\chapter{Related Work}
\label{ch:related-work}
This chapter gives a comprehensive overview of different projects trying to protect the users' personal data in \acp{OSN}. Hereby, six different approaches are presented. First, extensions are considered that make the use of established social networks more secure. Then, alternative social networks will be presented that have placed the protection of personal data at the center. After that two next-generation social networks will be considered, which take advantage of the blockchain technology and belong to the group of dApps. Finally, the ActivityPub protocol is presented, which maps the communication in decentralized platforms. The chapter concludes with a summary of the related work.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% For each project, write about
% - how is data stored
% - how is communication realized
% - how is data accessed (authorization)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Extensions for better privacy
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Privacy through Extensions}
\label{sec:extensions}
Existing connections to other people and already created content can bind users to platforms. This so-called lock-in effect prevents users from switching to another platform. If switching to another platform is not an option, how can the use of the platforms be made more secure and user data better protected? In the following, two approaches (Twitterize and FaceCloak) are presented which try to increase the privacy and anonymity on Facebook and Twitter.

\subsection{Twitterize}
\label{sec:twitterize}
\input{content/03-related-work/twitterize}

\subsection{FaceCloak}
\label{sec:facecloak}
\input{content/03-related-work/facecloak}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Privacy-protecting Social Networks
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Privacy-protecting Social Networks}
\label{sec:privacy-protecting-social-networks}
In the business models of the large, popular \acp{OSN}, user data plays an essential role. The data is evaluated and used to make a profit, for example through personalized advertising. Anonymity and the protection of privacy are not among the overriding objectives. 

In the following, two social networks, diaspora* and LifeSocial, are presented which have placed the protection of data at the center.

\subsection{diaspora*}
\label{sec:diaspora}
\input{content/03-related-work/diaspora}

\subsection{LifeSocial.KOM}
\label{sec:lifesocial}
\input{content/03-related-work/lifesocial}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% dApps
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{\acp{dApp} - The Next Generation Social Networks}
As mentioned in Chapter \ref{sec:dapps}, \acp{dApp} use emerging technologies, like the blockchain and cryptocurrencies, to build decentralized applications. With Peepeth and AKASHA, two \ac{dApp} \acp{OSN} are presented in this chapter. They both use Ethereum as blockchain and \ac{IPFS} to store data.

\subsection{Akasha}
\label{sec:akasha}
\input{content/03-related-work/akasha}

\subsection{Peepeth}
\label{sec:peepeth}
\input{content/03-related-work/peepeth}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Protocols
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Protocols}
\label{sec:protocols}
This part is about protocols that describe communication in decentralized applications. With the rise of the decentralized \ac{OSN} Mastodon, the ActivityPub protocol became popular which is introduced in the following.

\subsection{ActivityPub}
\label{sec:activitypub}
\input{content/03-related-work/activitypub}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Summary
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Summary}
\label{sec:related-work-summary}