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(); } } }