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PROPOSED STANDARD

Internet Engineering Task Force (IETF)                         G. Huston
Request for Comments: 6481                                    R. Loomans
Category: Standards Track                                  G. Michaelson
ISSN: 2070-1721                                                    APNIC
                                                           February 2012


        A Profile for Resource Certificate Repository Structure

Abstract

   This document defines a profile for the structure of the Resource
   Public Key Infrastructure (RPKI) distributed repository.  Each
   individual repository publication point is a directory that contains
   files that correspond to X.509/PKIX Resource Certificates,
   Certificate Revocation Lists and signed objects.  This profile
   defines the object (file) naming scheme, the contents of repository
   publication points (directories), and a suggested internal structure
   of a local repository cache that is intended to facilitate
   synchronization across a distributed collection of repository
   publication points and to facilitate certification path construction.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6481.
















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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
   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. Introduction ....................................................3
      1.1. Terminology ................................................3
   2. RPKI Repository Publication Point Content and Structure .........4
      2.1. Manifests ..................................................5
      2.2. CA Repository Publication Points ...........................6
   3. Resource Certificate Publication Repository Considerations ......8
   4. Certificate Reissuance and Repositories ........................10
   5. Synchronizing Repositories with a Local Cache ..................10
   6. Security Considerations ........................................11
   7. IANA Considerations ............................................12
      7.1. Media Types ...............................................12
           7.1.1. application/rpki-manifest ..........................12
           7.1.2. application/rpki-roa ...............................13
      7.2. RPKI Repository Name Scheme Registry ......................13
   8. Acknowledgements ...............................................13
   9. References .....................................................14
      9.1. Normative References ......................................14
      9.2. Informative References ....................................14
















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1.  Introduction

   To validate attestations made in the context of the Resource Public
   Key Infrastructure (RPKI) [RFC6480], relying parties (RPs) need
   access to all the X.509/PKIX Resource Certificates, Certificate
   Revocation Lists (CRLs), and signed objects that collectively define
   the RPKI.

   Each issuer of a certificate, CRL, or a signed object makes it
   available for download to RPs through the publication of the object
   in an RPKI repository.

   The repository system is a collection of all signed objects that MUST
   be globally accessible to all RPs.  When certificates, CRLs and
   signed objects are created, they are uploaded to a repository
   publication point, from whence they can be downloaded for use by RPs.

   This profile defines the recommended object (file) naming scheme, the
   recommended contents of repository publication points (directories),
   and a suggested internal structure of a local repository cache that
   is intended to facilitate synchronization across a distributed
   collection of repository publication points and facilitate
   certification path construction.

   A resource certificate attests to a binding of an entity's public key
   to a set of IP address blocks and AS numbers.  The subject of a
   resource certificate can demonstrate that it is the holder of the
   resources enumerated in the certificate by using its private key to
   generate a digital signature (that can be verified using the public
   key from the certificate).

1.1.  Terminology

   It is assumed 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], and "X.509
   Extensions for IP Addresses and AS Identifiers" [RFC3779].

   In addition, the following terms are used in this document:

   Repository Object (or Object):
      This refers to a terminal object in a repository publication
      point.  A terminal object is conventionally implemented as a file
      in a publicly accessible directory, where the file is not a
      directory itself, although another form of object that has an
      analogous public appearance to a file is encompassed by this term.





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   Repository Publication Point:
      This refers to a collection of Repository Objects that are
      published at a common publication point.  This is conventionally
      implemented as a directory in a publicly accessible filesystem
      that is identified by a URI [RFC3986], although another form of
      local storage that has an analogous public appearance to a simple
      directory of files is also encompassed by this term.

   Repository Instance:
      This refers to a collection of one or more Repository Publication
      Points that share a common publication instance.  This
      conventionally is implemented as a collection of filesystem
      directories that share a common URI prefix, where each directory
      is also identifiable by its own unique URI.

   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].

2.  RPKI Repository Publication Point Content and Structure

   The RPKI does not require that a single repository instance contain
   all published RPKI objects.  Instead, the RPKI repository system is
   comprised of multiple repository instances.  Each individual
   repository instance is composed of one or more repository publication
   points.  Each repository publication point is used by one or more
   entities referenced in RPKI certificates, as defined in the
   certificate's Subject Information Access (SIA) extension.

