XML Signatures: Behind the Curtain - Signature Elements
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Take a look at the signature element. The data objects are first digested (a digest is fixed-length representation of a variable length data object and is created using an algorithm like SHA-1) and the resulting value is placed in an element (with other information). This element is then digested and cryptographically signed. The signature element has the following structure (where "?" denotes zero or one occurrence, "+" denotes one or more occurrences, and "*" denotes zero or more occurrences):
Listing 1
<Signature>
<SignedInfo>
(CanonicalizationMethod)
(SignatureMethod)
(<Reference (URI=)? >
(Transforms)?
(DigestMethod)
(DigestValue)
</Reference>)+
</SignedInfo>
(SignatureValue)
(KeyInfo)?
(Object)*
</Signature>
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