Signature validation in Adobe Acrobat
While SecureBlackbox produces signatures that are fully compliant with PDF specification, it is not guaranteed that other software will hadle them absolutly correct. This article summarizes known problems with validation and display of SecureBlackbox signatures in Adobe Acrobat. First thing to do if the signature is not shown, not validated or bad, is to check Acrobat's version, e.g., Acrobat 9 does not understand LTV signatures. Also, Acrobat is very sensitive to certificate validation, and you have ensure that all necessary certificate information is accessible, and the certificate chain is available.
Acrobat won't recognize a timestamp.
Acrobat is very sensitive to the TSP (Time-Stamping Protocol) reply received from the TSP server. For example, the certificate chain has to be completely validated by Acrobat in order for the timestamp to be detected. In addition, the certificate should contain the key usage field set in a specific way. Other problems with TSP replies could arise, such as slightly different DER encoding in TSP reply that might prevent Acrobat from handling the timestamp properly.