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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group R. Gagliano 3 Internet-Draft Cisco Systems 4 Intended status: Standards Track S. Kent 5 Expires: April 22, 2013 BBN Technologies 6 S. Turner 7 IECA, Inc. 8 October 19, 2012 10 Algorithm Agility Procedure for RPKI. 11 draft-ietf-sidr-algorithm-agility-08 13 Abstract 15 This document specifies the process that Certification Authorities 16 (CAs) and Relying Parties (RPs) participating in the Resource Public 17 Key Infrastructure (RPKI) will need to follow to transition to a new 18 (and probably cryptographically stronger) algorithm set. The process 19 is expected to be completed in a time scale of months or years. 20 Consequently, no emergency transition is specified. The transition 21 procedure defined in this document supports only a top-down migration 22 (parent migrates before children). 24 Status of this Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on April 22, 2013. 41 Copyright Notice 43 Copyright (c) 2012 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 59 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 61 4. Key Rollover steps for algorithm migration . . . . . . . . . . 8 62 4.1. Milestones definition . . . . . . . . . . . . . . . . . . 8 63 4.2. Process overview . . . . . . . . . . . . . . . . . . . . . 8 64 4.3. Phase 0 . . . . . . . . . . . . . . . . . . . . . . . . . 10 65 4.3.1. Milestone 1 . . . . . . . . . . . . . . . . . . . . . 11 66 4.4. Phase 1 . . . . . . . . . . . . . . . . . . . . . . . . . 12 67 4.5. Phase 2 . . . . . . . . . . . . . . . . . . . . . . . . . 13 68 4.6. Phase 3 . . . . . . . . . . . . . . . . . . . . . . . . . 14 69 4.7. Phase 4 . . . . . . . . . . . . . . . . . . . . . . . . . 15 70 4.8. Return to Phase 0 . . . . . . . . . . . . . . . . . . . . 16 71 5. Multi Algorithm support in the RPKI provisioning protocol . . 17 72 6. Validation of multiple instance of signed products . . . . . . 18 73 7. Revocation . . . . . . . . . . . . . . . . . . . . . . . . . . 19 74 8. Key rollover . . . . . . . . . . . . . . . . . . . . . . . . . 20 75 9. Repository structure . . . . . . . . . . . . . . . . . . . . . 21 76 10. Deprecating an Algorithm Suite . . . . . . . . . . . . . . . . 22 77 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 78 12. Security Considerations . . . . . . . . . . . . . . . . . . . 25 79 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26 80 14. Normative References . . . . . . . . . . . . . . . . . . . . . 27 81 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 28 82 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30 84 1. Requirements notation 86 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 87 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 88 document are to be interpreted as described in [RFC2119]. 90 2. Introduction 92 The RPKI must accommodate transitions between the public keys used by 93 CAs. Transitions of this sort are usually termed "key rollover". 94 Planned key rollover will occur at regular intervals throughout the 95 life of the RPKI, as each CA changes its public keys, in a non- 96 coordinated fashion. (By non-coordinated we mean that the time at 97 which each CA elects to change its keys is locally determined, not 98 coordinated across the RPKI.) Moreover, because a key change might 99 be necessitated by suspected private key compromise, one can never 100 assume coordination of these events among all of the CAs in the RPKI. 101 In an emergency key rollover, the old certificate is revoked and a 102 new certificate with a new key is issued. The mechanisms to perform 103 a key rollover in RPKI (either planned or in an emergency), while 104 maintaining the same algorithm suite, are covered in [RFC6489]. 106 This document describes the mechanism to perform a key rollover in 107 RPKI due to the migration to a new signature algorithm suite. A 108 signature algorithm suite encompasses both a signature algorithm 109 (with a specified key size range) and a one-way hash algorithm. It 110 is anticipated that the RPKI will require the adoption of updated key 111 sizes and/or different algorithm suites over time. This document 112 treats the adoption of a new hash algorithm while retaining the 113 current signature algorithm as equivalent to an algorithm migration, 114 and requires the CA to change its key. Migration to a new algorithm 115 suite will be required in order to maintain an acceptable level of 116 cryptographic security and protect the integrity of certificates, 117 CRLs and signed objects in the RPKI. All of the data structures in 118 the RPKI explicitly identify the signature and hash algorithms being 119 used. However, experience has demonstrated that the ability to 120 represent algorithm IDs is not sufficient to enable migration to new 121 algorithm suites (algorithm agility). One also must ensure that 122 protocols, infrastructure elements, and operational procedures also 123 accommodate the migration from one algorithm suite to another. 124 Algorithm migration is expected to be very infrequent and it will 125 require support of a "current" and "next" suite for a prolonged 126 interval, probably several years. 