2.1.7.21 XML Signatures Storage (_xmlsignatures)
The XML Signatures Storage is specified in [MS-OFFCRYPTO] section 2.5.2.
The name of this storage MUST be "_xmlsignatures". A file MUST contain at most one XML Signatures Storage<12>.
When generating the DigestValue, as specified in [XMLDSig] section 4.3.3.6, the record data, as specified in the Record section (section 2.1.4), in the WriteAccess record (section 2.4.349) in the Globals Substream (section 2.1.7.20.3) is skipped.