public class EncryptString
    {
    private static byte[] Key64 = {42, 16, 93, 156, 78, 4, 218, 32};
    private static byte[] IV64  = {55, 103, 246, 79, 36, 99, 167, 3};
    private static byte[] Key192 = {42, 16, 93, 156, 78, 4, 218, 32,15, 167,
    44,80, 26, 250, 155, 112,2, 94, 11, 204, 119, 35, 184, 197};
    private static byte[] IV192  = {55, 103, 246, 79, 36, 99, 167, 3,42,
    5, 62,83, 184, 7, 209, 13,145, 23, 200, 58, 173, 10, 121, 222};
    public static String Encrypt(String valueString)
    {
    if(valueString != "")
    {   //定义DES的Provider
    DESCryptoServiceProvider desprovider =
    new DESCryptoServiceProvider();
    //定义内存流
    MemoryStream memoryStream = new MemoryStream();
    //定义加密流
    CryptoStream cryptoStream = new CryptoStream(memoryStream,
    desprovider.CreateEncryptor(Key64,IV64),
    CryptoStreamMode.Write);
    //定义写IO流
    StreamWriter writerStream = new StreamWriter(cryptoStream);
    //写入加密后的字符流
    writerStream.Write(valueString);
    writerStream.Flush();
    cryptoStream.FlushFinalBlock();
    memoryStream.Flush();
    //返回加密后的字符串
    return(Convert.ToBase64String(memoryStream.GetBuffer(),0,
    (int)memoryStream.Length));
    }
    return(null);
    }
    public static String Decrypt(String valueString)
    {
    if(valueString != "")

  {   //定义DES的Provider
    DESCryptoServiceProvider desprovider =
    new DESCryptoServiceProvider();
    //转换解密的字符串为二进制
    byte[] buffer = Convert.FromBase64String(valueString);
    //定义内存流
    MemoryStream memoryStream = new MemoryStream();
    //定义加密流
    CryptoStream cryptoStream = new CryptoStream(memoryStream,
    desprovider.CreateEncryptor(Key64,IV64),
    CryptoStreamMode.Read);
    //定义读IO流
    StreamReader readerStream = new StreamReader(cryptoStream);
    //返回解密后的字符串
    return(readerStream.ReadToEnd());
    }
    return(null);
    }
    public static String EncryptTripleDES(String valueString)
    {
    if(valueString != "")
    {   //定义TripleDES的Provider
    TripleDESCryptoServiceProvider triprovider =
    new TripleDESCryptoServiceProvider();
    //定义内存流
    MemoryStream memoryStream = new MemoryStream();
    //定义加密流
    CryptoStream cryptoStream = new CryptoStream(memoryStream,
    triprovider.CreateEncryptor(Key192,IV192),
    CryptoStreamMode.Write);
    //定义写IO流
    StreamWriter writerStream = new StreamWriter(cryptoStream);
    //写入加密后的字符流
    writerStream.Write(valueString);
    writerStream.Flush();
    cryptoStream.FlushFinalBlock();
    memoryStream.Flush();
    //返回加密后的字符串
    return(Convert.ToBase64String(memoryStream.GetBuffer(),0,
    (int)memoryStream.Length));
    }
    return(null);
    }
    public static String DecryptTripleDES(String valueString)
    {
    if(valueString != "")
    {   //定义TripleDES的Provider
    TripleDESCryptoServiceProvider triprovider =
    new TripleDESCryptoServiceProvider();
    //转换解密的字符串为二进制
    byte[] buffer = Convert.FromBase64String(valueString);
    //定义内存流
    MemoryStream memoryStream = new MemoryStream();
    //定义加密流

  CryptoStream cryptoStream = new CryptoStream(memoryStream,
    triprovider.CreateEncryptor(Key64,IV64),
    CryptoStreamMode.Read);
    //定义读IO流
    StreamReader readerStream = new StreamReader(cryptoStream);
    //返回解密后的字符串
    return(readerStream.ReadToEnd());
    }
    return(null);
    }
    }