128 This document defines how entities in the RPKI execute (planned) CA 129 key rollover when the algorithm suite changes. The description 130 covers actions by CAs, repository operators, and RPs. It describes 131 the behavior required of both CAs and RPs to make such key changes 132 work in the RPKI context, including how the RPKI repository system is 133 used to support key rollover. 135 This document does not specify any algorithm suite per se. The RPKI 136 Certificate Policy (CP) [RFC6484] mandates the use of the algorithms 137 defined in [RFC6485] by CAs and RPs. When an algorithm transition is 138 initiated, [RFC6485] will be updated (as defined in Section 4.1 of 139 this document) redefining the required algorithm(s) for compliant 140 RPKI CAs and RPs under the CP. The CP will not change as a side 141 effect of algorithm transition (and thus the policy OID in RPKI 142 certificates will not change.) 144 An additional document, the algorithm transition timetable, will be 145 published (as an IETF BCP) to define the dates for each milestone 146 defined in this document. It will define dates for the phase 147 transitions, consistent with the descriptions provided in Section 4. 148 It also will describe how the RPKI community will measure the 149 readiness of CAs and RPs to transition to each phase. CAs publish 150 certificates, CRLs, and other signed objects under the new algorithm 151 suite as the transition progresses. This provides visibility into 152 the deployment of the new algorithm suite, enabling the community to 153 evaluate deployment progress. The transition procedure allows CAs to 154 remove old certificates, CRLs, and signed products, after the 155 twilight date. This provides an ability to observe and measure the 156 withdrawal of the old algorithm suite. Thus the phases defined in 157 this document enable the community to evaluate the progress of the 158 transition. The timetable document will also describe procedures to 159 amend the timetable if problems arise in implementing later phases of 160 the transition. It is RECOMMENDED that the timetable document be 161 developed by representatives of the RPKI community, e.g., IANA, 162 Internet Registries, and network operators. 164 3. Terminology 166 This document assumes that the reader is familiar with the terms and 167 concepts described in "Internet X.509 Public Key Infrastructure 168 Certificate and Certificate Revocation List (CRL) Profile" [RFC5280], 169 "X.509 Extensions for IP Addresses and AS Identifiers" [RFC3779], and 170 "A Profile for Resource Certificate Repository Structure" [RFC6481]. 171 Additional terms and conventions used in examples are provided below. 173 Algorithm migration: A planned transition from one signature and 174 hash algorithm to a new signature and hash algorithm. 176 Algorithm Suite A: The "current" algorithm suite used for hashing 177 and signing, in examples in this document 179 Algorithm Suite B: The "next" algorithm suite used for hashing and 180 signing, used in examples in this document 182 Algorithm Suite C: The "old" algorithm suite used for hashing and 183 signing, used in examples in this document 185 CA X: The CA that issued CA Y's certificate (i.e., CA Y's 186 parent), used in examples in this document. 188 CA Y: The non-leaf CA used in examples this document 190 CA Z: A CA that is a "child" of CA Y, used in examples this 191 document 193 Non-Leaf CA: A CA that issues certificates to other CAs is a non- 194 leaf CA. 196 Leaf CA: A leaf CA is a CA that issues only EE certs. 198 PoP (proof of possession): Execution of a protocol that demonstrates 199 to an issuer that a subject requesting a certificate 200 possesses the private key corresponding to the public key 201 in the certificate request submitted by the subject. 203 Signed Product Set (or Set or Product Set): A collection of 204 certificates, signed objects, a CRL and a manifest that 205 are associated by virtue of being verifiable under the 206 same parent CA certificate 208 Correspond: Two certificates, issued under different Algorithm Suites 209 correspond to one another if they are issued to the same 210 entity by the same CA and bind identical Internet Number 211 Resoureces (INRs) to that entity. Two CRLs correspond if 212 they are issued by the same CA and enumerate 213 corresponding certificates. Two signed objects (other 214 than manifests) correspond if they are verified using 215 corresponding EE certificates and they contain the same 216 encapsulated Context Info field. Two manifests 217 correspond if they encompass corresponding certificates, 218 ROAs, CRLs, and (other) signed objects (the term 219 "equivalent" is used synonymously when referring to such 220 RPKI signed products.) 222 4. Key Rollover steps for algorithm migration 224 The "current" RPKI algorithm suite (Suite A) is defined in the RPKI 225 CP document, by reference to [RFC6485]. When a migration of the RPKI 226 algorithm suite is needed, the first step MUST be an update of 227 [RFC6485] to define the new algorithm suite. The algorithm 228 transition timeline document MUST also be published (as a BCP), to 229 inform the community of the dates selected for milestones in the 230 transition process, as described in Section 4.1. 