Efficiency Improvements of the Private Message Service

Based on the private message service described in [4] we show efficiency improvements of that private message service in the computational setting. Regarding an attacker which may control all but one of the queried servers we describe a private message service with a total communication complexity of blinded read between client and private message service of n bit upstream and k bit downstream, where n denotes the number of cells in the database and k the size of one cell. Apart from a registration mechanism, the communication complexity between client and service is independent of the number of queried servers. Our improvement of the private message service is not only extremely efficient in terms of communication, but also in terms of computation. Further we describe how to use the message service in case of messages which are addressed using visible implicit addresses. After that we prove that at least parts of messages which are addressed using invisible implicit addresses must be broadcasted. We generalize the message service to operations in ZZN (N ≥ 2) and prove the security of blinded read.