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Versions: 00 01 02 03 04                                                
   Internet Engineering Task Force                           Brian Weis, Editor
   INTERNET-DRAFT                                                 Cisco Systems
   draft-weis-sobgp-certificates-00.txt
   Expires: December, 2003                                           June, 2003



                  Secure Origin BGP (soBGP) Certificates

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet
   Engineering Task Force (IETF), its areas, and its working groups.
   Note that other groups may also distribute working documents as
   Internet Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
        http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
        http://www.ietf.org/shadow.html.

Abstract

   This document describes the format of digital certificates that are
   used by the Secure Origin BGP (soBGP) extensions to BGP, as well as
   acceptable use of those certificates. Included are certificates
   providing authentication, authorization, and policy distribution.











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Table of Contents

1.0 Introduction......................................................4
  1.1 Key Words.......................................................4
2.0 Overview..........................................................4
  2.1 Entitycert Overview.............................................5
  2.2 Authcert Overview...............................................5
  2.3 Policy Certificates Overview....................................6
  2.4 Digital Signature Algorithms....................................6
3.0 Entity Certificate (Entitycert)...................................6
  3.1 Format..........................................................7
    3.1.1 Using the Autonomous System as an Identifier................7
  3.2 Creation........................................................8
    3.2.1 Certificate Uniqueness......................................8
    3.2.2 Certificate Encoding........................................8
    3.2.3 Multiplicity of Entitycerts.................................8
  3.3 Distribution....................................................9
  3.4 Validation......................................................9
    3.4.1 Web of Trust................................................9
    3.4.2 Self-signed Entitycerts....................................10
  3.5 Revocation and Expiration......................................10
4.0 Authorization Certificates (Authcert)............................11
  4.1 Format.........................................................11
    4.1.1 Authcert Header............................................11
    4.1.2 The Authorizing AS.........................................11
    4.1.3 Authorized Originator......................................12
    4.1.4 The Serial Number TLV......................................12
    4.1.5 Authorizing AS Entitycert Uniform Resource Locator.........13
    4.1.6 Authorizing AS Validation List Uniform Resource Locator....13
    4.1.7 The Address Block TLV......................................14
    4.1.8 Signature..................................................14
  4.2 Creation.......................................................15
    4.2.1 Certificate Uniqueness.....................................15
    4.2.2 Certificate Encoding.......................................16
  4.3 Distribution...................................................16
  4.4 Validation.....................................................16
    4.4.1 Self-generated Authcerts...................................17
  4.5 Revocation.....................................................17
5.0 Prefix Policy Certificates (PrefixPolicycert)....................17
  5.1 Format.........................................................18
    5.1.1 PrefixPolicycert Header....................................18
    5.1.2 The Originating Autonomous System..........................18
    5.1.3 The Serial Number..........................................18
    5.1.4 Authorizing AS Entitycert Uniform Resource Locator.........19
    5.1.5 Authcert...................................................19
    5.1.6 Policies...................................................20
    5.1.7 Signature..................................................21

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  5.2 Creation.......................................................22
    5.2.1 Certificate Uniqueness.....................................22
    5.2.2 Certificate Encoding.......................................22
  5.3 Distribution...................................................23
  5.4 Validation.....................................................23
  5.5 Revocation.....................................................24
6.0 AS Policy Certificates (ASPolicycert)............................24
  6.1 Format.........................................................24
    6.1.1 ASPolicycert Header........................................24
    6.1.2 The Originating Autonomous System..........................25
    6.1.3 The Serial Number..........................................25
    6.1.4 Authorizing AS Entitycert Uniform Resource Locator.........26
    6.1.5 Attached Transit Autonomous Systems........................26
    6.1.6 Attached Non-transit Autonomous Systems....................27
    6.1.7 Revoked Entity Certificate List............................27
    6.1.8 Authorization Certificate Validity List....................28
    6.1.9 Prefix Policy Certificate Validity List....................29
    6.1.10 Most Recent AS Policy Certificate Uniform Resource Locator29
    6.1.11 Signature.................................................30
  6.2 Creation.......................................................31
    6.2.1 Certificate Uniqueness.....................................31
    6.2.2 Certificate Encoding.......................................31
  6.3 Distribution...................................................31
  6.4 Validation.....................................................31
  6.5 Revocation.....................................................32
7.0 Security Considerations..........................................32
  7.1 Entitycerts....................................................32
  7.2 Authcerts......................................................33
  7.3 PrefixPolicycerts..............................................33
  7.4 ASPolicycerts..................................................34
  7.5 Entitycert Uniform Resource Locators...........................34
8.0 IANA Considerations..............................................34
  8.1 Authorization Certificate......................................34
    8.1.1 Signature Type.............................................34
  8.2 Prefix Policy Certificate......................................35
    8.2.1 Policies Type..............................................35
    8.2.2 Signature Type.............................................36
  8.3 AS Policy Certificate..........................................36
    8.3.1 Validity Ranges............................................36
    8.3.2 Signature Type.............................................36
9.0 Acknowledgments..................................................37
10.0 References......................................................37
  10.1 Normative References..........................................37
  10.2 Informative References........................................37
Editor's Address.....................................................38

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1.0 Introduction

   There is a great deal of concern over the security of routing systems
   within the Internet, particularly in relation to the Border Gateway
   Protocol [BGP], which is used to provide routing information between
   autonomous systems. Extensions to BGP supporting distribution of
   digitally signed authentication, authorization, and policy objects
   have been defined in [SOBGP-BGP]. This document defines the format of
   those objects, as well as how they are to be used.

1.1 Key Words

   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].

2.0 Overview

   Participants within the routing system are called entities, and they
   are identified through the use of Entity Certificates (Entitycerts).
   Each entity must have an Autonomous System (AS) number, issued from
   some centralized authority, such as a Regional Internet Routing
   (RIR) authority, to participate in soBGP, either to act as a trusted
   signer, an authorizer of address blocks, or a route originator.

   The authorization to advertise prefixes or routes within a block of
   address (within a given address space) is validated through
   Authorization Certificates (Authcerts). These certificates are
   issued by the entity that authorized any other entity to advertise
   reachability to a given set of addresses.

   Policies about routes, and the information required to build a list
   of known valid paths in the routing system, are provided through
   Prefix Policy Certificates (PrefixPolicycerts). Policies specific to
   Autonomous System are provided through AS Policy Certificates
   (ASPolicycerts).

   The following figure illustrates the relationship between these
   certificates. In the figure, an Entitycert at the head of an arrow
   is used to validate the certificate at the end of the arrow. Note
   that certificates are issued in the reverse direction of the arrows.
   That is, after an Entitycert is issued, it can be used to create the
   certificates that point to it.



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                 (Manually Configured Entitycerts)
                               ^
                               |
                          validated by
                               |
                         +-----+------+
                 +------>| Entitycert |
                /        +------------+
               /               ^
              /                |
      +------+---+       +-----+------+         +------------------+
      | Authcert |   +-->| Entitycert |<------- | PrefixPolicycert |
      +----------+  /    +------------+         +------------------+
                   /           ^    ^
                  /            |    |           +------------------+
                 /             |    +---------- |     ASPolicycert |
                /              |                +------------------+
               /               |
      +-------+--+       +-----+------+         +------------------+
      | Authcert |       | Entitycert |<------- | PrefixPolicycert |
      +----------+       +------------+         +------------------+
                                    ^
                                    |           +------------------+
                                    +---------- |     ASPolicycert |
                                                +------------------+

                  Figure 1. Certificate validation paths


   Each of the soBGP certificates is discussed below, and also in more
   detail in subsequent sections of this document.