232 4.1. Milestones definition 234 CA Ready Algorithm B Date: After this date, all (non-leaf) CAs MUST 235 be ready to process a request from a child CA to issue a 236 certificate under the Algorithm Suite B. All CAs 237 publishing an [RFC6490] Trust Anchor Locator (TAL) for 238 Algorithm Suite A, MUST also publish the correspondent 239 TAL for Algorithm Suite B. 241 CA Go Algorithm B Date: After this date, all CAs MUST have reissued 242 all of their signed product sets under the Algorithm 243 Suite B. 245 RP Ready Algorithm B Date: After this date, all RPs MUST be prepared 246 to process signed material issued under the Algorithm 247 Suite B. 249 Twilight Date: After this date, a CA MAY cease issuing signed 250 products under the Algorithm Suite A. Also, after this 251 date, a RP MAY cease to validate signed materials issued 252 under the Algorithm Suite A. 254 End Of Life (EOL) Date: After this date, the Algorithm Suite C is 255 MUST be deprecated using the process in Section 10 and 256 all Algorithm Suite C TALs MUST be removed from their 257 publication points. 259 4.2. Process overview 261 The migration process described in this document involves a series of 262 steps that MUST be executed in chronological order by CAs and RPs. 263 The only milestone at which both CAs and RPs take action at the same 264 time is the EOL Date. Due to the decentralized nature of the RPKI 265 infrastructure, it is expected that an algorithm transition will span 266 several years. 268 In order to facilitate the transition, CAs will start issuing 269 certificates using the Algorithm B in a hierarchical top-down 270 fashion. In our example, CA Y will issue certificates using the 271 Algorithm Suite B only after CA X has started to do so (CA Y Ready 272 Algorithm B Date > CA X Ready Algorithm B Date). This ordered 273 transition avoids issuance of "mixed" suite CA certificates, e.g., a 274 CA certificate signed using Suite A, containing a key from Suite B. 275 In the RPKI, a CA MUST NOT sign a CA certificate carrying a subject 276 key that corresponds to an algorithm suite that differs from the one 277 used to sign the certificate. (X.509 accommodates such mixed 278 algorithm certificates, but this process avoids using that 279 capability.) A not top-down transition approach would require use of 280 such mixed mode certificates, and would lead to exponential growth of 281 the RPKI repository. Also, because the RPKI CP mandates Proof of 282 Possession (PoP) for certificate requests, it is not possible for a 283 CA to request a certificate for Algorithm Suite B, until its parent 284 CA supports that Suite. (See Section 5 for more details.) 286 The algorithm agility model described here does not prohibit a CA 287 from issuing an EE certificate with a subject public key from a 288 different algorithm suite, if that certificate is not used to verify 289 repository objects. This exception to the mixed algorithm suite 290 certificate rule is allowed because an EE certificate that is not 291 used to verify repository objects does not interfere with the ability 292 of RPs to download and verify repository content. As noted above, 293 every CA in the RPKI is required to perform a PoP check for the 294 subject public key when issuing a certificate. In general a subject 295 cannot assume that a CA is capable of supporting a different 296 algorithm. However, if the subject is closely affiliated with the 297 CA, it is reasonable to assume that there are ways for the subject to 298 know whether the CA can support a request to issue an EE certificate 299 containing a specific, different public key algorithm. This document 300 does not specify how a subject can determine whether a CA is capable 301 of issuing a mixed suite EE certificate, because it anticipates that 302 such certificates will be issued only in contexts where the subject 303 and CA are sufficiently closely affiliated (for example, an ISP 304 issuing certificates to devices that it manages). 306 The following figure gives an overview of the process: 308 Process for RPKI CAs: 310 Phase 0 Phase 1 Phase 2 Phase 4 Phase 0 311 -----------x---------x-------------------x--------x----------- 312 ^ ^ ^ ^ ^ 313 | | | | | 314 (1) (2) (3) (5) (6) 316 Process for RPKI RPs: 318 Phase 0 Phase 3 Phase 4 Phase 0 319 -------------------------------x---------x--------x----- 320 ^ ^ ^ ^ 321 | | | | 322 (1) (4) (5) (6) 324 (1) RPKI algorithm document is updated and the algorithm transition timeline document is issued 325 (2) CA Ready Algorithm B Date 326 (3) CA Go Algorithm B Date 327 (4) RP Ready Algorithm B Date 328 (5) Twilight Date 329 (6) End Of Live (EOL) Date 331 Each of these milestones is discussed in the next section when 332 describing each phase of the transition process. 334 Two situations have been identified that motivate pausing or rolling 335 back the transition process. The first situation arises if the RPKI 336 community is not ready to make the transition. For example, many CAs 337 might not be prepared to issue signed products under Suite B, or many 338 RPs might not be ready to process Suite B products. Under these 339 circumstances, the timetable MUST be reissued, postponing the date 340 for the phase in question, and pushing back the dates for later 341 phases. The other situation arises if, during the transition, 342 serious concerns arise about the security of the Suite B algorithms. 343 Such concerns would motivate terminating the transition and rolling 344 back signed products, i.e., reverting to Suite A. In this case the 345 timetable MUST be republished, and the RPKI algorithm document MUST 346 be superseded. The phase descriptions below allude to these two 347 situations, as appropriate. 