为什么要对AssetBundle进行加密
防止资源被破解
加密算法
因为对AB包进行加密后还需要再加载AB包时进行解密，所以选择AES加密方式。AES是对称加密算法，在加密时会设定一个密钥，通过该密钥进行加密。在游戏运行过程中加载AB包时，先使用同样的密钥对其进行解密，然后再加载AB包。
- 为了识别文件是否已经被加密过（防止多次加密）。需要定一个文件的识别头（这里设置的”AESEncrypt”），在加密时会将这个头写入到文件的头部，当加密时读取最前面的和识别头相等长度的字节与识别头进行比较，如果相等则表示加密过，否则就进行加密。
- 进行解密时，需要将识别字节头给移除再进行解密
下面是进行AES加密的脚本代码，具体原理网上有很多讲解（我也是搬运过来的 2333333…）
using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
using UnityEngine;
public class AES
{
// 加密识别头（用来识别文件是否已经加密过）
private const string AES_HEAD = "AESEncrypt";
/// <summary>
/// 文件加密，传入文件路径
/// </summary>
/// <param name="path"></param>
/// <param name="EncrptyKey"></param>
public static void AESFileEncrypt(string path, string EncrptyKey)
{
if (!File.Exists(path))
return;
try
{
using (FileStream fs = new FileStream(path, FileMode.OpenOrCreate, FileAccess.ReadWrite))
{
if (fs != null)
{
//读取字节头，判断是否已经加密过了
byte[] headBuff = new byte[10];
fs.Read(headBuff, 0, headBuff.Length);
string headTag = Encoding.UTF8.GetString(headBuff);
if (headTag == AES_HEAD)
{
#if UNITY_EDITOR
Debug.Log(path + "已经加密过了！");
#endif
return;
}
//加密并且写入字节头
fs.Seek(0, SeekOrigin.Begin);
byte[] buffer = new byte[fs.Length];
fs.Read(buffer, 0, Convert.ToInt32(fs.Length));
fs.Seek(0, SeekOrigin.Begin);
fs.SetLength(0);
byte[] headBuffer = Encoding.UTF8.GetBytes(AES_HEAD);
fs.Write(headBuffer, 0, headBuffer.Length);
byte[] EncBuffer = AESEncrypt(buffer, EncrptyKey);
fs.Write(EncBuffer, 0, EncBuffer.Length);
}
}
}
catch (Exception e)
{
Debug.LogError(e);
}
}
/// <summary>
/// 文件解密，传入文件路径（会改动加密文件，不适合运行时）
/// </summary>
/// <param name="path"></param>
/// <param name="EncrptyKey"></param>
public static void AESFileDecrypt(string path, string EncrptyKey)
{
if (!File.Exists(path))
{
return;
}
try
{
using (FileStream fs = new FileStream(path, FileMode.OpenOrCreate, FileAccess.ReadWrite))
{
if (fs != null)
{
byte[] headBuff = new byte[10];
fs.Read(headBuff, 0, headBuff.Length);
string headTag = Encoding.UTF8.GetString(headBuff);
if (headTag == AES_HEAD)
{
byte[] buffer = new byte[fs.Length - headBuff.Length];
fs.Read(buffer, 0, Convert.ToInt32(fs.Length - headBuff.Length));
fs.Seek(0, SeekOrigin.Begin);
fs.SetLength(0);
byte[] DecBuffer = AESDecrypt(buffer, EncrptyKey);
fs.Write(DecBuffer, 0, DecBuffer.Length);
}
}
}
}
catch (Exception e)
{
Debug.LogError(e);
}
}
/// <summary>
/// 文件解密，传入文件路径，返回字节
/// </summary>
/// <returns></returns>
public static byte[] AESFileByteDecrypt(string path, string EncrptyKey)
{
if (!File.Exists(path))
{
return null;
}
byte[] DecBuffer = null;
try
{
using (FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read))
{
if (fs != null)
{
byte[] headBuff = new byte[10];
fs.Read(headBuff, 0, headBuff.Length);
string headTag = Encoding.UTF8.GetString(headBuff);
if (headTag == AES_HEAD)
{
byte[] buffer = new byte[fs.Length - headBuff.Length];
fs.Read(buffer, 0, Convert.ToInt32(fs.Length - headBuff.Length));
DecBuffer = AESDecrypt(buffer, EncrptyKey);
}
}
}
}
catch (Exception e)
{
Debug.LogError(e);
}
return DecBuffer;
}
/// <summary>
/// AES 加密(高级加密标准，是下一代的加密算法标准，速度快，安全级别高，目前 AES 标准的一个实现是 Rijndael 算法)
/// </summary>
/// <param name="EncryptString">待加密密文</param>
/// <param name="EncryptKey">加密密钥</param>
public static string AESEncrypt(string EncryptString, string EncryptKey)
{
return Convert.ToBase64String(AESEncrypt(Encoding.Default.GetBytes(EncryptString), EncryptKey));
}
/// <summary>
/// AES 加密(高级加密标准，是下一代的加密算法标准，速度快，安全级别高，目前 AES 标准的一个实现是 Rijndael 算法)
/// </summary>
/// <param name="EncryptString">待加密密文</param>
/// <param name="EncryptKey">加密密钥</param>
public static byte[] AESEncrypt(byte[] EncryptByte, string EncryptKey)
{
if (EncryptByte.Length == 0) { throw (new Exception("明文不得为空")); }
if (string.IsNullOrEmpty(EncryptKey)) { throw (new Exception("密钥不得为空")); }
byte[] m_strEncrypt;
byte[] m_btIV = Convert.FromBase64String("Rkb4jvUy/ye7Cd7k89QQgQ==");
byte[] m_salt = Convert.FromBase64String("gsf4jvkyhye5/d7k8OrLgM==");
