/// <summary>
            /// 
            /// </summary>
            /// <param name="_cert">Сертификат</param>
            /// <param name="_data">Массив байт шифруемой строки</param>
            /// <returns></returns>
static public byte[] GetDetachedSignatureBase64(X509Certificate2 _cert, byte[] _data)
        {
            Gost3410CryptoServiceProvider gost = (Gost3410CryptoServiceProvider)_cert.PrivateKey;
            Gost3411CryptoServiceProvider gostHash = new Gost3411CryptoServiceProvider();

            byte[] signedValue = gost.SignData(_data, gostHash);
            return signedValue;
        }