using System;

using System.Text;

using System.Security.Cryptography;

using System.Collections.Generic;

public class Program

{

    public static void Main() {

//      string hash = getMD5("HELLO WORLD");

//      Console.WriteLine(hash);

//      Console.WriteLine("361fadf1c712e812d198c4cab5712a79");

        string fakeSalt = "C5";

        findCollision(fakeSalt);

//      string testHash0 = getMD5("Hello World!", "C5");

//      string testHash1 = getMD5("AQJCMW0DGL", "C5");

//      string testHash2 = getMD5("I95ORWB1A7", "C5");

//      

//      Console.WriteLine(testHash0);

//      Console.WriteLine(testHash1);

//      Console.WriteLine(testHash2);

    }

    public static void findCollision(string salt) {

        Dictionary<string, string> hashesSoFar = new Dictionary<string, string>();

        string all = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

        Random rand = new Random();

        bool found = false;

        while (!found) {

            string toHash = "";

            for (int i = 0; i < 4; i++) {

                toHash += all[rand.Next(all.Length)];

            }

            string hashOfString = getMD5(toHash, salt);

            Console.WriteLine(toHash);

            if (hashesSoFar.ContainsKey(hashOfString)) {

                string output;

                if (hashesSoFar.TryGetValue(hashOfString, out output)) {

                    Console.WriteLine(toHash + "," + output);

                    found = true;

                }

            }

            //foreach(KeyValuePair<string, string> entry in hashesSoFar) {

            //  Console.WriteLine("ENTRY.VALUE = " + entry.Value);

            //  Console.WriteLine("HASHOFSTRING = " + hashOfString);

            //  if (string.Equals(entry.Value, hashOfString)) {

            //      Console.WriteLine(toHash + "," + entry.Key);

            //      Console.WriteLine("FOUNDFOUNDFOUNDFOUNDFOUNDFOUNDFOUNDFOUNDFOUNDFOUNDFOUND");

            //      found = true;

            //  }

            //}

            hashesSoFar.Add(hashOfString, toHash);  

        }

    }

    public static string getMD5(string input, string salt) {

        MD5 md5 = System.Security.Cryptography.MD5.Create();

        Encoding utf8 = Encoding.UTF8;

        byte[] bArray = utf8.GetBytes(input);

        byte[] arrayToHash = new byte[bArray.Length+1];

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

            arrayToHash[i] = bArray[i];

        }

        arrayToHash[arrayToHash.Length-1] = Convert.ToByte(salt, 16);

        byte[] md5hash = md5.ComputeHash(arrayToHash);

        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < 5; i++) {

            sb.Append(md5hash[i].ToString("X2"));

        }

//      Console.WriteLine(sb);

//      Console.WriteLine("b10a8db164e0754105b7a99be72e3fe5");

        return sb.ToString();

    }

}

​