2.1 Entitycert Overview

   Entitycerts provide authentication, providing a binding of an
   identity (i.e., autonomous system number) to a public key. The
   authenticity of the binding is verified with a digital signature,
   where the public key of the certificate issuer has been previously
   accepted by an receiver as valid. Issuer public keys can either be
   manually configured, or are verified through the use of another
   issuer's trusted public key in a "web of trust" built by the
   receiver.

   When Entitycerts form a web of trust, well-known trusted members of
   the routing system sign the Entitycerts of other members of the
   routing system.

2.2 Authcert Overview

   Entitycerts validate the contents of Authcerts. Authcerts authorize
   an entity to advertise particular address spaces. They are generated
   in a hierarchical manner following the order of address space
   allocation (i.e., from RIR, to ISP, to ISP customer), and are
   distributed along with the address space allocation. Receivers use

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   the Authcert to validate announcements received in BGP UPDATE
   messages.

   The authenticity of Authcerts is verified with a digital signature
   from the issuing autonomous system. Authcerts do not contain public
   keys. Rather, they bind an address space to a particular identity
   (i.e., autonomous system), which are then distributed by route
   originators within PrefixPolicycerts.

2.3 Policy Certificates Overview

   Entitycerts also validate the contents of PrefixPolicycerts, which
   carry policy information sourced from route originators, and
   ASPolicycerts, which carryautonomous system topology information  .
   These certificates are generated and distributed from route
   originators.

   PrefixPolicycerts and ASPolicycerts are verified with a digital
   signature from the autonomous system generating the policy. These
   policy certificates do not contain public keys. Rather, they bind a
   particular policy to a particular identity (i.e., autonomous
   system).


2.4 Digital Signature Algorithms

   The RSA Public Key Algorithm [RSA] is a widely deployed public key
   algorithm commonly used for digital signatures. Compared to other
   public key algorithms, signature verification is relatively quick.
   This property is useful considering the large number of signature
   verifications that will be done on soBGP certificates. The RSA
   Algorithm is commonly supported in hardware, and is no longer
   encumbered by intellectual property claims. All soBGP implementations
   MUST support a digital signature of a SHA1 digest encrypted with the
   RSA algorithm.


3.0 Entity Certificate (Entitycert)

   Entitycerts are used to verify, through a trust model, the existence
   of an entity within the routing system, and the value of that
   entity's public key for use in the routing system. Each entity
   within the routing system MUST generate a public/private key pair.
   The public key portion of this pair is then signed, verifying that
   anyone using this public key is actually the entity in question.
   This signature may be provided by various other trusted parties
   within the routing system, including (but not limited to):

   ¡ The authority that issued the autonomous system number.

   ¡ An external commercial authority that provides authentication
     certificates for other commercial transactions.


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   ¡ Any other trusted party within the domain of Internet routing,
     such as a well known Service Provider.

   ¡ Self-signed if the entity is well known within the routing system.

   This public key is used to verify the validity of other messages
   transmitted by this entity within the routing system.

   The public key, along with other verifying information, is formatted
   into an Entitycert, as described in the next section.


3.1 Format

   An Entitycert MUST be formatted as an X.509 authentication
   certificate, as defined in [RFC3280]. The Entitycert MUST be
   generated with a signature of type sha1withRSAEncryption [RFC3279].

   The primary identity in soBGP is the autonomous system number. An
   extension to RFC 3280 allowing this identity is proposed in Section
   3.1.1. Each entity that signs Entitycerts MUST be assigned an AS
   number, even if they do not originate routes into the internetwork.

   In order for an X.509 certificate to be used as an Entitycert, the
   following fields MUST be present and defined as Critical. Other
   fields are also necessary for the purposes of creating an X.509
   certificate. The following fields are mentioned either because there
   are special requirements, or for clarification of later text.

   ¡ SubjectAltName. The autonomous system number of the entity owning
     the public key MUST be included in the SubjectAltName.
   ¡ IssuerAltName. The autonomous system number of the issuer MUST be
     included in the IssuerAltName.
   ¡ CertificateSerialNumber. This is a unique identifier for a
     particular issuer.
   ¡ SubjectPublickeyInfo. This is the actual public key of the
     subject, as vouched for by the issuer.
   ¡ SignatureValue. This is the signature of the authenticating
     autonomous system.


3.1.1 Using the Autonomous System as an Identifier

   The autonomous system of an entity MUST be defined in the
   GeneralName namespace as defined in RFC 3280, section 4.2.1.7. This
   document adds the "autonomousSystemID" identifier to the
   GeneralNames list. The GeneralNames list is used by a number of
   fields defined in RFC 3280, including SubjectAltName and
   issuerAltName.

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        GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName

        GeneralName ::= CHOICE {
        .
        .
        .
   autonomousSystemID      [9]     INTEGER}

3.2 Creation

   An Entitycert is usually created with the following steps:

   ¡ The receiving autonomous system generates a signature key pair
   ¡ The receiving autonomous system forwards its identity (including
     its AS number) and the public key to an issuing autonomous system
     using a trusted certificate registration mechanism  that is
     outside the scope of this document.
   ¡ The issuing autonomous system verifies that the identity of the
     receiving autonomous system, generates an Entitycert including
     that identity, and signs it with its own private key.
   ¡ The issuing autonomous system returns the Entitycert to the
     receiving autonomous system.


3.2.1 Certificate Uniqueness

   Digital certificates are created as uniquely named objects, which
   allows them to be uniquely identified. The pair of
   CertificateSerialNumber and IssuerAltName values uniquely identifies
   entity Certificates.


3.2.2 Certificate Encoding

   Entitycerts distributed in [SOBGP-BGP] use their native DER [X.690]
   form. If Entitycerts are manually distributed (e.g., through
   electronic mail) they may need to be base64 encoded into ASCII.
   Authcerts SHOULD be encoded as PEM objects (described in [RFC1421]).

   There are times that Entitycerts are referred to by name (e.g., the
   target of a URL). In this case, the extension on the name MUST
   define the format of the Entitycert. A suffix of ".der" defines DER
   encoding. A suffix of ".pem" defines base64 encoding.


3.2.3 Multiplicity of Entitycerts

   An autonomous system MAY acquire more than one Entitycert. Acquiring
   certificates from different well-known entities within the routing
   system may increase the probability of other autonomous systems
   accepting their public key. Or, it may simply result in other
   autonomous systems accepting their public key faster, which
   increases BGP convergence times.

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   If an entity detects that an autonomous system has valid Entitycerts
   from different issuers, the entity SHOULD treat the various
   Entitycerts as independent. Revocation from one issuer does not
   necessarily imply that Entitycerts from other issuers are invalid.
   An issuer may revoke a certificate for reasons other than key
   comprimise.

   However, even if an issuer states key compromise as the reason for
   revocation, a receiving entity SHOULD treat this state as specific
   to the issuer. Note that if the state of one issuer were instead
   considered transitive, the erroneous revocation of a single issuer
   would result in a Denial of Service attack on the victim autonomous
   system.

   In the face of inconsistent state from different issuers, a receiver
   MAY choose to trust one issuer over another. For example, a receiver
   may choose to prefer the result of an issuer they directly trust
   over an issuer that was verified further away in the "web of trust".
   .

3.3 Distribution

   Entitycerts may be distributed using any number of methods, for
   example:

   ¡ maintained in a directory maintained by the issuing autonomous
     system,
   ¡ distributed via some out of band mechanism, or
   ¡ distributed within BGP using extensions defined in [SOBGP-BGP].

   To ensure interoperability, the receiving autonomous system SHOULD
   distribute its Entitycert within BGP.


