SIDR G. Huston Internet-Draft G. Michaelson Intended status: Standards Track R. Loomans Expires: January 29, 2007 APNIC July 28, 2006 A Profile for X.509 PKIX Resource Certificates draft-ietf-sidr-res-certs-02.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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. This Internet-Draft will expire on January 29, 2007. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This document defines a standard profile for X.509 certificates for the purposes of supporting validation of assertions of "right-to-use" of an Internet Number Resource (IP Addresses and Autonomous System Numbers). This profile is used to convey the issuer's authorization of the subject to be regarded as the current holder of a "right-of- use" of the IP addresses and AS numbers that are described in the associated Resource Certificate. Huston, et al. Expires January 29, 2007 [Page 1] Internet-Draft Resource Certificate Profile July 2006 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 2. Describing Resources in Certificates . . . . . . . . . . . . . 5 3. Resource Certificate Fields . . . . . . . . . . . . . . . . . 6 3.1. Version . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2. Serial number . . . . . . . . . . . . . . . . . . . . . . 6 3.3. Signature Algorithm . . . . . . . . . . . . . . . . . . . 6 3.4. Issuer . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.5. Subject . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.6. Valid From . . . . . . . . . . . . . . . . . . . . . . . . 7 3.7. Valid To . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.8. Subject Public Key Info . . . . . . . . . . . . . . . . . 8 3.9. Resource Certificate Version 3 Extension Fields . . . . . 8 3.9.1. Basic Constraints . . . . . . . . . . . . . . . . . . 8 3.9.2. Subject Key Identifier . . . . . . . . . . . . . . . . 9 3.9.3. Authority Key Identifier . . . . . . . . . . . . . . . 9 3.9.4. Key Usage . . . . . . . . . . . . . . . . . . . . . . 9 3.9.5. CRL Distribution Points . . . . . . . . . . . . . . . 10 3.9.6. Authority Information Access . . . . . . . . . . . . . 10 3.9.7. Subject Information Access . . . . . . . . . . . . . . 11 3.9.8. Certificate Policies . . . . . . . . . . . . . . . . . 11 3.9.9. Subject Alternate Name . . . . . . . . . . . . . . . . 11 3.9.10. IP Resources . . . . . . . . . . . . . . . . . . . . . 11 3.9.11. AS Resources . . . . . . . . . . . . . . . . . . . . . 12 4. Resource Certificate Revocation List Profile . . . . . . . . . 12 4.1. Version . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.2. Issuer Name . . . . . . . . . . . . . . . . . . . . . . . 12 4.3. This Update . . . . . . . . . . . . . . . . . . . . . . . 13 4.4. Next Update . . . . . . . . . . . . . . . . . . . . . . . 13 4.5. Signature . . . . . . . . . . . . . . . . . . . . . . . . 13 4.6. Revoked Certificate List . . . . . . . . . . . . . . . . . 13 4.6.1. Serial Number . . . . . . . . . . . . . . . . . . . . 13 4.6.2. Revocation Date . . . . . . . . . . . . . . . . . . . 13 4.7. CRL Extensions . . . . . . . . . . . . . . . . . . . . . . 13 4.7.1. Authority Key Identifier . . . . . . . . . . . . . . . 14 4.7.2. CRL Number . . . . . . . . . . . . . . . . . . . . . . 14 5. Resource Certificate Request Profile . . . . . . . . . . . . . 14 5.1. PCKS#10 Profile . . . . . . . . . . . . . . . . . . . . . 14 5.1.1. PKCS#10 Resource Certificate Request Template Fields . . . . . . . . . . . . . . . . . . . . . . . . 14 5.2. CRMF Profile . . . . . . . . . . . . . . . . . . . . . . . 15 5.2.1. CRMF Resource Certificate Request Template Fields . . 16 5.2.2. Resource Certificate Request Control Fields . . . . . 16 5.3. Certificate Extension Attributes in Certificate Requests . . . . . . . . . . . . . . . . . . . . . . . . . 17 6. Resource Certificate Validation . . . . . . . . . . . . . . . 19 Huston, et al. Expires January 29, 2007 [Page 2] Internet-Draft Resource Certificate Profile July 2006 6.1. Trust Anchors for Resource Certificates . . . . . . . . . 20 6.2. Resource Extension Validation . . . . . . . . . . . . . . 20 6.3. Resource Certificate Path Validation . . . . . . . . . . . 21 7. Security Considerations . . . . . . . . . . . . . . . . . . . 23 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23 10. Normative References . . . . . . . . . . . . . . . . . . . . . 23 Appendix A. Example Resource Certificate . . . . . . . . . . . . 24 Appendix B. Example Certificate Revocation List . . . . . . . . . 26 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27 Intellectual Property and Copyright Statements . . . . . . . . . . 29 Huston, et al. Expires January 29, 2007 [Page 3] Internet-Draft Resource Certificate Profile July 2006 1. Introduction This document defines a standard profile for X.509 certificates for use in the context of certification of IP Addresses and AS Numbers. These Resource Certificates are X.509 certificates that conform to the PKIX profile [RFC3280] and also conform to the constraints specified in this profile. Resource Certificates attest that the issuer has granted the subject a "right-to-use" a listed set of IP addresses and Autonomous System numbers. A Resource Certificate describes an action by the certificate issuer that binds a list of IP Address blocks and AS Numbers to the subject of the certificate. The binding is identified by the association of the subject's private key with the subject's public key contained in the Resource Certificate, signed by the private key of the certificate's issuer. In the context of the public Internet, and use of public number resources in this context, it is intended that Resource Certificates are used in a manner that is aligned to the public number resource distribution function. Specifically, when a number resource is allocated or assigned by a number registry to an entity, this allocation can be described by a Resource Certificate that is issued by the registry with a subject corresponding to the entity that is the recipient of this number assignment or allocation. In the context of the public number distribution function, this corresponds to a hierarchical PKI structure, where Resource Certificates are only issued in one 'direction' and there is a single unique path from a "Root" Certificate Authority to a valid certificate. Validation of a Resource Certificate in such a hierarchical PKI can be undertaken