KExp15 (Р 1323565.1.017) key wrapping mechanism uses GOST cryptography algorithms. KEK is 32+8+32=72 bytes long. Kenc || IV || Kauth = KEK KExp15(Kenc, Kauth, IV, CEK) = Kuznechik-CTR( Kenc, CEK || Kuznechik-CMAC(Kauth, IV || CEK), IV=IV) Kuznechik is GOST R 34.12-2015 encryption algorithm, RFC 7801. => https://datatracker.ietf.org/doc/html/rfc7801.html RFC 7801 CMAC (OMAC1) is described in GOST R 34.13-2015.