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Versions: (draft-rgaglian-sidr-algorithm-agility) 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 6916

Network Working Group                                        R. Gagliano
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                                 S. Kent
Expires: July 20, 2012                                  BBN Technologies
                                                               S. Turner
                                                              IECA, Inc.
                                                        January 17, 2012


                 Algorithm Agility Procedure for RPKI.
                  draft-ietf-sidr-algorithm-agility-05

Abstract

   This document specifies the process that Certification Authorities
   (CAs) and Relying Parties (RP) participating in the Resource Public
   Key Infrastructure (RPKI) will need to follow to transition to a new
   (and probably cryptographically stronger) algorithm set.  The process
   is expected to be completed in a time scale of months or years.
   Consequently, no emergency transition is specified.  The transition
   procedure defined in this document supports only a top-down migration
   (parent migrates before children).

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

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

   This Internet-Draft will expire on July 20, 2012.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Requirements notation  . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  Key Rollover steps for algorithm migration . . . . . . . . . .  7
     4.1.  Milestones definition  . . . . . . . . . . . . . . . . . .  7
     4.2.  Process overview . . . . . . . . . . . . . . . . . . . . .  7
     4.3.  Phase 0  . . . . . . . . . . . . . . . . . . . . . . . . .  9
       4.3.1.  Milestone 1  . . . . . . . . . . . . . . . . . . . . . 10
     4.4.  Phase 1  . . . . . . . . . . . . . . . . . . . . . . . . . 11
     4.5.  Phase 2  . . . . . . . . . . . . . . . . . . . . . . . . . 12
     4.6.  Phase 3  . . . . . . . . . . . . . . . . . . . . . . . . . 13
     4.7.  Phase 4  . . . . . . . . . . . . . . . . . . . . . . . . . 14
     4.8.  Return to Phase 0  . . . . . . . . . . . . . . . . . . . . 15
   5.  Multi Algorithm support in the RPKI provisioning protocol  . . 16
   6.  Validation of multiple instance of signed products . . . . . . 17
   7.  Revocations  . . . . . . . . . . . . . . . . . . . . . . . . . 18
   8.  Key rollover . . . . . . . . . . . . . . . . . . . . . . . . . 19
   9.  Repository structure . . . . . . . . . . . . . . . . . . . . . 20
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 21
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 22
   12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 24
     13.2. Informative References . . . . . . . . . . . . . . . . . . 25
   Appendix A.  Change Log  . . . . . . . . . . . . . . . . . . . . . 26
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 28















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1.  Requirements notation

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














































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2.  Introduction

   The RPKI must accommodate transitions between the public keys used by
   CAs.  Transitions of this sort are usually termed "key rollover".
   Planned key rollover will occur at regular intervals throughout the
   life of the RPKI, as each CA changes its public keys, in a non-
   coordinated fashion.  (By non-coordinated we mean that the time at
   which each CA elects to change its keys is locally determined, not
   coordinated across the RPKI.)  Moreover, because a key change might
   be necessitated by suspected private key compromise, one can never
   assume coordination of these events among all of the CAs in the RPKI.
   In an emergency key rollover, the old certificate is revoked and a
   new certificate with a new key is issued.  The mechanisms to perform
   a key rollover in RPKI (either planned or in an emergency), while
   maintaining the same algorithm suite, are covered in
   [I-D.ietf-sidr-keyroll].

   This document describes the mechanism to perform a key rollover in
   RPKI due to the migration to a new signature algorithm suite.  A
   signature algorithm suite encompasses both a signature algorithm
   (with a specified key size range) and a one-way hash algorithm.  It
   is anticipated that the RPKI will require the adoption of updated key
   sizes and/or different algorithm suites over time.  This document
   treats the adoption of a new hash algorithm while retaining the
   current signature algorithm as equivalent to an algorithm migration,
   and requires the CA to change its key.  Migration to a new algorithm
   suite will be required in order to maintain an acceptable level of
   cryptographic security and protect the integrity of certificates,
   CRLs and signed objects in the RPKI.  All of the data structures in
   the RPKI explicitly identify the signature and hash algorithms being
   used.  However, experience has demonstrated that the ability to
   represent algorithm IDs is not sufficient to enable migration to new
   algorithm suites (algorithm agility).  One also must ensure that
   protocols, infrastructure elements, and operational procedures also
   accommodate migration from one algorithm suite to another.  Algorithm
   migration is expected to be very infrequent, but it also will require
   support of a "current" and "next" suite for a prolonged interval,
   probably several years.

