Network Working Group J. Schaad Internet-Draft Soaring Hawk Consulting Updates: 2634 (if approved) January 4, 2007 Intended status: Standards Track Expires: July 8, 2007 ESS Update: Adding CertID Algorithm Agility draft-ietf-smime-escertid-04.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 July 8, 2007. Copyright Notice Copyright (C) The Internet Society (2007). Schaad Expires July 8, 2007 [Page 1]
Internet-Draft ESSCertID Update January 2007 Abstract In the original Enhanced Security Services for S/MIME document (RFC 2634), a structure for cryptographically linking the certificate to be used in validation with the signature was introduced, this structure was hardwired to use SHA-1. This document allows for the structure to have algorithm agility and defines a new attribute for this purpose. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Notation . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Updates to RFC 2634 . . . . . . . . . . . . . . . . . . . 3 2. Replace Section 5.4 'Signing Certificate Attribute Definitions' . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Insert new section 5.4.1 'Signing Certificate Attribute Definition Version 2' . . . . . . . . . . . . . . . . . . . . 5 4. Insert new section 5.4.1.1 'Certificate Identification Version 2' . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5. Insert new section 5.4.2 ' Signing Certificate Attribute Defintion Version 1 . . . . . . . . . . . . . . . . . . . . . 9 6. Renumber Section 5.4.1 Certificate Identification Version 1 . 11 7. Normative References . . . . . . . . . . . . . . . . . . . . . 12 Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 13 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 18 Intellectual Property and Copyright Statements . . . . . . . . . . 19 Schaad Expires July 8, 2007 [Page 2]
Internet-Draft ESSCertID Update January 2007 1. Introduction In the original Enhanced Security Services (ESS) for S/MIME document [ESS], a structure for cryptographically linking the certificate to be used in validation with the signature was defined. This structure, called ESSCertID was hardwired to use a SHA-1 hash value. The recent attacks on SHA-1 require that we define a new attribute which allows for the use of a different algorithms. This document performs that task. This document defines the structure ESSCertIDv2 along with a new attribute SigningCertificateV2 which uses the updated structure. This document allows for the structure to have algorithm agility and defines new attributes to deal with the updating. 1.1. Notation The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 1.2. Updates to RFC 2634 This document updates section 5.4 of RFC 2634. Once the updates are applied, the revised section will have the following structure: 5.4 Signing Certificate Attribute Definitions 5.4.1 Signing Certificate Attribute Definition Version 2 5.4.1.1 Certificate Identification Version 2 5.4.2 Signing Certificate Attribute Definition Version 1 5.4.2.1 Certificate Identification Version 1 In addition, the ASN.1 module in Appendix A is replaced. Schaad Expires July 8, 2007 [Page 3]
Internet-Draft ESSCertID Update January 2007 2. Replace Section 5.4 'Signing Certificate Attribute Definitions' The signing certificate attribute is designed to prevent simple substitution and re-issue attacks, and to allow for a restricted set of certificates to be used in verifying a signature. Two different attributes exist for this due to a flaw in the original design. The only substantial difference between the two attributes is that SigningCertificateV2 allows for hash algorithm agility, while SigningCertificate forces the use of the SHA-1 hash algorithm. With the recent advances in the ability to create hash collisions for SHA-1 it is wise to move forward sooner rather than later. When the SHA-1 hash function is used, the SigningCertificate attribute MUST be used. The SigningCertificateV2 attribute MUST be used if any algorithm other than SHA-1 is used and SHOULD NOT be used for SHA-1. Applications SHOULD recognize both attributes as long as they consider SHA-1 able to distinguish between two different certificates. (I.e. the possibility of a collision is sufficently low.) Four cases exist which need to be taken into account when using this attribute for correct processing: 1. Signature Validates and the hashes match: This is the success case. 2. Signature Validates and the hashes do not match: In this case the