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This is a Last Call XML Signature Requirements public Working Draft. This report is not expected to be advanced to Recommendation. Instead, this Last Call designation is (1) a representation of WG consensus, (2) an invitation for comments that will affect the future course of the technical specification, and (3) an opportunity to identify and obtain commitments regarding WG dependencies. This document will be referred to at least the W3C XML Plenary Interest Group and W3C Chairs Working Group. Last Call period ends when dependencies between WGs have been acknowledged and the Signature Chairs have procured commitments of review. This is expected to take six weeks from the date of publication.
This document attempts to capture the Working Group's consensus though it
contains points which are still uncertain or not well specified. Issues
which are still being actively discussed during the publication of this document
class="discuss" and rendered in navy by style sheet compliant
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This document lists the design principles, scope, and requirements for the XML Digital Signature specification. It includes requirements as they relate to the signature syntax, data model, format, cryptographic processing, and external requirements and coordination.
The XML 1.0 Recommendation [XML] describes the syntax of a class of data objects called XML documents. The mission of this working group is to develop a XML syntax used for representing signatures on digital content and procedures for computing and verifying such signatures. Signatures will provide data integrity, authentication, and/or non-repudiatability.
This document lists the design principles, scope, and requirements over three things: (1) the scope of work available to the WG, (2) the XML signature specification, and (3) applications that implement the specification. It includes requirements as they relate to the signature syntax, data model, format, cryptographic processing, and external requirements and coordination. Those things that are required are designated as "must," those things that are optional are designated by "may," those things that are optional but recommended are designated as "should."
Comment: Scenarios are being explored which examine the ability to sign without
requiring a manifest whereas the scope of the signed content is designated
by the relative placement of signature elements in the XML stream/tree. For
<html> .....</body><dsig xmlns="http://..."
xmlns="http://..."> ... </dsig></html>
Comment: A more formal definition of a signed resource is the following evaluates
as true "definition(inputs):constraints" where R is a resource., I is a resource
identifier (URI), and C is content (sequence-of-octects).
signed-resource(I, C, key, sig): there was some request R such that GET(R) = C and address(R) = I and sign-doc(C, key, sig)
sign-doc(C, key, sig): sig is the value of a strong one-way
function over content and key that yields C integrity/validity and K non-repudiability
The WG may specify security requirements that constrain the operation of these dependencies to ensure consistent and secure signature generation and operation. [Oslo]
Comment: A related requirement under consideration is requiring the specification
to support the ability to indicate those portions of a document one signs
via exclusion of those portions one does not wish to sign. This feature allows
one to create signatures that have document closure, retain ancestor information,
and retain element order of non-continuous regions that must be signed. We
are considering implementing this requirement via (1) a special
<dsig:exclude> element, (2) an exclude list accompanying
the resource locator, or (3) a request to change the XML-Fragment or XPointer
specifications to yield this functionality. See
for further discussion of this issue.
Comment: Another possibility is that an error should be generated, however it isn't where a conflict will be flagged between the various function and application layers regardless.
Comment: Members of the WG are very interested in signing and processing XML fragments and packaged components. Boyer asserts that [XML-fragment] does not "identify non-contiguous portions of a document in such a way that the relative positions of the connected components is preserved." Packaging is a capability critical to XML-Signature applications, but it is clearly dependent on clear trust/semantic definitions, package application requirements, and even cache-like application requirements. It is not clear how this work will be addressed.