What are the possible options for signing documents online, the user's digital signature, in accordance with GOST R 34.10-2012?

Question

Browsers

Good afternoon, I still do not quite have information on this topic. Tell me what options, perhaps,
the signatures of the archive, in the next. case:
The user has an EDS installed, he uploads the archive to our server, on the server he goes through the pre-processing :).
And it is necessary to send this archive back to the user for signature. The archive can weigh more than 50M.
I am considering using the browser api, but there is an assumption that this api can be used if
the document weighs no more than 25M.
Or can look at the sstunel-a settings?
Thanks

Answer 1

When you sign a file - in fact, this happens in 2 stages:
1) a hash is taken from the file (according to the appropriate algorithm, you will also have a guest one)
2) this hash is signed
Accordingly, the solution for you is this:
1) On the server, count the hash file and send it to the user for signing
2) the user signs the hash
You can do this through BouncyCastle
Or you can do it through the rutoken libraries
But OpenSSL will not work - in its current form it can take a guest hash, can sign a file, but it cannot sign a ready-made hash (unless what is to act not through the compiled executable file but through api)

Answer 2

If the developers of the crypto-library have already told you that there are file size limits, then why do you think that they will say something different here?
Divide the file into pieces (you can use the archiver to make multi-volume archives) and sign each part separately. True, on the receiving side it will be necessary to collect it back. If that side is not under your control, then this option disappears and there is only one thing left - to reduce the document to an acceptable size.