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Idea

In this post we have summarized the necessary steps to add software licensing into a Unity game. Unity uses Mono runtime, which means that a special version of our .NET client library can be used.
We recommend to read the Considerations section in the end of the tutorial that can help when troubleshooting common errors.

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Implementation

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Client library

To implement license key verification a Unity game, we can use a special build of the client library for .NET that is platform independent. You can download it here. Make sure to reference the binary with the name Cryptolens.Licensing.CrossPlatform.dll. You can also install it through NuGet.

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A note about Newtonsoft.Json

Cryptolens.Licensing.CrossPlatform depends on the Newtonsoft.Json library. In earlier versions of Unity, the Newtonsoft.Json.dll had to be included alongside the Cryptolens.Licensing.CrossPlatform.dll file (it is provided in the same zip file as our library). In later versions (from our tests, since 2020.3.16f1), Unity added Newtonsoft.Json as an internal package, meaning that it no longer needs to be included in the Asset folder. However, depending on the Newtonsoft.Json version used by Unity, you may have to recompile our library to target that version. In sum, there are three cases: If Unity does not have an internal Newtonsoft.Json package This is the case for older versions of Unity (from our tests, for versions earlier than 2020.3.16f1). In this case, you need to include both Cryptolens.Licensing.CrossPlatform.dll and Newtonsoft.Json.dll. If Unity uses Newtonsoft.Json v13 In this case, we recommend using the .NET Framework 4.8 binary (in the net48 folder) without including the Newtonsoft.Json.dll file. It should be possible to use the .NET Standard assembly too, and this has been tested in 2022.3.39f1. However, if you are using an older version of Unity, you might need to change a setting to enable .NET Standard. We have outlined this in the Considerations section at the bottom of this page.
If you are using the latest LTS version of Unity, it should already by targeting Newtonsoft.Json v13.
If Unity uses a different version of Newtonsoft.Json In this case, our library needs to be recompiled with a few changes. The steps are as follows: 
...
<SignAssembly>true</SignAssembly>
<DelaySign>false</DelaySign>
<AssemblyOriginatorKeyFile>certifikat.pfx</AssemblyOriginatorKeyFile>
...
  • Step 4: Change Newtonsoft.Json version from 13.0.1 to 12.0.3(or any other version you would like to use) in the section below:
<ItemGroup Condition="'$(TargetFramework)' == 'netstandard2.0' or '$(TargetFramework)' == 'net47' or '$(TargetFramework)' == 'net471' or '$(TargetFramework)' == 'net48'">
    <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />
</ItemGroup>
  • Step 5: Go back to the main folder (with sln files) and run the following command: dotnet build Cryptolens.Licensing.CrossPlatform.sln.
  • Step 6: Navigate to Cryptolens.Licensing\bin\Debug\net48 (or Cryptolens.Licensing\bin\Release\net48) and copy the Cryptolens.Licensing.CrossPlatform.dll into the assets folder.
If you have any questions, please reach out to us at support@cryptolens.io.

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License key verification

Once you have the binaries, we can get license key verification up and running quite quickly. We assume that already have an account and a product. There are just two things left:
  1. Add the Cryptolens.Licensing.dll and in some cases Newtonsoft.Json.dll into the Assets folder (please check out the section earlier when Newtonsoft.Json needs to be included).
  2. Include the license key verification logic.
Note: we recommend to avoid using Key.Activate that takes in an ActivateModel since signature verification will not work on some platforms. Instead, we recommend to use a special version of Key.Activate as shown below:
// call to activate
var result = Key.Activate(token: auth, productId: 3349, key: "GEBNC-WZZJD-VJIHG-GCMVD", machineCode: "foo");

// obtaining the license key (and verifying the signature automatically).
var license = LicenseKey.FromResponse("RSAPubKey", result);
Also, when implementing offline verification, please call LoadFromFile and LoadFromString with the RSAPubKey. The format of the license file should be set to Other languages (see more here) when downloading it in the dashboard or using Activation Forms. You can download a sample project here.

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Other licensing models

Since Unity uses C# as the scripting interface, you can use all of the .NET examples provided in this wiki. As a next step, please take a look at the available licensing models. Please keep in mind if you use the version of Key.Activate that was suggested earlier, you would need to create a license key object from the response such as LicenseKey.FromResponse(result).SaveToFile() to be able to use the extension methods, eg. result.LicenseKey.SaveToFile() will not work.

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Considerations

The GetMachineCode() and IsOnRightMachine() methods require root access on Linux. If you are using Unity with IL2CCP, Helpers.GetMacAddress() can be a better alternative, since other methods may throw an error. Some users who build and then run the unity project may get a null response from Key.Activate, which will be treated as if the license key is invalid. We recommend to set API Compatibility level to .NET 4.x in Edit > Project Settings > Player > Other Settings > API Compatibility Level. In this case, the the binaries for .NET 4.* need to be used, i.e. not the .NET Standard version.