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Paper 2017/1005

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

Tsunekazu Saito and Keita Xagawa and Takashi Yamakawa

Abstract

Key-encapsulation mechanisms secure against chosen ciphertext attacks (IND-CCA-secure KEMs) in the quantum random oracle model have been proposed by Boneh, Dagdelen, Fischlin, Lehmann, Schafner, and Zhandry (CRYPTO 2012), Targhi and Unruh (TCC 2016-B), and Hofheinz, Hövelmanns, and Kiltz (TCC 2017). However, all are non-tight and, in particular, security levels of the schemes obtained by these constructions are less than half of original security levels of their building blocks. In this paper, we give a conversion that tightly converts a weakly secure public-key encryption scheme into an IND-CCA-secure KEM in the quantum random oracle model. More precisely, we define a new security notion for deterministic public key encryption (DPKE) called the disjoint simulatability, and we propose a way to convert a disjoint simulatable DPKE scheme into an IND-CCA-secure key-encapsulation mechanism scheme without incurring a significant security degradation. In addition, we give DPKE schemes whose disjoint simulatability is tightly reduced to post-quantum assumptions. As a result, we obtain IND-CCA-secure KEMs tightly reduced to various post-quantum assumptions in the quantum random oracle model.

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.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
A major revision of an IACR publication in EUROCRYPT 2018
Keywords
Tight securitychosen-ciphertext securitypost-quantum cryptographyKEM
Contact author(s)
xagawa keita @ lab ntt co jp
History
2021-08-25: last of 6 revisions
2017-10-13: received
See all versions
Short URL
https://ia.cr/2017/1005
License
Creative Commons Attribution
CC BY
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