Anti-Forgery Tokens using MVC, Web API and AngularJS

Hi All,

There are a couple of super articles on thwarting CRSF attacks that I've found:

http://blog.novanet.no/anti-forgery-tokens-using-mvc-web-api-and-angularjs/

http://www.bitwisejourneys.com/extending-the-mvc-anti-forgery-token-concept-to-work-with-asp-net-web-api-and-angularjs/

Both of these solutions rely on System.Web.Helpers.AntiForgery. I'm trying to build this solution into a new ASP.NET 5 web application that has a web api w/Angular as the front end. I'm just not finding where AntiForgery has gone now that System.Web doesn't contain Helpers. Any clues?

Thanks,
-Brian