   This document defines how entities in the RPKI execute (planned) CA
   key rollover when the algorithm suite changes.  The description
   covers actions by CAs, repository operators, and RPs.  It describes
   the behavior required of both CAs and RPs to make such key changes
   work in the RPKI context, including how the RPKI repository system is
   used to support key rollover.

   This document does not specify any algorithm suite per se. The RPKI
   Certificate Policy (CP) [I-D.ietf-sidr-cp] mandates the use of the



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   algorithms defined in [I-D.ietf-sidr-rpki-algs] by CAs and RPs.  When
   an algorithm transition is initiated, [I-D.ietf-sidr-rpki-algs] will
   be updated (as defined in Section 4.1 of this document) redefining
   the required algorithm(s) for compliant RPKI CAs and RPs under the
   CP.  The CP will not change as a side effect of algorithm transition
   (and thus the policy OID in RPKI certificates will not change.)

   An additional document, the algorithm transition timetable, will be
   published (as a BCP) to define the dates for each milestone defined
   in this document.  It will define dates for the phase transitions,
   consistent with the descriptions provided in Section 4.  It also will
   describe how the RPKI community will measure the readiness of CAs and
   RPs to transition to each phase.  CAs publish certificates, CRLs, and
   other signed objects under the new algorithm suite as the transition
   progresses.  This provides visibility into the deployment of the new
   algorithm suite, enabling the community to evaluate deployment
   progress.  The transition procedure allows CAs to remove old
   certificates, CRLs, and signed products, after the twilight date.
   This provides an ability to observe and measure the withdrawal of the
   old algorithm suite.  Thus the phases defined in this document enable
   the community to evaluate the progress of the transition.  The
   timetable document will also describe procedures to amend the
   timetable if problems arise in implementing later phases of the
   transition.  It is RECOMMENDED that the timetable document be
   developed by representatives of the RPKI community, e.g., IANA,
   Internet Registries, and network operators.

























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3.  Terminology

   This document assumes that the reader is familiar with the terms and
   concepts described in "Internet X.509 Public Key Infrastructure
   Certificate and Certificate Revocation List (CRL) Profile" [RFC5280],
   "X.509 Extensions for IP Addresses and AS Identifiers" [RFC3779], and
   "A Profile for Resource Certificate Repository Structure"
   [I-D.ietf-sidr-repos-struct].  Additional terms and conventions used
   in examples are provided below.

   Algorithm migration  A planned transition from one signature and hash
               algorithm to a new signature and hash algorithm.

   Algorithm Suite A  The "current" algorithm suite used for hashing and
               signing, in examples in this document

   Algorithm Suite B  The "next" algorithm suite used for hashing and
               signing, used in examples in this document

   Algorithm Suite C  The "old" algorithm suite used for hashing and
               signing, used in examples in this document

   CA X        The CA that issued CA Y's certificate (i.e., CA Y's
               parent), used in examples in this document.

   CA Y        The non-leaf CA used in examples this document

   CA Z        A CA that is a "child" of CA Y, used in examples this
               document

   Non-Leaf CA A CA that issues certificates to other CAs is a non-leaf
               CA.

   Leaf CA     A leaf CA is a CA that issues only EE certs.

   PoP (proof of possession)  Execution of a protocol that demonstrates
               to an issuer that a subject requesting a certificate
               possesses the private key corresponding to the public key
               in the certificate submitted by the subject.

   Signed Product Set (or Set or Product Set)  A collection of
               certificates, signed objects, a CRL and a manifest that
               are associated by virtue of being verifiable under the
               same parent CA certificate







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4.  Key Rollover steps for algorithm migration

   The "current" RPKI algorithm suite (Suite A) is defined in the RPKI
   CP document, by reference to [I-D.ietf-sidr-rpki-algs].  When a
   migration of the RPKI algorithm suite is needed, the first step MUST
   be an update of the [I-D.ietf-sidr-rpki-algs] document to define the
   new algorithm suite.  The algorithm transition timeline document MUST
   also be published (as a BCP), to inform the community of the dates
   selected for milestones in the transition process, as described in
   Section 4.1.

4.1.  Milestones definition

   CA Ready Algorithm B Date  - After this date, all (non-leaf) CAs MUST
               be ready to process a request from a child CA to issue a
               certificate under the Algorithm B suite.

   CA Go Algorithm B Date  - After this date, all (non-leaf) CAs MUST
               have reissued all of their signed product sets under the
               Algorithm B suite.

   RP Ready Algorithm B Date  - After this date, all RPs MUST be
               prepared to process signed material issued under the
               Algorithm B suite.

