Chosen ciphertext secure public key encryption with a simple structure

Abstract

In this paper, we present a new public key encryption scheme with an easy-to-understand structure. More specifically, in the proposed scheme, for fixed group elements g 1,...,g in the public key a sender computes only for encryption where r is a single random number. Due to this simple structure, its security proof becomes very short (and one would easily understand the simulator's behavior for simultaneously dealing with embedding a hard problem and simulating a decryption oracle). Our proposed scheme is provably chosen-ciphertext secure under the gap Diffie-Hellman assumption (without random oracles). A drawback of our scheme is that its ciphertext is much longer than known practical schemes. We also propose a modification of our scheme with improved efficiency. © 2008 Springer Berlin Heidelberg.