I am wondering if I understand the following correctly:
0x40 Timestamp signature.
It is calculated directly on any document like a 0x00 signature (BTW, it
would probably makes sense to introduce a 0x41 timestamp for textual
documents), but the issuer of the signature does not claim authorship or
endorse the document, just states the fact that the document existed at the
time when the signature was issued.
This one I do not understand at all:
0x50 Third-Party Confirmation signature.
What is the signature calculated on? The document? The certified signature?
Both?
My guess would be that it is calculated on te document and includes in
one (or more) subpackets the canonical hash of the certified signature(s).
In this case the notary certifies the fact that the signatures are valid at
the time of issuing this signature.
But in this case a blind notary that certifies only the fact that the
signature has been made before the time of issuing the singature should use
standalone (0x02) signatures with a target signature subpacket. There is
absolutely no point in 0x50 signatures without target signature subpackets
in this setting, but I might have misunderstood something.
Thanks in advance for the clarification.
--
Daniel