   Twilight Algorithm B  - After this date, a CA MAY cease issuing
               signed products under the Algorithm A suite.  Also, after
               this date, a RP MAY cease to validate signed materials
               issued under the Algorithm A suite.

   End Of Life (EOL) Algorithm A  - After this date every CA MUST NOT
               generate certificates, CRLs, or other RPKI signed objects
               under the Algorithm A suite.  Also, after this date, no
               RP SHOULD accept as valid any certificate, CRL or signed
               object using the Algorithm A suite.

4.2.  Process overview

   The migration process described in this document involves a series of
   steps that MUST be executed in chronological order by CAs and RPs.
   The only milestone at which both CAs and RPs take action at the same
   time is the "EOL Algorithm A" date.  Due to the decentralized nature
   of the RPKI infrastructure, it is expected that an algorithm
   transition will span several years.

   In order to facilitate the transition, CAs will start issuing
   certificates using the Algorithm B in a hierarchical top-down
   fashion.  In our example, CA Y will issue certificates using the



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   Algorithm B suite only after CA X has started to do so (CA Y Ready
   Algorithm B Date > CA X Ready Algorithm B Date).  This ordered
   transition avoids issuance of "mixed" suite certificates, e.g., a CA
   certificate signed using Suite A, containing a key from Suite B. In
   the RPKI, a CA MUST NOT sign a CA certificate carrying a subject key
   that corresponds to an algorithm suite that differs from the one used
   to sign the certificate (X.509 accommodates such mixed algorithm
   certificates, but this process avoids using that capability.)  A not
   top-down transition approach would require use of such mixed mode
   certificates, but this would lead to exponential growth of the RPKI
   repository.  Also, because the RPKI CP mandates "proof of possession"
   for certificate requests, it is not possible for a CA to request a
   certificate for Algorithm Suite B, until its parent CA supports that
   Suite.  (See Section 5 for more details.)

   The algorithm agility model described here does not prohibit a CA
   from issuing an EE certificate with a subject public key from a
   different algorithm suite, if that certificate is not used to verify
   repository objects.  This exception to the mixed algorithm suite
   certificate rule is allowed because an EE certificate that is not
   used to verify repository objects does not interfere with the ability
   of RPs to download and verify repository content.  As noted above,
   every CA in the RPKI is required to perform a Proof of Possession
   (PoP) check for the subject public key when issuing a certificate.
   In general a subject cannot assume that a CA is capable of supporting
   a different algorithm.  However, if the subject is closely affiliated
   with the CA, it is reasonable to assume that there are ways for the
   subject to know whether the CA can support a request to issue an EE
   certificate containing a specific, different public key algorithm.
   This document does not specify how a subject can determine whether a
   CA is capable of issuing a mixed suite EE certificate, because it
   anticipates that such certificates will be issued only in contexts
   where the subject and CA are sufficiently closely affiliated (for
   example, an ISP issuing certificates to devices that it manages).

   The following figure gives an overview of the process:















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Process for RPKI CAs:

  Phase 0    Phase 1   Phase 2             Phase 4  Phase 0
-----------x---------x-------------------x--------x-----------
  ^        ^         ^                   ^        ^
  |        |         |                   |        |
 (1)      (2)       (3)                 (5)      (6)

Process for RPKI RPs:

            Phase 0              Phase 3   Phase 4  Phase 0
-------------------------------x---------x--------x-----
  ^                            ^         ^        ^
  |                            |         |        |
 (1)                          (4)       (5)      (6)

(1) RPKI algorithm document is updated and the algorithm transition timeline document is issued
(2) CA Ready Algorithm B Date
(3) CA Go Algorithm B Date
(4) RP Ready Algorithm B Date
(5) Twilight Date
(6) End Of Live (EOL) Date

   Each of these milestones is discussed in the next section as part of
   describing each phase of the transition process.

   Two situations have been identified that motivate pausing or rolling
   back the transition process.  The first situation arises if the RPKI
   community is not ready to make the transition.  For example, many CAs
   might not be prepared to issue signed products under Suite B, or many
   RPs might not be ready to process Suite B product sets.  Under these
   circumstances, the timetable MUST be reissued, postponing the date
   for the phase in question, and pushing back the dates for later
   phases.  The other situation arises if, during the transition,
   serious concerns arise about the security of the Suite B algorithms.
   Such concerns would motivate terminating the transition and rolling
   back signed products, i.e., reverting to Suite A. In this case the
   timetable MUST be republished, and the RPKI algorithm document MUST
   be superseded.  The phase descriptions below allude to these two
   situations, as appropriate.

