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Topic: About Security Handler
Conf: (P-PDF) Developers, Msg: 75572
From: DC06
Date: 11/1/2002 02:37 PM

I got a problem when developing security and signature handlers
plug-in in Acrobat. How can I
tell Acrobat that one document has already been opened such that it
can eliminate the reopening of the document.

I started the development using the plugin samples in the Acrobat SDK,
namely SecurityHandler
and SignDoc. They both work well independently. But problem comes when
they work together...

After I encrypt a document using SecurityHandler plugin, I can sign
the encrypted document very smoothly for the very first time. After
one signature is applied, whenever I want to add a new signature on
the encrypted document, it prompts a dialog asking for password in
order to modify the contents. This is due to the reopening of the
encrypted document in Acrobat, but I don't think this is a necessary
step for each signature if the document is already opened by the
document owner or a person with full access right.

As comparison, I tried using the self-sign security in Acrobat. First,
I encrypted the document using Self-Sign Security Handler, then I
apply multiple signatures on the encrypted document, it never prompt
for password again after the first logging in. I doubted how it is
implemented in Acrobat.

I have inspected the Core API and Digital Signature API, I found that
when the document is signed for its first time, Acrobat somehow does a
full save operation. After that, even though the session is valid and
the document is still being opened in Acrobat, whenever I want to
sign, it reopens the document again in its memory. The reopening will
inspect the access rights of the document and then start the
authorization procedure again, which consequently prompt the password
dialog box again. Such procedure is very inconvenient, I want to learn
from Acrobat Self-Security model, but no information is available.

The operation is done by the internal callbacks started by Acrobat, I
would like to know more how to eliminate the checking again. For
example, How can I tell Acrobat that the document has already been
opened such that it can bypass the checking again.

There are not many experts doing the security and digital signature
plugins for Acrobat, I have tried very hard to solve the problem but
in vain. Could any one tell me the secrets inside or any pointers to
solve the problem and my frustration ? Thank you very much.

David


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