RC2加密算法在C#的应用

using System;
using System.Security.Cryptography;
using System.Text;
using System.IO;
using System.Windows.Forms;

namespace Curllion
{
 public class Crypt
 {
  /// <summary>
  /// 新建一个大小为10261B的文件，以便将加密数据写入固定大小的文件。
  /// </summary>
  /// <param name="filePath">文件保存的地址，包含文件名</param>
  public static void InitBinFile(string filePath)
  {
   byte[] tmp = new byte[10261];
   try  //创建文件流，将其内容全部写入0
   {
    System.IO.FileStream writeFileStream = new FileStream(filePath,
     System.IO.FileMode.Create,
     System.IO.FileAccess.Write,
     System.IO.FileShare.None,512,false);

    for(int i = 0 ;i< 10261;i++)
     tmp[i] = 0; 
    writeFileStream.Write(tmp,0,10261);
    writeFileStream.Flush();
    writeFileStream.Close();
   }
   catch(System.IO.IOException)
   {
    MessageBox.Show("文件操作错误！","错误！",MessageBoxButtons.OK,MessageBoxIcon.Error);
   }
  }
  /// <summary>
  /// 将文本数据加密后写入一个文件，其中，这个文件是用InitBinFile建立的，这个文件将被分成十块，
  /// 用来分别保存10组不同的数据，第一个byte位保留，第2位到第21位分别用来存放每块数据的长度，但
  /// 一个byte的取值为0-127，所以，用两个byte来存放一个长度。
  /// </summary>
  /// <param name="toEncryptText">要加密的文本</param>
  /// <param name="filePath">要写入的文件</param>
  /// <param name="dataIndex">写入第几块，取值为1--10</param>
  /// <returns>是否操作成功</returns>
  public static bool EncryptToFile(string toEncryptText,string filePath,int dataIndex)
  {
   bool r = false;
   if(dataIndex > 10 && dataIndex < 1)
   {
    MessageBox.Show("数据索引的取值范围在1至10之间！","错误！",
     MessageBoxButtons.OK,MessageBoxIcon.Error);
    return r;
   }
   byte[] encrypted;  
   //初始化向量
   byte[] key = {106,51,25,141,157,142,23,111,234,159,187,154,215,34,37,204};   
   //密匙
   byte[] IV = {135,186,133,136,184,149,153,144};
   //创建UTF-16 编码，用来在byte[]和string之间转换
   System.Text.UnicodeEncoding textConverter = new UnicodeEncoding();
   //创建RC2服务
      RC2CryptoServiceProvider rc2CSP = new RC2CryptoServiceProvider();
   //打开要写入的文件，主要是为了保持原文件的内容不丢失
   System.IO.FileStream tmpFileStream= new FileStream(filePath,
    System.IO.FileMode.Open,
    System.IO.FileAccess.Read,
    System.IO.FileShare.None,1024,true);

   byte[] index = new byte[10261];
   //将读取的内容写到byte数组
   tmpFileStream.Read(index,0,10261);
   tmpFileStream.Close();
   //定义基本的加密转换运算
   System.Security.Cryptography.ICryptoTransform Encryptor = rc2CSP.CreateEncryptor(key,IV);
   System.IO.MemoryStream msEncrypt = new MemoryStream();
   //在此加密转换流中，加密将从csEncrypt，加密后，结果在msEncrypt流中。
   System.Security.Cryptography.CryptoStream csEncrypt = new CryptoStream(msEncrypt,
    Encryptor,CryptoStreamMode.Write);
   //将要加密的文本转换成UTF-16 编码，保存在tmp数组。
   byte[] tmp = textConverter.GetBytes(toEncryptText);
   //将tmp输入csEncrypt,将通过Encryptor来加密。
   csEncrypt.Write(tmp,0,tmp.Length);
   //输出到msEnctypt
   csEncrypt.FlushFinalBlock();
   //将流转成byte[]
   encrypted = msEncrypt.ToArray();
   if(encrypted.Length>1024)
   {
    MessageBox.Show("加密后，数据长度大于1KB，无法保存");
    return false;
   }
   //得到加密后数据的大小，将结果存在指定的位置。
   index[dataIndex*2 - 1] = Convert.ToByte(Convert.ToString(encrypted.Length/128));
   index[dataIndex*2]     = Convert.ToByte(Convert.ToString(encrypted.Length%128));
   //将加密后的结果写入index（覆盖）
   for(int i=0;i<encrypted.Length;i++)
    index[1024*(dataIndex-1)+21+i]=encrypted[i];
   //建立文件流
   tmpFileStream = new FileStream(filePath,
    System.IO.FileMode.Truncate,
    System.IO.FileAccess.Write,
    System.IO.FileShare.None,1024,true);
   //写文件
   tmpFileStream.Write(index,0,10261);
   tmpFileStream.Flush();
   r = true;
   tmpFileStream.Close();
   return r;
  }
  /// <summary>
  /// 从一个文件中解密出一段文本，其中，这个文件是由InitBinFile建立的，并且由 EncryptToFile加密的
  /// </summary>
  /// <param name="filePath">要解密的文件</param>
  /// <param name="dataIndex">要从哪一个块中解密</param>
  /// <returns>解密后的文本</returns>
  public static string DecryptFromFile(string filePath,int dataIndex)
  {
   string r = "";
   if(dataIndex > 10 && dataIndex < 1)
   {
    MessageBox.Show("数据索引的取值范围在1至10之间！","错误！",
     MessageBoxButtons.OK,MessageBoxIcon.Error);
    return r;
   }
   byte[] decrypted;
   byte[] key = {106,51,25,141,157,142,23,111,234,159,187,154,215,34,37,204};
   byte[] IV = {135,186,133,136,184,149,153,144};
   System.Text.UnicodeEncoding textConverter = new UnicodeEncoding();
   RC2CryptoServiceProvider rc2CSP = new RC2CryptoServiceProvider();
   System.IO.FileStream tmpFileStream = new FileStream(filePath,
    System.IO.FileMode.Open,
    System.IO.FileAccess.Read,
    System.IO.FileShare.None,1024,true);

