C#字符串使用密钥进行加解密

public class desencrypt
  {
    /// <summary>
    /// 算法偏移量
    /// </summary>
    const string m_iv = "12345678";
 
    /// <summary>
    /// 功能描述:根据输入的密钥生成8位密钥
    /// 作　　者: 爱给模板网 2gei.cn
    /// 创建日期:2015-07-20 17:25:26
    /// </summary>
    /// <param name="strkey">strkey</param>
    /// <returns>8位密钥</returns>
    private static string getkey(string strkey)
    {
      if (string.isnullorempty(strkey))
      {
        strkey = "infocoll";
      }
      if (strkey.length % 8 == 0)
      {
        return strkey;
      }
      else
      {
        return getkey(strkey + "0");
      }
    }
 
    /// <summary>
    /// 功能描述:加密字符串
    /// 作　　者: 爱给模板网 2gei.cn
    /// 创建日期:2015-07-20 17:18:31
    /// 任务编号:
    /// </summary>
    /// <param name="strsourcestring">原字符串</param>
    /// <param name="strkey">密钥</param>
    /// <returns>加密后的字符串</returns>
    public static string encrypt(string strsourcestring, string strkey)
    {
      strkey = getkey(strkey);
      byte[] btkey = encoding.utf8.getbytes(strkey);
 
      byte[] btiv = encoding.utf8.getbytes(m_iv);
 
      descryptoserviceprovider des = new descryptoserviceprovider();
 
      using (memorystream ms = new memorystream())
      {
        try
        {
          byte[] indata = encoding.utf8.getbytes(strsourcestring);
          using (cryptostream cs = new cryptostream(ms, des.createencryptor(btkey, btiv), cryptostreammode.write))
          {
            cs.write(indata, 0, indata.length);
 
            cs.flushfinalblock();
          }
 
          return convert.tobase64string(ms.toarray());
        }
        catch
        {
          return strsourcestring;
        }
      }
    }
 
    /// <summary>
    /// 功能描述:解密字符串
    /// 作　　者: 爱给模板网 2gei.cn
    /// 创建日期:2015-07-20 17:18:49
    /// 任务编号:
    /// </summary>
    /// <param name="strencryptedstring">原字符串</param>
    /// <param name="strkey">密钥</param>
    /// <returns>解密后的字符串</returns>
    public static string decrypt(string strencryptedstring, string strkey)
    {
      strkey = getkey(strkey);
      byte[] btkey = encoding.utf8.getbytes(strkey);
 
      byte[] btiv = encoding.utf8.getbytes(m_iv);
 
      descryptoserviceprovider des = new descryptoserviceprovider();
 
      using (memorystream ms = new memorystream())
      {
        try
        {
          byte[] indata = convert.frombase64string(strencryptedstring);
          using (cryptostream cs = new cryptostream(ms, des.createdecryptor(btkey, btiv), cryptostreammode.write))
          {
            cs.write(indata, 0, indata.length);
 
            cs.flushfinalblock();
          }
 
          return encoding.utf8.getstring(ms.toarray());
        }
        catch
        {
          return strencryptedstring;
        }
      }
    }
  }

using system.security.cryptography;
using system.io;
//默认密钥向量
    private static byte[] keys = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef };

    /// <summary>
    /// des加密字符串
    /// </summary>
    /// <param name="encryptstring">待加密的字符串</param>
    /// <param name="encryptkey">加密密钥,要求为8位</param>
    /// <returns>加密成功返回加密后的字符串，失败返回源串 </returns>
    public static string encryptdes(string encryptstring, string encryptkey)
    {
      try
      {
        byte[] rgbkey = encoding.utf8.getbytes(encryptkey.substring(0, 8));//转换为字节
        byte[] rgbiv = keys;
        byte[] inputbytearray = encoding.utf8.getbytes(encryptstring);
        descryptoserviceprovider dcsp = new descryptoserviceprovider();//实例化数据加密标准
        memorystream mstream = new memorystream();//实例化内存流
        //将数据流链接到加密转换的流
        cryptostream cstream = new cryptostream(mstream, dcsp.createencryptor(rgbkey, rgbiv), cryptostreammode.write);
        cstream.write(inputbytearray, 0, inputbytearray.length);
        cstream.flushfinalblock();
        return convert.tobase64string(mstream.toarray());
      }
      catch
      {
        return encryptstring;
      }
    }

    /// <summary>
    /// des解密字符串
    /// </summary>
    /// <param name="decryptstring">待解密的字符串</param>
    /// <param name="decryptkey">解密密钥,要求为8位,和加密密钥相同</param>
    /// <returns>解密成功返回解密后的字符串，失败返源串</returns>
    public static string decryptdes(string decryptstring, string decryptkey)
    {
      try
      {
        byte[] rgbkey = encoding.utf8.getbytes(decryptkey);
        byte[] rgbiv = keys;
        byte[] inputbytearray = convert.frombase64string(decryptstring);
        descryptoserviceprovider dcsp = new descryptoserviceprovider();
        memorystream mstream = new memorystream();
        cryptostream cstream = new cryptostream(mstream, dcsp.createdecryptor(rgbkey, rgbiv), cryptostreammode.write);
        cstream.write(inputbytearray, 0, inputbytearray.length);
        cstream.flushfinalblock();
        return encoding.utf8.getstring(mstream.toarray());
      }
      catch
      {
        return decryptstring;
      }
    }



      string encryptstr = encryptdesstring.encryptdes("aaaaaaaaaa", "ssssssss"); //返回加密后的字符串
      string decryptstr = encryptdesstring.decryptdes(encryptstr, "ssssssss");//解密字符串