3.4 Validation

   Any device receiving an Entitycert can verify it by validating the
   signature on the certificate, along with the verifying information.
   If a Certificate Revocation List (CRL) is available for that issuer,
   it MUST be consulted to verify that this certificate has not been
   revoked. Once validation is complete, the public key contained in
   this certificate may be used to verify messages purportedly sent by
   this entity.


3.4.1 Web of Trust

   An soBGP entity uses the "web of trust" paradigm for purposes of
   Entitycert validation, where the entity learns the validity of
   public keys over time. An entity usually follows the following
   procedure.


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   ¡ A small number of Entitycerts are manually configured and copied
     to a device's local configuration. These are implicitly trusted as
     being previously verified and authenticated.
   ¡ When the entity receives a new Entitycert, it checks to see if it
     has the public key of the issuing autonomous system in its
     configuration. If so, it attempts to validate the Entitycert,
     using the previously known public key, and any revocation material
     that is available from the issuer.
   ¡ If the new Entitycert proves valid, it is added to the device's
     local configuration and may be used to validate subsequently
     received Entitycerts.

   An autonomous system may define local policy that restricts the
   scope of the web of trust. For example, they may choose to only
   accept only a certain "depth" of signatures, trusting second party
   signatures, but not third party signatures. However it should be
   noted that any local policy restricting the web of trust reduces the
   value of soBGP authorization and path validation.

3.4.2 Self-signed Entitycerts

   Entitycerts MAY be self-signed, but MUST only be accepted from
   autonomous systems when an alternative method exists of validating
   that the self-signed certificate is genuine. For example,
   distribution out-of-band using a trusted delivery procedure would be
   acceptable.

   Typical users of a self-signed Entitycert would be:

   ¡ A commercial authority in the business of provides authentication
     certificates for many types of commercial transactions
   ¡ An Entitycert issuer that is at the top of a hierarchy of issuers
   ¡ A well-known trusted party within the domain of Internet routing


3.5 Revocation and Expiration

   Any entity issuing an Entitycert may have need to revoke it. The
   entity MAY use any form for propagating that revocation list, but
   SHOULD also send it as part of an AS Policy Certificate (distributed
   using [SOBGP-BGP]). This allows autonomous systems that cannot route
   to the issuing autonomous system to verify that the Entitycert has
   not been revoked.

   X.509 certificates contain expiration dates. Any device validating
   Entitycerts MUST have a time of day clock that is close to real time
   in order to properly deal with expired certificates. It is
   RECOMMENDED that Entitycerts do not expire before the expected life
   of their RSA key pair (e.g., current recommendations on the life of
   a key pair generated with a particularly sized modulus).

   If an Entitycert is discarded due to either expiration or
   revocation, the Authcert and Policy databases shall be examined, and

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   any Authcerts and Policy certificates that were validated using the
   discarded certificate should be removed from the database.

4.0 Authorization Certificates (Authcert)

   The authorization certificate binds one or more prefix blocks to a
   particular autonomous system. It is typically provided by an entity
   issuing a prefix block to an autonomous system, and is digitally
   signed by the issuing autonomous system. The Authcert can be thought
   of as an "Attribute Certificate" in the spirit of RFC 3281, although
   it does not follow the syntax of that document.


4.1 Format

   The Authcert is defined as a header block followed by a set of
   Type/Length/Value attributes, as identified in the following
   sections. Each Authcert TLV includes a type, which is treated as a
   16 bit (two octet) unsigned integer. The TLVs described must be
   placed within the Authcert in type order; every Authcert should
   begin with a TLV type 1 (Autonomous System and Options). All TLVs
   are REQUIRED to be in an Authcert unless otherwise noted.


4.1.1 Authcert Header


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +---------------+---------------+-------------------------------+
      | Cert. Marker  |    Type Id    | Length                        |
      +---------------+---------------+-------------------------------+
      | TLVs
      +----------------

   o    Certificate Marker: "162(0xa2), identifying this as an soBGP
        certificate.

   o    Type ID: "1(0x01), identifying this as an Authcert.

   o    Length: Set to the length of the TLVs.

   o    TLVs: The Type/Length/Value attributes making up an Authcert.


4.1.2 The Authorizing AS


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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Autonomous System                                             |
      +---------------------------------------------------------------+

   o    TLV type: 1 (0x0001)

   o    Length: Set to 4.

   o    AS: (4 octets), the autonomous system authorizing other
        entities to advertise prefixes within this block. AS numbers
        containing only two octets should be placed in the least
        significant octets of this four-octet field (the two rightmost
        octets).

   Each authorizing entity MUST have an autonomous system number, used
   as a unique identifier, even though they may not advertise prefixes
   into the routing system.


4.1.3 Authorized Originator

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Autonomous System                                             |
      +---------------------------------------------------------------+

   o    TLV type: 2 (0x0002)

   o    Length: Set to 4.

   o    AS: (4 octets), the autonomous system of an entity authorized
        to advertise prefixes within this block. AS numbers containing
        only two octets should be placed in the least significant
        octets of this four-octet field (the two rightmost octets).

   Multiple authorized originator TLVs may be included in the Authcert.


4.1.4 The Serial Number TLV


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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Serial Number                                                 |
      +---------------------------------------------------------------+

   o    TLV type: 3 (0x0003)

   o    Length: Set to 4.

   o    Serial Number: (4 octets), unsigned integer taken from a number
        space maintained by the Authorizing AS indicating the serial
        number of this Authorization certificate. The Authorizing AS
        MUST manage the number space as a monotonically increasing
        value so that a relative ordering of Authcerts is maintained.


4.1.5 Authorizing AS Entitycert Uniform Resource Locator

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | URL                                                           |
      +----------------

   o    TLV type: 4 (0x0004)

   o    Length: Denotes the length of the URL in octets.

   o    URL: A uniform resource locator indicating a location where the
        Authorizing ASÆs Entitycert can be found.

   An Authcert may omit this TLV. However, an implementation is
   REQUIRED to correctly parse them if they are present. A receiving
   device MAY choose to ignore the URL TLV.


4.1.6 Authorizing AS Validation List Uniform Resource Locator

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | URL                                                           |
      +----------------

   o    TLV type: 5 (0x0005)

   o    Length: Denotes the length of the URL in octets.

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   o    URL: A uniform resource locator indicating a location where the
        Authorizing ASÆs Validation List can be found.

   An Authcert may omit this TLV. However, an implementation is
   REQUIRED to correctly parse them if they are present. A receiving
   device MAY choose to ignore the URL TLV.


4.1.7 The Address Block TLV

   The address block TLV shall define blocks of address within which
   the authorized AS' are allowed to advertise prefixes (or routes).

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | NLRI Data                                                     |
      +----------------

   o    TLV Type: 14 (0x000D)

   o    Length (2 octets), set to the length of the NLRI Data.

   o    NLRI Data: An address block as described in [RFC2858].


4.1.8 Signature

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Signature Type                | Number of Issuers             |
      +-------------------------------+-------------------------------+
      | Entity Certificate Issuer Autonomous System                   |
      +-------------------------------+-------------------------------+
      | Entity Certificate Serial Number                              |
      +-------------------------------+-------------------------------+
      | ...                                                           |
      +---------------------------------------------------------------+
      | Signature                                                     |
      +------------------


   o    TLV type: 65535 (0xFFFF)

   o    Length: (2 octets), unsigned integer denoting the length of the
        payload bytes which follow.


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   o    Signature Type: (2 octets), unsigned integer denoting the type
        of signature (the algorithm used to build this signature). Each
        possible signing algorithm is assigned an integer from this
        field. Signature type 1 is defined as an RSA encryption of a
        SHA1 digest.

   o    Number of Issuers (2 octets): The number of Entitycert
        references included in the signature payload. If more than one
        Entitycert reference follows, all Entitycerts MUST contain the
        same public key for the same authorizing autonomous system.

   o    Entity Certificate Issuer Autonomous System: (4 octets), the
        autonomous system of the entity that provided the Entitycert to
        the Authorizing AS. AS numbers containing only two octets
        should be placed in the least significant octets of this four-
        octet field (the two rightmost octets).

   o    Entity Certificate Serial Number: (4 octets), the Entitycert
        serial number containing the public key of the Authorizing AS.

   o    Signature: The signature itself.