Rijndael m_AESProvider = Rijndael.Create();
try
{
MemoryStream m_stream = new MemoryStream();
PasswordDeriveBytes pdb = new PasswordDeriveBytes(EncryptKey, m_salt);
ICryptoTransform transform = m_AESProvider.CreateEncryptor(pdb.GetBytes(32), m_btIV);
CryptoStream m_csstream = new CryptoStream(m_stream, transform, CryptoStreamMode.Write);
m_csstream.Write(EncryptByte, 0, EncryptByte.Length);
m_csstream.FlushFinalBlock();
m_strEncrypt = m_stream.ToArray();
m_stream.Close(); m_stream.Dispose();
m_csstream.Close(); m_csstream.Dispose();
}
catch (IOException ex) { throw ex; }
catch (CryptographicException ex) { throw ex; }
catch (ArgumentException ex) { throw ex; }
catch (Exception ex) { throw ex; }
finally { m_AESProvider.Clear(); }
return m_strEncrypt;
}
/// <summary>
/// AES 解密(高级加密标准，是下一代的加密算法标准，速度快，安全级别高，目前 AES 标准的一个实现是 Rijndael 算法)
/// </summary>
/// <param name="DecryptString">待解密密文</param>
/// <param name="DecryptKey">解密密钥</param>
public static string AESDecrypt(string DecryptString, string DecryptKey)
{
return Convert.ToBase64String(AESDecrypt(Encoding.Default.GetBytes(DecryptString), DecryptKey));
}
/// <summary>
/// AES 解密(高级加密标准，是下一代的加密算法标准，速度快，安全级别高，目前 AES 标准的一个实现是 Rijndael 算法)
/// </summary>
/// <param name="DecryptString">待解密密文</param>
/// <param name="DecryptKey">解密密钥</param>
public static byte[] AESDecrypt(byte[] DecryptByte, string DecryptKey)
{
if (DecryptByte.Length == 0) { throw (new Exception("密文不得为空")); }
if (string.IsNullOrEmpty(DecryptKey)) { throw (new Exception("密钥不得为空")); }
byte[] m_strDecrypt;
byte[] m_btIV = Convert.FromBase64String("Rkb4jvUy/ye7Cd7k89QQgQ==");
byte[] m_salt = Convert.FromBase64String("gsf4jvkyhye5/d7k8OrLgM==");
Rijndael m_AESProvider = Rijndael.Create();
try
{
MemoryStream m_stream = new MemoryStream();
PasswordDeriveBytes pdb = new PasswordDeriveBytes(DecryptKey, m_salt);
ICryptoTransform transform = m_AESProvider.CreateDecryptor(pdb.GetBytes(32), m_btIV);
CryptoStream m_csstream = new CryptoStream(m_stream, transform, CryptoStreamMode.Write);
m_csstream.Write(DecryptByte, 0, DecryptByte.Length);
m_csstream.FlushFinalBlock();
m_strDecrypt = m_stream.ToArray();
m_stream.Close(); m_stream.Dispose();
m_csstream.Close(); m_csstream.Dispose();
}
catch (IOException ex) { throw ex; }
catch (CryptographicException ex) { throw ex; }
catch (ArgumentException ex) { throw ex; }
catch (Exception ex) { throw ex; }
finally { m_AESProvider.Clear(); }
return m_strDecrypt;
}
}
打包AssetBundle
首先搭建一个简单的界面，将其制作成预制体
接下来需要设置预制体的AssetBundle名称
编写打包的脚本代码（该脚本需要放置在Editor目录下），脚本名称随意，这里就只贴出打包的方法
[MenuItem("Tools/Build")]
static void Build()
{
string path = Application.streamingAssetsPath + "/" + EditorUserBuildSettings.activeBuildTarget;
if (!Directory.Exists(path))
{
Directory.CreateDirectory(path);
}
BuildPipeline.BuildAssetBundles(path, BuildAssetBundleOptions.ChunkBasedCompression, EditorUserBuildSettings.activeBuildTarget);
AssetDatabase.Refresh();
}
等Unity编译完后再顶部菜单中会出现Tools选项，点击下方的Build进行打包
打包完的AssetBundle
尝试用使用AssetStudio查看一下ab包，将panel拖入AssetStudio中，成功看到打包到ab包中的图片
加密AssetBundle
同打包一样，在打包的脚本中添加一个加密方法进行测试，点击菜单中的加密
[MenuItem("Tools/加密")]
static void EncryptAssetBundle()
{
string path = Application.streamingAssetsPath + "/" + EditorUserBuildSettings.activeBuildTarget + "/panel";
AES.AESFileEncrypt(path, SECRET_KEY);
AssetDatabase.Refresh();
}
用记事本打开panel，发现前面出现了标识头AESEncrypt
再用AssteStudio看一下能不能查看到里面的资源，结果是空空如也，没有任何内容
解密和加载AB包
同上一样，写一个方法测试一下对AB包进行解密，并将界面实力化出来
[MenuItem("Tools/解密")]
static void DecryptAssetBunld()
{
string path = Application.streamingAssetsPath + "/" + EditorUserBuildSettings.activeBuildTarget + "/panel";
// 对AB包进行解密
byte[] bytes = AES.AESFileByteDecrypt(path, SECRET_KEY);
// 从内存中加载AB包
AssetBundle ab = AssetBundle.LoadFromMemory(bytes);
// 加载AB包中的名字为Panel预制体
GameObject prefab = ab.LoadAsset<GameObject>("Panel");
// 实例化预制体到Canvas下
GameObject.Instantiate(prefab,GameObject.Find("Canvas").transform);
}
点击Tools菜单下的解密，成功实例化界面
