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Invalid signature after Signing PDF - "document has been changed"

Also by EldoS: MsgConnect
Cross-platform protocol-independent communication framework for building peer-to-peer and client-server applications and middleware components.
#13919
Posted: 07/15/2010 03:06:52
by Roman Krejci (Basic support level)
Joined: 07/15/2010
Posts: 8

I have an evaluation version of EldoS blackbox for Delphi (D7) downloaded just yesterday (july 14 2010). I managed to compile the "TinySigner" demo project with Delphi 7. As an input PDF I use a PDF created by PDF Creator. The destination file is set to non existing PDF file name. The Certificate is selected from system cert store. All other fields are left default. After processing the program reports success. However, after opening the destination PDF with AdobeReader 9.3.3, reader reports that the signature is invalid because the document has been changed since signing. What can be wrong?
Thank you for any suggestion.

Roman Krejci
#13920
Posted: 07/15/2010 03:13:45
by Ken Ivanov (EldoS Corp.)

Thank you for contacting us.

Could you please post the document that can be used to reproduce the issue here? It would be great to have both unsigned and signed versions.
#13921
Posted: 07/15/2010 04:25:41
by Roman Krejci (Basic support level)
Joined: 07/15/2010
Posts: 8

Many thanks for the quick response.
I attached a zip with two pdfs


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#13928
Posted: 07/15/2010 08:22:31
by Dmytro Bogatskyy (EldoS Corp.)

This pdf document is not well-formed. It have an extra whitespace characters in entries in the cross-reference section. Normally Adobe ignores them, but in verification stage this could matter.
I attached a zip with a fixed pdf document that should sign ok.
In fact we already have a workaround for this issue, but it is not publicly available yet (will be included in the next version).


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#13929
Posted: 07/15/2010 09:10:32
by Roman Krejci (Basic support level)
Joined: 07/15/2010
Posts: 8

Many thanks for the quick response.
Unfortunately, the "not well formed" document
has been created by widely used tool, so I am
afraid the customers will insist on having
the option to sign it :-(. May I ask when
approximately will the workaround be available?
Thanks again and best regards

Roman Krejci
#13940
Posted: 07/16/2010 02:34:16
by Ken Ivanov (EldoS Corp.)

We are preparing the build at the moment. It is likely to be made available in the middle of next week.
#13941
Posted: 07/16/2010 02:56:43
by Roman Krejci (Basic support level)
Joined: 07/15/2010
Posts: 8

I just tried the altered test-mod.pdf (the well-formed version)
attached to message from Bogatskyy. Unfortunately, after
signing this PDF with TinySigner, the situation remains the same.
That is, AcrobatReader 9.3.3 reports that the document has been
changed after signing. Again, I am attaching a zip with two PDFs
(original and signed). The same error occurs with PDFs of different
origin (that is, even with those not created by PDFCreator)

Could this be a limitation of the trial version?

Bast regards

Roman Krejci


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#13942
Posted: 07/16/2010 04:15:45
by Dmytro Bogatskyy (EldoS Corp.)

Quote
The same error occurs with PDFs of different
origin (that is, even with those not created by PDFCreator)

Quote

The Certificate is selected from system cert store.

Possible my assumption about what causing this issue was wrong or incomplete.
Could you please try to sign with a test certificate from "%ProgramFiles%\EldoS\SecureBlackbox\Extra\Certificates"
Quote

Could this be a limitation of the trial version?

No, it shouldn't
#13943
Posted: 07/16/2010 05:44:23
by Roman Krejci (Basic support level)
Joined: 07/15/2010
Posts: 8

Hi Dmytro,
I tried to sign the test-mod.pdf by using certificate in the file
cert_no_pwd.pfx, as you suggested. However, on the
Document.Close(Success);
line of the TinySigner project in the routine
procedure TfrmMain.btnOKClick(Sender: TObject);
an exception has been raised with message:
"Error: No signing certificate found"
Variable success was TRUE at the moment of call.
No signed PDF is created.

If I import the certificate from cert_no_pwd.pfx into system store,
the certificate imports OK and I can select it in TinySigner combo
and no error occurs. However, the resutlting signed PDF file
is still reported as modified after signing by the reader.

configuration: Delphi 7, Win7

Roman Krejci
#13945
Posted: 07/16/2010 08:40:27
by Dmytro Bogatskyy (EldoS Corp.)

It rather strange.
Let's clarify a few things:
Did you had any previous version of SecureBlackbox?
Did you downloaded and installed latest version "SecureBlackbox for Delphi 4-7 - Version 8.0.176 (58923 Kb) . Released on 05/23/2010" available at: http://eldos.com/sbb/download-release.php
Because we checked this version with certificate "cert_no_pwd.pfx" with document "test-mod.pdf" on Windows 7 and Windows XP, and everything work fine.
Also by EldoS: CallbackFilter
A component to monitor and control disk activity, track file and directory operations (create, read, write, rename etc.), alter file data, encrypt files, create virtual files.

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