Encoding enc = Encoding.GetEncoding("ASCII");
string key = "53fa36cd57881e5a68e1c70558028b9dded8d72fbb1ea18f42832174313a5753";
string packet = project.Variables["input_string"].Value;
System.Security.Cryptography.HMACSHA256 hm = new System.Security.Cryptography.HMACSHA256(enc.GetBytes(key));
byte[] result = hm.ComputeHash(enc.GetBytes(packet));
String hex = BitConverter.ToString(result);
hex = hex.Replace("-", "");
return hex.ToLower();