Video Surveillance: A Distributed Approach to protect Privacy

Abstract. The topmost concern of users who are kept under surveil-lance by a CCTV-System is the loss of their privacy. To gain a high acceptance by the monitored users, we have to assure, that the recorded video-material is only available to a subset of authorized users under ex-actly previously defined circumstances. In this paper we propose a CCTV video surveillance system providing privacy in a distributed way using threshold multi-party computation. Due to the flexibility of the access structure, we can handle the problem of loosing private-key-shares that are necessary for reconstructing video-material as well as adding new users to the system. If a pre-defined threshold is reached, a shared up-date of the master secret and the according re-encryption of previously stored ciphertext without revealing the plaintext is provided.