certificate contained the correct public key, but the certificate containing the public key is not the one that the signer intended to be used. In this case the application should attempt a search for a different certificate with the same public key and for which the hashes match. If no such certificate can be found, this is a failure case. 3. Signature Fails Validation and the hashes match: In this case it can be assumed that the signature has been modified in some fashion. This is a failure case. 4. Signature Fails Validation and the Hashes do not match: In this case it can be either that the signature has been modified, or that the wrong certificate has been used. Applications should attempt a search for a different certificate which matches the hash value in the attribute and use the new certificate to retry the signature validation. Schaad Expires July 8, 2007 [Page 4]
Internet-Draft ESSCertID Update January 2007 3. Insert new section 5.4.1 'Signing Certificate Attribute Definition Version 2' 5.4.1 Signing Certificate Attribute Definition Version 2 The signing certificate attribute is designed to prevent the simple substitution and re-issue attacks, and to allow for a restricted set of certificates to be used in verifying a signature. SigningCertificateV2 is identified by the OID: id-aa-signingCertificateV2 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9) smime(16) id-aa(2) 47 } The attribute has the ASN.1 definition: SigningCertificateV2 ::= SEQUENCE { certs SEQUENCE OF ESSCertIDv2, policies SEQUENCE OF PolicyInformation OPTIONAL } certs contains the list of certificates that are to be used in validating the message. The first certificate identified in the sequence of certificate identifiers MUST be the certificate used to verify the signature. The encoding of the ESSCertIDv2 for this certificate SHOULD include the issuerSerial field. If other constraints ensure that issuerAndSerialNumber will be present in the SignerInfo, the issuerSerial field MAY be omitted. The certificate identified is used during the signature verification process. If the hash of the certificate does not match the certificate used to verify the signature, the signature MUST be considered invalid. If more than one certificate is present, subsequent certificates limit the set of certificates that are used during signature validation. Certificates can be either attribute certificates or normal certificates. The issuerSerial field (in the ESSCertIDv2 structure) SHOULD be present for these certificates, unless the client who is validating the signature is expected to have easy access to all the certificates required for validation. If only the signing certificate is present in the sequence, there are no restrictions on the set of certificates used in validating the signature. Schaad Expires July 8, 2007 [Page 5]
Internet-Draft ESSCertID Update January 2007 policies contains a sequence of policy information terms that identify those certificate policies that the signer asserts apply to the certificate, and under which the certificate should be relied upon. This value suggests a policy value to be used in the relying party's certification path validation. The definition of PolicyInformation can be found in [PKIXCERT]. If present, the SigningCertificateV2 attribute MUST be a signed attribute; it MUST NOT be an unsigned attribute. CMS defines SignedAttributes as a SET OF Attribute. A SignerInfo MUST NOT include multiple instances of the SigningCertificate attribute. CMS defines the ASN.1 syntax for the signed attributes to include attrValues SET OF AttributeValue. A SigningCertificate attribute MUST include only a single instance of AttributeValue. There MUST NOT be zero or multiple instances of AttributeValue present in the attrValues SET OF AttributeValue. Schaad Expires July 8, 2007 [Page 6]
