-1

I was able to sign a pdf file using GOST3411 digest and ECGOST3410 signature algorithm. Now, I want Adobe Reader to read the signature, but it says that there is no digest algorithm or digest is unknown. Whatever, the reader could not decrypt signature in document. If anybody have an approach to solved that problem, please, help.

Thanks!

divanov
  • 6,173
  • 3
  • 32
  • 51
Big Sam
  • 29
  • 8
  • Does my answer answer your question? – mkl May 24 '16 at 09:41
  • I know that it's posible to create a plugin for pdf and use it for custom algorithms, but could not find any piece of code or example how to make it work. I already have a code signing certificate. Also I've asked this questions in Adobe forum, but there is no answer yet. Your answer did not solve my problem, but thank you anyway, it contains usefull information. – Big Sam May 25 '16 at 03:14
  • Ok. Unfortunately I cannot help with details; the last time I wrote an Acrobat plugin was in the 20th century ;), and that wasn't even a security related one. I would propose starting from reading the Acrobat Digital Signature API I linked in my answer (or a newer version if available). – mkl May 25 '16 at 06:55

2 Answers2

1

The PDF specification ISO 32000-1 clearly states which algorithms may be used in PDFs for interoperability:

Table 257

The signature related code in Adobe Reader is implemented along the lines of this specification, its successor ISO 32000-2 (which still is work-in-progress), and the ETSI PAdES specifications. Neither of those mentions any GOST algorithm. Thus, by default Adobe Reader does not support GOST.

If you need Adobe Reader to support such non-standard signatures (non-standard in respect to their use in PDFs), you can implement an Acrobat plug-in signature handler enabling it to work with GOST. Of course you still have to roll out the handler to your users.

In the (old) Technical Note #5192 the Acrobat Digital Signature API (which your signature handler would have to interact with) is documented.

Beware, to use an own signature handler in the free Acrobat Reader, you will probably need to buy a specific code signing key from Adobe

By the way, GOST might not be your only problem, Adobe Reader only supports a very limited set of curves for elliptic curve cryptography, and according to your previous question you are interested in ECGOST signatures.

mkl
  • 90,588
  • 15
  • 125
  • 265
1

Russian company CryptoPro created a free plugin (link only in Russian) for validation of GOST 34.10 signatures embedded in PDF. So you would need to either install this plugin or develop a similar one using Acrobat Digital Signature API.

divanov
  • 6,173
  • 3
  • 32
  • 51