   The signature is calculated using the private key of the authorizing
   entity across all the TLVs within the Authcert. The Signature TLV
   MUST be appended as the last TLV in the Authcert after the signature
   has been computed.


4.2 Creation

   An Authcert is usually created by the authorizing autonomous system
   with the following steps:

   ¡ Allocate a prefix block to the receiving autonomous system.
   ¡ Build an Authcert by adding TLVs containing its own AS number, the
     receiving (authorized) AS number, the prefix block, a unique
     sequence number, and any other information (e.g., URL pointing to
     the Entitycert that signed this Authcert.).
   ¡ Sign the Authcert by hashing and encrypting the Authcert TLVs.
     Place the signature (and other required) information in a
     Signature TLV, and append it to the Authcert.


4.2.1 Certificate Uniqueness

   Digital certificates are created as uniquely named objects, which
   allows them to be uniquely identified. An Authcert is uniquely
   identified by the pair of Authorized Originator and Serial Number
   TLV values.


4.2.2 Certificate Encoding


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   Authcerts distributed in [SOBGP-BGP] are distributed in TLV form.
   However if they are manually distributed (e.g., through electronic
   mail) they may need to be base64 encoded into ASCII. Authcerts SHOULD
   be encoded as described in Section 4.3 of [RFC1421].

   There are times that Authcerts are referred to by name (e.g., the
   target of a URL). In this case, the extension on the name MUST
   define the format of the Authcert. A suffix of ".tlv" defines the
   raw TLV encoding. A suffix of ".pem" defines base64 encoding.


4.3 Distribution

   Authcerts are distributed as part of a Prefix Policy Certificate, so
   that an autonomous system can reliably match distribution policy to
   the prefix block.


4.4 Validation

   The Authcert is validated using the following steps.

   ¡ Identify the Entitycert that signed the Authcert. The correct
     Entitycert is uniquely identified with the Entity Certificate
     Issuer Autonomous System and Entity Certificate Serial Number
     contained in the Signature TLV. The Entity Certificate Issuer
     Autonomous System is compared with the AS number in the Entitycert
     IssuerAltName field. The Entity Certificate Serial Number is
     compared with the Entitycert CertificateSerialNumber.
   ¡ Obtain the Entitycert that signed the Authcert, and validate it.
     The Entitycert may be in a local cache (already received via BGP
     extensions), retrieved using the URL in the Authcert, or through
     other means. If an entity does not have the validating public key
     it MUST NOT assume the Authcert is valid.
   ¡ Verify that the autonomous system identifier in SubjectAltname
     matches the Authorized Originator TLV value of the Authcert.
   ¡ If an Authorization Certificate Validity List is available,
     validate that the issuer of the Entitycert has not invalidated the
     Authcert. Validity lists may be distributed in the signers
     ASPolicycert, or a pointer to the list may be distributed in the
     Authcert in an Authorizing AS Validation List URL. If no
     Authorization Certificate Validity List is available, an entity
     MAY accept the certificate. However if a validation list is
     received later, the entity MUST check the validity of all
     certificates that had been previously accepted.
   ¡ Hash the Authcert TLVs.
   ¡ Extract the signature from the Authcert.
   ¡ Extract the public key from the Entitycert, and use it to decrypt
     the signature.
   ¡ Accept the Authcert as valid if the computed hash matches the
     decrypted hash.



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4.4.1 Self-generated Authcerts

   Self-generated Authcerts are dangerous, because a responsible third
   party does not assign the authorization. Trusting an autonomous
   system to declare its own address space nullifies most of the
   protections outlined in this document.

   However, the autonomous systems at the highest level of allocation
   (e.g. Regional Internet Registries (RIRs) or Tier-1 Internet Service
   Providers (ISPs)) may not be able to find a responsible third party
   to sign their Authcerts. In this case, self-generated Authcerts may
   be unavoidable.

   Authcerts MAY be self-generated, but MUST only be accepted from
   autonomous systems that have been explicitly authorized and locally
   configured. For example, a device may be configured to accept
   Authcerts for the RIR autonomous systems.


4.5 Revocation

   Any entity issuing an Authcert MUST keep an Authcert revocation
   list. The entity MAY use any form for propagating that revocation
   list.

   Because BGP routers do not necessarily have synchronized clocks,
   Authcerts do not carry expiration times, and thus do not expire.
   Revocation is only method of invalidating an Authcert.

   Revocation information may be represented as a "validation list". A
   validation list includes lists of both valid and invalid (i.e.,
   revoked) certificates. Any number not appearing in the list MUST be
   considered invalid. Validation list may be more efficient than a
   pure revocation list for Authcerts in the case where a large number
   of serial numbers have been revoked by an issuer.

   An autonomous system SHOULD include an Authcert validation list  in
   their AS Policy Certificate (distributed using [SOBGP-BGP]). This
   allows autonomous systems that cannot route to the issuing
   autonomous system to verify that the Entitycert has not been
   revoked.


5.0 Prefix Policy Certificates (PrefixPolicycert)

   The PrefixPolicycert provides a specific set of policy regarding one
   or more prefix blocks. The owner of the prefix block creates it.
   There is only one valid PrefixPolicycert for each prefix block at
   any given time.


5.1 Format


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   This certificate is formatted as a series of TLVs. Each TLV will
   include a type, which is treated as a 16 bit (two octet) unsigned
   integer, a length, which is also two octets, and a variable length
   data field. TLVs MUST be placed in the PrefixPolicycert in type
   order.


5.1.1 PrefixPolicycert Header


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +---------------+---------------+-------------------------------+
      | Cert. Marker  |    Type Id    | Length                        |
      +---------------+---------------+-------------------------------+
      | TLVs
      +----------------

   o    Certificate Marker: "162(0xa2), identifying this as an soBGP
        certificate.

   o    Type ID: "2(0x02), identifying this as an PrefixPolicycert.

   o    Length: Set to the length of the TLVs.

   o    TLVs: The Type/Length/Value attributes making up an
        PrefixPolicycert.

5.1.2 The Originating Autonomous System

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Originating Autonomous System                                 |
      +---------------------------------------------------------------+

   o    TLV type: 1 (0x0001)

   o    Length: Set to 4.

   o    Originating Autonomous System: (4 octets), the autonomous
        system which originated this certificate. AS numbers containing
        only two octets should be placed in the least significant
        octets of this four-octet field (the two rightmost octets).


5.1.3 The Serial Number


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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Serial Number                                                 |
      +---------------------------------------------------------------+

   o    TLV type: 2 (0x0002)

   o    Length: Set to 4.

   o    Serial Number: (4 octets), A serial number which identifies
        this PrefixPolicycert, taken from a 32 bit number space.


5.1.4 Authorizing AS Entitycert Uniform Resource Locator

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | URL                                                           |
      +----------------

   o    TLV type: 3 (0x0003)

   o    Length: Denotes the length of the URL in octets.

   o    URL: A uniform resource locator indicating a location where the
        Authorizing ASÆs Entitycert can be found.

   An PrefixPolicycert may omit this TLV. However, an implementation is
   REQUIRED to correctly parse them if they are present. A receiving
   device MAY choose to ignore the URL TLV.


