入口引數有三個:key、data、mode。 key為加密解密使用的金鑰，data為加密解密的資料，mode為其工作模式。當模式為加密模式時，明文按照64位進行分組，形成明文組，key用於對資料加密，當模式為解密模式時，key用於對資料解密。實際運用中，金鑰只用到了64位中的56位，這樣才具有高的安全性。

Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/--> 1 /// <summary>

  /// DES對稱加密
  /// </summary>
  public sealed class DES {
    /// <summary>
    /// Des解密方法
    /// </summary>
    /// <param name="val"></param>
    /// <param name="key"></param>
    /// <param name="IV"></param>
    /// <returns></returns>
    public static string Decrypt(string val, string key, string IV) {
      try {
        byte[] buffer1 = Convert.FromBase64String(key);
        byte[] buffer2 = Convert.FromBase64String(IV);
        DESCryptoServiceProvider provider1 = new DESCryptoServiceProvider();
        provider1.Mode = CipherMode.ECB;
        provider1.Key = buffer1;
        provider1.IV = buffer2;
        ICryptoTransform transform1 = provider1.CreateDecryptor(provider1.Key, provider1.IV);
        byte[] buffer3 = Convert.FromBase64String(val);
        MemoryStream stream1 = new MemoryStream();
        CryptoStream stream2 = new CryptoStream(stream1, transform1, CryptoStreamMode.Write);
        stream2.Write(buffer3, 0, buffer3.Length);
        stream2.FlushFinalBlock();
        stream2.Close();
        return Encoding.Default.GetString(stream1.ToArray());
      }
      catch// (System.Exception ex)
      {
        return "";
      }
    }


    /// <summary>
    /// Des加密方法
    /// </summary>
    /// <param name="val"></param>
    /// <param name="key"></param>
    /// <param name="IV"></param>
    /// <returns></returns>
    public static string Encrypt(string val, string key, string IV) {
      try {
        byte[] buffer1 = Convert.FromBase64String(key);
        byte[] buffer2 = Convert.FromBase64String(IV);


        DESCryptoServiceProvider provider1 = new DESCryptoServiceProvider();
        provider1.Mode = CipherMode.ECB;
        provider1.Key = buffer1;
        provider1.IV = buffer2;
        ICryptoTransform transform1 = provider1.CreateEncryptor(provider1.Key, provider1.IV);
        byte[] buffer3 = Encoding.Default.GetBytes(val);
        MemoryStream stream1 = new MemoryStream();
        CryptoStream stream2 = new CryptoStream(stream1, transform1, CryptoStreamMode.Write);
        stream2.Write(buffer3, 0, buffer3.Length);
        stream2.FlushFinalBlock();
        stream2.Close();
        return Convert.ToBase64String(stream1.ToArray());
      }
      catch// (Exception ex)
      {
        return "";
      }
    }
  }