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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