by establishing a valid issuer - subject chain from a trust anchor certificate authority to the certificate [RFC4158], with the additional constraint of ensuring that each subject's listed resources are fully encompassed by those of the issuer at each step in the issuer-subject chain. Resource Certificates may be used in the context of the operation of secure inter-domain routing protocols to convey a right-to-use of an IP number resource that is being passed within the routing protocol, to verify legitimacy and correctness of routing information. Related use contexts include validation of access to Internet Routing Registries for nominated routing objects, validation of routing requests, and detection of potential unauthorized used of IP addresses. This profile defines those fields that are used in a Resource Certificate that MUST be present for the certificate to be valid. Huston, et al. Expires January 29, 2007 [Page 4] Internet-Draft Resource Certificate Profile July 2006 Relying Parties SHOULD check that a Resource Certificate conforms to this profile as a requisite for validation of a Resource 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" [RFC3280], "X.509 Extensions for IP Addresses and AS Identifiers" [RFC3779], "Internet Protocol" [RFC0791], "Internet Protocol Version 6 (IPv6) Addressing Architecture" [RFC4291], "Internet Registry IP Allocation Guidelines" [RFC2050], and related regional Internet registry address management policy documents. The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. 2. Describing Resources in Certificates The framework for describing an association between the subject of a certificate and the resources currently under the subject's current control is described in [RFC3779]. There are three aspects of this resource extension that are noted in this profile: 1. RFC 3779 notes that this resource extension SHOULD be a CRITICAL extension to the X.509 Certificate. This Resource Certificate profile further specifies that the use of this certificate extension MUST be used and MUST be marked as CRITICAL. 2. RFC 3779 defines a sorted canonical form of describing a resource set, with maximal spanning ranges and maximal spanning prefix masks as appropriate. All valid certificates in this profile MUST use this sorted canonical form of resource description 3. A test of the resource extension in the context of certificate validity includes the first condition that the resources described in the issuer's resource extension must encompass those of the subject's resource extension. In this context "encompass" allows for the issuer's resource set to be the same as, or a strict superset of, any subject's resource set. Appropriate Resource Certificate management in the context of this profile also includes the constraint that no two (or more) certificates issued by a single issuer to two (or more) different subjects have a non-null intersection of resources. In other words an Huston, et al. Expires January 29, 2007 [Page 5] Internet-Draft Resource Certificate Profile July 2006 issuer can certify at most one unique entity as the unique holder of a right-to-use for any particular resource. A test of certificate validity entails the identification of a sequence of valid certificates in an issuer-subject chain (where the subject field of one certificate appears as the issuer in the next certificate in the sequence) from one, and only one, trust anchor to the certificate being validated, and that the resource extensions in this certificate sequence from the trust anchor to the certificate form a sequence of encompassing relationships. 3. Resource Certificate Fields A Resource Certificate is a valid X.509 v3 public key certificate, consistent with the PKIX profile [RFC3280], containing the fields listed in this section. Unless specifically noted as being OPTIONAL, all the fields listed here MUST be present, and any other field MUST NOT appear in a conforming Resource Certificate. Where a field value is specified here this value MUST be used in conforming Resource Certificates. 3.1. Version Resource Certificates are X.509 Version 3 certificates. This field MUST be present, and the Version MUST be 3 (i.e. the value of this field is 2). 3.2. Serial number The serial number value is a positive integer that is unique per Issuer. 3.3. Signature Algorithm This field describes the algorithm used to compute the signature on this certificate. This profile specifies SHA-256 with RSA (sha256WithRSAEncryption), and, accordingly, the value for this field MUST be the OID value 1.2.840.113549.1.1.11 [RFC4055]. 3.4. Issuer This field identifies the entity that has signed and issued the certificate. The value of this field is a valid X.501 name. If the certificate is a subordinate certificate issued by virtue of the CA bit set in the immediate superior certificate, then the issuer name MUST correspond to the subject name as contained in the Huston, et al. Expires January 29, 2007 [Page 6] Internet-Draft Resource Certificate Profile July 2006 immediate superior certificate. 3.5. Subject This field identifies the entity to whom the resource has been allocated / assigned. The value of this field is a valid X.501 name. In this profile the subject name is determined by the issuer, and each distinct entity certified by the issuer MUST be identified using a subject name that is unique per issuer. This field MUST be non-empty. 3.6. Valid From The starting time at which point the certificate is valid. In this profile the "Valid From" time SHOULD be no earlier than the time of certificate generation. As per Section 4.1.2.5 of [RFC3280], Certificate Authorities (CAs) conforming to this profile MUST always encode the certificate's "Valid From" date through the year 2049 as UTCTime, and dates in 2050 or later MUST be encoded as GeneralizedTime. These two time formats are defined in [RFC3280]. In this profile, it is valid for a certificate to have a value for this field that pre-dates the same field value in any superior certificate. However, it is not valid to infer from this information that a certificate was, or will be, valid at any particular time other than the current time. 3.7. Valid To The Valid To time is the date and time at which point in time the certificate's validity ends. It represents the anticipated lifetime of the resource allocation / assignment arrangement between the issuer