Paper 2017/1005

Tightly-Secure Key-Encapsulation Mechanism in the Quantum Random Oracle Model

Tsunekazu Saito and Keita Xagawa and Takashi Yamakawa

Abstract

We give a first tight security reduction for a conversion from a weakly secure public-key encryption scheme to an IND-CCA-secure key-encapsulation mechanism scheme in the quantum random oracle model. To the best of our knowledge, previous reductions are non-tight as the security levels of the obtained schemes are degraded to at most half or quater of the original security level (Boneh, Dagdelen, Fischlin, Lehmann, Schafner, and Zhandry (CRYPTO 2012), Targhi and Unruh (TCC 2016-B), and Hofheinz, Hövelmanns, and Kiltz (TCC 2017)).

Note: Correct typos and update implementation results.