   This section describes the collection of objects (RPKI certificates,
   CRLs, manifests, and signed objects) held in repository publication
   points.

   For every Certification Authority (CA) certificate in the RPKI, there
   is a corresponding repository publication point that is the
   authoritative publication point for all current certificates and CRLs
   issued by this CA.  The certificate's SIA extension contains a URI
   [RFC3986] that references this repository publication point and
   identifies the repository access mechanisms.  Additionally, a
   certificate's Authority Information Access (AIA) extension contains a
   URI that references the authoritative location for the CA certificate
   under which the given certificate was issued.

   For example, if the subject of certificate A has issued certificates
   B and C, then the AIA extensions of certificates B and C both point
   to the publication point for the certificate A object, and the SIA
   extension of certificate A points to a repository publication point
   (directory) containing certificates B and C (see Figure 1).



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                         +--------+
              +--------->| Cert A |<----+
              |          |  AIA   |     |
              |  +--------- SIA   |     |
              |  |       +--------+     |
              |  |                      |
              |  |  +-------------------|------------------+
              |  |  |                   |                  |
              |  +->|   +--------+      |   +--------+     |
              |     |   | Cert B |      |   | Cert C |     |
              |     |   | CRLDP-------+ |   | CRLDP-----+  |
              +----------- AIA   |    | +----- AIA   |  |  |
                    |   |  SIA------+ |     |  SIA------------+
                    |   +--------+  | |     +--------+  |  |  |
                    |               | V                 V  |  |
                    |               | +-----------------+  |  |
                    |               | | CRL issued by A |  |  |
                    | A's Repository| +-----------------+  |  |
                    | Directory     |                      |  |
                    +---------------|----------------------+  |
                                    |                         |
          +----------------+        |    +----------------+   |
          | B's Repository |<-------+    | C's Repository |<--+
          |  Directory     |             |  Directory     |
          +----------------+             +----------------+

          Figure 1.  Use of AIA and SIA Extensions in the RPKI

   In Figure 1, certificates B and C are issued by CA A.  Therefore, the
   AIA extensions of certificates B and C point to (certificate) A, and
   the SIA extension of certificate A points to the repository
   publication point of CA A's subordinate products, which includes
   certificates B and C, as well as the CRL issued by A.  The CRL
   Distribution Points (CRLDP) extension in certificates B and C both
   point to the CRL issued by A.

   In this distributed repository structure, an instance of a CA's
   repository publication point contains all published certificates
   issued by that CA, and the CRL issued by that CA.  This repository
   also contains all published digitally signed objects that are
   verified by an end-entity (EE) certificate issued by this CA.

2.1.  Manifests

   Every repository publication point MUST contain a manifest [RFC6486].
   The manifest contains a list of the names of all objects, as well as
   the hash value of each object's contents that are currently published
   by a CA or an EE.



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   An authority MAY perform a number of object operations on a
   publication repository within the scope of a repository change before
   issuing a single manifest that covers all the operations within the
   scope of this change.  Repository operators SHOULD implement some
   form of directory management regime function on the repository to
   ensure that RPs who are performing retrieval operations on the
   repository are not exposed to intermediate states during changes to
   the repository and the associated manifest.  (It is noted that if no
   such access regime is in place, then RPs MAY be exposed to
   intermediate repository states where the manifest and the repository
   contents may not be precisely aligned.  Specific cases and actions in
   such a situation of misalignment of the manifest and the repository
   contents are considered in [RFC6486].)

2.2.  CA Repository Publication Points

   A CA certificate has two accessMethod elements specified in its SIA
   field.  The id-ad-caRepository accessMethod element has an associated
   accessLocation element that points to the repository publication
   point of the certificates issued by this CA, as specified in
   [RFC6487].  The id-ad-rpkiManifest accessMethod element has an
   associated accessLocation element that points to the manifest object,
   as an object URI (as distinct to a directory URI), that is associated
   with this CA.

   A CA's publication repository contains the current (non-expired and
   non-revoked) certificates issued by this CA, the most recent CRL
   issued by this CA, the current manifest, and all other current signed
   objects that can be verified using an EE certificate [RFC6487] issued
   by this CA.