349 4.3. Phase 0 351 Phase 0 is the initial phase of the process, throughout this phase 352 the algorithm suite A is the only supported algorithm suite in RPKI. 353 This is also the steady state for the RPKI. 355 The following figure illustrates the format used to describe signed 356 objects in the repository. It reflects the algorithm suites in use, 357 and shows the relationship between three CAs (X, Y, and Z) that form 358 a chain. 360 During Phase 0, CAs X, Y and Z are required to generate signed 361 product sets using only the Algorithm Suite A. Also, RPs are required 362 to validate signed product sets issued using only Algorithm Suite A. 364 CA X-Certificate-Algorithm-Suite-A (Cert-XA) 365 | 366 |-> CA-Y-Certificate-Algorithm-Suite-A (Cert-YA) 367 |-> CA-Z-Certificate-Algorithm-Suite-A (Cert-ZA) 368 |-> CA-Z-CRL-Algorithm-Suite-A (CRL-ZA) 369 |-> CA-Z-Signed-Objects-Algorithm-Suite-A 370 |-> CA-Y-CRL-Algorithm-Suite-A (CRL-YA) 371 |-> CA-Y-Signed-Objects-Algorithm-Suite-A 372 |-> CA-X-CRL-Algorithm-Suite-A (CRL-XA) 373 |-> CA-X-Signed-Objects-Algorithm-Suite-A 375 Note: Cert-XA represent the certificate for CA X, that is signed 376 using the algorithm suite A. 378 4.3.1. Milestone 1 380 The first milestone initiates the migration process. It updates 381 [RFC6485] with the following definitions for the RPKI: 383 o Algorithm Suite A 385 o Algorithm Suite B 387 Additionally, the new algorithm transition timeline document will be 388 published with the following information: 390 o CA Ready Algorithm B Date 392 o CA Go Algorithm B Date 394 o RP Ready Algorithm B Date 396 o Twilight Date 398 o EOL Date 400 o Readiness metrics for CAs and RPs in each phase 402 Each date specified here is assumed at one minute after midnight, 403 UTC. No finer granularity time specification is required or 404 supported. 406 4.4. Phase 1 408 Phase 1 starts at the CA Ready Algorithm B Date. During Phase 1, all 409 (non-leaf) CAs MUST be ready to process a request from a child CA to 410 issue or revoke a certificate using the Algorithm Suite B. If it is 411 determined that a substantial number of CAs are not ready, the 412 algorithm transition timeline document will be reissued, as noted in 413 Section 4.2. However, CAs that are capable of issuing Suite B 414 certificates may continue to do so, if requested by their child CAs. 415 Since this phase does not require any RPs to process signed objects 416 under Suite B, and since Suite B product sets SHOULD be stored at 417 independent publication points, there is no adverse impact on RPs. 418 If the Suite B algorithm is deemed unsuitable, the algorithm 419 transition timeline and the algorithm specification documents MUST be 420 replaced, the Algorithm Suite B MUST be deprecated using the process 421 described in Section 10. 423 As the transition will happen using a (hierarchic) top-down model, a 424 child CA will be able to issue certificates using the Algorithm Suite 425 B only after its parent CA has issued its own. The RPKI provisioning 426 protocol can identify if a parent CA is capable of issuing 427 certificates using the Algorithm Suite B, and can identify the 428 corresponding algorithm suite in each Certificate Signing Request 429 (see Section 5). During much of this phase the Suite B product tree 430 will be incomplete, i.e., not all CAs will have issued products under 431 Suite B. Thus for production purposes, RPs MUST fetch and validate 432 only Suite A products. Suite B products should be fetched and 433 processed only for testing purposes. 435 The following figure shows the status of repository entries for the 436 three example CAs during this Phase. Two distinct certificate chains 437 are maintained and CA Z has not yet requested any material using the 438 Algorithm Suite B. 440 CA X-Certificate-Algorithm-Suite-A (Cert-XA) 441 | 442 |-> CA-Y-Certificate-Algorithm-Suite-A (Cert-YA) 443 |-> CA-Z-Certificate-Algorithm-Suite-A (Cert-ZA) 444 |-> CA-Z-CRL-Algorithm-Suite-A (CRL-ZA) 445 |-> CA-Z-Signed-Objects-Algorithm-Suite-A 446 |-> CA-Y-CRL-Algorithm-Suite-A (CRL-YA) 447 |-> CA-Y-Signed-Objects-Algorithm-Suite-A 448 |-> CA-X-CRL-Algorithm-Suite-A (CRL-XA) 449 |-> CA-X-Signed-Objects-Algorithm-Suite-A 451 CA X-Certificate-Algorithm-Suite-B (Cert-XB) 452 | 453 |-> CA-Y-Certificate-Algorithm-Suite-B (Cert-YB) 454 |-> CA-Y-CRL-Algorithm-Suite-B (CRL-YB) 455 |-> CA-Y-Signed-Objects-Algorithm-Suite-B 456 |-> CA-X-CRL-Algorithm-Suite-B (CRL-XB) 457 |-> CA-X-Signed-Objects-Algorithm-Suite-B 459 4.5. Phase 2 461 Phase 2 starts at the CA Go Algorithm B Date. At the start of this 462 phase, each signed product set MUST be available using both Algorithm 463 Suite A and Algorithm Suite B. Thus, prior to the start of this 464 phase, every CA MUST ensure that there is a Suite B product 465 corresponding to each Suite A product that the CA has issued. 466 Throughout this Phase, each CA MUST maintain this correspondence. 