5.1.5 Authcert

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Authentication Certificate                                    |
      +----------------

   o    TLV type: 4 (0x0004)

   o    Length: Set to the length of the Authentication Certificate.

   o    Authentication Certificate containing a prefix block for which
        the PrefixPolicycert applies.

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   One or more Authcert TLVs MUST be included in the PrefixPolicycert.


5.1.6 Policies

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Options                       | SubTVs
      +-------------------------------+--------------

   o    TLV type: 5 (0x0005)

   o    Length: Set to the sum of the Options size (2) and the length
        of the SubTVs.

   o    Options: (2 octets), a bit field describing various policies
        which should be applied to the prefixes indicated.

   o    SubTVs: (variable length), zero or more fields, the length of
        which is determined by the type, as described below.


5.1.6.1 Option bits

      The options bit field describes policies that should be applied
   to the address block described in the TLV. These options are:

   o    Bit 0: Path Check. If this bit is set, the receiver should not
        accept any prefix for which the path cannot be verified as
        described in the section Verifying the Path, below.

   o    Bit 1: Second Hop Check. If this bit is set, the receiver
        should not accept any prefix for which the second entry in the
        AS PATH cannot be verified as described in the section
        Verifying the Second Hop, below.

   o    Bits 2-15: Reserved for future use.


5.1.6.2 SubTVs

   The Authcert Policy subTVs provide optional policy information for
   the block of addresses included in the Authcert indicated; each
   subTV is of a fixed length, as determined by its type.


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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+------------------------------+
      | TV Type                       | Data....
      +-------------------------------+-------------------------

   o    TV Type: (2 octets), An unsigned integer indicating the type of
        subTV

      Types defined within this specification are:

      - Type 1: Must Include AS, 4 octets of data, an AS which must be
        included in the AS path of any prefix falling within this block
        of addresses.

      - Type 2: OR Include AS, 4 octets of data, at least one of the
        included OR Include AS' must be included in the AS path of any
        prefix falling within this block of addresses.

      - Type 3: Maximum Prefix Length, 1 octet of data, the maximum
        length of any prefix allowed within this block of prefixes.


5.1.7 Signature

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Signature Type                | Number of Issuers             |
      +-------------------------------+-------------------------------+
      | Entity Certificate Issuer Autonomous System                   |
      +-------------------------------+-------------------------------+
      | Entity Certificate Serial Number                              |
      +-------------------------------+-------------------------------+
      | ...                                                           |
      +---------------------------------------------------------------+
      | Signature                                                     |
      +------------------


   o    TLV type: 65535 (0xFFFF)

   o    Length: (2 octets), unsigned integer denoting the length of the
        payload bytes which follow.

   o    Signature Type: (2 octets), unsigned integer denoting the type
        of signature (the algorithm used to build this signature). Each
        possible signing algorithm is assigned an integer from this
        field. Signature type 1 is defined as an RSA encryption of a
        SHA1 digest.


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   o    Number of Issuers (2 octets): The number of Entitycert
        references included in the signature payload. If more than one
        Entitycert reference follows, all Entitycerts MUST contain the
        same public key for the same authorizing autonomous system.

   o    Entity Certificate Issuer Autonomous System: (4 octets), the
        autonomous system of the entity that provided the Entitycert to
        the AS issuing the PrefixPolicycert. AS numbers containing only
        two octets should be placed in the least significant octets of
        this four-octet field (the two rightmost octets).

   o    Entity Certificate Serial Number: (4 octets), the Entitycert
        serial number containing the public key of the AS issuing the
        PrefixPolicycert.

   o    Signature: The signature itself.

   The signature is calculated using the private key of the authorizing
   entity across all the TLVs within the PrefixPolicycert. The
   Signature TLV MUST be appended as the last TLV in the
   PrefixPolicycert after the signature has been computed.


5.2 Creation

   An PrefixPolicycert is created by an autonomous system for prefix
   blocks that it owns. An autonomous system creates it with the
   following steps:

   ¡ Build an PrefixPolicycert by adding TLVs containing its own AS
     number, a unique sequence number, policy related to one or more
     prefix blocks, and the Authcert or Authcerts defining the prefix
     blocks to which this policy applies.
   ¡ Sign the PrefixPolicycert by hashing and encrypting the
     PrefixPolicycert TLVs. Place the signature (and other required)
     information in a Signature TLV, and append it to the
     PrefixPolicycert.


5.2.1 Certificate Uniqueness

   Digital certificates are created as uniquely named objects, which
   allows them to be uniquely identified. A PrefixPolicycert is
   uniquely identified by the pair of Authorized Originator and Serial
   Number TLV values.

5.2.2 Certificate Encoding

   PrefixPolicycert distributed in [SOBGP-BGP] are distributed in TLV
   form. However if they are manually distributed (e.g., through
   electronic mail) they may need to be encoded into ASCII.
   PrefixPolicycert SHOULD be base64 encoded as described in Section
   4.3 of [RFC1421].


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   There are times that PrefixPolicycert are referred to by name (e.g.,
   the target of a URL). In this case, the extension on the name MUST
   define the format of the PrefixPolicycert . A suffix of ".tlv"
   defines the raw TLV encoding. A suffix of ".pem" defines base64
   encoding.


5.3 Distribution

   PrefixPolicycerts may be distributed using any number of methods,
   for example:

   ¡ maintained in a directory maintained by the issuing autonomous
     system,
   ¡ distributed via some out of band mechanism, or
   ¡ distributed within BGP using extensions defined in [SOBGP-BGP].

   To ensure interoperability, an autonomous system SHOULD distribute
   its PrefixPolicycerts within BGP.


5.4 Validation

   The Authcert included in the Authcert TLV MUST be validated as
   correct before the Policy TLV can be accepted. Thus, the Authcert
   should be extracted from the PrefixPolicycert and validated before
   the PrefixPolicycert is validated.

   The PrefixPolicycert is validated using the following steps.

   ¡ Identify the Entitycert that signed the PrefixPolicycert. The
     correct Entitycert is uniquely identified with the Entity
     Certificate Issuer Autonomous System and Entity Certificate Serial
     Number contained in the Signature TLV. The Entity Certificate
     Issuer Autonomous System is compared with the AS number in the
     Entitycert IssuerAltName field. The Entity Certificate Serial
     Number is compared with the Entitycert CertificateSerialNumber.
   ¡ Obtain the Entitycert that signed the Authcert, and validate it.
     The Entitycert may be in a local cache (already received via BGP
     extensions), retrieved using the URL in the Authcert, or through
     other means. If an entity does not have the validating public key
     it MUST NOT assume the PrefixPolicycert is valid.
   ¡ Verify that the autonomous system identifier in SubjectAltname
     matches the Authorized Originator TLV value of the
     PrefixPolicycert.
   ¡ Hash the PrefixPolicycert TLVs.
   ¡ Extract the signature from the PrefixPolicycert.
   ¡ Extract the public key from the Entitycert, and use it to decrypt
     the signature.
   ¡ Validate that the computed hash matches the decrypted hash.

   Once a PrefixPolicycert has been validated, any PrefixPolicycert
   that matches the following criteria MUST be discarded:
   ¡ has a lower serial number from the same originating AS, and

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   ¡ includes an Authcert with the same prefix block

5.5 Revocation

   Any entity issuing an PrefixPolicycert MUST keep a revocation list.
   The entity MAY use any form for propagating that revocation list.

   Because BGP routers do not necessarily have synchronized clocks,
   PrefixPolicycert do not carry expiration times, and thus do not
   expire. Revocation is only method of invalidating an
   PrefixPolicycert.

   Revocation information may be represented as a "validation list". A
   validation list includes lists of both valid and invalid (i.e.,
   revoked) certificates. Any number not appearing in the list MUST be
   considered invalid. Validation list may be more efficient than a
   pure revocation list for PrefixPolicycerts in the case where a large
   number of serial numbers have been revoked by an issuer.

