using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Security.Cryptography;
using System.IO;
using System.Runtime.InteropServices;

namespace DevilStudioCrypter
{
    class Program
    {
        //  Call this function to remove the key from memory after use for security
        [System.Runtime.InteropServices.DllImport("KERNEL32.DLL", EntryPoint = "RtlZeroMemory")]
        public static extern bool ZeroMemory(IntPtr Destination, int Length);

        // Function to Generate a 64 bits Key.
        static string GenerateKey()
        {
            // Create an instance of Symetric Algorithm. Key and IV is generated automatically.
            DESCryptoServiceProvider desCrypto = (DESCryptoServiceProvider)DESCryptoServiceProvider.Create();

            // Use the Automatically generated key for Encryption. 
            return ASCIIEncoding.ASCII.GetString(desCrypto.Key);
        }

        static void EncryptFile(string sInputFilename,
           string sOutputFilename,
           string sKey)
        {
            FileStream fsInput = new FileStream(sInputFilename,
               FileMode.Open,
               FileAccess.Read);

            FileStream fsEncrypted = new FileStream(sOutputFilename,
               FileMode.Create,
               FileAccess.Write);
            DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
            DES.Key = ASCIIEncoding.ASCII.GetBytes(sKey);
            DES.IV = ASCIIEncoding.ASCII.GetBytes(sKey);
            ICryptoTransform desencrypt = DES.CreateEncryptor();
            CryptoStream cryptostream = new CryptoStream(fsEncrypted,
               desencrypt,
               CryptoStreamMode.Write);

            byte[] bytearrayinput = new byte[fsInput.Length];
            fsInput.Read(bytearrayinput, 0, bytearrayinput.Length);
            cryptostream.Write(bytearrayinput, 0, bytearrayinput.Length);
            cryptostream.Close();
            fsInput.Close();
            fsEncrypted.Close();
        }

        static void DecryptFile(string sInputFilename,
           string sOutputFilename,
           string sKey)
        {
            DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
            //A 64 bit key and IV is required for this provider.
            //Set secret key For DES algorithm.
            DES.Key = ASCIIEncoding.ASCII.GetBytes(sKey);
            //Set initialization vector.
            DES.IV = ASCIIEncoding.ASCII.GetBytes(sKey);

            //Create a file stream to read the encrypted file back.
            FileStream fsread = new FileStream(sInputFilename,
               FileMode.Open,
               FileAccess.Read);
            //Create a DES decryptor from the DES instance.
            ICryptoTransform desdecrypt = DES.CreateDecryptor();
            //Create crypto stream set to read and do a 
            //DES decryption transform on incoming bytes.
            CryptoStream cryptostreamDecr = new CryptoStream(fsread,
               desdecrypt,
               CryptoStreamMode.Read);
            //Print the contents of the decrypted file.
            StreamWriter fsDecrypted = new StreamWriter(sOutputFilename);
            fsDecrypted.Write(new StreamReader(cryptostreamDecr).ReadToEnd());
            fsDecrypted.Flush();
            fsDecrypted.Close();
        }

        static void Main()
        {
            string[] args = Environment.GetCommandLineArgs();
            if (args.Length < 5)
            {
                Console.WriteLine("Too small arguments");
                Environment.Exit(1);
            }

            string file_source = args[3];
            string file_dest = args[4];
            string sSecretKey = args[2];

            switch (args[1])
            {
                case "e":
                    File.WriteAllBytes(file_dest, EncDec.Encrypt(File.ReadAllBytes(file_source), sSecretKey));
                    break;
                case "d":
                    File.WriteAllBytes(file_dest, EncDec.Decrypt(File.ReadAllBytes(file_source), sSecretKey));
                    break;
                default:
                    Console.WriteLine("Invalid argument " + args[1]);
                    Environment.Exit(2);
                    break;
            }
        }
    }
}