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Christiane2684282179o8
Participant
October 28, 2022
Question

Signature Validation error

  • October 28, 2022
  • 2 replies
  • 1722 views

Dear community,

 

We have errors in pdf forms which have a signature created using a smart card.

The sample signature in the screenshot was created in version 2021.007.20099 and when we click on validate we receive the below messages. 

We are sure the documents were not changed after the signature, because we uploaded/downloaded them from a part 11 compliant archive....

Could this be related to the comment in this post Adobe post

"When you mentioned that upgrading to 9.3 didn't fix the problem, did you mean when creating a new signature in Acrobat/Reader 9.3 or did you mean opening a previously signed file and doing the signature verification?

If you meant the later, no version of Acrobat will be able to decode the signature if it was created incorrectly, which is what I fear you are referring to. What happened was Acrobat 9.0 changed the default digest method from the older SHA-1 to the the new SHA-256, but if the device that encrypts the digest (the actual signing operation) cannot handle the larger digest Acrobat is supposed to fall back to the older, smaller SHA-1 digest. There was a bug where Acrobat wasn't re-computing the digest if the smart card couldn't handle SHA-256 and creating a corrupt signature. Once this corrupt signature is written out to the PDF file there is no getting around it. Update 9.3 fixes the problem at signature creation and you should be able to successfully sign using your CAC card, but sadly there is no fixing the existing corrupt signatures"

 

Kind Regards,

Christiane

This topic has been closed for replies.

2 replies

C
Christiane2684282179o8Author
Participant
October 28, 2022

It is a warning, you are right, it says in screenshot #1:

Signed and all signatures are valid, but with unsigned changes after the last signature. [...]
And in screenshot #2:
The revision of the document that was covered by this signature has not been altered; however, there have been subsequent changes to the document.

MikelKlink
MikelKlink
Participating Frequently
October 28, 2022

Such unexpected reports of changes may occur under a number of circumstances:

  • If there are certain kinds of errors in the PDF structure, Adobe Acrobat repairs the PDF during loading and displays warnings or even errors in the signature validation.
  • JavaScript code or other event triggered actions in the PDF may automatically apply changes to a document upon load or upon display of the initial page. Adobe Acrobat may display warnings or even errors because of such changes.
  • There actually may be changes after the last signature in the document you are not aware of.

Without the PDF in question, we can merely guess.

C
Christiane2684282179o8Author
Participant
October 31, 2022

Thanks for your feedback. Can you tell if the  2021.007.20099 version matches the 9.0 versionsß

MikelKlink
MikelKlink
Participating Frequently
October 28, 2022
quote

We have errors in pdf forms which have a signature created using a smart card.

I cannot recognize any errors in your screenshot.

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