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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'FIPS-180-3' -- Possible downref: Non-RFC (?) normative reference: ref. 'FIPS-186-3' ** Downref: Normative reference to an Informational RFC: RFC 5114 -- Obsolete informational reference (is this intentional?): RFC 4634 (Obsoleted by RFC 6234) -- Obsolete informational reference (is this intentional?): RFC 5430 (Obsoleted by RFC 6460) Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group P. Hoffman 3 Internet-Draft VPN Consortium 4 Intended status: Standards Track July 6, 2009 5 Expires: January 7, 2010 7 Elliptic Curve DSA for DNSSEC 8 draft-hoffman-dnssec-ecdsa-00 10 Status of this Memo 12 This Internet-Draft is submitted to IETF in full conformance with the 13 provisions of BCP 78 and BCP 79. This document may contain material 14 from IETF Documents or IETF Contributions published or made publicly 15 available before November 10, 2008. The person(s) controlling the 16 copyright in some of this material may not have granted the IETF 17 Trust the right to allow modifications of such material outside the 18 IETF Standards Process. Without obtaining an adequate license from 19 the person(s) controlling the copyright in such materials, this 20 document may not be modified outside the IETF Standards Process, and 21 derivative works of it may not be created outside the IETF Standards 22 Process, except to format it for publication as an RFC or to 23 translate it into languages other than English. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF), its areas, and its working groups. Note that 27 other groups may also distribute working documents as Internet- 28 Drafts. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 The list of current Internet-Drafts can be accessed at 36 http://www.ietf.org/ietf/1id-abstracts.txt. 38 The list of Internet-Draft Shadow Directories can be accessed at 39 http://www.ietf.org/shadow.html. 41 This Internet-Draft will expire on January 7, 2010. 43 Copyright Notice 45 Copyright (c) 2009 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents in effect on the date of 50 publication of this document (http://trustee.ietf.org/license-info). 51 Please review these documents carefully, as they describe your rights 52 and restrictions with respect to this document. 54 Abstract 56 This document describes how to specify Elliptic Curve DSA keys and 57 signatures in DNSSEC. It lists curves of different sizes, and uses 58 the SHA-2 family of hashes for signatures. 60 1. Introduction 62 DNSSEC, which is broadly defined in RFCs 4033, 4034, and 4035 63 ([RFC4033], [RFC4034], and [RFC4035]), uses cryptographic keys and 64 digital signatures to provide authentication of DNS data. Currently, 65 the most popular signature algorithm is RSA with SHA-1, using keys 66 1024 or 2048 bits long. 68 This document defines the DNSKEY and RRSIG resource records (RRs) of 69 three new signing algorithms: ECDSA with curve P-224 and SHA-256, 70 ECDSA with curve P-256 and SHA-256, and ECDSA with curve P-384 and 71 SHA-384. It also defines the DS RR for the SHA-384 one-way hash 72 algorithm; the associated DS RR for SHA-256 is already defined in RFC 73 4509 [RFC4509]. 75 Current estimates are that ECDSA with curve P-256 has an approximate 76 equivalent strength to RSA with 3072-bit keys. Using ECDSA with 77 curve P-256 in DNSSEC has some advantages and disadvantages relative 78 to using RSA with SHA-256 and with 3072-bit keys. ECDSA keys are 79 much shorter than RSA keys; at this size, the difference is 256 80 versus 3072 bits. Similarly, ECDSA signatures are much shorter than 81 RSA signatures. This is relevant because DNSSEC stores and transmits 82 both keys and signatures. 84 Signing with ECDSA is significantly faster than with RSA (over 20 85 times in some implementations). However, validating RSA signatures 86 is significantly faster than validating ECDSA signatures (about 5 87 times faster in some implementations). 89 Some of the material in this document is copied liberally from RFC 90 5430 [RFC5430]. 92 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 93 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 94 document are to be interpreted as described in RFC 2119 [RFC2119]. 96 2. SHA-384 DS Records 98 SHA-384 is defined in FIPS 180-3 [FIPS-180-3] and RFC 4634 [RFC4634], 99 and is similar to SHA-256 in many ways. The implementation of SHA- 100 384 in DNSSEC follows the implementation of SHA-256 as specified in 101 RFC 4509 except that the underlying algorithm is SHA-384, the digest 102 value is 48 bytes long, and the digest type code is {TBA-1}. 104 3. ECDSA Parameters 106 Verifying ECDSA signatures require agreement between the signer and 107 the verifier of the parameters used. FIPS 186-3 [FIPS-186-3] lists 108 some NIST-recommended elliptic curves. These are the same curves 109 listed in RFC 5114 [RFC5114]. The curves used in this document are: 111 FIPS 186-3 RFC 5114 112 ------------------------------------------------------------------ 113 P-224 (Section D.1.2.2) 224-bit Random ECP Group (Section 2.5) 114 P-256 (Section D.1.2.3) 256-bit Random ECP Group (Section 2.6) 115 P-384 (Section D.1.2.4) 384-bit Random ECP Group (Section 2.7) 117 4. DNSKEY and RRSIG Resource Records for ECDSA 119 ECDSA public keys consist of a single value, called "Q" in FIPS 120 186-3. In DNSSEC keys, Q is a simple bit string that represents the 121 uncompressed form of the curve. 