Internet-Draft ESSCertID Update January 2007 4. Insert new section 5.4.1.1 'Certificate Identification Version 2' Insert the following text as a new section 5.4.1.1 Certificate Identification Version 2 The best way to identify certificates is an often-discussed issue. The ESSCertIDv2 structure supplies two different fields that are used for this purpose. The hash of the entire certificate allows for a verifier to check that the certificate used in the verification process was the same certificate the signer intended. Hashes are convenient in that they are frequently used by certificate stores as a method of indexing and retrieving certificates as well. The use of the hash is required by this structure since the detection of substituted certificates is based on the fact they would map to different hash values. The issuer/serial number pair is the method of identification of certificates used in [PKIXCERT]. That document imposes a restriction for certificates that the issuer distinguished name must be present. The issuer/serial number pair would therefore normally be sufficient to identify the correct signing certificate. (This assumes the same issuer name is not re-used from the set of trust anchors.) The issuer/serial number pair can be stored in the sid field of the SignerInfo object. However the sid field is not covered by the signature. In the cases where the issuer/serial number pair is not used in the sid or the issuer/serial number pair needs to be signed, it SHOULD be placed in the issuerSerial field of the ESSCertIDv2 structure. Attribute certificates and additional public key certificates containing information do not have an issuer/serial number pair represented anywhere in a SignerInfo object. When an attribute certificate or an additional public key certificate is not included in the SignedData object, it becomes much more difficult to get the correct set of certificates based only on a hash of the certificate. For this reason, these certificates SHOULD be identified by the IssuerSerial object. This document defines a certificate identifier as: Schaad Expires July 8, 2007 [Page 7]
Internet-Draft ESSCertID Update January 2007 ESSCertIDv2 ::= SEQUENCE { hashAlgorithm AlgorithmIdentifier DEFAULT {algorithm id-sha256 parameters NULL}, certHash Hash, issuerSerial IssuerSerial OPTIONAL } Hash ::= OCTET STRING IssuerSerial ::= SEQUENCE { issuer GeneralNames, serialNumber CertificateSerialNumber } The fields of ESSCertIDv2 are defined as follows: hashAlg contains the identifier of the algorithm used in computing certHash. certHash is computed over the entire DER encoded certificate including the signature. issuerSerial holds the identification of the certificate. The issuerSerial would normally be present unless the value can be inferred from other information (e.g. the sid field of the SignerInfo object). The fields of IssuerSerial are defined as follows: issuer contains the issuer name of the certificate. For non- attribute certificates, the issuer MUST contain only the issuer name from the certificate encoded in the directoryName choice of GeneralNames. For attribute certificates, the issuer MUST contain the issuer name field from the attribute certificate. serialNumber holds the serial number that uniquely identifies the certificate for the issuer. Schaad Expires July 8, 2007 [Page 8]
Internet-Draft ESSCertID Update January 2007 5. Insert new section 5.4.2 ' Signing Certificate Attribute Defintion Version 1 5.4.2 Signing Certificate Attribute Definition Version 1 The signing certificate attribute is designed to prevent the simple substitution and re-issue attacks, and to allow for a restricted set of certificates to be used in verifying a signature. The definition of SigningCertificate is SigningCertificate ::= SEQUENCE { certs SEQUENCE OF ESSCertID, policies SEQUENCE OF PolicyInformation OPTIONAL } id-aa-signingCertificate OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9) smime(16) id-aa(2) 12 } The first certificate identified in the sequence of certificate identifiers MUST be the certificate used to verify the signature. The encoding of the ESSCertID for this certificate SHOULD include the issuerSerial field. If other constraints ensure that issuerAndSerialNumber will be present in the SignerInfo, the issuerSerial field MAY be omitted. The certificate identified is used during the signature verification process. If the hash of the certificate does not match the certificate used to verify the signature, the signature MUST be considered invalid. If more than one certificate is present in the sequence of ESSCertIDs, the certificates after the first one limit the set of certificates that are used during signature validation. Certificates can be either attribute certificates or public key certificates. The issuerSerial field (in the ESSCertID structure) SHOULD be present for these certificates, unless the client who is validating the signature is expected to have easy access to all the certificates required for validation. If only the signing certificate is present in the sequence, there are no restrictions on the set of certificates used in validating the signature. The sequence of policy information terms identifies those certificate policies that the signer asserts apply to the certificate, and under which the certificate should be relied upon. This value suggests a policy value to be used in the relying party's certification path validation. If present, the SigningCertificate attribute MUST be a signed Schaad Expires July 8, 2007 [Page 9]
