Public-Key Encryption Schemes With Bounded CCA Security and Optimal Ciphertext Length Based on the CDH and HDH Assumptions

In a public key encryption scheme was proposed against adversaries with a bounded number of decryption queries based on the decisional Diffie-Helman Problems. In this paper, we show that the same result can be easily obtained based on weaker computational assumptions, namely: the computational Diffie-Helman assumption and the hashed Diffie-Helman assumption.