Functional Explanation of Changes in XML Signature 1.1

2.1 Algorithms Added

• Add Elliptic Curve signature algorithms: ECDSA-SHA1 (OPTIONAL), ECDSA-SHA256 (REQUIRED), ECDSA-SHA384 (OPTIONAL), and ECDSA-SHA512 (OPTIONAL)
• Generally extend SHA beyond SHA-1
  • Add digest algorithms: SHA224 (OPTIONAL), SHA256 (REQUIRED), SHA384 (OPTIONAL), SHA512 (OPTIONAL)
  • Add RSA signing algorithms: RSAwithSHA256 (REQUIRED), RSAwithSHA384 (OPTIONAL),RSAwithSHA512 (OPTIONAL)
• Update canonicalization algorithms to reflect existing practice
  • Add Exclusive XML Canonicalization 1.0 (omits comments) REQUIRED.
  • Add Exclusive XML Canonicalization 1.0 (with Comments) RECOMMENDED.
• Add XPath Filter 2.0 as RECOMMENDED transform algorithm. (alternative to URI fragment identifiers).

For all algorithms added, algorithm identifiers and information were added to the specification.

2.2 Algorithms Changed

• Discourage use of SHA-1 but allow it for compatibility
  • SHA-1 use is DISCOURAGED (but support is still REQUIRED).
  • Added text to SHA-1 to state that use is DISCOURAGED (but still REQUIRED).
  • Added text to HMAC-SHA1 to state that use is DISCOURAGED
  • Change so that DSAwithSHA1 is only REQUIRED as Signature algorithm for Signature verification, but is OPTIONAL for Signature generation. Previously it was REQUIRED for both.
  • Added text to indicate that use of RSA-SHA1 and ECDSA-SHA1 is DISCOURAGED.
• Enable alternatives to SHA-1
  • Changed HMAC-SHA256 to REQUIRED
  • Changed HMAC-SHA384, HMAC-SHA512 to RECOMMENDED (from OPTIONAL).
• Discourage use of XPath transform by adding a note that implementation requirements for XPath transform may be downgraded to optional in future version of specification.
• Added minimum output length for HMACOutputLength parameter in SignatureMethod

2.3 Other Algorithm-related Changes

• Clarify DSA family with respect to FIPS 186-3.
• Clarify RSA SignatureValue computation.
• Clarify inputs and outputs of algorithms, specifically Canonical XML 1.0 and Canonical XML 1.1 canonicalization, Base64, XPath filtering, and Enveloped Signature Transform, and XSLT Transform algorithms.
• Add recommendation to use least expressive transform possible to achieve result.

2.4 KeyInfo Changes

2.5 Clarifications

• Clarify that C14N is needed as part of Reference validation since changes could occur in serialization after Signature generation.
• Clarify canonicalization, removing Normalization Form C material.

2.6 Security Considerations Changes

• Note possible concerns with digest algorithm resistance to collisions and strongly recommending use of SHA-256 in preference to SHA-1
• Add new security consideration for implementations to limit information included in error responses for security algorithms.
• Add security considerations regarding DSA key sizes.

2.7 Other Changes

• No DTD use, XML Schema authoritative, RELAX NG informative.
• New 1.1 namespace for new 1.1 schema items