On your public-facing website consider enabling the anonymous search REST API to publish your content to other channels such as topic sites and mobile apps.
SharePoint 2013 offers new capabilities for publishing content to multiple channels. Using the new cross-site content publishing model you can centralize your content management process and reuse your content across multiple channels including companion apps.
In order to publish content from your website to a mobile app you will very likely be using the SharePoint 2013 Search REST API. By default all SharePoint 2013 REST APIs require you to authenticate before you can use them. The Search REST API is an exception in the collection of SharePoint’s REST APIs as it can be exposed to anonymous users while keeping the rest of your website secured. Since all of the content on your website is publicly available anyway, allowing for anonymous use of the Search REST API will simplify the architecture of your app and prevent you from storing credentials in it.