4.3 library(xmldsig): XML Digital signature

See also

- http://www.di-mgt.com.au/xmldsig.html
- https://www.bmt-online.org/geekisms/RSA_verify
- http://stackoverflow.com/questions/5576777/whats-the-difference-between-nid-sha-and-nid-sha1-in-openssl

This library deals with XMLDSIG, RSA signed XML documents.

[det]xmld_signed_DOM(+DOM, -SignedDOM, +Options)

Translate an XML DOM structure in a signed version. Options:

key_file(+File)

File holding the private key needed to sign

key_password(+Password)

String holding the password to op the private key.

The SignedDOM must be emitted using xml_write/3 or xml_write_canonical/3. If xml_write/3 is used, the option layout(false) is needed to avoid changing the layout of the SignedInfo element and the signed DOM, which will cause the signature to be invalid.

[det]xmld_verify_signature(+DOM, +SignatureDOM, -Certificate, +Options)

Confirm that an ds:Signature element contains a valid signature. Certificate is bound to the certificate that appears in the element if the signature is valid. It is up to the caller to determine if the certificate is trusted or not.

Note: The DOM and SignatureDOM must have been obtained using the load_structure/3 option keep_prefix(true) otherwise it is impossible to generate an identical document for checking the signature. See also xml_write_canonical/3.