Internet-Draft ESSCertID Update January 2007 attribute; it MUST NOT be an unsigned attribute. CMS defines SignedAttributes as a SET OF Attribute. A SignerInfo MUST NOT include multiple instances of the SigningCertificate attribute. CMS defines the ASN.1 syntax for the signed attributes to include attrValues SET OF AttributeValue. A SigningCertificate attribute MUST include only a single instance of AttributeValue. There MUST NOT be zero or multiple instances of AttributeValue present in the attrValues SET OF AttributeValue. Schaad Expires July 8, 2007 [Page 10]
Internet-Draft ESSCertID Update January 2007 6. Renumber Section 5.4.1 Certificate Identification Version 1 Change the number on this section from 5.4.1 to 5.4.2.1. Change the title on this section to "Certificate Identification Version 1". Schaad Expires July 8, 2007 [Page 11]
Internet-Draft ESSCertID Update January 2007 7. Normative References [ESS] Hoffman, P., "Enhanced Security Services for S/MIME", RFC 2634, June 1999. [PKIXCERT] Housley, R., Ford, W., Polk, W., and D. Solo, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 3280, April 2002. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, BCP 14, March 1997. [RFC3280] Housley, R., Ford, W., Polk, W., and D. Solo, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 3280, April 2002. [RFC3852] Housley, R., "Cryptographic Message Syntax (CMS)", RFC 3852, July 2004. Schaad Expires July 8, 2007 [Page 12]
Internet-Draft ESSCertID Update January 2007 Appendix A. ASN.1 Module Replace the ASN.1 module in RFC 2634 with this one. ExtendedSecurityServices-2006 { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) modules(0) id-mod-ess-2006(30) } DEFINITIONS IMPLICIT TAGS ::= BEGIN IMPORTS -- Cryptographic Message Syntax (CMS) [RFC 3852] ContentType, IssuerAndSerialNumber, SubjectKeyIdentifier FROM CryptographicMessageSyntax2004 { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) modules(0) cms-2004(24)} -- PKIX Certificate and CRL Profile, Section A.1 Explicity Tagged Module -- 1988 Syntax [RFC 3280] AlgorithmIdentifier, CertificateSerialNumber FROM PKIX1Explicit88 { iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7) id-mod(0) pkix1-explicit(18) } ; -- PKIX Certificate and CRL Profile, Sec A.2 Implicitly Tagged Module, -- 1988 Syntax [RFC 3280] PolicyInformation, CertificateSerialNumber, GeneralNames FROM PKIX1Implicit88 {iso(1) identified-organization(3) dod(6) internet(1) security(5) mechanisms(5) pkix(7)id-mod(0) id-pkix1-implicit(19)}; -- Extended Security Services -- The construct "SEQUENCE SIZE (1..MAX) OF" appears in several ASN.1 -- constructs in this module. A valid ASN.1 SEQUENCE can have zero or -- more entries. The SIZE (1..MAX) construct constrains the SEQUENCE to -- have at least one entry. MAX indicates the upper bound is unspecified. -- Implementations are free to choose an upper bound that suits their -- environment. -- UTF8String ::= [UNIVERSAL 12] IMPLICIT OCTET STRING -- The contents are formatted as described in [UTF8] -- Section 2.7 ReceiptRequest ::= SEQUENCE { signedContentIdentifier ContentIdentifier, Schaad Expires July 8, 2007 [Page 13]
Internet-Draft ESSCertID Update January 2007 receiptsFrom ReceiptsFrom, receiptsTo SEQUENCE SIZE (1..ub-receiptsTo) OF GeneralNames } ub-receiptsTo INTEGER ::= 16 id-aa-receiptRequest OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 1} ContentIdentifier ::= OCTET STRING id-aa-contentIdentifier OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 7} ReceiptsFrom ::= CHOICE { allOrFirstTier [0] AllOrFirstTier, -- formerly "allOrNone [0]AllOrNone" receiptList [1] SEQUENCE OF GeneralNames } AllOrFirstTier ::= INTEGER { -- Formerly AllOrNone allReceipts (0), firstTierRecipients (1) } -- Section 2.8 Receipt ::= SEQUENCE { version ESSVersion, contentType ContentType, signedContentIdentifier ContentIdentifier, originatorSignatureValue OCTET STRING } id-ct-receipt OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-ct(1) 1} ESSVersion ::= INTEGER { v1(1) } -- Section 2.9 ContentHints ::= SEQUENCE { contentDescription UTF8String (SIZE (1..MAX)) OPTIONAL, contentType ContentType } id-aa-contentHint OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 4} -- Section 2.10 MsgSigDigest ::= OCTET STRING Schaad Expires July 8, 2007 [Page 14]
