C# DES加密解密用法

主要用到C#提供的以下三个类：
MemoryStream 内存流
DESCryptoServiceProvider 加密服务提供者类
CryptoStream 讲数据流连接到加密转换的流

下面是简易代码，已经过测试：

    public static string strKey = "abcdefgh";
    public static string strIV = "ijklmnop";
    private XmlDocument XmlDoc = null;
    private XmlElement XmlRoot = null;

    // 字符串加密
    public static string Encrypt(string _strQ)
    {
        byte[] buffer = Encoding.UTF8.GetBytes(_strQ);
        MemoryStream ms = new MemoryStream();
        DESCryptoServiceProvider tdes = new DESCryptoServiceProvider();
        CryptoStream encStream = new CryptoStream(ms, tdes.CreateEncryptor(Encoding.UTF8.GetBytes(strKey), Encoding.UTF8.GetBytes(strIV)), CryptoStreamMode.Write);
        encStream.Write(buffer, 0, buffer.Length);
        encStream.FlushFinalBlock();
        return Convert.ToBase64String(ms.ToArray()).Replace("+", "%");
    }

    // 字符串解密
    public static string Decrypt(string _strQ)
    {
        _strQ = _strQ.Replace("%", "+");
        byte[] buffer = Convert.FromBase64String(_strQ);
        MemoryStream ms = new MemoryStream();
        DESCryptoServiceProvider tdes = new DESCryptoServiceProvider();
        CryptoStream encStream = new CryptoStream(ms, tdes.CreateDecryptor(Encoding.UTF8.GetBytes(strKey), Encoding.UTF8.GetBytes(strIV)), CryptoStreamMode.Write);
        encStream.Write(buffer, 0, buffer.Length);
        encStream.FlushFinalBlock();
        return Encoding.UTF8.GetString(ms.ToArray());
    }

    // 解密加载
    public void XmlLoadDecrypt(XmlDocument xmlDoc, string fileName)
    {
        FileStream fileStream = new FileStream(fileName, FileMode.Open);
        byte[] bsXml = new byte[fileStream.Length];
        fileStream.Read(bsXml, 0, bsXml.Length);
        fileStream.Close();

        MemoryStream ms = new MemoryStream();
        DESCryptoServiceProvider tdes = new DESCryptoServiceProvider();
        CryptoStream encStream = new CryptoStream(ms, tdes.CreateDecryptor(Encoding.UTF8.GetBytes(strKey), Encoding.UTF8.GetBytes(strIV)), CryptoStreamMode.Write);
        encStream.Write(bsXml, 0, bsXml.Length);
        encStream.FlushFinalBlock();

        xmlDoc.Load(new MemoryStream(ms.ToArray()));
    }

    // 加密存储
    public void XmlSaveEncrypt(XmlDocument xmlDoc, string fileName)
    {
        if (!File.Exists(fileName))
            File.Create(fileName).Close();

        FileStream fileStream = new FileStream(fileName, FileMode.Truncate);
        MemoryStream msXml = new MemoryStream();
        xmlDoc.Save(msXml);

        DESCryptoServiceProvider tdes = new DESCryptoServiceProvider();
        CryptoStream cs = new CryptoStream(fileStream, tdes.CreateEncryptor(Encoding.UTF8.GetBytes(strKey), Encoding.UTF8.GetBytes(strIV)), CryptoStreamMode.Write);
        cs.Write(msXml.ToArray(), 0, msXml.ToArray().Length);
        cs.FlushFinalBlock();

        msXml.Close();
        fileStream.Close();
    }

    // 测试代码
    string str1 = "abcdefghijklmnopqrstuvwxyz";
    if (GUI.Button(new Rect(0, 300, 100, 50), "Encrypt"))
    {
        Debug.Log(Encrypt(str1));
    }
    if (GUI.Button(new Rect(0, 350, 100, 50), "Decrypt"))
    {
        Debug.Log(Decrypt(Encrypt(str1)));
    }
    if (GUI.Button(new Rect(0, 400, 100, 50), "Load Decrypt Xml"))
    {
        XmlDoc = new XmlDocument();
        XmlLoadDecrypt(XmlDoc, "Assets/123.xml");
        XmlRoot = XmlDoc.DocumentElement;
        Debug.Log(XmlRoot.GetAttribute("Test"));
    }
    if (GUI.Button(new Rect(0, 450, 100, 50), "Save Encrypt Xml"))
    {
        XmlDoc = new XmlDocument();
        XmlRoot = XmlDoc.CreateElement("RegisterRecords");
        XmlDoc.AppendChild(XmlRoot);
        XmlRoot.SetAttribute("Test", "something");
        XmlSaveEncrypt(XmlDoc, "Assets/123.xml");
    }