UltraVNCPasswordDecoder.cs

using System;
using System.Collections.Generic;
using System.Security.Cryptography;
using System.Text;

namespace UltraVNCPasswordDecoder
{
    class Program
    {
        public static string ByteArrayToHex(byte[] bytes)
        {
            char[] c = new char[bytes.Length * 2];
            byte b;
            for (int i = 0; i < bytes.Length; i++)
            {
                b = (byte)(bytes[i] >> 4);
                c[i * 2] = (char)(b > 9 ? b + 0x37 : b + 0x30);
                b = (byte)(bytes[i] & 0xF);
                c[(i * 2) + 1] = (char)(b > 9 ? b + 0x37 : b + 0x30);
            }
            return new string(c);
        }

        public static byte[] HexToByteArray(string hex)
        {
            if (hex.Length % 2 == 1)
            {
                throw new Exception("The binary key cannot have an odd number of digits");
            }
            byte[] arr = new byte[hex.Length >> 1];
            for (int i = 0; i < (hex.Length >> 1); ++i)
            {
                arr[i] = (byte)(((hex[i << 1] - (hex[i << 1] < 58 ? 48 : 55)) << 4) + (hex[(i << 1) + 1] - (hex[(i << 1) + 1] < 58 ? 48 : 55)));
            }
            return arr;
        }

        public static string EncryptPassword(string plainPassword)
        {
            DES des = CreateDES();
            ICryptoTransform cryptoTransfrom = des.CreateEncryptor();

            plainPassword = plainPassword + "\0\0\0\0\0\0\0\0";
            plainPassword = plainPassword.Length > 8 ? plainPassword.Substring(0, 8) : plainPassword;
            byte[] data = Encoding.ASCII.GetBytes(plainPassword);
            byte[] encryptedBytes = cryptoTransfrom.TransformFinalBlock(data, 0, data.Length);

            return ByteArrayToHex(encryptedBytes) + "00";
        }

        public static string DecryptPassword(string encryptedPassword)
        {
            DES des = CreateDES();
            ICryptoTransform cryptoTransfrom = des.CreateDecryptor();
            byte[] data = HexToByteArray(encryptedPassword.Substring(0, encryptedPassword.Length - 2));
            byte[] decryptedBytes = cryptoTransfrom.TransformFinalBlock(data, 0, data.Length);

            return Encoding.ASCII.GetString(decryptedBytes);
        }

        private static DES CreateDES()
        {
            byte[] key = { 0xE8, 0x4A, 0xD6, 0x60, 0xC4, 0x72, 0x1A, 0xE0 };
            DES des = DES.Create();
            des.Key = key;
            des.IV = key;
            des.Mode = CipherMode.ECB;
            des.Padding = PaddingMode.Zeros;
            return des;
        }

        static void Main(string[] args)
        {
            Console.Write("Please enter the encrypted UltraVNC password: ");
            string encryptedPassword = Console.ReadLine();

            try
            {
                string password = DecryptPassword(encryptedPassword);
                Console.WriteLine("Decrypted password: " + password);
                Console.Read();
            }
            catch(Exception e)
            {
                Console.WriteLine("ERROR: Could not decrypt the password");
                Console.Read();
            }
        }
    }
}