and the subject. As per Section 4.1.2.5 of [RFC3280], CAs conforming to this profile MUST always encode the certificate's "Valid To" date through the year 2049 as UTCTime, and dates in 2050 or later MUST be encoded as GeneralizedTime. These two time formats are defined in [RFC3280]. In this profile, it is valid for a certificate to have a value for this field that post-dates the same field value in any superior certificate. However, it is not valid to infer from this information that a certificate was, or will be, valid at any particular time other than the current time. Certificate Authorities typically are advised against issuing a certificate with a validity interval that exceeds the validity Huston, et al. Expires January 29, 2007 [Page 7] Internet-Draft Resource Certificate Profile July 2006 interval of the CA certificate that will be used to validate the issued certificate. However, in the context of this profile, it is anticipated that a CA may have good reason to issue a certificate with a validity interval that exceeds the validity interval of the CA's certificate. 3.8. Subject Public Key Info This field specifies the subject's public key and the algorithm with which the key is used. The public key algorithm MUST be RSA, and, accordingly, the OID for the algorithm is 1.2.840.113549.1.1.1. A minimum key size of 1024 bits is mandated in this profile. In the context of certifying resources it is recommended that certificates that are intended to be used as root certificates, and their immediate subordinates SHOULD use a key size of 2048 bits. Subordinates of these subordinate certificates, in the context of continued level of high trust, SHOULD use a key size of 2048 bits. In the application of this profile to certification of public number resources, it would be consistent with this recommendation that the Regional Internet Registries used a key size of 2048 bits, and that their immediate subordinate certificate authorities also use a key size of 2048 bits. All other subordinate certificates MAY use a key size of 1024 bits. 3.9. Resource Certificate Version 3 Extension Fields As noted in Section 4.2 of [RFC3280], each extension in a certificate is designated as either critical or non-critical. A certificate- using system MUST reject the certificate if it encounters a critical extension it does not recognize; however, a non-critical extension MAY be ignored if it is not recognized [RFC3280]. The following X.509 V3 extensions MUST be present in a conforming Resource Certificate. 3.9.1. Basic Constraints The basic constraints extension identifies whether the subject of the certificate is a CA and the maximum depth of valid certification paths that include this certificate. The issuer determines whether the cA boolean is set. If this bit is set, then it indicates that the subject is allowed to issue resources certificates within this overall framework (i.e. the subject is permitted be a CA). The Path Length Constraint is not specified in this profile and MUST Huston, et al. Expires January 29, 2007 [Page 8] Internet-Draft Resource Certificate Profile July 2006 NOT be present. The Basic Constraints extension field is a critical extension in the Resource Certificate profile, and MUST be present. 3.9.2. Subject Key Identifier The subject key identifier extension provides a means of identifying certificates that contain a particular public key. To facilitate certification path construction, this extension MUST appear in all Resource Certificates. This extension is non-critical. The value of the subject key identifier MUST be the value placed in the key identifier field of the Authority Key Identifier extension of immediate subordinate certificates (all certificates issued by the subject of this certificate). The Key Identifier used here is the 160-bit SHA-1 hash of the value of the DER-encoded ASN.1 bit string of the subject public key, as described in Section 4.2.1.2 of[RFC3280]. 3.9.3. Authority Key Identifier The subject key identifier extension provides a means of identifying certificates that are signed by the issuer's private key, by providing a hash value of the issuer's public key. To facilitate path construction, this extension MUST appear in all Resource Certificates. The keyIdentifier subfield MUST be present in all Resource Certificates, with the exception of a CA who issues a "self- signed" certificate. The authorityCertIssuer and authorityCertSerialNumber subfields MUST NOT be present. This extension is non-critical. The Key Identifier used here is the 160-bit SHA-1 hash of the value of the DER-encoded ASN.1 bit string of the issuer's public key, as described in Section 4.2.1.1 of [RFC3280]. 3.9.4. Key Usage This describes the purpose of the certificate. This is a critical extension, and it MUST be present. In certificates issued to CAs only the keyCertSign and CRLSign bits are set to TRUE and must be the only bits set to TRUE. In end-entity certificates the digitialSignature bit MUST be set and MUST be the only bit set to TRUE. Huston, et al. Expires January 29, 2007 [Page 9] Internet-Draft Resource Certificate Profile July 2006 3.9.5. CRL Distribution Points This field (CRLDP) identifies the location(s) of the CRL(s) associated with certificates issued by this Issuer. This profile uses the URI form of object identification. The preferred URI access mechanism is a single RSYNC URI ("rsync://") [rsync] that references a single inclusive CRL for each issuer. In this profile the certificate issuer is also the CRL issuer, implying at the CRLIssuer subfield MUST be omitted, and the distributionPoint subfield MUST be present. The Reasons subfield MUST be omitted. The distributionPoint MUST contain general names, and MUST NOT contain a nameRelativeToCRLIssuer. The type of the general name MUST be of type URI. In this profile, the scope of the CRL is specified to be all certificates issued by this issuer. The sequence of distributionPoint values MUST contain only a single DistributionPointName set. The DistributionPointName set MAY contain more than one URI value. An RSYNC URI MUST be present in the DistributionPointName set. This extension MUST be present and it is non-critical. 