   System.Security.Cryptography.ICryptoTransform Decryptor = rc2CSP.CreateDecryptor(key,IV);
   System.IO.MemoryStream msDecrypt = new MemoryStream();
   System.Security.Cryptography.CryptoStream csDecrypt = new CryptoStream(msDecrypt,
    Decryptor,CryptoStreamMode.Write);
   byte[] index = new byte[10261];

   tmpFileStream.Read(index,0,10261);
   int startIndex = 1024*(dataIndex-1)+21;
   int count      = index[dataIndex*2 - 1]*128 + index[dataIndex*2];
   byte[] tmp     = new byte[count];

   Array.Copy(index,1024*(dataIndex-1)+21,tmp,0,count);
   csDecrypt.Write(tmp,0,count);
   csDecrypt.FlushFinalBlock();
   decrypted = msDecrypt.ToArray();
   r = textConverter.GetString(decrypted,0,decrypted.Length);
   tmpFileStream.Close();
   return r;
  }
  /// <summary>
  /// 将一段文本加密后保存到一个文件
  /// </summary>
  /// <param name="toEncryptText">要加密的文本数据</param>
  /// <param name="filePath">要保存的文件</param>
  /// <returns>是否加密成功</returns>
  public static bool EncryptToFile(string toEncryptText,string filePath)
  {
   bool r = false;
   byte[] encrypted;
   byte[] key = {106,51,25,141,157,142,23,111,234,159,187,154,215,34,37,204};
   byte[] IV = {135,186,133,136,184,149,153,144};
   System.Text.UnicodeEncoding textConverter = new UnicodeEncoding();
   RC2CryptoServiceProvider rc2CSP = new RC2CryptoServiceProvider();
   System.IO.FileStream tmpFileStream = new FileStream(filePath,
    System.IO.FileMode.OpenOrCreate,
    System.IO.FileAccess.Write,
    System.IO.FileShare.None,1024,true);

   System.Security.Cryptography.ICryptoTransform Encryptor = rc2CSP.CreateEncryptor(key,IV);
   System.IO.MemoryStream msEncrypt = new MemoryStream();
   System.Security.Cryptography.CryptoStream csEncrypt = new CryptoStream(msEncrypt,
    Encryptor,CryptoStreamMode.Write);

   byte[] tmp = textConverter.GetBytes(toEncryptText);
   csEncrypt.Write(tmp,0,tmp.Length);
   csEncrypt.FlushFinalBlock();   
   encrypted = msEncrypt.ToArray();
   tmpFileStream.Write(encrypted,0,encrypted.Length);
   tmpFileStream.Flush();
   r = true;
   tmpFileStream.Close();
   return r;
  }
  /// <summary>
  /// 将一个被加密的文件解密
  /// </summary>
  /// <param name="filePath">要解密的文件</param>
  /// <returns>解密后的文本</returns>
  public static string DecryptFromFile(string filePath)
  {
   string r = "";
   byte[] decrypted;
   byte[] key = {106,51,25,141,157,142,23,111,234,159,187,154,215,34,37,204};
   byte[] IV = {135,186,133,136,184,149,153,144};
   System.Text.UnicodeEncoding textConverter = new UnicodeEncoding();
   RC2CryptoServiceProvider rc2CSP = new RC2CryptoServiceProvider();
   System.IO.FileStream tmpFileStream = new FileStream(filePath,
    System.IO.FileMode.Open,
    System.IO.FileAccess.Read,
    System.IO.FileShare.None,1024,true);
   System.Security.Cryptography.ICryptoTransform Decryptor = rc2CSP.CreateDecryptor(key,IV);
   System.IO.MemoryStream msDecrypt = new MemoryStream();
   System.Security.Cryptography.CryptoStream csDecrypt = new CryptoStream(msDecrypt,
    Decryptor,CryptoStreamMode.Write);

   byte[] tmp = new byte[tmpFileStream.Length];
   tmpFileStream.Read(tmp,0,tmp.Length);
   csDecrypt.Write(tmp,0,tmp.Length);
   csDecrypt.FlushFinalBlock();
   decrypted = msDecrypt.ToArray();    
   r = textConverter.GetString(decrypted,0,decrypted.Length);
   tmpFileStream.Close();
   return r;
  }
 }
}