GOST R 34.10-2012 must be used with Streebog (GOST R 34.11-2012)
hash function. Its digest must be big-endian serialised. Signature
is in BE(R)||BE(S) format.
Algorithm identifiers for the signature: gost3410-256A,
gost3410-512C.
Streebog is GOST R 34.11-2012 hashing algorithm, RFC 6986. GOST R 34.10-2012 is signing/key-aggreement algorithm, RFC 7091.