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Adobe Acrobat SDK
Working with Acrobat Extended APIs
Developing Plug-ins and Applications
Digital signature components 231
To register a handler with PubSec, perform the following tasks:
1. Implement the callbacks you need to provide customized functionality. Many of the callbacks for
PubSec can be specified as NULL, in which case PubSec provides default behavior. It is recommended
that you use the default behavior when possible.
2. Fill in the handler structure with pointers to your callback implementations (PubSecHandler).
3. Register the handler with PubSec by invoking the
PSRegisterHandler
method.
Digital signature components
Digital signatures contain two parts:
●
The signature field dictionary which is the PDF dictionary structure that stores information about the
signature.
●
The signature annotation with its associated appearance (including the background and layout of
name, time, and so on). A blind digital signature does not have an associated appearance.
Acrobat’s digital signature plug-in creates these two parts when the user chooses to sign a document. Your
plug-ins do not have to handle deleting the signature, as the DigSig plug-in does that transparently.
Digital signature scenarios
Acrobat supports three digital signature scenarios. Acrobat’s Digital Signature plug-in handles the first
case, and allows other plug-ins to further handle the second and the third cases.
1. If the user creates a signature field and does not specify a default signing method, DigSig handles that
case with no communication to your plug-ins:
●
DigSig creates the signature field dictionary.
●
DigSig creates the signature annotation dictionary.
●
DigSig creates the (blank) signature appearance dictionary.
2. The Forms plug-in also creates Signature fields. If the user creates a signature field and specifies a
default method, Forms calls DigSig to fill in default values:
●
DigSig creates the signature field dictionary, the signature annotation dictionary, and the (blank)
signature appearance dictionary.
●
DigSig calls the DSDefaultValueProc callback that your plug-in provides. This callback must
create the default signature value dictionary and create the /DV key in the signature field
dictionary to point to it.
3. If the user asks to sign a specific signature field using the plug-in, DigSig invokes callbacks into your
plug-in during a four-step sequence. Your plug-in must register these callbacks during the plug-in
initialization phase. The four callbacks required for this scenario are:
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dsNewSigData
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dsCommitSign
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dsFinshSign
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dsFreeSigData