Digital signature validation fails

[Lisa_lee]

kryukds ,We apologize for the trouble. Please help to send us the PDF file which coudl reproduce the issue you mentioned to [email protected](Attn.Lisa) and also indicate this thread link when you mail to us.

Look forward to your reply.

[kryukds]

The same issue reproduced with Windows natively available cryptography. The source PDF was produced with Microsoft Office Word 2010 (Save As - PDF) and signed with Foxit Reader 10.

The forum doesn't accept the PDF file reproducing this for some reason.

[richell_huang]

Validate a digital signature If the signature status is invalid, contact the signer about the problem. ... Open the PDF containing the signature, then click the signature.

gost certification

Could you please describe the signature issue you encountered in detail so we can better understand and further advise? Thank you.

[safurazaffir]

Validate a digital signature If the signature status is invalid, contact the signer about the problem. ... Open the PDF containing the signature, then click the signature.

gost certification

[amanda_liang]

kryukds sorry for the inconvenience. I have reported the issue to QA team for checking by ID#QCPHANTOM-25335, any updates will inform you. tks

[kryukds]

I'm trying to validate a digitally signed PDF document from one of Russian state services. Russian law requires the use of GOST R 43.11-2012 hash algorithm and GOST R 34.10-2012/34.11-2012 digital signature algorithm, so I downloaded and installed the VipNET CSP that implements this algorithm.
I have tried several PDF readers to verify the signature. The good thing to note is that Foxit Reader was the only one to say: "The document has not been modified since this signature was applied". It means that the cryptography in charge of verifying the signature was actually called and that it worked correctly.
The bad thing is that it failed to trust the signer certificate despite having the root certificate installed (both in Windows and in Foxit Reader). If I install the signer's certificate as trusted in Foxit Reader, it tells the signature is valid.
Why does Foxit Reader fail to trust the signer's certificate based on the root certificate?
Attached:
1) The document ul-1025500508593-20200506153538.pdf
2) Certificates certs.zip
3) Screenshot of Windows certificate viewer
4) Screenshot of Foxit Reader trusted certificate list