using System;

using System.Security.Cryptography;

using System.Text;  

public class Program

{

    public static void Main()

    {

        string nonce = new DateTimeOffset(DateTime.UtcNow).ToUnixTimeSeconds().ToString();

        string privateKey = "au6RRBKcqrmSnh9RN8KNEBaKBEEEDcwwKbChTWb7FPxsZMtsUzuvQWGXCj8V87QnpBWYrHtVfKK6csfAKJaxW7w58NdZ2jXMBnNrsRfdJnWhXzLXU52Lddc8Sfss35kn";

        string publicKey = "4LDVS4Kv5S5sxT83FNHp5LzDcKb9wnkE";

        string url = "https://preprod.api.catalizr.io/authorize/";

        HMACSHA512 hmac = new HMACSHA512(Encoding.ASCII.GetBytes(privateKey));          

        byte[] computedHash = hmac.ComputeHash(Encoding.UTF8.GetBytes(nonce + url + "{\"apiPublicKey\": \""+ publicKey +"\"}"));

        string signature = BitConverter.ToString(computedHash).Replace("-", string.Empty).ToLower();

        Console.WriteLine("Nonce : " + nonce);

        Console.WriteLine("Public key : " + publicKey);     

        Console.WriteLine("Signature : " + signature);

    }

}