Randomness in self-healing key distribution schemes

Self-healing key distribution schemes allow group managers to broadcast session keys to dynamic groups of users over unreliable channels. The main property of the scheme is that, if during a certain session some broadcasted packet gets lost, then users are still capable of recovering the session key for that session simply by using the packets they have received during a previous session and the packets they receive at the beginning of a subsequent one, without requesting additional transmission from the group manager. Such schemes are quite suitable in supporting secure communication in wireless networks and mobile wireless ad-hoc networks. In this paper we present a lower bound on the randomness required for implementing self-healing key distribution schemes. We also show that the lower bound in tight by describing a self-healing scheme meeting it