   An autonomous system SHOULD include an PrefixPolicycert validation
   list in their AS Policy Certificate (distributed using [SOBGP-BGP]).
   This allows autonomous systems that cannot route to the issuing
   autonomous system to verify that the Entitycert has not been
   revoked.

6.0 AS Policy Certificates (ASPolicycert)

   The ASPolicycert provides a specific set of policy relating to an
   autonomous system. An administrative entity within the autonomous
   system creates it. There is only one valid ASPolicycert for each
   autonomous system at any given time.


6.1 Format

   This certificate is formatted as a series of TLVs. Each TLV will
   include a type, which is treated as a 16 bit (two octet) unsigned
   integer, a length, which is also two octets, and a variable length
   data field. TLVs MUST be placed in the ASPolicycert in type order.


6.1.1 ASPolicycert Header


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +---------------+---------------+-------------------------------+
      | Cert. Marker  |    Type Id    | Length                        |
      +---------------+---------------+-------------------------------+
      | TLVs
      +----------------

   o    Certificate Marker: "162(0xa2), identifying this as an soBGP
        certificate.

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   o    Type ID: "3(0x03), identifying this as an ASPolicycert.

   o    Length: Set to the length of the TLVs.

   o    TLVs: The Type/Length/Value attributes making up an
        ASPolicycert.

6.1.2 The Originating Autonomous System

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Originating Autonomous System                                 |
      +---------------------------------------------------------------+

   o    TLV type: 1 (0x0001)

   o    Length: Set to 4.

   o    Originating Autonomous System: (4 octets), the autonomous
        system which originated this certificate. AS numbers containing
        only two octets should be placed in the least significant
        octets of this four-octet field (the two rightmost octets).


6.1.3 The Serial Number

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Serial Number                                                 |
      +---------------------------------------------------------------+

   o    TLV type: 2 (0x0002)

   o    Length: Set to 4.

   o    Serial Number: (4 octets), A serial number which identifies
        this ASPolicycert, taken from a 32 bit number space.


6.1.4 Authorizing AS Entitycert Uniform Resource Locator


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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | URL                                                           |
      +----------------

   o    TLV type: 3 (0x0003)

   o    Length: Denotes the length of the URL in octets.

   o    URL: A uniform resource locator indicating a location where the
        Authorizing ASÆs Entitycert can be found.

   An PrefixPolicycert may omit this TLV. However, an implementation is
   REQUIRED to correctly parse them if they are present. A receiving
   device MAY choose to ignore the URL TLV.




6.1.5 Attached Transit Autonomous Systems

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Autonomous System                                             |
      +---------------------------------------------------------------+

   o    TLV type: 4 (0x0004)

   o    Length: Set to 4.

   o    Autonomous System: (4 octets), autonomous systems which are
        connected to the originating autonomous system through some
        form of peering arrangement and which may transit traffic from
        the origin AS. AS numbers containing only two octets should be
        placed in the least significant octets of this four-octet field
        (the two rightmost octets).

   One or more Attached Transit AS TLVs may be included in the Policy
   Certificate. Each type 4 TLV indicates an AS which is connected to
   the AS which originates this ASPolicycert through a BGP peering
   relationship.


6.1.6 Attached Non-transit Autonomous Systems

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+

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      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Autonomous System                                             |
      +---------------------------------------------------------------+

   o    TLV type: 5 (0x0005)

   o    Length: Set to 4.

   o    Autonomous System: (4 octets), autonomous systems which are
        connected to the originating autonomous system through some
        form of peering arrangement and which may not transit traffic
        from the origin AS. AS numbers containing only two octets
        should be placed in the least significant octets of this four-
        octet field (the two rightmost octets).

   One or more Attached Non-Transit AS TLVs may be included in the
   ASPolicycert. Each type 5 TLV indicates an AS which is connected to
   the AS which originates this ASPolicycert through a BGP peering
   relationship.


6.1.7 Revoked Entity Certificate List

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Entity Certificate Revocation List
      +----------------

   o    TLV type: 6 (0x0006)

   o    Length: (2 octets), length of TLV data (the list of revoked
        Entity Certificates) in octets

   o    Entity Certificate Revocation List: A revocation list created
        by the autonomous system, which includes a list of revoked
        Entity Certificates issued by this autonomous system. The
        format of the revocation list MUST be as defined in [RFC3280].

   A single Revoked Entity Certificate List TLV MAY be included in an
   ASPolicycert, or it may be omitted.

   When an Entity Certificate Revocation List is received, all
   currently held Entitycerts from this issuer MUST be checked against
   the validity list. Entitycerts found to be invalid MUST be deleted.


6.1.8 Authorization Certificate Validity List


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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Validity Ranges
      +----------------

   o    TLV type: 7 (0x0007)

   o    Length: (2 octets), length of TLV data (the list of revoked
        Authorization Certificates) in octets

   o    Validity Ranges: A list of validity subTVs defining which
        serial numbers are valid and invalid. Validity ranges are
        interpreted in order until a match is found. For more
        information on validity lists, see Section 4.5.

   A single TLV of this type MAY be included in an ASPolicycert, or it
   may be omitted.

   When an Authorization Certificate Validity List is received, all
   currently held Authcerts from this issuer MUST be checked against
   the validity list. Authcerts found to be invalid MUST be deleted.


6.1.8.1 Validity Ranges

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | subTV Type                    | Size of Range                 |
      +-------------------------------+-------------------------------+
      | Lowest Authorization Serial Number                            |
      +---------------------------------------------------------------+

   o    subTV type: (2 octets).

          SubTV type                       Value
          ----------                       -----
          VALID                              0
          INVALID                            1

   o    Size of Range: (2 octets). Number of contiguous serial numbers
        defining a range.

   o    Lowest Authorization Serial Number (4 octets). The lowest value
        in the range.


6.1.9 Prefix Policy Certificate Validity List


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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Validity Ranges
      +----------------

   o    TLV type: 8 (0x0008)

   o    Length: (2 octets), length of TLV data (the list of revoked
        Authorization Certificates) in octets

   o    Validity Ranges: A list of validity subTVs (as defined in the
        previous section) defining which PrefixPolicycert serial
        numbers are valid and invalid. Validity ranges are interpreted
        in order until a match is found.. For more information on
        validity lists, see Section 5.5.

   A single TLV of this type MAY be included in an ASPolicycert, or it
   may be omitted.

   When an Prefix Policy Validity List is received, all currently held
   PrefixPolicycerts from this issuer MUST be checked against the
   validity list. PrefixPolicycerts found to be invalid MUST be
   deleted.



6.1.10 Most Recent AS Policy Certificate Uniform Resource Locator

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | URL                                                           |
      +----------------

   o    TLV type: 9 (0x0009)

   o    Length: Denotes the length of the URL in octets.

   o    URL: A uniform resource locator indicating a location where the
        most recent AS Policy Certificate can be found. This is useful
        for a receiver to verify that they have the most recent AS
        Policy Certificate for an AS.

   An PrefixPolicycert may omit this TLV. However, an implementation is
   REQUIRED to correctly parse them if they are present. A receiving
   device MAY choose to ignore the URL TLV.



