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Using Dynamic Secret Key

Dynamic secrets are suitable for modules that execute their logic after running for a period of time, often used in hot update assemblies. For detailed documentation, see Encryption.

This project demonstrates how to use dynamic secrets. For the complete sample project, see DynamicSecretKey.

Installation​

Same as Quick Start.

Project Setup​

  • Add Assembly-CSharp and HotUpdate assemblies to the AssembliesToObfuscate list in ObfuzSettings.AssemblySettings
  • Set custom values for DefaultStaticSecretKey and DefaultDynamicSecretKey in ObfuzSettings.SecretSettings
  • Add HotUpdate to the AssembliesUsingDynamicSecretKey list in ObfuzSettings.SecretSettings

Generate Encryption Virtual Machine and Keys​

  • Run the menu Obfuz/GenerateEncryptionVM to generate encryption virtual machine code. The default generated code file is Assets/Obfuz/GeneratedEncryptionVirtualMachine.cs.
  • Run the menu Obfuz/GenerateSecretKeyFile to generate two key files. The default output files are Assets/Resources/Obfuz/defaultStaticSecretKey.bytes and Assets/Resources/Obfuz/defaultDynamicSecretKey.bytes
  • Create a HotUpdate assembly with only one Entry class
  • Create a Bootstrap class in the Assets directory

The Entry class code is as follows:


using UnityEngine;

public class Entry : MonoBehaviour
{
    void Start()
    {
        Debug.Log("Entry Start");
    }
}

The Bootstrap class code is as follows:

using Obfuz;
using Obfuz.EncryptionVM;
using UnityEngine;


public class Bootstrap : MonoBehaviour
{
    [ObfuzIgnore]
    [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.AfterAssembliesLoaded)]
    private static void SetUpStaticSecretKey()
    {
        Debug.Log("SetUpStaticSecret begin");
        EncryptionService<DefaultStaticEncryptionScope>.Encryptor = new GeneratedEncryptionVirtualMachine(Resources.Load<TextAsset>("Obfuz/defaultStaticSecretKey").bytes);
        Debug.Log("SetUpStaticSecret end");
    }

    private static void SetUpDynamicSecret()
    {
        Debug.Log("SetUpDynamicSecret begin");
        EncryptionService<DefaultDynamicEncryptionScope>.Encryptor = new GeneratedEncryptionVirtualMachine(Resources.Load<TextAsset>("Obfuz/defaultDynamicSecretKey").bytes);
        Debug.Log("SetUpDynamicSecret end");
    }


    void Start()
    {
        // Delayed loading, load the dynamic key only before using the HotUpdate assembly code.
        // If the project uses hot update, generally after the hot update is completed,
        // load the dynamic key before loading the hot update code.
        SetUpDynamicSecret();
        this.gameObject.AddComponent<Entry>();
    }
}

Mount Script​

Create a GameObject in the scene, then add the Bootstrap script to this GameObject.

Run in Unity Editor to ensure there are no errors.

Build & Run​

Run Build And Run in Build Settings to build and run. Check the Player.log to verify that the running log is consistent with the running result in the Editor.

View Obfuscated Assembly-CSharp Assembly​

Use ILSpy to open Assembly-CSharp.dll and HotUpdate.dll under Library/Obfuz/{buildTarget}/ObfuscatedAssemblies. You will find that the assemblies are indeed obfuscated. And Assembly-CSharp uses the static key, while HotUpdate uses the dynamic key.

The decompiled code of the obfuscated Bootstrap class is as follows:

using $a;
using $A;
using UnityEngine;

public class Bootstrap : MonoBehaviour
{
    [RuntimeInitializeOnLoadMethod(/*Could not decode attribute arguments.*/)]
    private static void SetUpStaticSecretKey()
    {
        Debug.Log((object)"SetUpStaticSecret begin");
        $A.$C<$A.$c>.$L = new global::$a.$A(Resources.Load<TextAsset>("Obfuz/defaultStaticSecretKey").bytes);
        Debug.Log((object)"SetUpStaticSecret end");
    }

    private static void $a()
    {
        $d.$a($A.$C<$A.$c>.$K(global::$C.$A, 0, 24, 137, 1750859568), $A.$C<$A.$c>.$d(1718597184, 154, 2114032877));
        $A.$C<$A.$B>.$L = new global::$a.$A($d.$b($d.$A($A.$C<$A.$c>.$K(global::$C.$A, 24, 29, 98, -1513390007), $A.$C<$A.$c>.$d(-394605899, 193, -1119998407)), $A.$C<$A.$c>.$d(1579960075, 194, -1028386777)));
        $d.$a($A.$C<$A.$c>.$K(global::$C.$A, 53, 22, 61, -331274448), $A.$C<$A.$c>.$d(1718597184, 154, 2114032877));
    }

    private void Start()
    {
        $d.$B($A.$C<$A.$c>.$d(-1185287704, 255, -1146758192));
        $d.$C($d.$c(this, $A.$C<$A.$c>.$d(694999971, 214, -840892815)), $A.$C<$A.$c>.$d(1262757717, 165, 2108602561));
    }
}

The obfuscated Entry class code is as follows:

using $A;
using UnityEngine;

public class Entry : MonoBehaviour
{
    private void Start()
    {
        $C.$a($A.$C<$A.$B>.$K($c.$A, 0, 11, 128, -835666756), $A.$C<$A.$B>.$d(1717964360, 44, -2091590008));
    }
}