With the popularity of group-oriented applications, secure and efficient communication among all group members has become a major issue. An efficient key management mechanism is the base and critical technology of secure group communications. A distributed grouporiented key management scheme without the participation of third parties is proposed in the paper. The scheme deploys Elliptic Curve Diffie-Hellman (ECDH) which is more lightweight compared to regular Diffie-Hellman. The approach includes group key establishment and rekeying algorithms when there are membership changes. By using a distributed architecture, the load of key management is reduced. Specifically, the scheme can be extended to hybrid architecture to provide better scalability. Consequently, the extended scheme is both fault-tolerant and efficient in terms of integrity and confidentiality. In all protocol suites, the shared group key is calculated by scalar multiplication. According to performance comparisons with other schemes, the proposed scheme dramatically reduces communication overhead and computational costs. Security analysis indicates that the proposal provides a number of desirable security properties, including group key secrecy, forward secrecy and backward secrecy.