Internet-Draft ESSCertID Update January 2007 id-aa-msgSigDigest OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 5} -- Section 2.11 ContentReference ::= SEQUENCE { contentType ContentType, signedContentIdentifier ContentIdentifier, originatorSignatureValue OCTET STRING } id-aa-contentReference OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 10 } -- Section 3.2 ESSSecurityLabel ::= SET { security-policy-identifier SecurityPolicyIdentifier, security-classification SecurityClassification OPTIONAL, privacy-mark ESSPrivacyMark OPTIONAL, security-categories SecurityCategories OPTIONAL } id-aa-securityLabel OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 2} SecurityPolicyIdentifier ::= OBJECT IDENTIFIER SecurityClassification ::= INTEGER { unmarked (0), unclassified (1), restricted (2), confidential (3), secret (4), top-secret (5) } (0..ub-integer-options) ub-integer-options INTEGER ::= 256 ESSPrivacyMark ::= CHOICE { pString PrintableString (SIZE (1..ub-privacy-mark-length)), utf8String UTF8String (SIZE (1..MAX)) } ub-privacy-mark-length INTEGER ::= 128 SecurityCategories ::= SET SIZE (1..ub-security-categories) OF SecurityCategory ub-security-categories INTEGER ::= 64 Schaad Expires July 8, 2007 [Page 15]
Internet-Draft ESSCertID Update January 2007 SecurityCategory ::= SEQUENCE { type [0] OBJECT IDENTIFIER, value [1] ANY DEFINED BY type } --Note: The aforementioned SecurityCategory syntax produces identical --hex encodings as the following SecurityCategory syntax that is --documented in the X.411 specification: -- --SecurityCategory ::= SEQUENCE { -- type [0] SECURITY-CATEGORY, -- value [1] ANY DEFINED BY type } -- --SECURITY-CATEGORY MACRO ::= --BEGIN --TYPE NOTATION ::= type | empty --VALUE NOTATION ::= value (VALUE OBJECT IDENTIFIER) --END -- Section 3.4 EquivalentLabels ::= SEQUENCE OF ESSSecurityLabel id-aa-equivalentLabels OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 9} -- Section 4.4 MLExpansionHistory ::= SEQUENCE SIZE (1..ub-ml-expansion-history) OF MLData id-aa-mlExpandHistory OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9) smime(16) id-aa(2) 3} ub-ml-expansion-history INTEGER ::= 64 MLData ::= SEQUENCE { mailListIdentifier EntityIdentifier, expansionTime GeneralizedTime, mlReceiptPolicy MLReceiptPolicy OPTIONAL } EntityIdentifier ::= CHOICE { issuerAndSerialNumber IssuerAndSerialNumber, subjectKeyIdentifier SubjectKeyIdentifier } MLReceiptPolicy ::= CHOICE { none [0] NULL, Schaad Expires July 8, 2007 [Page 16]
Internet-Draft ESSCertID Update January 2007 insteadOf [1] SEQUENCE SIZE (1..MAX) OF GeneralNames, inAdditionTo [2] SEQUENCE SIZE (1..MAX) OF GeneralNames } -- Section 5.4 SigningCertificate ::= SEQUENCE { certs SEQUENCE OF ESSCertID, policies SEQUENCE OF PolicyInformation OPTIONAL } id-aa-signingCertificate OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9) smime(16) id-aa(2) 12 } SigningCertificateV2 ::= SEQUENCE { certs SEQUENCE OF ESSCertIDv2, policies SEQUENCE OF PolicyInformation OPTIONAL } id-aa-signingCertificateV2 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9) smime(16) id-aa(2) 47 } id-sha256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) organization(1) gov(101) csor(3) nistalgorithm(4) hashalgs(2) 1 } ESSCertIDv2 ::= SEQUENCE { hashAlgorithm AlgorithmIdentifier DEFAULT {algorithm id-sha256 parameters NULL}, certHash Hash, issuerSerial IssuerSerial OPTIONAL } ESSCertID ::= SEQUENCE { certHash Hash, issuerSerial IssuerSerial OPTIONAL } Hash ::= OCTET STRING IssuerSerial ::= SEQUENCE { issuer GeneralNames, serialNumber CertificateSerialNumber } END -- of ExtendedSecurityServices-2006 Schaad Expires July 8, 2007 [Page 17]
Internet-Draft ESSCertID Update January 2007 Author's Address Jim Schaad Soaring Hawk Consulting PO Box 675 Gold Bar, WA 98251 Phone: (425) 785-1031 Email: jimsch@exmsft.com Schaad Expires July 8, 2007 [Page 18]
Internet-Draft ESSCertID Update January 2007 Full Copyright Statement Copyright (C) The Internet Society (2007). 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. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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). Schaad Expires July 8, 2007 [Page 19]