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6.1.11 Signature

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-------------------------------+-------------------------------+
      | TLV Type                      | Length                        |
      +-------------------------------+-------------------------------+
      | Signature Type                | Number of Issuers             |
      +-------------------------------+-------------------------------+
      | Entity Certificate Issuer Autonomous System                   |
      +-------------------------------+-------------------------------+
      | Entity Certificate Serial Number                              |
      +-------------------------------+-------------------------------+
      | ...                                                           |
      +---------------------------------------------------------------+
      | Signature                                                     |
      +------------------


   o    TLV type: 65535 (0xFFFF)

   o    Length: (2 octets), unsigned integer denoting the length of the
        payload bytes which follow.

   o    Signature Type: (2 octets), unsigned integer denoting the type
        of signature (the algorithm used to build this signature). Each
        possible signing algorithm is assigned an integer from this
        field. Signature type 1 is defined as an RSA encryption of a
        SHA1 digest.

   o    Number of Issuers (2 octets): The number of Entitycert
        references included in the signature payload. If more than one
        Entitycert reference follows, all Entitycerts MUST contain the
        same public key for the same authorizing autonomous system.

   o    Entity Certificate Issuer Autonomous System: (4 octets), the
        autonomous system of the entity that provided the Entitycert to
        the AS issuing the PrefixPolicycert. AS numbers containing only
        two octets should be placed in the least significant octets of
        this four-octet field (the two rightmost octets).

   o    Entity Certificate Serial Number: (4 octets), the Entitycert
        serial number containing the public key of the AS issuing the
        PrefixPolicycert.

   o    Signature: The signature itself.

   The signature is calculated using the private key of the authorizing
   entity across all the TLVs within the ASPolicycert. The Signature
   TLV MUST be appended as the last TLV in the ASPolicycert after the
   signature has been computed.



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6.2 Creation

   An ASPolicycert is created by an autonomous system in order to relay
   its own policy. An autonomous system creates it with the following
   steps:

   ¡ Build an ASPolicycert by adding TLVs containing its own AS number,
     a unique sequence number, and policy related to the autonomous
     system.
   ¡ Sign the ASPolicycert by hashing and encrypting the ASPolicycert
     TLVs. Place the signature (and other required) information in a
     Signature TLV, and append it to the ASPolicycert.


6.2.1 Certificate Uniqueness

   Digital certificates are created as uniquely named objects, which
   allows them to be uniquely identified. An ASPolicycert is uniquely
   identified by the pair of Authorized Originator and Serial Number
   TLV values.


6.2.2 Certificate Encoding

   ASPolicycert distributed in [SOBGP-BGP] are distributed in TLV form.
   However if they are manually distributed (e.g., through electronic
   mail) they may need to be encoded into ASCII. ASPolicycert SHOULD be
   base64 encoded following Section 4.3 of [RFC1421].

   There are times that ASPolicycerts are referred to by name (e.g.,
   the target of a URL). In this case, the extension on the name MUST
   define the format of the ASPolicycert. A suffix of ".tlv" defines
   the raw TLV encoding. A suffix of ".pem" defines base64 encoding.



6.3 Distribution

   ASPolicycert may be distributed using any number of methods, for
   example:

   ¡ maintained in a directory maintained by the issuing autonomous
     system,
   ¡ distributed via some out of band mechanism, or
   ¡ distributed within BGP using extensions defined in [SOBGP-BGP].

   To ensure interoperability, an autonomous system SHOULD distribute
   its ASPolicycert within BGP.


6.4 Validation

   The ASPolicycert is validated using the following steps.


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   ¡ Identify the Entitycert that signed the ASPolicycert. The correct
     Entitycert is uniquely identified with the Entity Certificate
     Issuer Autonomous System and Entity Certificate Serial Number
     contained in the Signature TLV. The Entity Certificate Issuer
     Autonomous System is compared with the AS number in the Entitycert
     IssuerAltName field. The Entity Certificate Serial Number is
     compared with the Entitycert CertificateSerialNumber.
   ¡ Obtain the Entitycert that signed the ASPolicycert, and validate
     it. The Entitycert may be in a local cache (already received via
     BGP extensions), retrieved using the URL in the Authcert, or
     through other means. If an entity does not have the validating
     public key it MUST NOT assume the ASPolicycert is valid.
   ¡ Verify that the autonomous system identifier in SubjectAltname
     matches the Authorized Originator TLV value of the ASPolicycert.
   ¡ Hash the ASPolicycert TLVs.
   ¡ Extract the signature from the ASPolicycert.
   ¡ Extract the public key from the Entitycert, and use it to decrypt
     the signature.
   ¡ Validate that the computed hash matches the decrypted hash.

   Once an ASPolicycert has been validated, any ASPolicycert with a
   lower serial number from the same originating AS MUST be discarded.

6.5 Revocation

   Each ASPolicycert issued by an autonomous system overrides any
   previously issued ASPolicycerts from this autonomous system.
   Therefore, revocation is not required.

   If present, a receiver has the opportunity of using the Most Recent
   AS Policy Certificate URL in the ASPolicycert to verify that they
   have the most recent policy certificate.

7.0 Security Considerations

   This document describes the format of authentication, authorization,
   and policy certificates used to with [SOBGP-BGP]. Each certificate
   type is digitally signed, and therefore requires no external
   protection to ensure its integrity. There are no restrictions on how
   they may be distributed. Revocation schemes are defined for all
   certificate types.

   The following sections describe the security considerations of each
   of those objects.

7.1 Entitycerts

   Entitycerts provide authentication, providing a binding of an
   identity (i.e., autonomous system number) to a public key. The
   authenticity of the binding is verified with a digital signature,
   where the public key of the certificate issuer has been previously
   accepted as valid. Issuer public keys can either be manually
   configured, or are verified through the use of another issuer's
   trusted public key in a "web of trust" built by the receiver.

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   Certificate issuers MUST maintain certificate revocation lists
   (CRLs). Entities verifying Entitycerts SHOULD reference the
   certificate revocation lists whenever possible. (Mandating the
   consultation of a CRL as part of the verification process is not
   possible, because the CRL may not be available at the time
   verification is performed. For example, if the issuer maintains the
   CRL on a directory server to which routing is not yet setup.)
   Issuers SHOULD distribute their CRLs within their AS Policy
   Certificates to increase the likelihood of a receiver having the CRL
   available.

   Self-signed Entitycerts may be necessary in order to start a chain
   of trust. However self-signed Entitycerts MUST be manually validated
   as accurate before the enclosed public key is used, else the "web of
   trust" breaks down.


7.2 Authcerts

   Authcerts provide authorization, where the issuer of a prefix block
   certifies that it has given that prefix block to a specific
   autonomous system. Receivers use the Authcert to validate
   announcements received in BGP UPDATE messages.

   The authenticity of Authcerts is verified with a digital signature,
   where the public key of the certificate issuer is distributed in an
   Entitycert. Before a receiver can verify the Authcert, they MUST
   first check that the verifying Entitycert is authentic.

   The Authcert issuer MUST keep an Authcert validation list describing
   which certificates are valid, and which are invalid. The receivers
   of an Authcert SHOULD consult the Authcert validation list to ensure
   that the authorization has not been revoked.

   Autonomous systems may need to authorize their own use of prefix
   blocks if the autonomous system that issued their prefix blocks does
   not issue them an Authcert. However, such self-generated Authcerts
   are dangerous, since unrestricted use of self-signed Authcerts
   defeats the goal of authorization. Thus an entity MUST accept self-
   generated Authcerts only from autonomous systems that have been
   explicitly configured as trusted to claim authorization without the
   confirmation of a third party.


7.3 PrefixPolicycerts

   PrefixPolicycerts bind policy generated by an autonomous system for
   prefix blocks that they advertise. This policy is bound to a
   particular Authcert, which verifies that they are authorized to
   advertise those prefix blocks.

   PrefixPolicycerts are verified with a digital signature, where the
   public key of the certificate issuer is distributed in an

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   Entitycert. Before a receiver can verify the PrefixPolicycert, they
   MUST first verify that the verifying Entitycert is authentic.