4.3.  Phase 0

   Phase 0 is the initial phase of the process, throughout this phase
   the algorithm suite A is the only supported algorithm suite in RPKI.
   This is also the steady state for the RPKI.

   The following figure illustrates the format used to describe signed



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   objects in the repository.  It reflects the algorithm suites in use,
   and shows the relationship between three CAs (X, Y, and Z) that form
   a chain.

   During Phase 0, CAs X, Y and Z are required to generate signed
   product sets using only the Algorithm Suite A. Also, RPs are required
   to validate signed product sets issued using only Algorithm Suite A.

   CA X-Certificate-Algorithm-Suite-A (Cert-XA)
           |
           |-> CA-Y-Certificate-Algorithm-Suite-A (Cert-YA)
                   |-> CA-Z-Certificate-Algorithm-Suite-A (Cert-ZA)
                           |-> CA-Z-CRL-Algorithm-Suite-A (CRL-ZA)
                           |-> CA-Z-Signed-Objects-Algorithm-Suite-A
                   |-> CA-Y-CRL-Algorithm-Suite-A (CRL-YA)
                   |-> CA-Y-Signed-Objects-Algorithm-Suite-A
           |-> CA-X-CRL-Algorithm-Suite-A (CRL-XA)
           |-> CA-X-Signed-Objects-Algorithm-Suite-A

   Note: Cert-XA represent the certificate for CA X, that is signed
   using the algorithm suite A.

4.3.1.  Milestone 1

   The first milestone initiates the migration process.  It updates the
   [I-D.ietf-sidr-rpki-algs] document with the following definitions for
   the RPKI:

   o  Algorithm Suite A

   o  Algorithm Suite B

   Additionally, the new algorithm transition timeline document will be
   published with the following information:

   o  CA Ready Algorithm B Date

   o  CA Go Algorithm B Date

   o  RP Ready Algorithm B Date

   o  Twilight Date

   o  EOL Date

   o  Readiness metrics for CAs and RPs in each phase

   All Dates MUST be represented using the local UTC date-time format



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   specified in [RFC3339].

4.4.  Phase 1

   Phase 1 starts at the CA Ready Algorithm B Date.  During Phase 1, all
   (non-leaf) CAs MUST be ready to process a request from a child CA to
   issue or revoke a certificate using the Algorithm B suite.  If it is
   determined that a substantial number of CAs are not ready, the
   algorithm transition timeline document will be reissued, as noted in
   Section 4.2.  However, CAs that are capable of issuing Suite B
   certificates may continue to do so, if requested by their child CAs.
   Since this phase does not require any RPs to process signed objects
   under Suite B, and since Suite B product sets SHOULD be stored at
   independent publication points, there is no adverse impact on RPs.
   If the Suite B algorithm is deemed unsuitable, the algorithm
   transition timeline and the algorithm specification documents MUST be
   replaced, CAs MUST cease accepting requests for certificates under
   Suite B, and Suite B certificates that have been issued MUST be
   revoked.

   As the transition will happen using a (hierarchic) top-down model, a
   child CA will be able to issue certificates using the Algorithm B
   suite only after its parent CA has issued its own.  The RPKI
   provisioning protocol can identify if a parent CA is capable of
   issuing certificates using the Algorithm Suite B, and can identify
   the corresponding algorithm suite in each Certificate Signing Request
   (see Section 5).

   The following figure shows the status of repository entries for the
   three example CAs during this Phase.  Two distinct certificate chains
   are maintained and CA Z has not yet requested any material using the
   Algorithm B suite.



















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   CA X-Certificate-Algorithm-Suite-A (Cert-XA)
           |
           |-> CA-Y-Certificate-Algorithm-Suite-A (Cert-YA)
                   |-> CA-Z-Certificate-Algorithm-Suite-A (Cert-ZA)
                           |-> CA-Z-CRL-Algorithm-Suite-A (CRL-ZA)
                           |-> CA-Z-Signed-Objects-Algorithm-Suite-A
                   |-> CA-Y-CRL-Algorithm-Suite-A (CRL-YA)
                   |-> CA-Y-Signed-Objects-Algorithm-Suite-A
           |-> CA-X-CRL-Algorithm-Suite-A (CRL-XA)
           |-> CA-X-Signed-Objects-Algorithm-Suite-A

   CA X-Certificate-Algorithm-Suite-B (Cert-XB)
           |
           |-> CA-Y-Certificate-Algorithm-Suite-B (Cert-YB)
                   |-> CA-Y-CRL-Algorithm-Suite-B (CRL-YB)
                   |-> CA-Y-Signed-Objects-Algorithm-Suite-B
           |-> CA-X-CRL-Algorithm-Suite-B (CRL-XB)
           |-> CA-X-Signed-Objects-Algorithm-Suite-B

4.5.  Phase 2

   Phase 2 starts at the CA Go Algorithm B Date.  At the start of this
   phase, each signed product set MUST be available using both Algorithm
   Suite A and Algorithm Suite B. During this phase, RPs MUST be
   prepared to validate sets issued using Algorithm Suite A and MAY be
   prepared to validate sets issued using the Algorithm Suite B.

