我将如何读写加密的XML文件

有一个全面的类集合可供您随意使用，以保护System.Security.Cryptography.Xml Namespace中的XML数据。

花点时间阅读以下文章MSDN文章:

• 如何使用对称密钥加密XML元素
• 如何使用对称密钥解密XML元素
• 如何使用数字签名对XML文档进行签名

如果您访问链接的任何文章的导航菜单中的根节点，您可以查看更多关于XML安全性的文章。

我猜，你可以直接保存用户保存的字符串，然后用加密的字符串编写一个普通的XML文件?

这里有一个例子

public class Crypto
{
    private static byte[] _salt = Encoding.ASCII.GetBytes("o6806642kbM7c5");
    /// <summary>
    /// Encrypt the given string using AES.  The string can be decrypted using 
    /// DecryptStringAES().  The sharedSecret parameters must match.
    /// </summary>
    /// <param name="plainText">The text to encrypt.</param>
    /// <param name="sharedSecret">A password used to generate a key for encryption.</param>
    public static string EncryptStringAES(string plainText, string sharedSecret)
    {
        if (string.IsNullOrEmpty(plainText))
            throw new ArgumentNullException("plainText");
        if (string.IsNullOrEmpty(sharedSecret))
            throw new ArgumentNullException("sharedSecret");
        string outStr = null;                       // Encrypted string to return
        RijndaelManaged aesAlg = null;              // RijndaelManaged object used to encrypt the data.
        try
        {
            // generate the key from the shared secret and the salt
            Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(sharedSecret, _salt);
            // Create a RijndaelManaged object
            aesAlg = new RijndaelManaged();
            aesAlg.Key = key.GetBytes(aesAlg.KeySize / 8);
            // Create a decrytor to perform the stream transform.
            ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);
            // Create the streams used for encryption.
            using (MemoryStream msEncrypt = new MemoryStream())
            {
                // prepend the IV
                msEncrypt.Write(BitConverter.GetBytes(aesAlg.IV.Length), 0, sizeof(int));
                msEncrypt.Write(aesAlg.IV, 0, aesAlg.IV.Length);
                using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                {
                    using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                    {
                        //Write all data to the stream.
                        swEncrypt.Write(plainText);
                    }
                }
                outStr = Convert.ToBase64String(msEncrypt.ToArray());
            }
        }
        finally
        {
            // Clear the RijndaelManaged object.
            if (aesAlg != null)
                aesAlg.Clear();
        }
        // Return the encrypted bytes from the memory stream.
        return outStr;
    }
    /// <summary>
    /// Decrypt the given string.  Assumes the string was encrypted using 
    /// EncryptStringAES(), using an identical sharedSecret.
    /// </summary>
    /// <param name="cipherText">The text to decrypt.</param>
    /// <param name="sharedSecret">A password used to generate a key for decryption.</param>
    public static string DecryptStringAES(string cipherText, string sharedSecret)
    {
        if (string.IsNullOrEmpty(cipherText))
            throw new ArgumentNullException("cipherText");
        if (string.IsNullOrEmpty(sharedSecret))
            throw new ArgumentNullException("sharedSecret");
        // Declare the RijndaelManaged object
        // used to decrypt the data.
        RijndaelManaged aesAlg = null;
        // Declare the string used to hold
        // the decrypted text.
        string plaintext = null;
        try
        {
            // generate the key from the shared secret and the salt
            Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(sharedSecret, _salt);
            // Create the streams used for decryption.                
            byte[] bytes = Convert.FromBase64String(cipherText);
            using (MemoryStream msDecrypt = new MemoryStream(bytes))
            {
                // Create a RijndaelManaged object
                // with the specified key and IV.
                aesAlg = new RijndaelManaged();
                aesAlg.Key = key.GetBytes(aesAlg.KeySize / 8);
                // Get the initialization vector from the encrypted stream
                aesAlg.IV = ReadByteArray(msDecrypt);
                // Create a decrytor to perform the stream transform.
                ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);
                using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                {
                    using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                        // Read the decrypted bytes from the decrypting stream
                        // and place them in a string.
                        plaintext = srDecrypt.ReadToEnd();
                }
            }
        }
        finally
        {
            // Clear the RijndaelManaged object.
            if (aesAlg != null)
                aesAlg.Clear();
        }
        return plaintext;
    }
    private static byte[] ReadByteArray(Stream s)
    {
        byte[] rawLength = new byte[sizeof(int)];
        if (s.Read(rawLength, 0, rawLength.Length) != rawLength.Length)
        {
            throw new SystemException("Stream did not contain properly formatted byte array");
        }
        byte[] buffer = new byte[BitConverter.ToInt32(rawLength, 0)];
        if (s.Read(buffer, 0, buffer.Length) != buffer.Length)
        {
            throw new SystemException("Did not read byte array properly");
        }
        return buffer;
    }
}