Network Working Group W. Hardaker Internet-Draft Sparta Expires: May 14, 2006 November 10, 2005 Use of SHA-256 in DNSSEC Delegation Signer (DS) Resource Records (RRs) draft-ietf-dnsext-ds-sha256-00.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 May 14, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This document defines the use of the SHA-256 digest type for creating digests of DNSKEY Resource Records (RRs). These digests can then be published in Delegation Signer (DS) resource records (RRs) by a parent zone. Hardaker Expires May 14, 2006 [Page 1] Internet-Draft Use of SHA-256 in DNSSEC DS RRs November 2005 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Implementing the SHA-256 algorithm for DS record support . . . 3 2.1. DS record field values . . . . . . . . . . . . . . . . . . 3 2.2. DS Record with SHA-256 Wire Format . . . . . . . . . . . . 3 3. Implementation Requirements . . . . . . . . . . . . . . . . . . 4 4. Deployment Requirements . . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 8.1. Normative References . . . . . . . . . . . . . . . . . . . 5 8.2. Informative References . . . . . . . . . . . . . . . . . . 5 Appendix A. Example . . . . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . . . 7 Hardaker Expires May 14, 2006 [Page 2] Internet-Draft Use of SHA-256 in DNSSEC DS RRs November 2005 1. Introduction The DNSSEC [RFC4033] [RFC4034] [RFC4035] DS RR is published by parent zones to distribute a cryptographic digest of a child's Key Signing Key (KSK) DNSKEY RR. This DS RR is signed using the parent zone's private half of it's DNSKEY and is published in a RRSIG record. 2. Implementing the SHA-256 algorithm for DS record support This document specifies that the digest type code [XXX: To be assigned by IANA; likely 2] is to be assigned to SHA-256 [SHA256] for use within DS records. The results of the digest algorithm MUST NOT be truncated and the entire 32 byte digest result is to be published in the DS record. 2.1. DS record field values Using the SHA-256 digest algorithm within a DS record will make use of the following DS-record fields: Digest type: [XXX: To be assigned by IANA; likely 2] Digest: A SHA-256 bit digest value calculated by using the following formula ("|" denotes concatenation). The resulting value is not truncated and the entire 32 byte result is to used in the resulting DS record and related calculations. digest = SHA_256(DNSKEY owner name | DNSKEY RDATA) where DNSKEY RDATA is defined by [RFC4034] as: DNSKEY RDATA = Flags | Protocol | Algorithm | Public Key The Key Tag field and Algorithm fields remain unchanged by this document and are specified in the [RFC4034] specification. 2.2. DS Record with SHA-256 Wire Format The resulting packet format for the resulting DS record will be [XXX: IANA assignment should replace the 2 below]: Hardaker Expires May 14, 2006 [Page 3] Internet-Draft Use of SHA-256 in DNSSEC DS RRs November 2005 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Key Tag | Algorithm | DigestType=2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / / / Digest (length for SHA-256 is 32 bytes) / / / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| 3. Implementation Requirements Implementations MUST support the use of the SHA-256 algorithm in DS RRs. Implementations that support SHA-256 MUST prefer DS records with SHA- 256 (digest type number [XXX: RFC to be assigned by IANA; likely 2]) digests over DS records with SHA-1 (digest type number 1) digests. 4. Deployment Requirements Deployments SHOULD publish both SHA-1 and SHA-256 based DS records for 2 years from the publication date of this RFC (XXX: RFC Editor: Please insert the calculated date here). 5. IANA Considerations The Digest Type to be used for supporting SHA-256 within DS records needs to be assigned by IANA. This document requests that the Digest Type value of 2 be assigned to the SHA-256 digest algorithm. 6. Security Considerations Because of the weaknesses recently discovered within the SHA-1 algorithm, users of DNSSEC are encouraged to deploy the use of SHA- 256 as soon as software implementations in use allow for it. At the time of this publication, the SHA-256 algorithm is considered sufficiently strong for the immediate future. It is considered also considered sufficient for use in DNSSEC DS RRs for the immediate future. However, future published attacks may, of course, weaken the usability of this algorithm within the DS RRs. Hardaker Expires May 14, 2006 [Page 4] Internet-Draft Use of SHA-256 in DNSSEC DS RRs November 2005 7. Acknowledgments This document is a minor extension to the existing DNSSEC documents and those authors are gratefully appreciated for the hard work that went into the base documents. 8. References 8.1. Normative References [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "DNS Security Introduction and Requirements", RFC 4033, March 2005. [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "Resource Records for the DNS Security Extensions", RFC 4034, March 2005. [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "Protocol Modifications for the DNS Security Extensions", RFC 4035, March 2005. [SHA256] National Institute of Standards and Technology, "Secure Hash Algorithm. NIST FIPS 180-2", August 2002. 8.2. Informative References Appendix A. Example TBD Hardaker Expires May 14, 2006 [Page 5] Internet-Draft Use of SHA-256 in DNSSEC DS RRs November 2005 Author's Address Wes Hardaker Sparta P.O. Box 382 Davis 95617 US Email: hardaker@tislabs.com Hardaker Expires May 14, 2006 [Page 6] Internet-Draft Use of SHA-256 in DNSSEC DS RRs November 2005 Intellectual Property Statement 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. 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Disclaimer of Validity 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. Copyright Statement Copyright (C) The Internet Society (2005). 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Hardaker Expires May 14, 2006 [Page 7]