467 During this phase, RPs MUST be prepared to validate sets issued using 468 Algorithm Suite A and MAY be prepared to validate sets issued using 469 the Algorithm Suite B. 471 If it is determined that a substantial number of CAs are not ready, 472 the algorithm transition timeline document will be reissued, as noted 473 in Section 4.2. (Since the processing requirement for RPs here is a 474 MAY, if RPs have problems with Suite B products this does not require 475 pushing back the Phase 2 milestone, but it does motivate delaying the 476 start of Phase 3.) CAs that are capable of publishing products under 477 Suite B MAY continue to do so. Phase 2, like Phase 1, does not 478 require any RPs to process signed objects under Suite B. Also, Suite 479 B product SHOULD be stored at independent publication points, so 480 there is no adverse impact on RPs that are not prepared to process 481 suite B products. If the Suite B algorithm is deemed unsuitable, the 482 algorithm transition timeline and the algorithm specification 483 documents MUST be replaced and the Algorithm Suite B MUST be 484 deprecated using the process described in Section 10. 486 It is RECOMMENDED that RPs that can process Algorithm Suite B fetch 487 and validate Suite B products. RPs that are not ready to process 488 Suite B products MUST continue to make use of Suite A products. An 489 RP that elects to validate signed product sets using both Algorithm 490 Suite A or Algorithm Suite B should expect the same results. If 491 there are discrepancies when evaluating corresponding signed product 492 sets, successful validation of either product set is acceptable. A 493 detailed analysis of the validation of multiple instances of signed 494 objects is included in Section 6. 496 The following figure shows the status of the repository entries for 497 the three example CAs throughout this phase, where all signed objects 498 are available using both algorithm suites. 500 CA X-Certificate-Algorithm-Suite-A (Cert-XA) 501 | 502 |-> CA-Y-Certificate-Algorithm-Suite-A (Cert-YA) 503 |-> CA-Z-Certificate-Algorithm-Suite-A (Cert-ZA) 504 |-> CA-Z-CRL-Algorithm-Suite-A (CRL-ZA) 505 |-> CA-Z-Signed-Objects-Algorithm-Suite-A 506 |-> CA-Y-CRL-Algorithm-Suite-A (CRL-YA) 507 |-> CA-Y-Signed-Objects-Algorithm-Suite-A 508 |-> CA-X-CRL-Algorithm-Suite-A (CRL-XA) 509 |-> CA-X-Signed-Objects-Algorithm-Suite-A 511 CA X-Certificate-Algorithm-Suite-B (Cert-XB) 512 | 513 |-> CA-Y-Certificate-Algorithm-Suite-B (Cert-YB) 514 |-> CA-Z-Certificate-Algorithm-Suite-B (Cert-ZB) 515 |-> CA-Z-CRL-Algorithm-Suite-B (CRL-ZB) 516 |-> CA-Z-Signed-Objects-Algorithm-Suite-B 517 |-> CA-Y-CRL-Algorithm-Suite-B (CRL-YB) 518 |-> CA-Y-Signed-Objects-Algorithm-Suite-B 519 |-> CA-X-CRL-Algorithm-Suite-B (CRL-XB) 520 |-> CA-X-Signed-Objects-Algorithm-Suite-B 522 4.6. Phase 3 524 Phase 3 starts at the RP Ready Algorithm B Date. During this phase, 525 all signed product sets are available using both algorithm suites and 526 all RPs MUST be able to validate them. (The correspondence between 527 Suite A and Suite B products was required for Phase 2, and maintained 528 throughout that Phase. The same requirements apply throughout this 529 Phase.) It is RECOMMENDED that, in preparation for Phase 4, RPs 530 retrieve and process Suite B product sets first, and treat them as 531 the preferred product sets for validation throughout this phase. 532 Thus an RP SHOULD try to validate the sets of signed products 533 retrieved from the Algorithm Suite B repository first. 535 If a substantial number of RPs are unable to process product sets 536 signed with Suite B, the algorithm transition timeline document MUST 537 be reissued, pushing back the date for this and later milestones, as 538 discussed in Section 4.2. Since the Suite B products SHOULD be 539 published at distinct publication points, RPs that cannot process 540 Suite B products can be expected to revert to the Suite A products 541 that still exist. If the Suite B algorithm is deemed unsuitable, the 542 algorithm transition timeline and the algorithm specification 543 documents MUST be replaced and the Algorithm Suite B MUST be 544 deprecated using the process described in Section 10. 546 There are no changes to the CA behavior throughout this phase. 548 4.7. Phase 4 550 Phase 4 starts at the Twilight Date. At that date, the Algorithm A 551 is labeled as "old" and the Algorithm B is labeled as "current": 553 Before Twilight --> After Twilight 555 Algorithm Suite A ("current") --> Algorithm Suite C ("old") 556 Algorithm Suite B ("new") --> Algorithm Suite A ("current") 558 During this phase, all signed product sets MUST be issued using 559 Algorithm Suite A (formerly B) and MAY be issued using Algorithm 560 Suite C (formerly A). All signed products sets issued using Suite A 561 MUST be published at their corresponding publication points. Signed 562 products sets issued using Suite C might not be available at their 563 corresponding publication points. Every RP MUST validate signed 564 product sets using Suite A. RPs MAY validate signed product sets 565 using Suite C. However, RPs SHOULD NOT assume that the collection of 566 Suite C product sets is complete. Thus RPs SHOULD make use of only 567 Suite A products sets. (See Section 6 for further details.) 569 If it is determined that many RPs are not capable of processing the 570 new algorithm suite, the algorithm transition timeline document MUST 571 be reissued pushing back the date for this and the next milestone. 