Android App to query WebAPI with Windows Authentication

For the last few years I have been working on a fairly comprehensive Intranet for the company I work for. I use Visual Studio, C#, MVC and Entity Framework and the whole thing is secured with Windows Authentication which is supplied by the user's PC when they are in the office, or explicity via a login box if they want to access the Intranet from home.

Recently I've been asked to consider writing a mobile app which excites me and terrifies me at the same time. What I would like to know is the best way of accomplishing this using as much of my existing code and as much of my existing skillset as possible.

This is what I think I need to do - is this the right way to go/will it work?

Write a WebAPI which accepts Windows Credentials and returns data to external users Use Xamarin Forms to create a mobile front end Require the user to enter their Windows Credentials on first use Use these credentials to query our internal databases through the API

If someone can suggest a better way, please do, but my real concern is that I should be using a different system of authentication.

Any advice would be greatly appreciated.

Thanks,

Matt