HashAlgorithm myhash = HashAlgorithm.Create("GOST3411");
            using (fsh = new FileStream(MessageDirPath,
                FileMode.Open, FileAccess.Read, FileShare.Read))
            {
                myhash.ComputeHash(fsh);
            }
            byte[] hashValue = myhash.Hash;
            fsh.Dispose();
            FileStream fileSt = new FileStream(HashPath, FileMode.OpenOrCreate,
               FileAccess.ReadWrite, FileShare.ReadWrite);
            fileSt.Write(hashValue, 0, hashValue.Length);
            fileSt.Dispose();
            myhash.Clear();

            //Подписываем хеш
            byte[] SignedHashValue = GostFormatter.CreateSignature(hashValue);
            FileStream fileStl = new FileStream(SignatureFilePath, FileMode.OpenOrCreate,
               FileAccess.ReadWrite, FileShare.ReadWrite);
            fileStl.Write(SignedHashValue, 0, SignedHashValue.Length);
            fileStl.Dispose();
            myhash.Clear();