Abstract: To solve the security problem in ad hoc network, a new multicast key management scheme in ad hoc environment is given as a better solution to the generation, distribution and management of dynamic members of cipher keys. Introducing the key management mechanism of secure multicast under the cluster framework of two-level management pattern, an EBS-based multicast key management protocol is put forward to assist the transmission of group communication messages by virtue of karnaugh map. Besides meeting the security requirements, the number of keys to be stored in each and every node and the communication costs required for group key updating in the key management mechanism are both much less than those of other mechanisms.