c#通过DES加密算法加密大文件的方法

using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Text;
using System.IO;
using System.Security.Cryptography;
public partial class Default2 : System.Web.UI.Page
{
  protected void Page_Load(object sender, EventArgs e)
  {
  }
  private static byte[] Keys = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };//自定义密匙
  private string filePathA;//储存文件路径
  private string filePathB;//储存文件复制后的路径
  /// <summary>
  /// 文件加密
  /// </summary>
  /// <param name="inFile">文件储存路径</param>
  /// <param name="outFile">储存文件复制的路径</param>
  /// <param name="encryptKey"></param>
  /// <returns></returns>
  public bool EncryptDES(string inFile, string outFile, string encryptKey)
  {
   byte[] rgb = Keys;
   try
   {
    byte[] rgbKeys = Encoding.UTF8.GetBytes(encryptKey.Substring(0, 8));
    FileStream inFs = new FileStream(inFile, FileMode.Open, FileAccess.Read);//读入流
    FileStream outFs = new FileStream(outFile, FileMode.OpenOrCreate, FileAccess.Write);// 等待写入流
    outFs.SetLength(0);//帮助读写的变量
    byte[] byteIn = new byte[100];//放临时读入的流
    long readLen = 0;//读入流的长度
    long totalLen = inFs.Length;//读入流的总长度
    int everylen=0;//每次读入流的长度
    DES des = new DESCryptoServiceProvider();//将inFile加密后放到outFile
    CryptoStream encStream = new CryptoStream(outFs, des.CreateEncryptor(rgb, rgbKeys), CryptoStreamMode.Write);
    while (readLen < totalLen)
    {
     everylen = inFs.Read(byteIn, 0, 100);
     encStream.Write(byteIn, 0, everylen);
     readLen = readLen + everylen;
    }
    encStream.Close();
    inFs.Close();
    outFs.Close();
    return true;//加密成功
   }
   catch (Exception ex)
   {
    Response.Write(ex.Message.ToString());
    return false;//加密失败
   }
  }

  public bool DecryptDES(string inFile, string outFile, string encryptKey)
  {
   byte[] rgb = Keys;
   try
   {
    byte[] rgbKeys = Encoding.UTF8.GetBytes(encryptKey.Substring(0, 8));
    FileStream inFs = new FileStream(inFile, FileMode.Open, FileAccess.Read);//读入流
    FileStream outFs = new FileStream(outFile, FileMode.OpenOrCreate, FileAccess.Write);// 等待写入流
    outFs.SetLength(0);//帮助读写的变量
    byte[] byteIn = new byte[100];//放临时读入的流
    long readLen = 0;//读入流的长度
    long totalLen = inFs.Length;//读入流的总长度
    int everylen=0;//每次读入流的长度
    DES des = new DESCryptoServiceProvider();//将inFile加密后放到outFile
    CryptoStream encStream = new CryptoStream(outFs, des.CreateDecryptor(rgb, rgbKeys), CryptoStreamMode.Write);
    while (readLen < totalLen)
    {
     everylen = inFs.Read(byteIn, 0, 100);
     encStream.Write(byteIn, 0, everylen);
     readLen = readLen + everylen;
    }
    encStream.Close();
    inFs.Close();
    outFs.Close();
    return true;//加密成功
   }
   catch (Exception ex)
   {
    Response.Write(ex.Message.ToString());
    return false;//加密失败
   }
  }
  /// <summary>
  /// 拷贝文件
  /// </summary>
  public void copyFile()
  {
   filePathA = this.fei.PostedFile.FileName;//获取文件全部路径
   string fileName = this.fei.FileName;
   string path = System.IO.Path.GetDirectoryName(filePathA);
   filePathB = path + "\\1" + fileName;//重新设置文件名
   File.Copy(filePathA, filePathB);
  }
  protected void btnOK_Click(object sender, EventArgs e)
  {
   copyFile();
   if (EncryptDES(filePathB, filePathA, "mingrisoft"))
   {
    RegisterStartupScript("false", "<script>alert('加密成功!\\n');</script>");
   }
   else
   {
    RegisterStartupScript("false", "<script>alert('失败成功!\\n');</script>");
   }
   File.Delete(filePathB);
  }
  protected void btnCancel_Click(object sender, EventArgs e)
  {
   copyFile();
   if (DecryptDES(filePathB, filePathA, "mingrisoft"))
   {
    RegisterStartupScript("false", "<script>alert('加密成功!\\n');</script>");
   }
   else
   {
    RegisterStartupScript("false", "<script>alert('失败成功!\\n');</script>");
   }
   File.Delete(filePathB);
  }
}