关键词: 组群密钥交换, 组合公钥密码, 强安全性, 秘密共享, 动态组群

Abstract: Combined Public Key (CPK) cryptography does not need certificates to guarantee the authenticity of public keys, and avoids the problem that user’s private key completely depends on the Key Management Center (KMC). Based on CPK, a constantround group key exchange protocol was presented, which was provably secure under the intractability of computation DiffieHellman problem and achieved perfect forward secrecy. The protocol has only two communication rounds and it is more efficient than other protocols both in communication and computation. It supports group member join/leave operations efficiently and only needs minimum amount of computation and communication to renew the group key especially for multiple joins/leaves. At the same time, it also assures backward secrecy and forward secrecy. Moreover, the protocol achieves strong security. It can keep the session key secret from the adversary except that one party’s ephemeral private key and static private key are all revealed to the adversary. Lastly, the protocol provides a method to design efficient constantround group key exchange protocols with strong security and most secret sharing schemes can be adopted to construct the protocol.

Key words: group key exchange, CPK, strong security, secret sharing, dynamic group