123 The ECDSA signature is the combination of two non-negative integers, 124 called "r" and "s" in FIPS 186-3. The two integers, each of which is 125 formatted as a simple bit string, are combined into a single longer 126 bit string for DNSSEC as the concatenation "r | s". 128 The algorithm numbers associated with the DNSKEY and RRSIG resource 129 records are fully defined in the IANA Considerations section. They 130 are: 132 o DNSKEY and RRSIG RRs signifying ECDSA with the P-224 curve and 133 SHA-256 use the algorithm number {TBA-2}. 135 o DNSKEY and RRSIG RRs signifying ECDSA with the P-256 curve and 136 SHA-256 use the algorithm number {TBA-3}. 138 o DNSKEY and RRSIG RRs signifying ECDSA with the P-384 curve and 139 SHA-384 use the algorithm number {TBA-4}. 141 Conformant implementations MUST support signing and/or validation of 142 signatures with both ECDSA with the P-256 curve and SHA-256, and with 143 ECDSA with the P-384 curve and SHA-384. (ECDSA with the P-224 curve 144 and SHA-256 is defined here for systems that want to have a strength 145 equivalence of RSA with 2048-bit keys, but is not required for 146 conformance.) 148 5. Support for NSEC3 Denial of Existence 150 RFC 5155 [RFC5155] defines new algorithm identifiers for existing 151 signing algorithms, to indicate that zones signed with these 152 algorithm identifiers can use NSEC3 as well as NSEC records to 153 provide denial of existence. That mechanism was chosen to protect 154 implementations predating RFC 5155 from encountering resource records 155 they could not know about. This document does not define such 156 algorithm aliases. 158 A DNSSEC validator that implements the signing algorithms defined in 159 this document MUST be able to validate negative answers in the form 160 of both NSEC and NSEC3 with hash algorithm 1, as defined in RFC 5155. 161 An authoritative server that does not implement NSEC3 MAY still serve 162 zones that use the signing algorithms defined in this document with 163 NSEC denial of existence. 165 6. Examples 167 [[ To be filled in later. ]] 169 7. IANA Considerations 171 This document updates the IANA for digest types in DS records, 172 currently called "Delegation Signer Resource Record, Digest 173 Algorithms". The following entry is added: 175 Value {TBA-1} 176 Digest Type SHA-384 177 Status OPTIONAL 179 This document updates the IANA registry "Domain Name System Security 180 (DNSSEC) Algorithm Numbers". The following three entries are added 181 to the registry: 183 Number {TBA-2} 184 Description ECDSA Curve P-224 with SHA-256 185 Mnemonic ECDSAP224SHA256 186 Zone Signing Y 187 Trans. Sec. **** Unknown; will fill in later **** 188 Reference This document 190 Number {TBA-3} 191 Description ECDSA Curve P-256 with SHA-256 192 Mnemonic ECDSAP256SHA256 193 Zone Signing Y 194 Trans. Sec. **** Unknown; will fill in later **** 195 Reference This document 197 Number {TBA-4} 198 Description ECDSA Curve P-384 with SHA-384 199 Mnemonic ECDSAP384SHA384 200 Zone Signing Y 201 Trans. Sec. **** Unknown; will fill in later **** 202 Reference This document 204 8. Security Considerations 206 The cryptographic strength of ECDSA with curve P-224, P-256 or P-384 207 is generally considered to be equivalent to half the size of the key, 208 or 112 bits, 128 bits, and 192 bits, respectively. Such an 209 assessment could, of course, change in the future if new attacks that 210 work better than the ones known today. 212 9. References 214 9.1. Normative References 216 [FIPS-180-3] 217 National Institute of Standards and Technology, U.S. 218 Department of Commerce, "Secure Hash Standard (SHS)", 219 FIPS 180-3, October 2008. 221 [FIPS-186-3] 222 National Institute of Standards and Technology, U.S. 223 Department of Commerce, "Digital Signature Standard", 224 FIPS 186-3, June 2009. 226 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 227 Requirement Levels", BCP 14, RFC 2119, March 1997. 229 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 230 Rose, "DNS Security Introduction and Requirements", 231 RFC 4033, March 2005. 233 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. 234 Rose, "Resource Records for the DNS Security Extensions", 235 RFC 4034, March 2005. 237 [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. 238 Rose, "Protocol Modifications for the DNS Security 239 Extensions", RFC 4035, March 2005. 241 [RFC4509] Hardaker, W., "Use of SHA-256 in DNSSEC Delegation Signer 242 (DS) Resource Records (RRs)", RFC 4509, May 2006. 244 [RFC5114] Lepinski, M. and S. Kent, "Additional Diffie-Hellman 245 Groups for Use with IETF Standards", RFC 5114, 246 January 2008. 248 [RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS 249 Security (DNSSEC) Hashed Authenticated Denial of 250 Existence", RFC 5155, March 2008. 252 9.2. Informative References 254 [RFC4634] Eastlake, D. and T. Hansen, "US Secure Hash Algorithms 255 (SHA and HMAC-SHA)", RFC 4634, July 2006. 257 [RFC5430] Salter, M., Rescorla, E., and R. Housley, "Suite B Profile 258 for Transport Layer Security (TLS)", RFC 5430, March 2009. 260 Author's Address 262 Paul Hoffman 263 VPN Consortium 265 Email: paul.hoffman@vpnc.org