   The CA's manifest contains the names of this collection of objects,
   together with the hash value of each object's contents, with the
   single exception of the manifest itself.

   The RPKI design requires that a CA be uniquely associated with a
   single key pair.  Thus, the administrative entity that is a CA
   performs key rollover by generating a new CA certificate with a new
   subject name, as well as a new key pair [RFC6489].  (The reason for
   the new subject name is that in the context of the RPKI, the subject
   names in all certificates issued by a CA are intended to be unique,
   and because the RPKI key rollover procedure creates a new instance of
   a CA with the new key, the name constraint implies the need for a new
   subject name for the CA with the new key.)  In such cases, the entity
   SHOULD continue to use the same repository publication point for both
   CA instances during the key rollover, ensuring that the value of the
   AIA extension in indirect subordinate objects that refer to the
   certificates issued by this CA remain valid across the key rollover,



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   and that the reissuance of subordinate certificates in a key rollover
   is limited to the collection of immediate subordinate products of
   this CA [RFC6489].  In such cases, the repository publication point
   will contain the CRL, manifest and subordinate certificates of both
   CA instances.  (It is feasible for the entity to use distinct
   repository publication points for the old and new CA keys, but, in
   such a case, very careful coordination would be required with
   subordinate CAs and EEs to ensure that the AIA pointers in the
   indirect subordinate levels of the RPKI hierarchy are correctly
   aligned to the subordinate products of the new CA.)

   The following paragraphs provide guidelines for naming objects in a
   CA's repository publication point:

   CRL:
      When a CA issues a new CRL, it replaces the previous CRL (issued
      under the same CA key pair) in the repository publication point.
      CAs MUST NOT continue to publish previous CRLs in the repository
      publication point.  Thus, it MUST replace (overwrite) previous
      CRLs signed by the same CA (instance).  A non-normative guideline
      for naming such objects is that the file name chosen for the CRL
      in the repository be a value derived from the public key of the
      CA.  One such method of generating a CRL publication name is
      described in Section 2.1 of [RFC4387]; convert the 160-bit hash of
      a CA's public key value into a 27-character string using a
      modified form of Base64 encoding, with an additional modification
      as proposed in Section 5, table 2, of [RFC4648].  The filename
      extension of ".crl" MUST be used to denote the file as a CRL.
      Each ".crl" file contains exactly one CRL encoded in DER format.

   Manifest:
      When a new instance of a manifest is published, it MUST replace
      the previous manifest to avoid confusion.  CAs MUST NOT continue
      to publish previous CA manifests in the repository publication
      point.  A non-normative guideline for naming such objects is that
      the filename chosen for the manifest in the publication repository
      be a value derived from the public key part of the entity's key
      pair, using the algorithm described for CRLs above for generation
      of filenames.  The filename extension of ".mft" MUST be used to
      denote the object as a manifest.

   Certificates:
      Within the RPKI framework, it is possible that a CA MAY issue a
      series of certificates to the same subject name, the same subject
      public key, and the same resource collection.  However, a relying
      party requires access only to the most recently published
      certificate in such a series.  Thus, such a series of certificates
      SHOULD share the same filename.  This ensures that each successive



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      issued certificate in such a series effectively overwrites the
      previous instance of the certificate.  It is feasible to use
      different filenames, but this imposes a burden on the validating
      user.  A non-normative guideline for naming such objects is for
      the CA to adopt a (local) policy requiring a subject to use a
      unique key pair for each unique instance of a certificate series
      issued to the same subject, thereby allowing the CA to use a file
      name generation scheme based on the subject's public key, e.g.,
      using the algorithm described above for CRLs above.  Published
      certificates MUST use a filename extension of ".cer" to denote the
      object as a certificate.  Each ".cer" file contains exactly one
      certificate encoded in DER format.

   Signed Objects:
      RPKI signed objects [RFC6488] are published in the repository
      publication point referenced by the SIA of the CA certificate that
      issued the EE certificate used to validate the digital signature
      of the signed object (and are directly referenced by the SIA of
      that EE certificate).  A general non-normative guideline for
      naming such RPKI signed objects is for the filename of such
      objects to be derived from the associated EE certificate's public
      key, applying the algorithm described above.  Published RPKI
      signed objects MUST NOT use the filename extensions ".crl",
      ".mft", or ".cer".

