Cryptology ePrint Archive: Report 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 tighter 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 \emph{half, quarter, or an eighth} of the original security level (Boneh, Dagdelen, Fischlin, Lehmann, Schafner, and Zhandry (CRYPTO 2012), Targhi and Unruh (TCC 2016-B), and Hofheinz, H{\"o}velmanns, and Kiltz (TCC 2017)).

Category / Keywords: public-key cryptography / Tight security, chosen-ciphertext security, post-quantum cryptography, KEM

Date: received 10 Oct 2017, last revised 28 Dec 2017

Contact author: xagawa keita at lab ntt co jp

Available format(s): PDF | BibTeX Citation

Note: Please see the version notes in Section 1.5. For example, we replace PR-CPA with Disjoint Simulatability, replace THalf with TPunc, and add concrete instantiations.

Version: 20171228:072119 (All versions of this report)

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