Acrobat 9 Family of Products
Validating Signatures
Security Feature User Guide
Validating Signature Timestamps 111
What is a timestamp?
A timestamp is like a signature inside of a signature. Like signatures, timestamps are provided by someone
(a timestamp authority) who uses a certificate to confirm their identity. A timestamp’s certificate must be
valid (not revoked by the issuer) and trusted (by you) for the timestamp to be valid. Timestamp certificate
status appears in the Date/Time and Summary tabs of the Signature Property dialog:
Untrusted timestamp certificates appear as follows:
Figure 79 Timestamps: Untrusted stamp
Trusted timestamps that have been added to the Trusted Identities list and have been explicitly trusted
for signing appear as follows:
Figure 80 Timestamps: Trusted stamp
How Do I Validate a Timestamp in a Signature?
Validating a timestamp is the process by which you check to see if the timestamp was applied and that its
certificate is valid. In order to validate a timestamp, you need to manually verify:
The timestamp was applied
: If a timestamp fails for some reason (the server cannot be found, the
network is down, etc.), timestamping fails silently.
The timestamp certificate is trusted
: If a timestamp was applied, the certificate must be trusted by
adding to your trusted identities list.
To verify that a signature has been properly timestamped:
1. Display the Signature Properties dialog by right clicking on any signature in the document or the
Signatures tab and choosing
Show Signature Properties
.
2. Choose the Date/Time tab. Timestamp status is indicated by the icon and associated text:
Warning triangle
: Timestamping failed or a timestamp is not present and the local time is used.
Verify the signer used a timestamp.
Magnifying glass
: A timestamp may have been used but you have not yet trusted the timestamp
certificate. Proceed to the next step.
Clock
: A timestamp with a trusted certificate was used.
Figure 81 Timestamps: Date/Time tab