Extract date/time value from digital signature on InfoPath2007

Question

I'd like to display the date/time value from a digital signature on an InfoPath form in a separate date/time field. Is this possible, or am I better off just customizing the submit button in the form section to stamp the date/time field?

Answer 1

You'll need to pick the right digital signature (there can be more than one) from the data, then pull the "Signing Time" from the "Signer Info" in the PKCS#7 data structure. See section 9.2 of RFC 2315 / PKCS#7.

You could write your own software to do it, or use a digital signature verification library.

The Windows CryptoAPI would be a starting place for a Windows Dev.

What to do

If you will already be needing to (later on) verify the digital signature(s), then just use that sw to get the signing date. If the only interest you have in the data's signature is the signing time, then it may be a lot simpler to instead record the "submit time" as you suggest in your original q.