HOSN-app/thesis/content/04-concept/solution-strategy-client.tex

Concerning the implementation of the hybrid approach, two possibilities are conceivable. On the one hand, the extension of the original \ac{OSN} client (app or web front end) as an add-on. On the other hand, the creation of an entirely new client.

When an add-on extends the \ac{OSN}, there is no need to take care of the standard functionality of the \ac{OSN}. Therefore, the development can entirely focus on the add-on and the private extension. At crucial points, the add-on extends the interface by additional elements that enable secure data exchange. The service providers usually do not offer developers an interface to extend the \ac{OSN} with such own functionalities. With web front ends it is possible to manipulate the website content using browser add-ons. One example for doing so is FaceCloak. Since such browser extensions manipulate the \ac{DOM}, knowledge about the document structure is necessary for the successful function in order to make changes in the right places. The short release cycles of \acp{OSN} and the associated frequent changes to this \ac{DOM} structure make it difficult to keep up with the changes. When consuming the \ac{OSN} via the official apps on mobile devices, an extension or manipulation is not possible.

The alternative to the extension approach described above is a new hybrid client app. The entire functional range of the \ac{OSN} must be implemented and kept up to date. As already mentioned with the restrictions (see Chapter \ref{sec:requirements}), the functions are usually not entirely provided via an \ac{API}, and the crawling of the content 
confronts several challenges. By having complete control over the development of the client, the additional protected, secure communication can be added at the appropriate points. In the best-case scenario, at least one hybrid app is available for every operating system for which an official \ac{OSN} app exists.

Both approaches can be combined by displaying the (mobile) web page of the \ac{OSN} in a WebView in a separate app and executing \ac{DOM} manipulations via injected JavaScript code. For example, there are some alternative clients for Facebook (e.g. \enquote{Friendly for Facebook}\footnote{https://play.google.com/store/apps/details?id=io.friendly} \footnote{https://itunes.apple.com/de/app/friendly-for-facebook/id400169658}, \enquote{Metal Pro}\footnote{https://play.google.com/store/apps/details?id=com.nam.fbwrapper.pro}) that use this approach.