572 The document MUST require CA to not remove Suite C product sets if 573 this phase is delayed. If the Algorithm Suite A (former Algorithm 574 Suite B) is deemed unsuitable, the algorithm transition timeline and 575 the algorithm specification documents MUST be replaced and the 576 Algorithm Suite A MUST be deprecated using the process described in 577 Section 10. At this stage, RPs are still capable of processing Suite 578 C signed products, so the RPKI is still viable. 580 The following figure describes a possible status for the repositories 581 of the example CAs. 583 CA X-Certificate-Algorithm-Suite-C (Cert-XC) 584 | 585 |-> CA-Y-Certificate-Algorithm-Suite-C (Cert-YC) 586 |-> CA-Y-CRL-Algorithm-Suite-C (CRL-YC) 587 |-> CA-Y-Signed-Objects-Algorithm-Suite-C 588 |-> CA-X-CRL-Algorithm-Suite-C (CRL-XC) 589 |-> CA-X-Signed-Objects-Algorithm-Suite-C 591 CA X-Certificate-Algorithm-Suite-A (Cert-XA) 592 | 593 |-> CA-Y-Certificate-Algorithm-Suite-A (Cert-YA) 594 |-> CA-Z-Certificate-Algorithm-Suite-A (Cert-ZA) 595 |-> CA-Z-CRL-Algorithm-Suite-A (CRL-ZA) 596 |-> CA-Z-Signed-Objects-Algorithm-Suite-A 597 |-> CA-Y-CRL-Algorithm-Suite-A (CRL-YA) 598 |-> CA-Y-Signed-Objects-Algorithm-Suite-A 599 |-> CA-X-CRL-Algorithm-Suite-A (CRL-XA) 600 |-> CA-X-Signed-Objects-Algorithm-Suite-A 602 4.8. Return to Phase 0 604 The EOL Date triggers the return to Phase 0 (steady state). At this 605 point, the Algorithm Suite C MUST be deprecated using the process 606 described in Section 10. 608 This phase closes the loop as Algorithm Suite A is the only required 609 algorithm suite in RPKI. 611 If it is determined that many RPs are not capable of processing the 612 new algorithm suite, the algorithm transition timeline document MUST 613 be reissued pushing back the date for this milestone. 615 5. Multi Algorithm support in the RPKI provisioning protocol 617 The migration described in this document is a top-down process, where 618 two synchronization issues need to be solved between child and parent 619 CAs: 621 o A child CA needs to identify which algorithm suites are supported 622 by its parent CA 624 o A child CA needs to signal which algorithm suite should be used by 625 its parent CA to sign a Certificate Signing Request (CSR) 627 The RPKI provisioning protocol [RFC6492] supports multiple algorithms 628 suites by implementing different resource classes for each suite. 629 Several different resource classes also may use the same algorithm 630 suite for different resource sets. 632 A child CA that wants to identify which algorithm suites are 633 supported by its parent CA MUST perform the following tasks: 635 1. Establish a provisioning protocol session with its parent CA 637 2. Perform a "list" command as described in Section 3.3.1 of 638 [RFC6492] 640 3. From the Payload in the "list response" resource class, extract 641 the "issuer's certificate" for each class. The Algorithm Suite 642 for each class will match the Algorithm Suite used to issue the 643 corresponding "issuer's certificate" (as specified in the 644 SubjectPublicKeyInfo field of that certificate) 646 A child CA that wants to specify an Algorithm Suite to its parent CA 647 (e.g., in a certificate request) MUST perform the following tasks: 649 1. Perform the tasks described above to identify the algorithm 650 suites supported by its parent CA, and the resource class 651 corresponding to each suite 653 2. Identify the corresponding resource class in the appropriate 654 provisioning protocol command (e.g. "issue" or "revoke") 656 Upon receipt of a certificate request from a child CA, a parent CA 657 will verify the PoP of the private key. If a child CA requests 658 issuing a certificate using an algorithm suite that does not match a 659 resource class, the PoP validation will fail and the request will not 660 be performed. 662 6. Validation of multiple instance of signed products 664 During Phases 1,2,3 and 4, two algorithm suites will be valid 665 simultaneously in RPKI. In this section, we describe the RP behavior 666 when validating corresponding signed products using different 667 algorithm suites. 669 During Phase 1 two (corresponding) instances MAY be available for 670 each signed product, one signed under Algorithm Suite A and one under 671 Algorithm Suite B. As noted in Section 4.4, in this phase there is a 672 preference for Suite A product sets. All products are available 673 under Suite A, while only some products may be available under Suite 674 B. For production purposes an RP MAY fetch and validate only Suite A 675 products. Suite B products SHOULD be fetched and validated only for 676 test purposes. When product sets exist under both Suites, they 677 should yield equivalent results, which facilitates testing. (It is 678 not possible to directly compare Suite A and Suite B product sets, as 679 certs, CRLs, and manifests will appear syntactically different. 680 However, the output of the process, i.e., the ROA payloads (ASN and 681 prefix data), SHOULD match, modulo timing issues.) 683 During Phases 2 and 3 of this process, two (corresponding) instances 684 of all signed products MUST be available to RPs. As noted in Section 685 4.5, it is RECOMMENDED that Suite B capable RPs fetch and validate 686 Suite B products sets, during Phase 2. If an RP encounters 687 validation problems with the Suite B products, it SHOULD revert to 688 using Suite A products. RPs that are Suite B capable MAY fetch both 689 product sets and compare the results (e.g., ROA outputs) for testing. 