加密與解密算法

//加密
    public static string Encode(string data)
    {
        byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(KEY_64);
        byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(IV_64);

        DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
        int i = cryptoProvider.KeySize;
        MemoryStream ms = new MemoryStream();

        CryptoStream cst = new CryptoStream(ms, cryptoProvider.CreateEncryptor(byKey, byIV), CryptoStreamMode.Write);

        StreamWriter sw = new StreamWriter(cst);
        sw.Write(data);
        sw.Flush();
        cst.FlushFinalBlock();
        sw.Flush();
        return Convert.ToBase64String(ms.GetBuffer(), 0, (int)ms.Length);

    }
    //解密
    public static string Decode(string data)
    {
        byte[] byKey = System.Text.ASCIIEncoding.ASCII.GetBytes(KEY_64);
        byte[] byIV = System.Text.ASCIIEncoding.ASCII.GetBytes(IV_64);

        byte[] byEnc;
        try
        {
            byEnc = Convert.FromBase64String(data);
        }
        catch
        {
            return null;
        }

        DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
        MemoryStream ms = new MemoryStream(byEnc);
        CryptoStream cst = new CryptoStream(ms, cryptoProvider.CreateDecryptor(byKey, byIV), CryptoStreamMode.Read);
        StreamReader sr = new StreamReader(cst);
        return sr.ReadToEnd();
    }