C#：一个增强的TcpClient（六）数据加密

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

namespace Splash.Net.Sockets
{
/// <summary>
/// 实现传送数据的加解密
/// </summary>
public partial class TcpClientPlus
{
/// <summary>
/// 哈希算法的密钥
/// </summary>
private const String _hmackey = "昨夜星辰昨夜风，画楼西畔桂堂东。身无彩凤双飞翼，心有灵犀一点通。";

/// <summary>
/// AES对称算法的托管实现
/// </summary>
protected AesManaged _aes;

/// <summary>
/// 加密密钥字段
/// </summary>
private String _secretKey;

/// <summary>
/// 加密密钥属性
/// </summary>
public String SecretKey
{
get { return _secretKey; }
set
{
_secretKey = value;
if (String.IsNullOrEmpty(value))
{   // 关闭加密传输模块
SecurityClose();
}
else
{
if (_aes == null) _aes = new AesManaged();

// 更新加密密钥（256位）
using (SHA256Managed sha = new SHA256Managed())
{
_aes.Key = sha.ComputeHash(Encoding.UTF8.GetBytes(value + _salt));
sha.Clear();    // 清除敏感数据
}

// 更新初始向量（128位）
using (HMACMD5 hmacmd5 = new HMACMD5(Encoding.UTF8.GetBytes(_hmackey)))
{
_aes.IV = hmacmd5.ComputeHash(Encoding.UTF8.GetBytes(_salt));
hmacmd5.Clear();    // 清除敏感数据
}
}
}
}

/// <summary>
/// 最短密码佐料长度
/// </summary>
public const Int32 MinSaltLength = 16;

/// <summary>
/// 密码佐料字段
/// </summary>
private String _salt = "雄关漫道真如铁，而今迈步从头越。从头越，苍山如海，残阳如血。";

/// <summary>
/// 密码佐料属性
/// </summary>
public String Salt
{
get { return _salt; }
set
{   // 要求Salt的长度大于16个字符
if (!String.IsNullOrEmpty(value) && value.Length >= MinSaltLength)
{
_salt = value;
if (!String.IsNullOrEmpty(_secretKey))
{   // 更新加密密钥（256位）
using (SHA256Managed sha = new SHA256Managed())
{
_aes.Key = sha.ComputeHash(Encoding.UTF8.GetBytes(_secretKey + value));
sha.Clear();    // 清除敏感数据
}

// 更新初始向量（128位）
using (HMACMD5 hmacmd5 = new HMACMD5(Encoding.UTF8.GetBytes(_hmackey)))
{
_aes.IV = hmacmd5.ComputeHash(Encoding.UTF8.GetBytes(value));
hmacmd5.Clear();    // 清除敏感数据
}
}
}
}
}

/// <summary>
/// 加密数据
/// </summary>
/// <param name="buffer">原始数据</param>
/// <param name="offset">字节偏移量</param>
/// <param name="count">要写入当前流的字节数</param>
/// <returns>加密后的数据</returns>
private Byte[] Encrypt(Byte[] buffer, Int32 offset, Int32 count)
{
using(MemoryStream ms = new MemoryStream())
{
using (CryptoStream cs = new CryptoStream(ms, _aes.CreateEncryptor(), CryptoStreamMode.Write))
{
cs.Write(buffer, offset, count);
cs.Close();
return ms.ToArray();
}
}
}

/// <summary>
/// 解密数据
/// </summary>
/// <param name="buffer">原始数据</param>
/// <param name="offset">字节偏移量</param>
/// <param name="count">要写入当前流的字节数</param>
/// <returns>解密后的数据</returns>
private Byte[] Decrypt(Byte[] buffer, Int32 offset, Int32 count)
{
using (MemoryStream ms = new MemoryStream())
{
using (CryptoStream cs = new CryptoStream(ms, _aes.CreateDecryptor(), CryptoStreamMode.Write))
{
cs.Write(buffer, offset, count);
cs.Close();
return ms.ToArray();
}
}
}

/// <summary>
/// 关闭加密传输模块
/// </summary>
private void SecurityClose()
{
if (_aes != null)
{
_aes.Clear();    // 清除敏感数据
_aes.Dispose();  // 释放资源
_aes = null;
}
}
}
}