INTERNET-DRAFT Donald Eastlake 3rd
Motorola
Expires: October 2001 April 2001
Additional XML Digital Signature URIs
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<draft-eastlake-xmldsig-uri-00.txt>
Status of This Document
Distribution of this draft, which is intended to become an
Informational RFC, is unlimited. Comments should be sent to the
author or the XMLDSIG working group <w3c-ietf-xmldsig@w3.org>.
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026. Internet-Drafts are
working documents of the Internet Engineering Task Force (IETF), its
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The list of current Internet-Drafts can be accessed at
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Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
A number of algorithm URIs intended for use with XML Digital
Signatures are defined.
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Table of Contents
Status of This Document....................................1
Copyright Notice...........................................1
Abstract...................................................1
Table of Contents..........................................2
1. Introduction............................................3
2. URIs....................................................3
2.1 Message Digests........................................3
2.1.1 MD5..................................................3
2.1.2 SHA-256..............................................4
2.1.3 SHA-512..............................................4
2.1.4 SHA-384..............................................4
2.2 Message Authentication Codes...........................5
2.2.1 HMAC-MD5.............................................5
2.2.2 HMAC-SHA-256.........................................6
2.2.3 HMAC-SHA-512.........................................6
2.2.4 HMAC-SHA-384.........................................6
2.3 Signature Algorithms...................................7
2.3.1 RSA-MD5..............................................7
2.3.2 RSA-SHA-256..........................................7
2.3.3 RSA-SHA-512..........................................7
2.3.4 RSA-SHA-384..........................................7
2.4 Canonicalizaton Algorithms.............................7
2.4.1 Minimal Canonicalization.............................7
2.5 Transform Algorithms...................................8
3. IANA Considerations.....................................8
4. Security Considerations.................................8
References.................................................9
Authors Addresses..........................................9
Full Copyright Statement..................................10
Expiration and File Name..................................10
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1. Introduction
XML Digital Signatures have been standardized by the joint IETF/W3C
XMLDSIG working group. The Proposed Standard is specified in [RFC
3075]. In addition, Canonical XML, which is used by many digital
signatures, has been standardized by the W3C and is documented in
Informational [RFC 3076].
[RFC 3075] specifies URIs to identify algorithms. However, this
ppotocol is likely to be raised to Draft Standard soon, which
requires two independent interoperable implementations to exist.
This may require algorithms in which there appears to be substantial
interest to be dropped. This document is intended as a convenient
reference list of URIs and descriptions for any dropped from the
Proposed Standard due to lack of implementations plus additional
suggested algorithms in which there appears to be substantial
interest.
2. URIs
The sections below parallel those in Section 6 of RFC 3075 which
group various algorithms by there use in XML Digital Sigantures.
2.1 Message Digests
2.1.1 MD5
Identifier:
http://md.xmldsig.ietf.arpa#md5
The MD5 algorithm [RFC 1321] takes no explicit parameters. An example
of an MD5 DigestAlgorithm element is:
<DigestMethod Algorithm="http://md.xmldsig.ietf.arpa#md5"/>
An MD5 digest is a 128-bit string. The content of the DigestValue
element shall be the base64 [RFC 2045] encoding of this bit string
viewed as a 16-octet octet stream.
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2.1.2 SHA-256
Identifier:
http://md.xmldsig.ietf.arpa#sha256
The SHA-256 algorithm [SHA-256] takes no explicit parameters. An
example of a SHA-256 DigestAlgorithm element is:
<DigestMethod Algorithm="http://md.xmldsig.ietf.arpa#sha256/>
A SHA-256 disgest is a 256 bit string. The content of the
DigestValue element shall be the base64 [RFC 2045] encoding of this
string viewed as a 32-octet stream.
2.1.3 SHA-512
Identifier:
http://md.xmldsig.ietf.arpa#sha512
The SHA-512 algorithm [SHA-512] takes an optional truncation
parameter, SHAtruncation, in the range 0 to 512. An example of a
SHA-512 DigestAlgorithm element with such a parameter is:
<DigestMethod Algorith="http://md.xmldsig.ietf.arpa#sha512">
<SHAtruncation>400</SHAtruncation> </DigestMethod>
A SHA-512 digest is a 512 bit string except that, if the
SHA512truncation parameter is present specifying truncation to n
bits, it is the left most n bits of that string. In effect, the
truncation parameter defaults to 512.
Schema Definition:
<simpleType name="SHAtruncation">
<restriction base="integer"/> </simpleType>
DTD:
<!ELEMENT SHAtruncation (#PCDATA)>
2.1.4 SHA-384
Identifier:
http://md.xmldsig.ietf.arpa#sha384
The SHA-384 algorithm [SHA-384] takes an optional truncation
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parameter, SHAtruncation, in the range 0 to 512. An example of a
SHA-384 DigestAlforithm element without such a parameter is:
<DigestMethod Algorith="http://md.xmldsig.ietf.arpa#sha384"/>
A SHA-384 digest is the leftmost 384 bits of the 512 bit string that
the algorithm calculates internally except that, if the SHAtruncation
parameter is present specifying truncation to n bits, it is the left
most n bits of that string. In effect, the truncation parameter
defaults to 384. (The SHA-384 algorithm has the same internal
structure as the SHA-512 algorithm but a few different constants are
used, resulting in a different 512 bit hasj value, and it is normally
truncated to 384 bits.
