Realizing Chosen Ciphertext Security Generically in Attribute-Based Encryption and Predicate Encryption

We provide generic and black box transformations from any chosen plaintext secure Attribute-Based Encryption (ABE) or One-sided Predicate Encryption system into a chosen ciphertext secure system. Our transformation requires only the IND-CPA security of the original ABE scheme coupled with a pseudorandom generator (PRG) with a special security property. In particular, we consider a PRG with an n bit input s is an element of {0, 1}(n) and n . l bit output y(1),..., y(n) where each y(i) is an l bit string. Then for a randomly chosen s the following two distributions should be computationally indistinguishable. In the first distribution r(si), i = y(i) and r((s) over bari,i) is chosen randomly for i is an element of [n]. In the second distribution all r(b,i) are chosen randomly for i is an element of [n], b is an element of{0, 1}. We show that such PRGs can be built from either the computational Diffie-Hellman assumption (in non-bilinear groups) or the Learning with Errors (LWE) assumption (and potentially other assumptions). Thus, one can transform any IND-CPA secure system into a chosen ciphertext secure one by adding either assumption. (Or by simply assuming an existing PRG is hinting secure.) In addition, our work provides a new approach and perspective for obtaining chosen ciphertext security in the basic case of public key encryption.