3.9.6. Authority Information Access This field (AIA) identifies the point of publication of all certificates that are issued by the issuer's immediate superior CA. This is specified in RFC3280 as a sequence of reference objects. In this profile a single reference object to the immediate superior's publication location MUST be used. This profile uses a URI form of object identification. The preferred URI access mechanisms is "rsync", and an RSYNC URI MUST be specified with an accessMethod value of id-ad-caIssuers. The URI MUST reference the point of publication of all objects published by the issuer's immediate superior issuer. Other access method URIs referencing the same publication point MAY also be included in the value sequence of this extension. In the case of self-signed certificates that undertake the role of a "root" trust anchor within a certificate hierarchy the AIA extension field SHOULD be omitted. In all other cases this field MUST be present, and is non-critical. Huston, et al. Expires January 29, 2007 [Page 10] Internet-Draft Resource Certificate Profile July 2006 3.9.7. Subject Information Access This field (SIA) identifies the location of information and services relating to the subject of the certificate in which the SIA extension appears. Where the Subject is a CA in this profile, this information and service collection will include all current valid certificates that have been issued by this subject that are signed with the subject's corresponding private key. This profile uses a URI form of location identification. The preferred URI access mechanism is "rsync", and an RSYNC URI MUST be specified, with an access method value of id-ad-caRepository when the subject of the certificate is a CA. Other access method URIs that reference the same location MAY also be included in the value sequence of this extension. This field MUST be present when the subject is a CA, and is non- critical. Where the subject is not a CA this field MUST NOT be present. 3.9.8. Certificate Policies This extension MUST reference the Resource Certificate Policy, using the OID Policy Identifier value of "1.3.6.1.5.5.7.14.2". This field MUST be present and MUST contain only this value for Resource Certificates. PolicyQualifiers MUST NOT be used in this profile. This extension MUST be present and it is critical. 3.9.9. Subject Alternate Name This is an optional extension, and MAY contain an X.501 Name as supplied by the subject in the Certificate Request, or as assigned by the issuer. 3.9.10. IP Resources This field contains the list of IP address resources as per [RFC3779]. The value may specify the "inherit" element for a particular AFI value. In the context of resource certificates describing public number resources for use in the public Internet, the SAFI value MUST NOT be used. All Resource Certificates MUST include an IP Resources extension, an AS Resources extension, or both extensions. This extension, if present, MUST be marked critical. Huston, et al. Expires January 29, 2007 [Page 11] Internet-Draft Resource Certificate Profile July 2006 3.9.11. AS Resources This field contains the list of AS number resources as per [RFC3779], or may specify the "inherit" element. RDI values are NOT supported in this profile and MUST NOT be used. All Resource Certificates MUST include an IP Resources extension, an AS Resources extension, or both extensions. This extension, if present, MUST be marked critical. 4. Resource Certificate Revocation List Profile Each CA MUST issue a version 2 Certificate Revocation List (CRL), consistent with [RFC3280]. The CRL issuer is the CA, and no indirect CRLs are supported in this profile. The scope of the CRL MUST be "all certificates issued by this CA". The contents of the CRL are a list of all unexpired certificates issued by the CA that have been revoked by the CA. An entry MUST NOT be removed from the CRL until it appears on one regularly scheduled CRL issued beyond the revoked certificate's validity period. This profile does not allow issuance of Delta CRLs. The profile does not allow the issuance of multiple current CRLs with different scope by a single CA. No CRL fields other than those listed below are allowed in CRLs issued under this profile. Unless otherwise indicated, these fields MUST be present in the CRL. Where two or more CRLs issued by a single CA are present in a certificate repository, the CRL with the highest value of the "CRL Number" field supersedes all other CRLs issued by this CA. 4.1. Version Resource Certificate Revocation Lists are Version 2 certificates (the integer value of this field is 1). 4.2. Issuer Name The value of this field is the X.501 name of the issuing CA who is also the signer of the CRL, and is identical to the Issuer name in the Resource Certificates that are issued by this issuer. Huston, et al. Expires January 29, 2007 [Page 12] Internet-Draft Resource Certificate Profile July 2006 4.3. This Update This field contains the date and time that this CRL was issued. The value of this field MUST be encoded as UTCTime for dates through the year 2049, and MUST be encoded as GeneralizedTime for dates in the year 2050 or later. 4.4. Next Update This is the date and time by which the next CRL SHOULD be issued. The value of this field MUST be encoded as UTCTime for dates through the year 2049, and MUST be encoded as GeneralizedTime for dates in the year 2050 or later. 4.5. Signature This field contains the algorithm used to sign this CRL. The signature algorithm MUST be SHA-256 with RSA. This field MUST be present. 4.6. Revoked Certificate List When there are no revoked certificates, then the revoked certificate list MUST be absent. For each revoked resource certificate only the following fields MUST be present. No CRL entry extensions are supported in this profile, and CRL entry extensions MUST NOT be present in a CRL. 4.6.1. Serial Number The issuer's serial number of the revoked certificate. 4.6.2. Revocation Date The time the certificate was revoked. This time SHOULD NOT be a future date. The value of this field MUST be encoded as UTCTime for dates through the year 2049, and MUST be encoded as GeneralizedTime for dates in the year 2050 or later. 4.7. CRL Extensions The X.509 v2 CRL format allows extensions to be placed in a CRL. The following extensions are supported in this profile, and MUST be present in a CRL. Huston, et al. Expires January 29, 2007 [Page 13] Internet-Draft Resource Certificate Profile July 2006 4.7.1. Authority Key Identifier The authority key identifier extension provides a means of identifying the public key corresponding to the private key used to sign a CRL. Conforming CRL issuers MUST use the key identifier method. The syntax for this CRL extension is defined in section 4.2.1.1 of [RFC3280]. This extension is non-critical. 