Illustrates decrypting a file : File Cryptography : File Stream C# Source Code

    

/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy

Publisher: Sybex;
ISBN: 0782129110
*/

/*
  Example19_10.cs illustrates decrypting a file
*/

using System;
using System.IO;
using System.Security.Cryptography;

public class Example19_10 
{
    public static void Main() 
    {

        // Create a new crypto provider
        TripleDESCryptoServiceProvider tdes = 
            new TripleDESCryptoServiceProvider();

        // open the file containing the key and IV
        FileStream fsKeyIn = File.OpenRead(@"c:\temp\encrypted.key");
        
        // use a BinaryReader to read formatted data from the file
        BinaryReader br = new BinaryReader(fsKeyIn);

        // read data from the file and close it
        tdes.Key = br.ReadBytes(24);
        tdes.IV = br.ReadBytes(8);

        // Open the encrypted file
        FileStream fsIn = File.OpenRead(@"c:\\temp\\encrypted.txt");

        // Create a cryptostream to decrypt from the filestream
        CryptoStream cs = new CryptoStream(fsIn, tdes.CreateDecryptor(),
            CryptoStreamMode.Read);

        // Create a StreamReader to format the input
        StreamReader sr = new StreamReader(cs);

        // And decrypt the data
        Console.WriteLine(sr.ReadToEnd());
        sr.Close();

    }

}