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