using System;

using System.Collections.Generic;

using System.Net.Http;

using System.Security.Cryptography;

using System.Text;

public class Program

{

    public static Encoding encoding = Encoding.UTF8;

​

    public static void Main()

    {

           var keytest =

                "0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF";

            var msg = "toto";

​

            var binKey = pack(keytest);

            var hmac = string.Empty;

            var keyByte = encoding.GetBytes(binKey);

            using (var hmacsha512 = new HMACSHA512(keyByte))

            {

                hmacsha512.ComputeHash(encoding.GetBytes(msg));

                hmac = ByteToString(hmacsha512.Hash);

            }

​

            Console.WriteLine(hmac);

        }

        public static string ByteToString(byte[] buff)

        {

            string sbinary = "";

            for (int i = 0; i < buff.Length; i++)

                sbinary += buff[i].ToString("X2");

            return sbinary;

        }

        private static string pack(string input)

        {

            return Encoding.Default.GetString(FromHex(input));

        }

        public static byte[] FromHex(string hex)

        {

            hex = hex.Replace("-", "");

            byte[] raw = new byte[hex.Length / 2];

            for (int i = 0; i < raw.Length; i++)

            {

                raw[i] = Convert.ToByte(hex.Substring(i * 2, 2), 16);

            }

            return raw;

        }

}