The efficiency of re-keying is a main factor that influences the performance of secure multicast.Grouping keys into logical tree and periodic batch re-keying for users join/leave are effective ways to improve the efficiency of re-keying and reduce the burden that re-keying puts on key management as well as users.In this paper

we present a re-key algorithm which reduces the burden that re-keying put on key management system and users.We then investigate the performance of batch re-keying using our algorithm.