487/RFC4106, June 2005, 618 . 620 [RFC4307] Schiller, J., "Cryptographic Algorithms for Use in the 621 Internet Key Exchange Version 2 (IKEv2)", RFC 4307, 622 DOI 10.17487/RFC4307, December 2005, 623 . 625 [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. 626 Kivinen, "Internet Key Exchange Protocol Version 2 627 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 628 2014, . 630 [RFC5282] Black, D. and D. McGrew, "Using Authenticated Encryption 631 Algorithms with the Encrypted Payload of the Internet Key 632 Exchange version 2 (IKEv2) Protocol", RFC 5282, 633 DOI 10.17487/RFC5282, August 2008, 634 . 636 9.2. Informative References 638 [RFC7427] Kivinen, T. and J. Snyder, "Signature Authentication in 639 the Internet Key Exchange Version 2 (IKEv2)", RFC 7427, 640 DOI 10.17487/RFC7427, January 2015, 641 . 643 [RFC6989] Sheffer, Y. and S. Fluhrer, "Additional Diffie-Hellman 644 Tests for the Internet Key Exchange Protocol Version 2 645 (IKEv2)", RFC 6989, DOI 10.17487/RFC6989, July 2013, 646 . 648 [RFC7815] Kivinen, T., "Minimal Internet Key Exchange Version 2 649 (IKEv2) Initiator Implementation", RFC 7815, 650 DOI 10.17487/RFC7815, March 2016, 651 . 653 [IKEV2-IANA] 654 "Internet Key Exchange Version 2 (IKEv2) Parameters", 655 . 657 [TRANSCRIPTION] 658 Bhargavan, K. and G. Leurent, "Transcript Collision 659 Attacks: Breaking Authentication in TLS, IKE, and SSH", 660 NDSS , feb 2016. 662 [IEEE-802-15-4] 663 "IEEE Standard for Low-Rate Wireless Personal Area 664 Networks (WPANs)", IEEE Standard 802.15.4, 2015. 666 [IEEE-802-15-9] 667 "IEEE Recommended Practice for Transport of Key Management 668 Protocol (KMP) Datagrams", IEEE Standard 802.15.9, 2016. 670 Authors' Addresses 672 Yoav Nir 673 Check Point Software Technologies Ltd. 674 5 Hasolelim st. 675 Tel Aviv 6789735 676 Israel 678 EMail: ynir.ietf@gmail.com 680 Tero Kivinen 681 INSIDE Secure 682 Eerikinkatu 28 683 HELSINKI FI-00180 684 FI 686 EMail: kivinen@iki.fi 688 Paul Wouters 689 Red Hat 691 EMail: pwouters@redhat.com 692 Daniel Migault 693 Ericsson 694 8400 boulevard Decarie 695 Montreal, QC H4P 2N2 696 Canada 698 Phone: +1 514-452-2160 699 EMail: daniel.migault@ericsson.com