using System;using System.IO;using System.Security;using System.Security.Cryptography;using System.Runtime.InteropServices;using System.Text;namespace CSEncryptDecrypt{   class Class1   {      //  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()      {         // Must be 64 bits, 8 bytes.         // Distribute this key to the user who will decrypt this file.         string sSecretKey;                  // Get the Key for the file to Encrypt.         sSecretKey = GenerateKey();         // For additional security Pin the key.         GCHandle gch = GCHandle.Alloc( sSecretKey,GCHandleType.Pinned );                  // Encrypt the file.                 EncryptFile(@"C:\MyData.txt",             @"C:\Encrypted.txt",             sSecretKey);         // Decrypt the file.         DecryptFile(@"C:\Encrypted.txt",             @"C:\Decrypted.txt",             sSecretKey);         // Remove the Key from memory.          ZeroMemory(gch.AddrOfPinnedObject(), sSecretKey.Length * 2);         gch.Free();      }   }}