   If it is determined that a substantial number of CAs are not ready,
   the algorithm transition timeline document will be reissued, as noted
   in Section 4.2.  (Since the processing requirement for RPs here is a
   MAY, if RPs have problems with Suite B products this does not require
   pushing back the Phase 2 milestone, but it does motivate delaying the
   start of Phase 3.)  CAs that are capable of publishing products under
   Suite B MAY continue to do so.  Phase 2, like Phase 1, does not
   require any RPs to process signed objects under Suite B. Also, Suite
   B product SHOULD be stored at independent publication points, so
   there is no adverse impact on RPs.  If the Suite B algorithm is
   deemed unsuitable, the algorithm transition timeline and the
   algorithm specification documents MUST be replaced.  CAs MUST cease
   accepting requests for certificates under Suite B, and Suite B
   certificates that have been issued MUST be revoked.

   An RP that validates all signed product sets using both Algorithm
   Suite A or Algorithm Suite B SHOULD expect the same results.
   However, an object that validates using either Algorithm Suite A or
   Algorithm Suite B MUST be considered valid.  A detailed analysis on
   the validation of multiple instances of signed objects is included in
   Section 6



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   The following figure shows the status of the repository entries for
   the three example CAs throughout this phase, where all signed objects
   are available using both algorithm suites.

   CA X-Certificate-Algorithm-Suite-A (Cert-XA)
           |
           |-> CA-Y-Certificate-Algorithm-Suite-A (Cert-YA)
                   |-> CA-Z-Certificate-Algorithm-Suite-A (Cert-ZA)
                           |-> CA-Z-CRL-Algorithm-Suite-A (CRL-ZA)
                           |-> CA-Z-Signed-Objects-Algorithm-Suite-A
                   |-> CA-Y-CRL-Algorithm-Suite-A (CRL-YA)
                   |-> CA-Y-Signed-Objects-Algorithm-Suite-A
           |-> CA-X-CRL-Algorithm-Suite-A (CRL-XA)
           |-> CA-X-Signed-Objects-Algorithm-Suite-A

   CA X-Certificate-Algorithm-Suite-B (Cert-XB)
           |
           |-> CA-Y-Certificate-Algorithm-Suite-B (Cert-YB)
                   |-> CA-Z-Certificate-Algorithm-Suite-B (Cert-ZB)
                           |-> CA-Z-CRL-Algorithm-Suite-B (CRL-ZB)
                           |-> CA-Z-Signed-Objects-Algorithm-Suite-B
                   |-> CA-Y-CRL-Algorithm-Suite-B (CRL-YB)
                   |-> CA-Y-Signed-Objects-Algorithm-Suite-B
           |-> CA-X-CRL-Algorithm-Suite-B (CRL-XB)
           |-> CA-X-Signed-Objects-Algorithm-Suite-B

4.6.  Phase 3

   Phase 3 starts at the RP Ready Algorithm B Date.  During this phase,
   all signed product sets are available using both algorithm suites and
   all RPs MUST be able to validate them using either suite.  An object
   that validates using either Algorithm Suite A or Algorithm Suite B
   MUST be considered valid.  It is RECOMMENDED that, in preparation for
   Phase 4, RPs utilize Suite B as the first and preferred option for
   validation throughout this phase.  Thus, for example, an RP SHOULD
   try to validate the sets of signed products retrieved from the
   Algorithm Suite B repository first.  If this effort fails (relative
   to the local validation policy), the RP SHOULD revert to using the
   Algorithm Suite A repository.

   If a substantial number of RPs are unable to process product sets
   signed with Suite B, the algorithm transition timeline document MUST
   be reissued, pushing back the date for this and later milestones, as
   discussed in Section 4.2.  Since the Suite B products SHOULD be
   published at distinct publication points, RPs that cannot process
   Suite B products can be expected to revert to the Suite A products
   that still exist.  If the Suite B algorithm is deemed unsuitable, the
   algorithm transition timeline and the algorithm specification



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   documents MUST be replaced.  CAs MUST cease accepting requests for
   certificates under Suite B, and Suite B certificates that have been
   issued MUST be revoked.

