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From Jonathan Barbero <jonathan.barb...@gmail.com>
Subject Re: Detect modifications between signatures
Date Thu, 03 Nov 2016 13:43:13 GMT
Hi Tilman,

 Yes, I want to do that.
I'm going to look at the COS tree structure.

Thanks!

On Wed, Nov 2, 2016 at 4:10 PM, Tilman Hausherr <THausherr@t-online.de>
wrote:

> Am 29.10.2016 um 18:47 schrieb Jonathan Barbero:
>
>> Hi,
>>
>>   How could I detect any modification between two signatures (visibles or
>> not) ?
>>
>> For example:
>>
>>   An application signs a PDF with PDFbox. A user downloads it, and should
>> sign it (visible signature). I would like to check that the user didn't
>> add
>> any modification after the app signature (except it's own user signature).
>>
>> How could I check it? I guess it's different between a visible signature
>> and not visible.
>>
>
> I assume that what you want is to have something similar to Adobe Reader,
> which can detect whether users did more than just add a signature, and then
> tells "page X was changed".
>
> I can't think of a way to do this out of the box. Maybe compare the COS
> tree of both PDF structures.
>
> Tilman
>
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