Telerik signed PDFs aren't recognized due to time stamp

[Tim]

I've obtained a x509 signing certificate and able to use it with Telerik PDF processing to generate a signed PDF. The problem is that none of the signatures are valid because of the time stamp!

There doesn't appear to be any way to insert a TSA timestamp with the signing flow.

How can I fix this, the Telerik signatures are useless otherwise.

Thanks!

[Dess | Tech Support Engineer, Principal]

Hello, Tim,

I am sorry to hear that you are facing any difficulties with the PdfProcessing library.

Currently, the PdfProcessing library allows you to sign PDF documents using an X509 certificate, but it does not provide built-in support for embedding a trusted timestamp from a Time Stamping Authority (TSA) into the digital signature. This is why PDF viewers like Adobe Acrobat may flag the signature as invalid or untrusted due to the missing timestamp.

This functionality is related to a feature request we already have logged in our Feedback Portal. You can cast your vote for the item, track its progress, subscribe for status changes, and add your comments on the following link:  PdfProcessing: Provide API for enabling Long-Term Validation (LTV)

It would be greatly appreciated if you can provide more details about:

- Are you required to use a specific TSA or follow a particular validation policy for your signed PDFs?
- Which PDF viewers or validation tools are you using to check the signatures?
- Is your primary goal to ensure long-term validation (LTV) or compliance with standards such as PAdES?

Thank you in advance for your cooperation.

Regards,
Dess | Tech Support Engineer, Principal
Progress Telerik

[Dess | Tech Support Engineer, Principal]

Hello, Tim,

I have noticed you provided the needed information in the public feature request item. However, I would like to have a closer look into the digitally signed documents which are indicated as invalid in Adobe Reader that you mentioned.

The current functionality offered by RadPdfProcessing can be tested in our online demo:

PdfProcessing Digitally Sign Document Demo

The produced PDF document is digitally signed with a certificate and it is indicated as VALID:

Could you please give it a try and let me know how it works on your end?

Regards,
Dess | Tech Support Engineer, Principal
Progress Telerik

[Tim]

Thanks Dess for your quick response!!

I'm not going to upload my x509 and password, but I try a self-signed SSL with that online demo you shared. Unfortunately I got the same time issue. Perhaps I have a policy on my PDF clients / computer that requires TSA for signed PDFs? Would it be possible to share the PDF you generated (and indicated as VALID) so I can check your PDF with my PDF client?

[Dess | Tech Support Engineer, Principal]

Hello, Tim,

I have attached my sample document for your reference that was generated with the demo and a sample certificate used widely in the demo examples of multiple Telerik products.

Since this is a public forum, it is understandable that you are concerned about sharing any confidential information. I can offer you creating a private support ticket on your behalf. If that fits for you, please just let me know. You can also do it directly from your Telerik account. You can be certain that any documents provided in support tickets will be used only for investigation purposes of this case and your privacy will be respected. Confidentiality is also described in our product EULA - See Section 11 of the EULA and Article V Section 11 of the DevCraft Complete and DevCraft Ultimate EULAs. 

Should you have further questions please let me know.

Regards,
Dess | Tech Support Engineer, Principal
Progress Telerik