using System;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        //Wallet Digest for CompleteDirect Payment Transaction

        var transactionId = "930";

​

        //Test Merchant

        const string PublicKey = "0oa70WuefiddqLjqlTlp";

        const string PrivateKey = "m2vQxqNixqrEDcQ2heVr";

​

        var message = transactionId;

        var theDigest = CalculateDigest(PublicKey, PrivateKey, message);

        Console.WriteLine(theDigest);

    }

​

    public static string CalculateDigest(string publicKey, string privateKey, string message)

    {

        var digest = "";

        var hash = new System.Security.Cryptography.HMACSHA256(System.Text.Encoding.UTF8.GetBytes(privateKey));

        var correctHash = string.Join(string.Empty, hash.ComputeHash(System.Text.Encoding.UTF8.GetBytes(message)).Select(b => b.ToString("x2")));

        digest = publicKey + ":" + correctHash;

        return digest;

    }

}