I am using token authentication for small project based on this article: http://bitoftech.net/2014/06/09/angularjs-token-authentication-using-asp-net-web-api-2-owin-asp-net-iden
Override this method inside your OAuthAuthorizationServerProvider:
OAuthAuthorizationServerProvider
public override async Task ValidateClientAuthentication(OAuthValidateClientAuthenticationContext context) { context.Validated(); }