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");
    }
}