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Differentiate each type of change made to PDF after signed?

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#20613
Posted: 06/26/2012 07:00:01
by Draycir Thailand (Standard support level)
Joined: 04/03/2012
Posts: 9

i can use the Signature's getSignedVersion() and compare to the current file to detect change. but i'm wondering if i can further identify if there is actual change to the document itself or not?
if user just filled in the form field
add additional signature
add note
or actually modifying the document itself

Does SBB provide an easy way to do this? without me going into bytestream level to manually compare it?
#20614
Posted: 06/26/2012 07:17:40
by Vsevolod Ievgiienko (EldoS Corp.)

Hello.

Its impossible to check this in all cases. The only way is to check if signature is corrupted, but this will not happen if, for an instance, user added additional signature.
#20625
Posted: 06/26/2012 23:02:56
by Draycir Thailand (Standard support level)
Joined: 04/03/2012
Posts: 9

Not even in case of subsequent signature?
i mean if we have 2 signatures one right after the other without any change in between, couldn't we get signature1.getSignedVersion() compare to signature2.getSignedVersion() and check if the different is just the signature1 ??
any work around for this? as Adobe seem to be able to detect this kind of change
#20626
Posted: 06/27/2012 00:20:31
by Eugene Mayevski (EldoS Corp.)

Of course you can do what you describe as well as you can do object-to-object comparison of PDF structure, and this is likely what Adobe does. But PDFBlackbox is not a general PDF manipulation library and while we do build PDF structure inside, it's not available externally and SecureBlackbox doesn't do or offer any comparison techniques itself. This is beyond the scope of its functionality.


Sincerely yours
Eugene Mayevski

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