I am developing a Web API 2.1 service that needs to authenticate the connecting clients (HTML5/JS clients that I will create and control). Unfortunately, the user informatio
This might be a completely insane and invalid approach for you but I faced a similar challenge: New web app (MVVM + WebAPI), legacy system used to issue and validate tokens. Inspired by http://tech.pro/tutorial/1216/implementing-custom-authentication-for-aspnet, and because my application would primarily be used by its accompanied GUI (the MVVM webapp), I decided to use a "cookie based" token produced by FormsAuthentication. The FormsAutnentication cookie/ticket is secured by .net internal magic security (which I assume id completely safe and unbreakable).
In my case the cookie simply holds the ticket issued by the legacy system, (but you could store more details there as well, eg by JSONSerializing a custom type). During authorization, my system validates the token against the legacy system. I guess you could use something similar together with a custom AuthorizationFilter.