   There are no changes to the CA behavior throughout this phase.

4.7.  Phase 4

   Phase 4 starts at the Algorithm A Twilight Date.  At that date, the
   Algorithm A is labeled as "old" and the Algorithm B is labeled as
   "current":

   Before Twilight                 -->     After Twilight

   Algorithm Suite A ("current")   -->     Algorithm Suite C ("old")
   Algorithm Suite B ("new")       -->     Algorithm Suite A ("current")

   During this phase, all signed product sets MUST be issued using
   Algorithm Suite A (formerly B) and MAY be issued using Algorithm
   Suite C (formerly A).  All signed products sets issued using Suite A
   MUST be published at their corresponding publication points, but
   signed products sets issued using Suite C MAY NOT be published at
   their corresponding publication points.  Also, every RP MUST
   validate signed product sets using Suite A but also MAY validate
   signed product sets using Suite C. However, RPs SHOULD NOT assume the
   Suite C repository is complete.

   If it is determined that many RPs are not capable of processing the
   new algorithm suite, the algorithm transition timeline document MUST
   be reissued pushing back the date for this and the next milestone.
   The document MUST requires CA to not remove Suite C product sets if
   this phase is delayed.  If the Suite B algorithm is deemed
   unsuitable, the algorithm transition timeline and the algorithm
   specification documents MUST be replaced.  CAs MUST cease accepting
   requests for certificates under Suite A (formal Suite A), and Suite A
   certificates that have been issued MUST be revoked.  At this stage,
   RPs are still capable of processing Suite C signed products.

   The following figure describes a possible status for the repositories
   of the example CAs.  In this case, CA Z no longer issues signed
   products using the Algorithm Suite C.










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   CA X-Certificate-Algorithm-Suite-C (Cert-XC)
           |
           |-> CA-Y-Certificate-Algorithm-Suite-C (Cert-YC)
                   |-> CA-Y-CRL-Algorithm-Suite-C (CRL-YC)
                   |-> CA-Y-Signed-Objects-Algorithm-Suite-C
           |-> CA-X-CRL-Algorithm-Suite-C (CRL-XC)
           |-> CA-X-Signed-Objects-Algorithm-Suite-C

   CA X-Certificate-Algorithm-Suite-A (Cert-XA)
           |
           |-> CA-Y-Certificate-Algorithm-Suite-A (Cert-YA)
                   |-> CA-Z-Certificate-Algorithm-Suite-A (Cert-ZA)
                           |-> CA-Z-CRL-Algorithm-Suite-A (CRL-ZA)
                           |-> CA-Z-Signed-Objects-Algorithm-Suite-A
                   |-> CA-Y-CRL-Algorithm-Suite-A (CRL-YA)
                   |-> CA-Y-Signed-Objects-Algorithm-Suite-A
           |-> CA-X-CRL-Algorithm-Suite-A (CRL-XA)
           |-> CA-X-Signed-Objects-Algorithm-Suite-A


4.8.  Return to Phase 0

   The EOL Algorithm Date triggers a return to Phase 0 (steady state).
   At this phase, ALL signed product sets using Algorithm Suite C MUST
   be considered invalid.  CAs MUST neither issue nor publish signed
   products using Algorithm Suite C.

   This phase closes the loop as Algorithm Suite A is the only required
   algorithm suite in RPKI.

   If it is determined that many RPs are not capable of processing the
   new algorithm suite, the algorithm transition timeline document MUST
   be reissued pushing back the date for this milestone.  CAs MUST NOT
   remove Suite C product sets if this phase is delayed.

















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5.  Multi Algorithm support in the RPKI provisioning protocol

   The migration described in this document is a top-down process, where
   two synchronization issues need to be solved between child and parent
   CAs:

   o  A child CA needs to identify which algorithm suites are supported
      by its parent CA

   o  A child CA needs to identify which algorithm suite should be used
      to sign a Certificate Signing Request (CSR)

   The RPKI provisioning protocol [I-D.ietf-sidr-rescerts-provisioning]
   supports multiple algorithms suites by implementing different
   resource classes for each suite.  Several different resource classes
   also may use the same algorithm suite for different resource sets.

   A child CA that wants to identify which algorithm suites are
   supported by its parent CA MUST perform the following tasks:

   1.  Establish a provisioning protocol session with its parent CA

   2.  Perform a "list" command as described in Section 3.3.1 of
       [I-D.ietf-sidr-rescerts-provisioning]

   3.  From the Payload in the "list response" resource class, extract
       the "issuer's certificate" for each class.  The Algorithm Suite
       for each class will match the Algorithm Suite used to issue the
       corresponding "issuer's certificate".