691 In Phase 3 all RPs MUST be Suite B capable, and MUST fetch Suite B 692 product sets. If an RP encounters problems with Suite B product 693 sets, it can revert to Suite A products. RPs encountering such 694 problems SHOULD contact the relevant repository maintainers (e.g., 695 using the mechanism defined in [RFC6493] to report problems.) 697 During Phase 4 only Suite A (previously Suite B) product sets are 698 required to be present for all RPKI entities, as per Section 4.7. 699 Thus RPs SHOULD retrieve and validate only these product sets. 700 Retrieval of Suite C (old Suite A) products sets may yield an 701 incomplete set of signed products and is NOT RECOMMENDED. 703 7. Revocation 705 The algorithm migration process mandates the maintenance of two 706 parallel but equivalent certification hierarchies during Phases 2 and 707 3 of the process. During these phases, a CA MUST revoke and request 708 revocation of certificates consistently under both algorithm Suites. 709 When not performing a key rollover operation (as described in Section 710 8), a CA requesting the revocation of its certificate during these 711 two phases MUST perform that request for both algorithm suites (A and 712 B). A non-leaf CA SHOULD NOT verify that its child CAs comply with 713 this requirement. Note that a CA MUST request revocation of its 714 certificate relative to a specific algorithm suite using the 715 mechanism described in Section 5 717 During Phase 1, a CA that revokes a certificate under Suite A SHOULD 718 revoke the corresponding certificate under Suite B, if that 719 certificate exists. During Phase 4, a CA that revokes a certificate 720 under Suite A SHOULD revoke the corresponding certificate under Suite 721 C, if that certificate exists. 723 During Phase 1, a CA may revoke certificates under Suite B without 724 revoking them under Suite A, since the Suite B products are for test 725 purposes. During Phase 4 a CA may revoke certificates issued under 726 Suite C without revoking them under Suite A, since Suite C products 727 are being deprecated. 729 8. Key rollover 731 Key rollover (without algorithm changes) is effected independently 732 for each algorithm suite and MUST follow the process described in 733 [RFC6489]. 735 9. Repository structure 737 The two parallel hierarchies that will exist during the transition 738 process SHOULD have independent publications points. The repository 739 structures for each algorithm suite are described in [RFC6481]. 741 10. Deprecating an Algorithm Suite 743 To deprecate an algorithm suite, the following process MUST be 744 executed by every CA in the RPKI: 746 1. Each CA MUST cease issuing certificates under the suite. This 747 means that any request for a (CA) certificate from a child will 748 be rejected, e.g., sending an error_response message with error 749 code:"request - no such resource class" as defined in [RFC6492]. 751 2. Each CA MUST cease generating signed products, except the CRL and 752 Manifest, under the deprecated Algorithm Suite. 754 3. Each CA MUST revoke the EE certificates for all signed products 755 that it has issued under the deprecated Algorithm Suite. The CA 756 SHOULD delete these products from its publication point, to avoid 757 burdening RPs with downloading and processing these products. 759 4. Each CA MUST revoke all CA certificates that it has issued under 760 the deprecated Algorithm Suite. 762 5. Each CA SHOULD remove all CA certificates that it has issued 763 under the deprecated Algorithm Suite. 765 6. Each CA that publishes a TAL under the deprecated Algorithm Suite 766 MUST removed it from the TAL's publication point. 768 7. Each CA SHOULD continue to maintain the publication point for the 769 deprecated Algorithm Suite, maintained at least until the CRL 770 nextUpdate. This publication point MUST contain only the CRL and 771 a Manifest for that publication point. This behavior provides a 772 window in which RPs may be able to become aware of the revoked 773 status of the signed products that have been deleted. 775 8. Each RP MUST remove any TALs that is has published under the 776 deprecated Algorithm Suite. 778 CAs in the RPKI hierarchy may become aware of the deprecation of the 779 algorithm suite at different times, and may execute the procedure 780 above in an asynchronous fashion relative to one another. Thus, for 781 example, a CA may request revocation of its CA certificate only to 782 learn that the certificate has already been revoked by the issuing 783 CA. The revocation of a CA certificate makes the CRL and manifest 784 issued under it incapable of validation. The asynchronous execution 785 of this procedure likely will result in transient "inconsistencies" 786 among the publication points associated with the deprecated algorithm 787 suite. However, these inconsistencies should yield "fail safe" 788 results, i.e., the objects signed under the deprecated suite should 789 be rejected by RPs. 791 11. IANA Considerations 793 No IANA requirements 795 12. Security Considerations 797 An algorithm transition in RPKI should be a very infrequent event and 798 it requires wide community consensus. The events that may lead to an 799 algorithm transition may be related to a weakness of the 800 cryptographic strength of the algorithm suite in use by RPKI, which 801 is normal to happen over time. The procedure described in this 802 document will take years to complete an algorithm transition. During 803 that time, the RPKI system will be vulnerable to any cryptographic 804 weakness that may have triggered this procedure (i.e. downgrade 805 attack). 