Acrobat 9 Family of Products
Validating Signatures
Security Feature User Guide
Setting up Your Environment for Signature Validation 102
time a document is signed, a new digest is created. Thus, each signature is only valid for a specific version
of the document.
Because the application stores and numbers a document version for each signature, signature validators
can determine what was actually signed. When you validate a signature, a new message digest is created
and compared to the digest that was embedded in the document at signing time.
If the two digests are not identical the signature is invalid.
Both signers and signature validators should understand the following about the relationship between
signatures and document versions:
Every time a document is signed, the document’s state at the point of signing is stored in the PDF.
Versions are incrementally numbered beginning with “1.”
A document with 10 signatures will have 10 versions.
A signature applies to a version (e.g. signature X with version X and signature Y with version Y, etc.).
When you open a document in Adobe Acrobat or Adobe Reader, the current version always displays.
Note:
To learn more about how each signature results in a new version of the document, refer to
http:
//www.adobe.com/devnet/acrobat/pdfs/DigitalSignaturesInPDF.pdf
.
7.2 Setting up Your Environment for Signature Validation
Document recipients should configure their environment to handle incoming documents in a way that
enhances workflow efficiency or meets some business need. While Adobe Acrobat and Adobe Reader
provide default options, customizing the environment often provides a better user experience. In large,
enterprise environments, your environment may be preconfigured by a system administrator.
Options include the following:
Validating Signatures Automatically
: By default, validation occurs automatically. If signatures should
not be validated automatically when a document opens, turn this option off.
Setting Digital Signature Validation Preferences
: Accept the defaults or configure validation methods
such as plugin usage, time display, automatic revocation checking, and other settings.
Using Root Certificates in the Windows Certificate Store
: If you would like to trust and use certificates in
the Windows Certificate Store for signature validation, turn this option on. Trusting all of these
certificates is not recommended.
Controlling Multimedia
: When certified documents may contain multimedia, specify whether or not it
is allowed to run.
Certificate Trust Settings
: Specify whether a certificate should be a trust anchor, trusted for signing, and
trusted for certain behaviors in certified documents.
7.2.1 Validating Signatures Automatically
By default, signatures are automatically validated. However, you may want to turn it off for reasons such as:
You don’t care whether the signatures are valid.
The desktop cannot be configured to validate the signature.