See Schema Definition and DTD for SHA-512 above.
2.2 Message Authentication Codes
Some text in this section is duplicated from RFC 3075 for the
convenience of the reader.
2.2.1 HMAC-MD5
Identifier:
http://mac.xmldsig.ietf.arpa#hmac-md5
The HMAC algorithm (RFC2104 [HMAC]) takes the truncation length in
bits as a parameter; if the parameter is not specified then all the
bits of the hash are output. An example of an HMAC SignatureMethod
element:
<SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#hmac-
md5">
<HMACOutputLength>112</HMACOutputLength>
</SignatureMethod>
The output of the HMAC algorithm is ultimately the output (possibly
truncated) of the chosen digest algorithm. This value shall be base64
encoded in the same straightforward fashion as the output of the
digest algorithms. Example: the SignatureValue element for the HMAC-
MD5 digest
9294727A 3638BB1C 13F48EF8 158BFC9D
from the test vectors in [RFC 2104] would be
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<SignatureValue>kpRyejY4uxwT9I74FYv8nQ==</SignatureValue>
Schema Definition:
<simpleType name="HMACOutputLengthType">
<restriction base="integer"/> </simpleType>
DTD:
<!ELEMENT HMACOutputLength (#PCDATA)>
The Schema Definition and DTD immediately above are copied from RFC
3075.
Although some cryptographic suspicions have recently been cast on MD5
for use in signatures such as RSA-MD5 below, this does not effect use
of MD5 in HMAC.
2.2.2 HMAC-SHA-256
Identifier:
http://mac.xmldsig.ietf.arpa#hmac-sha256
SHA-256 [SHA-256] can also be used in HMAC as described in section
2.2.1 above.
2.2.3 HMAC-SHA-512
Identifier:
http://mac.xmldsig.ietf.arpa#hmac-sha512
SHA-512 [SHA-512] can also be used in HMAC as describe in section
2.2.1 above.
2.2.4 HMAC-SHA-384
Identifier:
http://mac.xmldsig.ietf.arpa#hmac-sha384
SHA-384 [SHA-384] can also be used in HMAC as described in section
2.2.1 above.
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2.3 Signature Algorithms
2.3.1 RSA-MD5
Identifier:
http://sig.xmldsig.ietf.arpa#rsa-md5
Due to increases in computer processor power and advances in
cryptography, use of RSA-MD5 is not recommended.
2.3.2 RSA-SHA-256
Identifier:
http://sig.xmldsig.ietf.arpa#rsa-sha256
2.3.3 RSA-SHA-512
Identifier:
http://sig.xmldsig.ietf.arpa#rsa-sha512
2.3.4 RSA-SHA-384
Identifier:
http://sig.xmldsig.ietf.arpa#rsa-sha384
2.4 Canonicalizaton Algorithms
2.4.1 Minimal Canonicalization
At this time there are not two independent interoperable
implementations of Minimal Canonicalization. Therefore, when XML
Digital Siganture is advanced from Proposed Standard to Draft
Standard, it must be dropped from the standard track documents.
However, there is still substantial interest and indicates of
possible future use for Minimal Canonicalization which can be found
in [RFC 3075], Section 6.5.1.
For reference, it's identifier is:
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http://www.w3.org/2000/09/xmldsig#minimal
2.5 Transform Algorithms
None included at present.
(Java?)
3. IANA Considerations
TBD.
4. Security Considerations
TBD.
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References
[RFC 1321] - "The MD5 Message-Digest Algorithm", R. Rivest, April
1992.
[RFC 2104] - "HMAC: Keyed-Hashing for Message Authentication", H.
Krawczyk, M. Bellare, R. Canetti, February 1997.
[RC 2045] - "Multipurpose Internet Mail Extensions (MIME) Part One:
Format of Internet Message Bodies", N. Freed, N. Borenstein, November
1996.
[RFC 3075] - "XML-Signature Syntax and Processing", D. Eastlake, J.
Reagle, D. Solo, March 2001. <http://www.w3.org/TR/2000/CR-
xmldsig-core-20001031>
[RFC 3076] - "Canonical XML Version 1.0", J. Boyer, March 2001.
<http://www.w3.org/TR/2001/REC-xml-c14n-20010315>
[SHA-256] -
[SHA-384] -
[SHA-512] -
Authors Addresses
Donald E. Eastlake 3rd
Motorola
155 Beaver Street
Milford, MA 01757 USA
Telephone: +1-508-634-2066 (h)
+1-508-261-5434 (w)
FAX: +1-508-261-4447 (w)
EMail: Donald.Eastlake@motorola.com
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Full Copyright Statement
Copyright (C) The Internet Society (2001). All Rights Reserved.
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Expiration and File Name
This draft expires October 2001.
Its file name is draft-eastlake-xmldsig-uri-00.txt.
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