Affiliations: Department and Graduate Institute of Computer Science and Information Engineering, Chaoyang University of Technology, 168, Gifeng E. Rd., Wufeng, Taichung County, Taiwan 413, R.O.C., e‐mail: [email protected] | Department of Information Management, Chaoyang University of Technology, 168, Gifeng E. Rd., Wufeng, Taichung County, Taiwan 413, R.O.C., e‐mail: [email protected]
Abstract: In the generalized group‐oriented cryptosystem, the sender can send a conditional message to a group of users such that only the specified sets of users in this group can cooperate to decrypt this message. In this paper, we will use an ElGamal cryptosystem and an elliptic curve ElGamal cryptosystem to achieve the purposes of generalization and group‐orientation, respectively. Both of our schemes are more efficient than Tsai et al.'s scheme in terms of sender's computational complexity.
