C#实现对文件进行加密解密的方法

using System;
using System.IO;
using System.Security.Cryptography;
public class Example19_9
{
 public static void Main()
 {
  // Create a new file to work with
  FileStream fsOut = File.Create(@"c:tempencrypted.txt");
  // Create a new crypto provider
  TripleDESCryptoServiceProvider tdes =
   new TripleDESCryptoServiceProvider();
  // Create a cryptostream to encrypt to the filestream
  CryptoStream cs = new CryptoStream(fsOut,tdes.CreateEncryptor(),CryptoStreamMode.Write);
  // Create a StreamWriter to format the output
  StreamWriter sw = new StreamWriter(cs);
  // And write some data
  sw.WriteLine("'Twas brillig,and the slithy toves");
  sw.WriteLine("Did gyre and gimble in the wabe.");
  sw.Flush();
  sw.Close();
  // save the key and IV for future use
  FileStream fsKeyOut = File.Create(@"c:tempencrypted.key");
  // use a BinaryWriter to write formatted data to the file
  BinaryWriter bw = new BinaryWriter(fsKeyOut);
  // write data to the file
  bw.Write( tdes.Key );
  bw.Write( tdes.IV );
  // flush and close
  bw.Flush();
  bw.Close();
 }
}

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:tempencrypted.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:tempencrypted.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();
 }
}