4.7.2. CRL Number The CRL Number extension conveys a monotonically increasing sequence number for a given CA. This extension allows users to easily determine when a particular CRL supersedes another CRL. The highest CRL Number value supersedes all other CRLs issued by the CA within the scope of this profile. This extension is non-critical. 5. Resource Certificate Request Profile 5.1. PCKS#10 Profile This profile refines the specification in [RFC2986], as it relates to Resource Certificates. A Certificate Request Message object, formatted according to PKCS#10, is passed to a Certificate Authority as the initial step in issuing a certificate. This request may be conveyed to the CA via a Registration Authority (RA), acting under the direction of a Subject. With the exception of the public key related fields, the CA is permitted to alter any requested field. 5.1.1. PKCS#10 Resource Certificate Request Template Fields This profile applies the following additional constraints to fields that may appear in a CertificationRequestInfo: Version This field is mandatory and MUST have the value 0. Huston, et al. Expires January 29, 2007 [Page 14] Internet-Draft Resource Certificate Profile July 2006 Subject The CA SHOULD consider this name as the subject's suggestion, but the CA is NOT bound to honour this suggestion, as the subject name MUST be unique per issuer. This field MAY be empty, in which case the issuer MUST generate a subject name that is unique in the context of the issuer. SubjectPublicKeyInfo This field specifies the subject's public key and the algorithm with which the key is used. The public key algorithm MUST be RSA, and the OID for the algorithm is 1.2.840.113549.1.1.1. This field also includes a bit-string representation of the entity's public key. For the RSA public-key algorithm the bit string contains the DER encoding of a value of PKCS #1 type RSAPublicKey. Attributes [RFC2986] defines the attributes field as key-value pairs where the key is an OID and the value's structure depends on the key. The only attribute used in this profile is the ExtensionRequest attribute as defined in [RFC2985]. This attribute contains X509v3 Certificate Extensions. The profile for extensions in certificate requests is specified in Section 5.3. This profile applies the following additional constraints to fields that may appear in a CertificationRequest Object: signatureAlgorithm Must be SHA-256 with RSA encryption (sha256WithRSAEncryption). Accordingly, the value for this field MUST be the OID value 1.2.840.113549.1.1.11 5.2. CRMF Profile This profile refines the Certificate Request Message Format (CRMF) specification in [RFC4211], as it relates to Resource Certificates. A Certificate Request Message object, formatted according to the CRMF, is passed to a Certificate Authority as the initial step in issuing a certificate. This request may be conveyed to the CA via a Registration Authority (RA), acting under the direction of a subject. With the exception of the public key related fields, the CA is permitted to alter any requested field. Huston, et al. Expires January 29, 2007 [Page 15] Internet-Draft Resource Certificate Profile July 2006 5.2.1. CRMF Resource Certificate Request Template Fields This profile applies the following additional constraints to fields that may appear in a Certificate Request Template: Version This field MAY be absent, or MAY specify the request of a Version 3 Certificate. It SHOULD be omitted. SerialNumber As per [RFC4211], this field is assigned by the CA and MUST be omitted in this profile. SigningAlgorithm As per [RFC4211], this field is assigned by the CA and MUST be omitted in this profile. Issuer This field is assigned by the CA and MUST be omitted in this profile. Validity This field MAY be omitted. If omitted, the CA will issue a Certificate with Validity dates as determined by the CA. If specified, then the CA MAY override the requested values with dates as determined by the CA. Subject As the subject name is assigned by the CA, this field MAY be omitted, in which case the subject name will be generated by the CA. If specified, the CA SHOULD consider this as the subject's suggestion, but the CA is NOT bound to honour this suggestion. PublicKey This field MUST be present. extensions This attribute contains X509v3 Certificate Extensions. The profile for extensions in certificate requests is specified in Section 5.3. 5.2.2. Resource Certificate Request Control Fields The following control fields are supported in this profile: Huston, et al. Expires January 29, 2007 [Page 16] Internet-Draft Resource Certificate Profile July 2006 Authenticator Control It is noted that the intended model of authentication of the subject in a long term one, and the advice as offered in [RFC4211] is that the Authenticator Control field be used. [Note - not for publication: The method of generation and authentication of this field is to be specified. The desirable properties include the ability to validate the subject and the authenticity of the provided public key.] Resource Class The profile defines an additional control for Resource Certificate Requests, namely a Resource Class control. The Subject MUST specify a Resource Class value as specified by the CA to which the request refers. The CA will issue a certificate with the IP Address and AS Number resources that match the subject's right-of-use of these resources with the class of resources specified by the Resource Class control value. [Note - not for publication: This specification of the resource class is related the various forms of resource allocation which imply that an entity may be the holder of resources with differing validation dates and differing validation paths, even when the entity is the recipient of resources allocated from a single 'upstream' issuing registry. Due to this consideration it may not be possible to issue a single certificate with an all-encompassing resource set. Alternatively it is possible to define a structure where there is no Resource Class specified and the issuer issues a set of spanning certificates for all resources held by the subject (i.e. all resources that fall under the