Improved Group-Oriented Encryption for Group Communication

In open network environment, a group-oriented encryption scheme is vulnerable to collude attack since lots of members are involved in such a scheme. In order to improve the security of Ma et al.'s encryption scheme and make it withstand collude attack, the identities of the users are used in designing the group-oriented encryption scheme in this paper. A sender in this scheme is allowed to encrypt a message using the group public key and send the ciphertext to the group. Any user in the group can independently decrypt the ciphertext via his private key. Finally, two theorems are given to show that the scheme also withstands adaptively chose ciphertext attack in random oracle model.