## CryptoDB

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

Authors: Venkata Koppula Brent Waters DOI: 10.1007/978-3-030-26951-7_23 Search ePrint Search Google 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 $s \in \{0,1\}^n$ and $n \cdot \ell$ bit output $y_1, \ldots , y_n$ where each $y_i$ is an $\ell$ bit string. Then for a randomly chosen s the following two distributions should be computationally indistinguishable. In the first distribution $r_{s_i, i} = y_i$ and $r_{\bar{s}_i, i}$ is chosen randomly for $i \in [n]$. In the second distribution all $r_{b, i}$ are chosen randomly for $i \in [n], b \in \{0,1\}$.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.
##### BibTeX
@article{crypto-2019-29902,
title={Realizing Chosen Ciphertext Security Generically in Attribute-Based Encryption and Predicate Encryption},
booktitle={Advances in Cryptology – CRYPTO 2019},
series={Lecture Notes in Computer Science},
publisher={Springer},
volume={11693},
pages={671-700},
doi={10.1007/978-3-030-26951-7_23},
author={Venkata Koppula and Brent Waters},
year=2019
}