Integrita: Protecting View-Consistency in Online Social Network with Federated Servers
Current designs of Online Social Networks (OSN) deploy a centralized architecture where a central OSN provider handles all the users’ read and write requests over the shared data (e.g., Facebook wall or a group page). The historical incidents demonstrate that such centralization is leveraged for censorship and violating view-consistency; a corrupted provider deliberately displays different views of the shared data to different users. Integrita provides a data-sharing mechanism that protects view-consistency by replacing the centralized architecture with the federated-server model consisting of N providers, N − 1 of which can be fully malicious and colluding. The state of the shared data is modeled by an append-only data structure, stored at the server-side, which contains the history of all the operations performed by the users. The consistency of the users’ views towards the shared data depends on their accessibility to the intact log of operations. Integrita guarantees that the servers cannot manipulate the log without being detected by the users. Unlike the state-of-the-art, Integrita accomplishes this neither by using storage-inefficient data replication nor by requiring users to exchange their views. Every user, without relying on the presence of other users, can verify whether his operation has been added to the log and is visible to the rest of the users. We introduce and achieve a new level of view-consistency, named q-detectable consistency, where any inconsistency between users’ views cannot remain undetected for more than q operations, where q is a function of the number of the servers. This level of consistency is stronger than what centralized counterparts offer. Also, our proposal reduces the storage overhead imposed by replication-based solutions by the multiplicative factor of 1 N . Furthermore, the application of Integrita is not limited to OSNs and can be integrated into any log-based systems, e.g., version control systems.