      One form of signed object defined at the time of publication of
      this document is a Route Origination Authorization (ROA)
      [RFC6482].  Published ROAs MUST use a filename extension of ".roa"
      to denote the object as a ROA.

3.  Resource Certificate Publication Repository Considerations

   Each issuer MAY publish its issued certificates and CRL in any
   repository.  However, there are a number of considerations that guide
   the choice of a suitable repository publication structure:

      *  The publication repository SHOULD be hosted on a highly
         available service and high-capacity publication platform.

      *  The publication repository MUST be available using rsync
         [RFC5781] [RSYNC].  Support of additional retrieval mechanisms
         is the choice of the repository operator.  The supported
         retrieval mechanisms MUST be consistent with the accessMethod
         element value(s) specified in the SIA of the associated CA or
         EE certificate.






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      *  Each CA repository publication point SHOULD contain the
         products of this CA, including those objects that can be
         verified by EE certificates that have been issued by this CA.
         The signed products of related CA's that are operated by the
         same entity MAY share this CA repository publication point.
         Aside from subdirectories, any other objects SHOULD NOT be
         placed in a repository publication point.

         Any such subdirectory SHOULD be the repository publication
         point of a CA or EE certificate that is contained in the CA
         directory.  These considerations also apply recursively to
         subdirectories of these directories.  Detection of content that
         is not a CA product has the potential to cause confusion to
         RPs, and in such a case RPs should exercise caution not to
         invalidate the valid CA products found at the CA's repository
         publication point.

      *  Signed objects are published in the location indicated by the
         SIA field of the EE certificate used to verify the signature of
         each object.  Signed objects are published in the repository
         publication point of the CA certificate that issued the EE
         certificate.  The SIA extension of the EE certificate
         references this object rather than the repository publication
         directory [RFC6487].

      *  Section 2.1 states that repository operators SHOULD implement
         some form of directory management regime function on the
         repository to ensure that RPs who are performing retrieval
         operations on the repository are not exposed to intermediate
         states during changes to the repository and the associated
         manifest.  Notwithstanding the following commentary, RPs SHOULD
         NOT assume that a consistent repository and manifest state are
         assured, and they SHOULD organize their retrieval operations
         accordingly (see Section 5).

         The manner in which a repository operator can implement a
         directory update regime that mitigates the risk of the manifest
         and directory contents being inconsistent, to some extent, is
         dependent on the operational characteristics of the filesystem
         that hosts the repository, so the following comments are non-
         normative in terms of any implicit guidelines for repository
         operators.

         A commonly used technique to avoid exposure to inconsistent
         retrieval states during updates to a large directory is to
         batch a set of changes to be made, create a working copy of the
         directory's contents, and then perform the batch of changes to
         the local copy of the directory.  On completion, rename the



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         filesystem symbolic link of the repository directory name to
         point to this working copy of the directory.  The old
         repository directory contents can be purged at a slightly later
         time.  However, it is noted that the outcomes of this technique
         in terms of ensuring the integrity of client synchronization
         functions performed over the directory depend on the
         interaction between the supported access mechanisms and the
         local filesystem behavior.  It is probable that this technique
         will not remove all possibilities for RPs to see inconsistent
         states between the manifest and the repository.  Because a
         repository has the potential to be in an partially updated
         state, it cannot be guaranteed to be internally self consistent
         all the time.

4.  Certificate Reissuance and Repositories

   If a CA certificate is reissued, e.g., due to changes in the set of
   resources contained in the number resource extensions, it should not
   be necessary to reissue all certificates issued under it.  Because
   these certificates contain AIA extensions that point to the
   publication point for the CA certificate, a CA SHOULD use a name for
   its repository publication point that persists across certificate
   reissuance events.  That is, reissued CA certificates SHOULD use the
   same repository publication point as previously issued CA
   certificates having the same subject and subject public key, such
   that certificate reissuance SHOULD intentionally overwrite the
   previously issued certificate within the repository publication
   point.