7.4 ASPolicycerts

   ASPolicycerts contain policy generated by an autonomous system, and
   contain policy about the autonomous system itself. The policy
   includes its neighbor autonomous systems, which can be used by other
   entities to validate valid inter-connections. The policy can also
   include revocation and validation lists (Authcert, PrefixPolicycert)
   .

   ASPolicycerts are verified with a digital signature, where the
   public key of the certificate issuer is distributed in an
   Entitycert. Before a receiver can verify the ASPolicycerts, they
   MUST first verify that the verifying Entitycert is authentic.

7.5 Entitycert Uniform Resource Locators

   Authcerts, PrefixPolicycerts, and ASPolicycerts may contain a URL
   that references the Entitycert used to validate it. Care should be
   taken in evaluating the URL since it is not yet known to be valid
   and could be used to propagate a denial of service attack.

8.0 IANA Considerations

   This document defines three certificate types, each of which contains
   a series of TLVs. IANA is expected to maintain a registry of all the
   values defined, according to the following sections.


8.1 Authorization Certificate

   The Authorization Certificate Type Field:

   o    Type values 1 through 4, 14 and 65535 are assigned in this
        document.

   o    Type values 5 through 13 and 15 through 16575 MUST be assigned
        using the "IETF Consensus"  policy defined in RFC 2434
        [RFC2434].

   o    Type values 16576 through 32895 SHOULD be assigned using the
        "Specification Required" policy defined in RFC 2434 [RFC2434].

   o    Type values 32896 through 65534 are for "Private Use" as defined
        in RFC 2434 [RFC2434].


8.1.1 Signature Type

   The Signature TLV Signature Type field:

   o    Type values 1 is assigned in this document.

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   o    Type values 2 through 16575 MUST be assigned using the "IETF
        Consensus"  policy defined in RFC 2434 [RFC2434].

   o    Type values 16576 through 32895 SHOULD be assigned using the
        "Specification Required" policy defined in RFC 2434 [RFC2434].

   o    Type values 32896 through 65534 are for "Private Use" as defined
        in RFC 2434 [RFC2434].


8.2 Prefix Policy Certificate

   o    Type values 1 through 5, 14 and 65535 are assigned in this
        document.

   o    Type values 6 through 13 and 15 through 16575 MUST be assigned
        using the "IETF Consensus"  policy defined in RFC 2434
        [RFC2434].

   o    Type values 16576 through 32895 SHOULD be assigned using the
        "Specification Required" policy defined in RFC 2434 [RFC2434].

   o    Type values 32896 through 65534 are for "Private Use" as defined
        in RFC 2434 [RFC2434].


8.2.1 Policies Type

   The Policies Type has two name spaces: Options flags and SubTVs.

   The Options Field:

   o    Bits 0 and 1 are assigned in this document.

   o    Bits 2 thru 7 MUST be assigned using the "IETF Consensus"
        policy defined in RFC 2434 [RFC2434].

   o    Bits 8 thru 15 are for "Private Use" as defined in RFC 2434
        [RFC2434].

   The subTV TV Type field:
   o    TV Type values 1 through 3 are assigned in this document.

   o    TV Type values 4 through 16575 MUST be assigned using the "IETF
        Consensus"  policy defined in RFC 2434 [RFC2434].

   o    TV Type values 16576 through 32895 SHOULD be assigned using the
        "Specification Required" policy defined in RFC 2434 [RFC2434].

   o    TV Type values 32896 through 65534 are for "Private Use" as
        defined in RFC 2434 [RFC2434].



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8.2.2 Signature Type

   The Signature TLV Signature Type field:

   o    Type values 1 is assigned in this document.

   o    Type values 2 through 16575 MUST be assigned using the "IETF
        Consensus"  policy defined in RFC 2434 [RFC2434].

   o    Type values 16576 through 32895 SHOULD be assigned using the
        "Specification Required" policy defined in RFC 2434 [RFC2434].

   o    Type values 32896 through 65534 are for "Private Use" as defined
        in RFC 2434 [RFC2434].


8.3 AS Policy Certificate

   o    Type values 1 through 9, 14 and 65535 are assigned in this
        document.

   o    Type values 10 through 16575 MUST be assigned using the "IETF
        Consensus"  policy defined in RFC 2434 [RFC2434].

   o    Type values 16576 through 32895 SHOULD be assigned using the
        "Specification Required" policy defined in RFC 2434 [RFC2434].

   o    Type values 32896 through 65534 are for "Private Use" as defined
        in RFC 2434 [RFC2434].


8.3.1 Validity Ranges

   o    Type values 1 through 2 are assigned in this document.

   o    Type values 3 through 16575 MUST be assigned using the "IETF
        Consensus"  policy defined in RFC 2434 [RFC2434].

   o    Type values 16576 through 32895 SHOULD be assigned using the
        "Specification Required" policy defined in RFC 2434 [RFC2434].

   o    Type values 32896 through 65534 are for "Private Use" as defined
        in RFC 2434 [RFC2434].


8.3.2 Signature Type

   The Signature TLV Signature Type field:

   o    Type values 1 is assigned in this document.

   o    Type values 2 through 16575 MUST be assigned using the "IETF
        Consensus"  policy defined in RFC 2434 [RFC2434].


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   o    Type values 16576 through 32895 SHOULD be assigned using the
        "Specification Required" policy defined in RFC 2434 [RFC2434].

   o    Type values 32896 through 65534 are for "Private Use" as defined
        in RFC 2434 [RFC2434].


9.0 Acknowledgments

   A large number of people contributed to or provided valuable feedback
   on this document; we've tried to include all of them here (in no
   particular order), but might have missed a few: James Ng, Russ White,
   Alvaro Retana, Dave Cook, John Scudder, David Ward, Martin Djernaes,
   Max Pritikin, Chris Lonvick, Tim Gage, Scott Fanning, Barry Friedman,
   Jim Duncan, Yi Yang, Robert Adams, Tony Tauber, Iljitsch van Beijnum,
   and Jonathan Natale.


10.0 References

10.1 Normative References

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

   [RFC2434] Narten, T., Alvestrand, H., "Guidelines for Writing an IANA
   Considerations Section in RFCs", RFC 2434, October 1998.

   [RFC2858] Bates, T., Chandra, R., Katz, D., and Rekhter, Y.,
   "Multiprotocol Extensions for BGP-4", RFC 2858, June 2000.

   [RFC3279] Polk, T., et. al., " Algorithms and Identifiers for the
   Internet X.509 Public Key Infrastructure Certificate and Certificate
   Revocation List (CRL) Profile", RFC 3279, April 2002.

   [RFC3280] Housley, R., et. al., "Internet X.509 Public Key
   Infrastructure Certificate and CRL Profile", RFC 3280, April 2002.

   [SOBGP-BGP] Ng J. (editor), "Extensions to BGP to Support Secure
   Origin BGP (soBGP)", draft-ng-sobgp-deployment-01.doc, November 2002

   [X.690] International Telecommunication Union, "ITU-T Recommendation
   X.660 Information Technology - ASN.1 encoding rules: Specification
   of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and
   Distinguished Encoding Rules (DER), 1997.


10.2 Informative References


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   [IAB-SC] Rescorla, E., B. Korver, and the Internet Architecture
   Board, "Guidelines for Writing RFC Text on Security Considerations",
   http://www.ietf.org/internet-drafts/draft-iab-sec-cons-03.txt, Work
   in progress, 2003.

   [RFC3281] Farrell, S., and R. Housley, " An Internet Attribute
   Certificate Profile for Authorization", RFC 3281, April 2002.


Editor's Address

   Brian Weis
   Cisco Systems
   170 W. Tasman Drive,
   San Jose, CA 95134-1706, USA
   (408) 526-4796
   bew@cisco.com

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