using System;

using System.Security.Cryptography;

using System.Text;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine(getAuthentication("post", "api-hcm", "12345678@a"));

    }

​

    public static String getAuthentication(String method, String User, String Password)

    {

        // Input data

        String value = String.Format("{0}:{1}:{2}", User, Password, Guid.NewGuid().ToString("N").ToLower());

        // Unique code

        var nonce = Guid.NewGuid().ToString("N").ToLower();

        DateTime epochStart = new DateTime(1970, 01, 01, 0, 0, 0, 0, DateTimeKind.Utc);

        TimeSpan currentTimes = DateTime.UtcNow - epochStart;

        var serverTotalSeconds = Convert.ToInt32(currentTimes.TotalSeconds);

        string data = String.Format("{0}{1}{2}", method, serverTotalSeconds, nonce);

        //Return value

        value = String.Format("{0}:{1}:{2}:{3}:{4}", getHashedData(data), nonce, serverTotalSeconds, User, Password);

        return value;

    }

​

    static string getHashedData(string data)

    {

        MD5 md5 = MD5.Create();

        var hash = md5.ComputeHash(Encoding.Default.GetBytes(data));

        return Convert.ToBase64String(hash);

    }

}