subject's "right-of-use")] 5.3. Certificate Extension Attributes in Certificate Requests This profile allows the following extensions to appear in a PKCS#10 and CRMF Certificate Request: BasicConstraints If this is omitted then this field is assigned by the CA. The Path Length Constraint is not supported in this Resource Certificate Profile, and this field MUST be omitted in this profile. Huston, et al. Expires January 29, 2007 [Page 17] Internet-Draft Resource Certificate Profile July 2006 The CA MAY honour the SubjectType CA bit set to on. If this bit is set, then it indicates that the Subject is allowed to issue resource certificates within this overall framework. The CA MAY honour the SubjectType CA bit set of off (End Entity certificate request). SubjectKeyIdentifier This field is assigned by the CA and MUST be omitted in this profile. AuthorityKeyIdentifier This field is assigned by the CA and MUST be omitted in this profile. KeyUsage The CA MAY honor KeyUsage extensions of CertificateSigning and CRLSigning if present, as long as this is consistent with the BasicConstraints SubjectType subfield, when specified. SubjectInformationAccess This field MAY be honoured by the CA on the condition that the CA issues a certificate with the BasicConstraints SubjectType CA bit set and the KeyUsage set to CertificateSigning and CRLSigning. If specified, this field contains a URI of the form of a single RSYNC URI that references a single publication point that will be used by the subject for all certificates that published by the subject for subordinate certificates, and MUST be honoured by the CA. If this field is omitted and KeyUsage is set to CertificateSigning then the CA MUST generate a URI value for the SubjectInformationAccess field based on out-of-band information that has been passed between the CA and the requester. [Note not for publication - if this field is missing than it is also an option for the Issuer to deny the request and not issue a certificate if the issued certificate was to have the CA bit set.] SubjectAlternateName This field MAY be present, and the CA MAY use this as the SubjectAltName in the issued Certificate. CRLDistributionPoints This field is assigned by the CA and MUST be omitted in this profile. Huston, et al. Expires January 29, 2007 [Page 18] Internet-Draft Resource Certificate Profile July 2006 AuthorityInformationAccess This field is assigned by the CA and MUST be omitted in this profile. SubjectInformationAccess This field MAY be honoured by the CA on the condition that the CA issues a certificate with the BasicConstraints SubjectType CA bit set and the KeyUsage set to CertificateSigning and CRLSigning. If specified, this field contains a URI of the form of a single rsync URL that references a single publication point that will be used by the subject for all certificates that published by the subject for subordinate certificates, and MUST be honoured by the CA. If this field is omitted and KeyUsage is set to CertificateSigning then the CA MUST generate a SIA URL based on out-of-band information that has been passed between the CA and the requester. [Note not for publication - the same considerations with respect to the CRL DistributionPoints apply to this field as well. i.e. if this field is missing than it is also an option for the Issuer to deny the request and not issue a certificate if the issued certificate was to have the CA bit set.] CertificatePolicies This field is assigned by the CA and MUST be omitted in this profile. SubjectAlternateName This field MAY be present, and the CA MAY use this as the SubjectAltName in the issued Certificate. IPResources This field is assigned by the CA and MUST be omitted in this profile. ASResources This field is assigned by the CA and MUST be omitted in this profile. With the exception of the publicKey field, the CA is permitted to alter any requested field. 6. Resource Certificate Validation This section describes the Resource Certificate validation procedure. Huston, et al. Expires January 29, 2007 [Page 19] Internet-Draft Resource Certificate Profile July 2006 This refines the generic procedure described in [RFC3280]: To meet this goal, the path validation process verifies, among other things, that a prospective certification path (a sequence of n certificates) satisfies the following conditions: 1. for all x in {1, ..., n-1}, the subject of certificate x is the issuer of certificate x+1; 2. certificate 1 is issued by a trust anchor; 3. certificate n is the certificate to be validated; and 4. for all x in {1, ..., n}, the certificate was valid at the time in question. 6.1. Trust Anchors for Resource Certificates The trust model that may be used in the resource certificate framework in the context of validation of assertions of public number resources in public-use contexts is one that readily maps to a top- down delegated CA model that mirrors the delegation of resources from a registry distribution point to the entities that are the direct recipients of these resources. Within this trust model these recipient entities may, in turn, operate a registry and perform further allocations or assignments. This is a strict hierarchy, in that any number resource and a corresponding recipient entity has only one 'parent' issuing registry for that number resource (i.e. there is always a unique parent entity for any resource and corresponding entity), and that the issuing registry is not a direct or indirect subordinate recipient entity of the recipient entity in question (i.e. no loops in the hierarchy). The only exception to the "no loop" condition would be where a putative trust anchor may issue a self-signed root certificate. The more general consideration is that selection of a trust anchor is a role undertaken by relying parties, and the structure of the resource certificate profile admits the same variety of trust models as the PKIX profile. There is only one additional caveat on the general applicability of trust models and PKIX frameworks, namely that in forming a validation path to a trust anchor, the sequence of certificates MUST preserve the resource extension validation property, as described in Section 6.2. 