private byte[] ComputeHMacSHA256(string data, byte[] key) { var hmacSha256Algorism = new HMac(new Sha256Digest()); hmacSha256Algorism.Init(new KeyParameter(key)); var dataUtf8 = Encoding.UTF8.GetBytes(data); hmacSha256Algorism.BlockUpdate(dataUtf8, 0, dataUtf8.Length); var result = new byte[hmacSha256Algorism.GetUnderlyingDigest().GetDigestSize()]; hmacSha256Algorism.DoFinal(result, 0); return(result); }