The growth of the Internet inspires lots of new network applications, and many of them are based on group communication models. Key trees are ideal for a group of users to efficiently and securely share a common secret key, the group key, which can encrypt transmitted data, or other session keys that protect group communication. An efficient group key management protocol is proposed for centralized dynamic groups, and one-way key derivation is integrated with key trees to reduce the communication overhead of rekeying operations. The server does not have to send new keys to those members who can derive the keys by themselves, and the total number of encrypted keys transmitted per rekeying operation becomes fewer. It is shown that the technique can be applied to both synchronous and asynchronous rekeying operations. The proposed protocol outperforms the other group key management protocols from our analysis and simulation, and is suitable for practical systems.