807 This document does not describe an emergency mechanism for algorithm 808 migration. Due to the distributed nature of RPKI, and the very large 809 number of CAs and RPs, the authors do not believe it is feasible to 810 effect an emergency algorithm migration procedure. 812 If a CA does not complete its migration to the new algorithm suite as 813 described in this document (after the EOL of the "old" algorithm 814 suite), its signed product set will no longer be valid. 815 Consequently, the RPKI may, at the end of Phase 4, have a smaller 816 number of valid signed products than before starting the process. 817 Conversely, a RP that does not follow this process will lose the 818 ability to validate signed products issued under the new algorithm 819 suite. The resulting incomplete view of routing info from the RPKI 820 (as a result of a failure by CAs or RPs to complete the transition) 821 could degrade routing in the public Internet. 823 13. Acknowledgements 825 The authors would like to acknowledge the work of the SIDR working 826 group co-chairs (Sandra Murphy and Chris Morrow) as well as the 827 contributions given by Geoff Huston, Arturo Servin, Brian Weis, Terry 828 Manderson, Brian Dickson and Danny McPherson. 830 14. Normative References 832 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 833 Requirement Levels", BCP 14, RFC 2119, March 1997. 835 [RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP 836 Addresses and AS Identifiers", RFC 3779, June 2004. 838 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 839 Housley, R., and W. Polk, "Internet X.509 Public Key 840 Infrastructure Certificate and Certificate Revocation List 841 (CRL) Profile", RFC 5280, May 2008. 843 [RFC6481] Huston, G., Loomans, R., and G. Michaelson, "A Profile for 844 Resource Certificate Repository Structure", RFC 6481, 845 February 2012. 847 [RFC6484] Kent, S., Kong, D., Seo, K., and R. Watro, "Certificate 848 Policy (CP) for the Resource Public Key Infrastructure 849 (RPKI)", BCP 173, RFC 6484, February 2012. 851 [RFC6485] Huston, G., "The Profile for Algorithms and Key Sizes for 852 Use in the Resource Public Key Infrastructure (RPKI)", 853 RFC 6485, February 2012. 855 [RFC6489] Huston, G., Michaelson, G., and S. Kent, "Certification 856 Authority (CA) Key Rollover in the Resource Public Key 857 Infrastructure (RPKI)", BCP 174, RFC 6489, February 2012. 859 [RFC6490] Huston, G., Weiler, S., Michaelson, G., and S. Kent, 860 "Resource Public Key Infrastructure (RPKI) Trust Anchor 861 Locator", RFC 6490, February 2012. 863 [RFC6492] Huston, G., Loomans, R., Ellacott, B., and R. Austein, "A 864 Protocol for Provisioning Resource Certificates", 865 RFC 6492, February 2012. 867 [RFC6493] Bush, R., "The Resource Public Key Infrastructure (RPKI) 868 Ghostbusters Record", RFC 6493, February 2012. 870 Appendix A. Change Log 872 Note to the RFC Editor: Please remove this section before 873 publication. 875 From 07 to 06 877 1. Typo in Section 10 879 2. Correct reference for RFC6493 881 From 06 to 07: 883 1. Added definition for "Correspond" 885 2. Added reference of correspondence between suites in phase 2 and 3 887 3. Small nit on the revocation definition. 889 From 05 to 06: 891 1. Added reference to published RFCs 893 2. Removed requirement on dates format 895 3. Changed revocation section to emphasize the differences between 896 phase 1,2,3 and 4. 898 4. Added Section 10: Deprecating an Algorithm Suite 900 5. Typos and editoral changes 902 From 04 to 05: 904 1. WGLC nits 906 From 03 to 04: 908 1. Added text for "roll-over" capability in each phase 910 2. Added the requirement for splitting the milestone 1 in two 911 documents: the update of the alg document and a new document 912 specifying the particular timelines 914 3. WGLC nits 916 From 02 to 03: 918 1. Explicitely named than "mixed" certificates are not allowed for 919 CA certs but may be possible for EE certs that are not used to 920 validate repository objects. 922 From 01 to 02: 924 1. Add reference to Multi-Objects validation 926 2. EOL Date is the only milestone that RP and CA take actions "at 927 the same time". 929 3. Updated references 931 4. Editorial 933 From 00 to 01: 935 1. Include text to clarify former Suites 937 2. Include text that documents that an RP that validates an object 938 signed with either suites in Phase 2 MUST consider it as valid 940 From individual submission to WG item: 942 1. Change form "laisez faire" to "top-down" 944 2. Included Multi Algorithm support in the RPKI provisioning 945 protocol 947 3. Included Validation of multiple instance of signed products 949 4. Included Revocations 951 5. Included Key rollover 953 6. Included Repository structure 955 7. Included Security Considerations 957 8. Included Acknowledgements 959 Authors' Addresses 961 Roque Gagliano 962 Cisco Systems 963 Avenue des Uttins 5 964 Rolle, 1180 965 Switzerland 967 Email: rogaglia@cisco.com 969 Stephen Kent 970 BBN Technologies 971 10 Moulton St. 972 Cambridge, MA 02138 973 USA 975 Email: kent@bbn.com 977 Sean Turner 978 IECA, Inc. 979 3057 Nutley Street, Suite 106 980 Fairfax, VA 22031 981 USA 983 Email: turners@ieca.com