Box JWT signature creation using .NET version 3.5?

Hello I am trying to build a integration to pull files from Box onto a Client platform (SharePoint 2010). I have created the "App" in Box and I'm going through the steps outlined in the Box guides (https://developer.box.com/v2.0/docs/construct-jwt-claim-manually ). The reason for the manual creation is that the framework version for SharePoint 2010 is limited to .Net 3.5 so I cannot use any of the new tooling.

Does anyone have a console application example of creating a JWT with the typical encrypted Box Private Key using .Net 3.5? I'm completely stuck at this point....