Cryptolens Licensing for .NET

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This API serves as a layer that simplifies communication with Cryptolens Web API 2 and 3 (https://app.cryptolens.io/docs/api).

You can access the documentation of the library at https://help.cryptolens.io/api/dotnet/.

Please check out our guide on common errors during integration: https://help.cryptolens.io/faq/index#troubleshooting-api-errors

Getting started

Install Nuget package

In Visual Studio package manager

PM> Install-Package Cryptolens.Licensing

Using dotnet CLI

dotnet add package Cryptolens.Licensing

If you are targeting Mac, Linux or Unity/Mono, we recommend to use the cross platform version of that package.

In Visual Studio package manager

PM> Install-Package Cryptolens.Licensing.CrossPlatform

Using dotnet CLI

dotnet add package Cryptolens.Licensing.CrossPlatform

Example code

• Key verification
• Offline verification

Recommended articles

• Unity 3D / Mono
• AutoCAD
• Rhinoceros / Grasshoper

Compatibility

To get access to all of the featues in the library, .NET Framework 4.6 or above has to be used. We have summarized the functionality that is included in each framework. Note, .NET Standard means the library can run on multiple platforms (eg. .NET Core), based on the following document.

• .NET Framework 4.0 - Verifying metadata signatures is not supported.
• .NET Framework 4.6 - All features supported.
• .NET Standard 2.0 - Computing machine codes is not supported. You can still use the available hash functions to compute a machine code, assuming you can collect machine specific information.
• Unity/Linux/Mac - You need to use the packages in the "Without System.Management" folder on the release page. You can find more info here.

Cryptolens.Licensing library does also work on Mono (eg. when running on Linux or Unity), however you need to use a special build that does not include System.Management. You can either install it through NuGet, download pre-compiled binaries (you need to use the library with the name Cryptolens.Licensing.CrossPlatform) or compile it yourself using the instructions below.

Compiling without System.Management (Linux, Unity, Mono)

The easiest way to get the platform independent library is by either installing it through NuGet or downloading pre-compiled binaries (the ones that are called Cryptolens.Licensing.CrossPlatform.dll). In this section, we describe how to compile it yourself:

To compile without System.Management, open Cryptolens.Licensing.csproj and remove the <DefineConstants>SYSTEM_MANAGEMENT</DefineConstants> below inside the <PropertyGroup> tag, i.e.

<PropertyGroup>
    ...

    <DefineConstants>SYSTEM_MANAGEMENT</DefineConstants>   <-- remove this
</PropertyGroup>

Make sure there are no other DefineConstants definitions later in the file, as these will override the value.

Other settings

Issues with Newtonsoft.Json on .NET 4.8

Some customers have reported an error with the right version of Newtonsoft.Json not being found. It seems to be localized to those that target .NET Framework 4.8, and the following error is shown:

System.IO.FileLoadException: Could not load file or assembly 'Newtonsoft.Json, Version=11.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference.

The error is thrown when a wrong version of Newtonsoft.Json is installed in the same project as Cryptolens.Licensing library. To fix this, you need to make sure that Newtonsoft.Json is uninstalled completely and then re-install Cryptolens.Licensing.

'System.MethodAccessException' when calling Helpers.GetMachineCode

In some Windows environments (e.g. when developing Excel addins), it might not be feasible to call Helpers.GetMachineCode on .NET Framework 4.6. The reason for this is the call we make to System.Runtime.InteropServices.RuntimeInformation.IsOSPlatform. To fix this, we have added a boolean flag in Helpers class. Before calling Helpers.GetMachineCode or Helpers.IsOnRightMachine, please set Helpers.WindowsOnly=True.

Helpers.WindowsOnly = true;
var machineCode = Helpers.GetMachineCode();

Turn off KeepAlive

In order to perform API calls with KeepAlive disabled, please set HelperMethods.KeepAlive=False. If you want to remove all references to code that uses KeepAlive that is true, you can compile the library with the KeepAliveDisabled flag, which is added the same way as SYSTEM_MANAGEMENT mentioned earlier. If you have multiple flags, they can be separated with a semicolon.

Proxy settings

To change proxy settings, you can use the variable HelperMethods.proxy.

Old examples

Check Against Time Rollback

In order to make sure that the local time (date and time) wasn't changed by the user, the following code can be used.

public void HasLocalTimeChanged()
{
    bool hasChanged = SKGL.SKM.TimeCheck();

    if(hasChanged)
    {
        Debug.WriteLine("The local time was changed by the user. Validation fails.");
    }
    else
    {
        Debug.WriteLine("The local time hasn't been changed. Continue validation.");
    }
}

Calculating Machine code

Machine code can be calculated with the function below. Any other hash algorithm will do, as long as it only contains letters and digits only.

public void TestingHashes()
{
    //eg. "61843235" (getEightDigitsLongHash)
    //eg. "D38F13CAB8938AC3C393BC111E1A85BB4BA2CCC9" (getSHA1)
    string machineID1 = SKGL.SKM.getMachineCode(SKGL.SKM.getEightDigitsLongHash);
    string machineID2 = SKGL.SKM.getMachineCode(SKGL.SKM.getSHA1);
}