TElXMLSignaturePolicyIdentifier class

    The following paragraphs were taken from the W3C note XML Advanced Electronic Signatures (XAdES):

    « The electronic signature can contain an explicit and unambiguous identifier of a Signature Policy together with a hash value of the signature policy, so it can be verified that the policy selected by the signer is the one being used by the verifier. An explicit signature policy has a globally unique reference, which, in this way, is bound to an electronic signature by the signer as part of the signature calculation. In these cases, for a given explicit signature policy there shall be one definitive form that has a unique binary encoded value. Finally, a signature policy identified in this way may be qualified by additional information. »

    « Alternatively, the electronic signature can avoid the inclusion of the aforementioned identifier and hash value. This will be possible when the signature policy can be unambiguously derived from the semantics of the type of data object(s) being signed, and some other information, e.g. national laws or private contractual agreements, that mention that a given signature policy must be used for this type of data content. In such cases, the signature will contain a specific empty element indicating that this implied way to identify the signature policy is used instead the identifier and hash value. »

If the first aforementioned possibility is applicable, than SignaturePolicyID element will appear, in another case, SignaturePolicyImplied property will be set to True.