A revocation scheme with minimal storage at receivers

Abstract

A revocation or a broadcast encryption technology allows a sender to transmit information securely over a broadcast channel to a select group of receivers excluding some revoked receivers. In this paper we propose two efficient revocation methods which are suitable for stateless receivers. The proposed methods use an a-ary key tree structure and require at most r _ log (N/r) log a + 1 _ ciphertexts broadcast. Our Method 1 requires only one key to be stored and O _ 2alog5N log a _ computational overhead at a receiver, whereas Method 2 requires logN log a keys and O (2a) computational overhead, where N and r respectively denote the total number of receivers and the number of revoked receivers. Our methods are very efficient with respect to the number of keys each receiver stores, especially Method 1 minimizes it.