   A child CA that wants to specify an Algorithm Suite to its parent CA
   (e.g., in a certificate request) MUST perform the following tasks:

   1.  Perform the tasks to identify the resource class for each
       Algorithm Suite supported by its parent CA (as above).

   2.  Identify the corresponding resource class in the appropriate
       provisioning protocol command (e.g. "issue" or "revoke")

   Upon receipt of a certificate request from a child CA, a parent CA
   will verify the PoP of the private key.  If a child CA requests
   issuing a certificate using an algorithm suite that does not match a
   resource class, the PoP validation will fail and the request will not
   be performed.







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6.  Validation of multiple instance of signed products

   During Phases 1,2,3 and 4, two algorithm suites will be valid
   simultaneously in RPKI.  In this section, we describe the RP behavior
   when validating instances of the same signed product but signed with
   different algorithm suites.  As a general rule, the validation of
   signed products using different algorithm suites are independent and
   the RP MUST NOT keep any relationship between the different
   hierarchies.

   During Phase 1 two (corresponding) instances MAY be available for
   each signed product, one signed under Algorithm Suite A and one under
   Algorithm Suite B.  When an RP validates these signed products, if
   either instance of an object validates, the product is accepted.  A
   failure to validate one instance of a product, under either algorithm
   Suite MUST NOT cause the RP to reject the other instance of the
   product.  Because both instances of such products MUST contain the
   same resources, relying on either instance will yield the same
   outcome.

   During Phases 2 and 3 of this process, two (corresponding) instances
   of all signed products MUST be available to RPs.  As in Phase 1, when
   an RP validates these signed products, if either instance validates,
   the product is accepted.  A failure to validate one instance of a
   product, under either algorithm Suite MUST NOT cause the RP to reject
   the other instance of the product.  Also, as above, if only one
   instance of a signed product can be validated, subordinate products
   issued under the other (non-validated) algorithm suite cannot be
   used, and thus SHOULD NOT be processed (or even retrieved).

   During Phase 4 two (corresponding) files for an object MAY be
   available for each signed product, one signed under Algorithm Suite A
   and one under Algorithm Suite C.  When an RP validates these signed
   products, if either instance of an object validates, the product is
   accepted.  A failure to validate one instance of a product, under
   either algorithm Suite MUST NOT cause the RP to reject the other
   instance of the product.  Because both instances of such products
   MUST contain the same resources, relying on either instance will
   yield the same outcome.












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7.  Revocations

   As the algorithm migration process mandates the maintenance of two
   parallel certificate hierarchies, revocations requests for each
   algorithm suite MUST be handled independently.  A Child CA MUST
   request revocation of a certificate relative to a specific algorithm
   suite.

   During phase 2 and phase 3, the two parallel certificate hierarchies
   are designed to carry identical information.  When not performing a
   key rollover operation (which process is described in Section 8), a
   child CA requesting the revocation of a certificate during these two
   phases MUST perform that request for both algorithm suites (A and B).
   A non-leaf CA is NOT required to verify that its child CAs comply
   with this requirement.




































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8.  Key rollover

   Key rollover (without algorithm changes) is effected independently
   for each algorithm suite and MUST follow the process described in
   [I-D.ietf-sidr-keyroll].














































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9.  Repository structure

   The two parallel hierarchies that will exist during the transition
   process SHOULD have independent publications points.  The repository
   structures for each algorithm suite are described in
   [I-D.ietf-sidr-repos-struct].













































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10.  IANA Considerations

   No IANA requirements
















































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11.  Security Considerations

   An algorithm transition in RPKI should be a very infrequent event and
   it requires wide community consensus.  The events that may lead to an
   algorithm transition may be related to a weakness of the
   cryptographic strength of the algorithm suite in use by RPKI, which
   is normal to happen over time.  The procedure described in this
   document will take years to complete an algorithm transition.  During
   that time, the RPKI system will be vulnerable to any cryptographic
   weakness that may have triggered this procedure (i.e. downgrade
   attack).

   This document does not describe an emergency mechanism for algorithm
   migration.  Due to the distributed nature of RPKI, and the very large
   number of CAs and RPs, the authors do not believe it is feasible to
   effect an emergency algorithm migration procedure.

   If a CA does not complete its migration to the new algorithm suite as
   described in this document (after the EOL of the "old" algorithm
   suite), its signed product set will no longer be valid.
   Consequently, the RPKI may, at the end of Phase 4, have a smaller
   number of valid signed products than before starting the process.
   Conversely, a RP that does not follow this process will lose the
   ability to validate signed products issued under the new algorithm
   suite.  The resulting incomplete view of routing info from the RPKI
   (as a result of a failure by CAs or RPs to complete the transition)
   could degrade routing in the public Internet.
