   It is noted in Section 2.2 that when a CA performs a key rollover,
   the entity SHOULD use a name for its repository publication point
   that persists across key rollover.  In such cases, the repository
   publication point will contain the CRLs and manifests of both CA
   instances as a transient state in the key rollover procedure.  The
   RPKI key rollover procedure [RFC6489] requires that the subordinate
   products of the old CA be overwritten in the common repository
   publication point by subordinate products issued by the new CA.

5.  Synchronizing Repositories with a Local Cache

   It is possible to perform the validation-related task of certificate
   path construction using the retrieval of individual certificates, and
   certificate revocation lists using online retrieval of individual
   certificates, sets of candidate certificates and certificate
   revocation lists based on the AIA, SIA, and CRLDP certificate fields.
   This is NOT recommended in circumstances where speed and efficiency
   are relevant considerations.




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   To enable efficient validation of RPKI certificates, CRLs, and signed
   objects, it is recommended that each relying party maintain a local
   repository containing a synchronized copy of all valid certificates,
   current certificate revocation lists, and all related signed objects.

   The general approach to repository synchronization is one of a "top-
   down" walk of the distributed repository structure.  This commences
   with the collection of locally selected trust anchor material
   corresponding to the local choice of Trust Anchors, which can be used
   to load the initial set of self-signed resource certificate(s) that
   form the "seed" of this process [RFC6490].  The process then
   populates the local repository cache with all valid certificates that
   have been issued by these issuers.  This procedure can be recursively
   applied to each of these subordinate certificates.  Such a repository
   traversal process SHOULD support a locally configured maximal chain
   length from the initial trust anchors.  If this is not done, then
   there might be a SIA pointer loop, or other degenerate forms of the
   logical RPKI hierarchy, that would cause an RP to malfunction when
   performing a repository synchronization operation with the RP's local
   RPKI cache.

   RPs SHOULD ensure that this local synchronization uses the retrieved
   manifests [RFC6486] to ensure that they are synchronizing against a
   current, consistent state of each repository publication point.  It
   is noted in Section 3 that when the repository publication point
   contents are updated, a repository operator cannot assure RPs that
   the manifest contents and the repository contents will be precisely
   aligned at all times.  RPs SHOULD use a retrieval algorithm that
   takes this potential for transient inconsistency into account.  For
   the RP to mitigate this situation, possible algorithms include
   performing the synchronization across the repository twice in
   succession, or performing a manifest retrieval both before and after
   the synchronization of the directory contents, and repeating the
   synchronization function if the second copy of the manifest differs
   from the first.

6.  Security Considerations

   Repositories are not assumed to be integrity-protected databases, and
   repository retrieval operations might be vulnerable to various forms
   of "man-in-the-middle" attacks.  Corruption of retrieved objects is
   detectable by a relying party through the validation of the signature
   associated with each retrieved object.  Replacement of newer
   instances of an object with an older instance of the same object is
   detectable through the use of manifests.  Insertion of revoked,
   deleted certificates is detected through the retrieval and processing





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   of CRLs at scheduled intervals.  However, even the use of manifests
   and CRLs will not allow a relying party to detect all forms of
   substitution attacks based on older (but not expired) valid objects.

   Confidentiality is not provided by the repository or by the signed
   objects published in the repository.  Data that is subject to
   controlled access should not be included in signed objects in the
   repository unless there is some specified mechanism used to ensure
   the confidentiality of the data contained in the signed object.

7.  IANA Considerations

7.1.  Media Types

   IANA has registered the following two media types:

      application/rpki-manifest
      application/rpki-roa

   This document also uses the .cer and .crl file extensions from the
   application/pkix-cert and application/pkix-crl media registries
   defined in [RFC2585].

