Notary-based self-healing mechanism for centralized peer-to-peer infrastructures

Abstract

Centralized architecture, due to its simplicity, fast and reliable user management mechanism (authorization, authentication and lookup) and O(1) searching capability, is still a preferable choice for many P2P-based services. However, it suffers from a “single point of failure” vulnerability, so networks based on this topology are highly vulnerable to DoS attacks or other blocking attempts. This paper describes a new mechanism that can be used for centralized P2P networks to prevent a P2P service unavailability after central server failure. High security level is obtained by using notary servers which track server public key changes and collect social feedback from users. This allows not only to detect popular attacks (like man-in-the middle) but also to assess whether the Central Server (CS) behaves properly. In the case of central server failure or when server becomes compromised, decentralized Condorcet voting is preformed and new CS is selected. Additionally, by incorporating a reputation mechanism which uses two kinds of scores respectively for providing good service and fair evaluation of other peers, the best candidates for a new Central Server can be chosen. Valuable data which is used to rebuild user database in new CS is stored in the encrypted form in peers and updated during the user-peer authorization process. The decryption key is divided between peers using the threshold secret sharing method.