Option to check if PDF was changed since last signed

[krupong]

How can I check pdf has not changed since last signed.

Please help !

Thanks !

[dealfonso]

Once the document has been signed, you can try to use the function get_revision and (maybe) function compare.

Taking doc A (original) and doc B (unknown), you can check if doc B is only 1 revision ahead of doc A, and the compare function only raises differences related to the nodes that are expected to change; probably the document is the same.

If you are using well-known products to sign documents (e.g., acrobat, autofirma, or others that you may know), you can check the signature structure of each of them to compare the differences and guess whether the doc has been modified or not (according to the changes are the expected or not).

Please, make a PR if you complete that task.

[dealfonso]

hi,
have you tried to make the verification?

[krupong]

Sorry,
I haven't tried yet.
To solve my problem, I count "%%EOF" compare with get_signature_count().

Something like this.

            $obj = PDFDoc::from_string(file_get_contents($file));
            preg_match_all("/%%EOF/", $content, $matches);
            $count = sizeof($matches[0]);
            
            $sigCount = $obj->get_signature_count();
            if ($count == $sigCount + 1) {
                $result = True; 
           } else {
               $result = False;
           }

It's works for me,but it hasn't been tested enough to make PR.
Thank you.