GEM: A generic chosen-ciphertext secure encryption method

Abstract

This paper proposes an efficient and provably secure transform to encrypt a message with any asymmetric one-way cryptosystem. The resulting scheme achieves adaptive chosen-ciphertext security in the random oracle model. Compared to previous known generic constructions (Bellare, Rogaway, Fujisaki, Okamoto, and Pointcheval), our embedding reduces the encryption size and/or speeds up the decryption process. It applies to numerous cryptosystems, including (to name a few) ElGamal, RSA, Okamoto- Uchiyama and Paillier systems.