6.2. Resource Extension Validation The IP resource extension definition [RFC3779] defines a critical extensions for Internet number resources. These are ASN.1 encoded Huston, et al. Expires January 29, 2007 [Page 20] Internet-Draft Resource Certificate Profile July 2006 representations of the IPv4 and IPv6 address range (either as a prefix/length, or start-end pair) and the AS number set. Valid Resource Certificates MUST have a valid IP address and/or AS number resource extension. In order to validate a Resource Certificate the resource extension must also be validated. This validation process relies on definitions of comparison of resource sets: more specific Given two IP address or AS number contiguous ranges, A and B, A is "more specific" than B if range B includes all IP addresses or AS numbers described by range A, and if range B is larger than range A. equal Given two IP address or AS number contiguous ranges, A and B, A is "equal" to B if range A describes precisely the same collection of IP addresses or AS numbers as described by range B. The definition of "inheritance" in [RFC3779]is equivalent to this "equality" comparison. encompass Given two IP address and AS number sets X and Y, X "encompasses" Y if, for every contiguous range of IP addresses or AS numbers elements in set Y, the range element is either more specific than or equal to a contiguous range element within the set X. Validation of a certificate's resource extension in the context of an ordered certificate sequence of {1,2, ... , n} where '1'is a trust anchor and 'n' is the target certificate, and where the subject of certificate 'x' is the issuer of certificate 'x' + 1, implies that the resources described in certificate 'x', for 'x' is greater than 1, "encompass" the resources described in certificate 'x' + 1. 6.3. Resource Certificate Path Validation Validation of signed resource data using a target resource certificate consists of assembling an ordered sequence (or 'Certificate Path') of certificates ({1,2,...n} where '1' is a trust anchor, and 'n' is the target certificate) verifying that all of the following conditions hold: 1. The certificate can be verified using the Issuer's public key and the signature algorithm 2. The current time lies within the certificate's Validity From and To values. Huston, et al. Expires January 29, 2007 [Page 21] Internet-Draft Resource Certificate Profile July 2006 3. The certificate contains all fields that MUST be present and contains field values as specified in this profile for all field values that MUST be present. 4. No field value that MUST NOT be present is present in the certificate. 5. The Issuer has not revoked the certificate by placing the certificate's serial number on the Issuer's current Certificate Revocation List, and the CRL is itself valid. 6. That the resource extension data is "encompassed" by the resource extension data contained in a valid certificate where this Issuer is the Subject (the previous certificate in the ordered sequence) 7. The Certificate Path originates at a trust anchor, and there exists a signing chain across the Certificate Path where the Subject of Certificate x in the Certificate Path matches the Issuer in Certificate x+1 in the Certificate Path. A certificate validation algorithm may perform these tests in any chosen order. A Resource Certificate may have a number of potential parent certificates, where a potential parent certificate is one where the subject name matches the issuer name of the resource certificate. A candidate parent certificate is any member of the parent certificate set where the resource extension validity constraint of "encompassing" is satisfied, and a valid candidate parent certificate is any candidate parent certificate that also matches validity conditions 1 through 6. A valid parent certificate is a valid candidate parent certificate that also matches validity condition 7. Certificates and CRLs used in this process may be found on a single repository, maintained by a regular top-down walk from the Root Trust Anchors via Issuer certificates and their SIA fields as forward pointers, plus the CRLDP. Alternatively, validation may be performed using a bottom-up process with on-line certificate access using the AIA and CRLDP pointers to guide the certificate retrieval process. There exists the possibility of encountering certificate paths that are arbitrarily long, or attempting to generate paths with loops as means of creating a potential DOS attack on a certificate validator. Some further heuristics may be required to halt the validation process in order to avoid some of the issues associated with attempts to validate such structures. It is suggested that implementations of Resource Certificate validation MAY halt with a validation failure if the certificate path length exceeds a pre-determined configuration Huston, et al. Expires January 29, 2007 [Page 22] Internet-Draft Resource Certificate Profile July 2006 parameter. In the context of Resource Certificates that are generated in respect of public resources and with the framework of the associated resource distribution process, it is suggested that this configuration parameter of maximum certificate path length be set to a value of 100. [Note - not for publication: There is no particular reason for suggesting this value other than the observation that it appears to be comfortably longer than any real distribution chain for public number resources, without being too long so as to pose potential DOS concerns for relying parties performing a validation operation.] 7. Security Considerations [to be completed] 8. IANA Considerations [There are no IANA considerations stated in this version of the document.] 9. Acknowledgements The authors would like to acknowledge the valued contributions from Stephen Kent, Robert Kisteleki, Randy Bush, Russ Housley, Ricardo Patara and Rob Austein in the preparation and subsequent review of this document. 