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12.  Acknowledgements

   The authors would like to acknowledge the work of the SIDR working
   group co-chairs (Sandra Murphy and Chris Morrow) as well as the
   contributions given by Geoff Huston, Arturo Servin, Brian Weis, Terry
   Manderson, Brian Dickson and Danny McPherson.













































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13.  References

13.1.  Normative References

   [I-D.ietf-sidr-cp]
              Kent, S., Kong, D., Seo, K., and R. Watro, "Certificate
              Policy (CP) for the Resource PKI (RPKI",
              draft-ietf-sidr-cp-17 (work in progress), April 2011.

   [I-D.ietf-sidr-keyroll]
              Huston, G., Michaelson, G., and S. Kent, "CA Key Rollover
              in the RPKI", draft-ietf-sidr-keyroll-05 (work in
              progress), December 2010.

   [I-D.ietf-sidr-repos-struct]
              Huston, G., Loomans, R., and G. Michaelson, "A Profile for
              Resource Certificate Repository Structure",
              draft-ietf-sidr-repos-struct-06 (work in progress),
              November 2010.

   [I-D.ietf-sidr-res-certs]
              Huston, G., Michaelson, G., and R. Loomans, "A Profile for
              X.509 PKIX Resource Certificates",
              draft-ietf-sidr-res-certs-21 (work in progress),
              December 2010.

   [I-D.ietf-sidr-rescerts-provisioning]
              Huston, G., Loomans, R., Ellacott, B., and R. Austein, "A
              Protocol for Provisioning Resource Certificates",
              draft-ietf-sidr-rescerts-provisioning-10 (work in
              progress), June 2011.

   [I-D.ietf-sidr-rpki-algs]
              Huston, G., "A Profile for Algorithms and Key Sizes for
              use in the Resource Public Key Infrastructure",
              draft-ietf-sidr-rpki-algs-04 (work in progress),
              November 2010.

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

   [RFC2560]  Myers, M., Ankney, R., Malpani, A., Galperin, S., and C.
              Adams, "X.509 Internet Public Key Infrastructure Online
              Certificate Status Protocol - OCSP", RFC 2560, June 1999.

   [RFC3339]  Klyne, G., Ed. and C. Newman, "Date and Time on the
              Internet: Timestamps", RFC 3339, July 2002.




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   [RFC3779]  Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP
              Addresses and AS Identifiers", RFC 3779, June 2004.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, October 2005.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, May 2008.

13.2.  Informative References

   [RFC5781]  Weiler, S., Ward, D., and R. Housley, "The rsync URI
              Scheme", RFC 5781, February 2010.




































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Appendix A.  Change Log

   Note to the RFC Editor: Please remove this section before
   publication.

   From 04 to 05:

   1.  WGLC nits

   From 03 to 04:

   1.  Added text for "roll-over" capability in each phase

   2.  Added the requirement for splitting the milestone 1 in two
       documents: the update of the alg document and a new document
       specifying the particular timelines

   3.  WGLC nits

   From 02 to 03:

   1.  Explicitely named than "mixed" certificates are not allowed for
       CA certs but may be possible for EE certs that are not used to
       validate repository objects.

   From 01 to 02:

   1.  Add reference to Multi-Objects validation

   2.  EOL Data is the only milestone that RP and CA take actions "at
       the same time".

   3.  Updated references

   4.  Editorial

   From 00 to 01:

   1.  Include text to clarify former Suites

   2.  Include text that documents that an RP that validates an object
       signed with either suites in Phase 2 MUST consider it as valid

   From individual submission to WG item:

   1.  Change form "laisez faire" to "top-down"





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   2.  Included Multi Algorithm support in the RPKI provisioning
       protocol

   3.  Included Validation of multiple instance of signed products

   4.  Included Revocations

   5.  Included Key rollover

   6.  Included Repository structure

   7.  Included Security Considerations

   8.  Included Acknowledgements





































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Authors' Addresses

   Roque Gagliano
   Cisco Systems
   Avenue des Uttins 5
   Rolle,   1180
   Switzerland

   Email: rogaglia@cisco.com


   Stephen Kent
   BBN Technologies
   10 Moulton St.
   Cambridge, MA  02138
   USA

   Email: kent@bbn.com


   Sean Turner
   IECA, Inc.
   3057 Nutley Street, Suite 106
   Fairfax, VA  22031
   USA

   Email: turners@ieca.com
























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