7.1.1.  application/rpki-manifest

   MIME media type name:  application
   MIME subtype name:  rpki-manifest
   Required parameters:  None
   Optional parameters:  None
   Encoding considerations:  binary
   Security considerations:  Carries an RPKI Manifest [RFC6486]
   Interoperability considerations:  None
   Published specification:  This document
   Applications that use this media type:  Any MIME-complaint transport
   Additional information:
      Magic number(s):  None
      File extension(s):  .mft
      Macintosh File Type Code(s):
   Person & email address to contact for further information:
      Geoff Huston <gih@apnic.net>
   Intended usage:  COMMON
   Author/Change controller:  Geoff Huston <gih@apnic.net>









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7.1.2.  application/rpki-roa

   MIME media type name:  application
   MIME subtype name:  rpki-roa
   Required parameters:  None
   Optional parameters:  None
   Encoding considerations:  binary
   Security considerations:  Carries an RPKI ROA [RFC6482]
   Interoperability considerations:  None
   Published specification:  This document
   Applications that use this media type:  Any MIME-complaint transport
   Additional information:
      Magic number(s):  None
      File extension(s):  .roa
      Macintosh File Type Code(s):
   Person & email address to contact for further information:
      Geoff Huston <gih@apnic.net>
   Intended usage:  COMMON
   Author/Change controller:  Geoff Huston <gih@apnic.net>

7.2.  RPKI Repository Name Scheme Registry

   IANA has created the "RPKI Repository Name Scheme" registry.  The
   registry contains three-letter filename extensions for RPKI
   repository objects.  The registry's contents are managed by IETF
   Review [RFC5226].  The initial contents of this registry are the
   following:

   Filename extension  RPKI Object                     Reference
      .cer             Certificate                     [RFC6481]
      .crl             Certificate Revocation List     [RFC6481]
      .mft             Manifest                        [RFC6481]
      .roa             Route Origination Authorization [RFC6481]

8.  Acknowledgements

   This document has benefitted from helpful review comments and input
   from Stephen Kent, Matt Lepenski, Michael Elkins, Russ Housley, and
   Sean Turner.












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9.  References

9.1.  Normative References

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

   [RFC6482] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route
             Origin Authorizations (ROAs)", RFC 6482, February 2012.

   [RFC6486] Austein, R., Huston, G., Kent, S., and M. Lepinski,
             "Manifests for the Resource Public Key Infrastructure
             (RPKI)", RFC 6486, February 2012.

   [RFC6487] Huston, G., Michaelson, G., and R. Loomans, "A Profile for
             X.509 PKIX Resource Certificates", RFC 6487, February 2012.

   [RFC6488] Lepinski, M., Chi, A., and S. Kent, "Signed Object Template
             for the Resource Public Key Infrastructure (RPKI)", RFC
             6488, February 2012.

   [RSYNC]   rsync web pages, <http://rsync.samba.org/>.

9.2.  Informative References

   [RFC2585] Housley, R. and P. Hoffman, "Internet X.509 Public Key
             Infrastructure Operational Protocols: FTP and HTTP", RFC
             2585, May 1999.

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

   [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
             Resource Identifier (URI): Generic Syntax", STD 66, RFC
             3986, January 2005.

   [RFC4387] Gutmann, P., Ed., "Internet X.509 Public Key Infrastructure
             Operational Protocols: Certificate Store Access via HTTP",
             RFC 4387, February 2006.

   [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
             Encodings", RFC 4648, October 2006.

   [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
             IANA Considerations Section in RFCs", BCP 26, RFC 5226, May
             2008.





Huston, et al.               Standards Track                   [Page 14]

RFC 6481              ResCert Repository Structure         February 2012


   [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.

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

   [RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support
             Secure Internet Routing", RFC 6480, February 2012.

   [RFC6489] Huston, G., Michaelson, G., and S. Kent, "Certification
             Authority (CA) Key Rollover in the Resource Public Key
             Infrastructure (RPKI)", BCP 174, RFC 6489, February 2012.

   [RFC6490] Huston, G., Weiler, S., Michaelson, G., and S. Kent,
             "Resource Public Key Infrastructure (RPKI) Trust Anchor
             Locator", RFC 6490, February 2012.

Authors' Addresses

   Geoff Huston
   APNIC

   EMail: gih@apnic.net
   URI:   http://www.apnic.net


   Robert Loomans
   APNIC

   EMail: robertl@apnic.net
   URI:   http://www.apnic.net


   George Michaelson
   APNIC

   EMail: ggm@apnic.net
   URI:   http://www.apnic.net











Huston, et al.               Standards Track                   [Page 15]


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