10. Normative References [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981. [RFC2050] Hubbard, K., Kosters, M., Conrad, D., Karrenberg, D., and J. Postel, "INTERNET REGISTRY IP ALLOCATION GUIDELINES", BCP 12, RFC 2050, November 1996. [RFC2985] Nystrom, M. and B. Kaliski, "PKCS #9: Selected Object Classes and Attribute Types Version 2.0", RFC 2985, November 2000. [RFC2986] Nystrom, M. and B. Kaliski, "PKCS #10: Certification Huston, et al. Expires January 29, 2007 [Page 23] Internet-Draft Resource Certificate Profile July 2006 Request Syntax Specification Version 1.7", RFC 2986, November 2000. [RFC3280] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 3280, April 2002. [RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP Addresses and AS Identifiers", RFC 3779, June 2004. [RFC4055] Schaad, J., Kaliski, B., and R. Housley, "Additional Algorithms and Identifiers for RSA Cryptography for use in the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 4055, June 2005. [RFC4158] Cooper, M., Dzambasow, Y., Hesse, P., Joseph, S., and R. Nicholas, "Internet X.509 Public Key Infrastructure: Certification Path Building", RFC 4158, September 2005. [RFC4211] Schaad, J., "Internet X.509 Public Key Infrastructure Certificate Request Message Format (CRMF)", RFC 4211, September 2005. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. [rsync] Tridgell, A., "rsync", April 2006, . Appendix A. Example Resource Certificate The following is an example Resource Certificate. Certificate Name: hu9fdDBq60mrk7cPRuX2DYuXSRQ-3.cer Data: Version: 3 Serial: 3 Signature Algorithm: Hash: SHA256, Encryption: RSA Issuer: CN=Demo Production APNIC CA - Not for real use, E=ca@apnic.net Validity: Not Before: Thu Jul 27 06:34:04 2006 GMT Not After: Fri Jul 27 06:34:04 2007 GMT Subject: CN=APNIC own-use network resources Huston, et al. Expires January 29, 2007 [Page 24] Internet-Draft Resource Certificate Profile July 2006 Subject Key Identifier: 86:ef:5f:74:30:6a:eb:49:ab:93:b7:0f:46:e5:f6:0d: 8b:97:49:14 Subject Key Identifier g(SKI): hu9fdDBq60mrk7cPRuX2DYuXSRQ Subject Public Key Info: Public Key Algorithm: rsaEncryption RSA Public Key: Modulus: c1:25:a1:b0:db:89:83:a0:fc:f1:c0:e4:7b:93:76:c1: 59:b7:0d:ac:25:25:ed:88:ce:00:03:ea:99:1a:9a:2a: 0e:10:2e:5f:c0:45:87:47:81:7b:1d:4d:44:aa:65:a3: f8:07:84:32:ea:04:70:27:05:2b:79:26:e6:e6:3a:cb: b2:9a:65:6c:c1:4e:d7:35:fb:f6:41:1e:8b:1c:b8:e4: 5a:3a:d6:d0:7b:82:9a:23:03:f8:05:4c:68:42:67:fe: e7:45:d9:2c:a6:d1:b3:da:cf:ad:77:c5:80:d2:e3:1e: 4d:e8:bf:a2:f2:44:10:b2:2f:61:bc:f4:89:31:54:7c: 56:47:d5:b1:c3:48:26:95:93:c9:6f:70:14:4d:ac:a5: c2:8e:3d:1f:6d:f8:d4:93:9d:14:c7:15:c7:34:8e:ba: dd:70:b3:c2:2b:08:78:59:97:dd:e4:34:c7:d8:de:5c: f7:94:6f:95:59:ba:29:65:f5:98:15:8f:8e:57:59:5d: 92:1f:64:2f:b5:3d:69:2e:69:83:c2:10:c6:aa:8e:03: d5:69:11:bd:0d:b5:d8:27:6c:74:2f:60:47:dd:2e:87: 24:c2:36:68:2b:3c:fd:bd:22:57:a9:4d:e8:86:3c:27: 03:ce:f0:03:2e:59:ce:05:a7:41:3f:2f:64:50:dd:e7 RSA Public Key: Exponent: 65537 Basic Constraints: CA: TRUE Subject Info Access: caRepository - rsync://repository.apnic.net/APNIC/ pvpjvwUeQix2e54X8fGbhmdYMo0/ q66IrWSGuBE7jqx8PAUHAlHCqRw/ hu9fdDBq60mrk7cPRuX2DYuXSRQ Key Usage: keyCertSign, cRLSign CRL Distribution Points: rsync://repository.apnic.net/APNIC/ pvpjvwUeQix2e54X8fGbhmdYMo0/ q66IrWSGuBE7jqx8PAUHAlHCqRw/ q66IrWSGuBE7jqx8PAUHAlHCqRw.crl Authority Info Access: caIssuers - rsync://repository.apnic.net/APNIC/ pvpjvwUeQix2e54X8fGbhmdYMo0/ q66IrWSGuBE7jqx8PAUHAlHCqRw Authority Key Identifier: Key Identifier: ab:ae:88:ad:64:86:b8:11:3b:8e:ac:7c:3c:05:07:02: 51:c2:a9:1c Authority Key Identifier: Key Identifier g(AKI): q66IrWSGuBE7jqx8PAUHAlHCqRw Certificate Policies: 1.3.6.1.5.5.7.14.2 IPv4: 202.12.27.0-202.12.29.255, 202.12.31.0/24, Huston, et al. Expires January 29, 2007 [Page 25] Internet-Draft Resource Certificate Profile July 2006 203.119.0.0/24, 203.119.42.0/23 IPv6: 2001:dc0::/32 ASNum: 4608, 4777, 9545, 18366-18370 Signature: c5:e7:b2:f3:62:cb:e3:bc:50:1e:6b:90:13:19:f4:5b: 4a:1c:1c:ab:b5:de:b1:a4:22:e0:28:f5:3b:d0:8c:59: 0f:85:f2:06:a6:ae:22:e6:d0:99:fe:cb:eb:1d:6a:e2: a3:f1:a2:25:95:ec:a7:7d:96:35:dc:16:a7:2f:f5:b7: 11:ba:97:05:57:5f:5d:07:5a:c8:19:c8:27:d3:f7:a3: 92:66:cb:98:2d:e1:7f:a8:25:96:ab:af:ed:87:02:28: f5:ae:b6:e3:0c:f7:18:82:70:82:f4:76:54:06:b9:9f: e1:a5:f7:ae:72:dd:ee:f0:d4:d2:78:bb:61:73:cf:51: 26:9f:ea:e8:20:49:06:ba:0c:ac:1d:f6:07:b8:63:a0: 4d:3d:8e:12:84:3a:d0:ec:94:7e:02:db:d4:85:cf:12: 5c:7b:12:1a:52:ab:3c:ba:00:f2:71:e7:f0:fd:b3:f4: 81:e8:a7:cb:07:ca:3a:a4:24:fe:dc:bb:51:16:6a:28: 33:40:a4:64:60:75:0e:c8:06:c8:5f:e5:98:be:16:a3: bc:19:e7:b3:4f:00:0a:8e:81:33:dd:4c:a0:fb:f5:1c: 1f:1d:3f:b5:90:8b:ec:98:67:76:95:56:8a:94:45:54: 52:3d:1c:69:4c:6f:8a:9f:09:ec:ef:b0:a9:bc:cf:9d Appendix B. Example Certificate Revocation List The following is an example Certificate Revocation List. Huston, et al. Expires January 29, 2007 [Page 26] Internet-Draft Resource Certificate Profile July 2006 CRL Name: q66IrWSGuBE7jqx8PAUHAlHCqRw.crl Data: Version: 2 Signature Algorithm: Hash: SHA256, Encryption: RSA Issuer: CN=Demo Production APNIC CA - Not for real use, E=ca@apnic.net This Update: Thu Jul 27 06:30:34 2006 GMT Next Update: Fri Jul 28 06:30:34 2006 GMT Authority Key Identifier: Key Identifier: ab:ae:88:ad:64:86:b8:11:3b:8e:ac:7c:3c:05: 07:02:51:c2:a9:1c Authority Key Identifier: Key Identifier g(AKI): q66IrWSGuBE7jqx8PAUHAlHCqRw CRLNumber: 4 Revoked Certificates: 1 Serial Number: 1 Revocation Date: Mon Jul 17 05:10:19 2006 GMT Serial Number: 2 Revocation Date: Mon Jul 17 05:12:25 2006 GMT Serial Number: 4 Revocation Date: Mon Jul 17 05:40:39 2006 GMT Signature: b2:5a:e8:7c:bd:a8:00:0f:03:1a:17:fd:40:2c:46: 0e:d5:64:87:e7:e7:bc:10:7d:b6:3e:39:21:a9:12: f4:5a:d8:b8:d4:bd:57:1a:7d:2f:7c:0d:c6:4f:27: 17:c8:0e:ae:8c:89:ff:00:f7:81:97:c3:a1:6a:0a: f7:d2:46:06:9a:d1:d5:4d:78:e1:b7:b0:58:4d:09: d6:7c:1e:a0:40:af:86:5d:8c:c9:48:f6:e6:20:2e: b9:b6:81:03:0b:51:ac:23:db:9f:c1:8e:d6:94:54: 66:a5:68:52:ee:dd:0f:10:5d:21:b8:b8:19:ff:29: 6f:51:2e:c8:74:5c:2a:d2:c5:fa:99:eb:c5:c2:a2: d0:96:fc:54:b3:ba:80:4b:92:7f:85:54:76:c9:12: cb:32:ea:1d:12:7b:f8:f9:a2:5c:a1:b1:06:8e:d8: c5:42:61:00:8c:f6:33:11:29:df:6e:b2:cc:c3:7c: d3:f3:0c:8d:5c:49:a5:fb:49:fd:e7:c4:73:68:0a: 09:0e:6d:68:a9:06:52:3a:36:4f:19:47:83:59:da: 02:5b:2a:d0:8a:7a:33:0a:d5:ce:be:b5:a2:7d:8d: 59:a1:9d:ee:60:ce:77:3d:e1:86:9a:84:93:90:9f: 34:a7:02:40:59:3a:a5:d1:18:fb:6f:fc:af:d4:02: d9 Huston, et al. Expires January 29, 2007 [Page 27] Internet-Draft Resource Certificate Profile July 2006 Authors' Addresses Geoff Huston Asia Pacific Network Information Centre Email: gih@apnic.net URI: http://www.apnic.net George Michaelson Asia Pacific Network Information Centre Email: ggm@apnic.net URI: http://www.apnic.net Robert Loomans Asia Pacific Network Information Centre Email: robertl@apnic.net URI: http://www.apnic.net Huston, et al. Expires January 29, 2007 [Page 28] Internet-Draft Resource Certificate Profile July 2006 Full Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Huston, et al. Expires January 29, 2007 [Page 29]