18.3. Message Authentication Codes
A Message Authentication Code (MAC) is calculated from the data to be authenticated and a secret quantity. The HMAC algorithm [RFC 2104] is the basis of all MACs that XML Security specifies, although other strong MAC techniques exist as well [Schneier]. You can use the HMAC algorithm with any hash code.
MAC algorithm identifiers appear as the value of the Algorithm attribute of SignatureMethod elements, as shown in Figure 18-3. Their implicit inputs consist of their keying material and the octet stream output by the signature's CanonicalizationMethod. MACs are syntactically identical to signatures but imply a shared secret key.
Figure 18-3. SignatureMethod algorithms
18.3.1. HMAC SHA-1
HMAC SHA-1 Identifier: ...
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