public partial class Startup
    {
        public static IDataProtector DataProtector;

        public void Configuration(IAppBuilder app)
        {
            //...
        }

        public void ConfigureOAuth(IAppBuilder app)
        {
            //...

            DataProtector = app.CreateDataProtector(typeof (OAuthAuthorizationServerMiddleware).Namespace,
                "Access_Token", "v1");
        }
    }