IACR News item: 20 July 2022
Ehsan Ebrahimi, Jeroen van Wier
ePrint Report
In this paper, we formalize the plaintext-awareness notion
in the superposition access model in which a quantum adversary may
implement the encryption oracle in a quantum device and make superposition queries to the decryption oracle. Due to various possible ways
an adversary can access the decryption oracles, we present six security
definitions to capture the plaintext-awareness notion with respect to each
way of access. We study the relationships between these definitions and
present various implications and non-implications.
Classically, the strongest plaintext-awareness notion (PA2) accompanied
by the indistinguishability under chosen-plaintext attack (IND-CPA) notion yields the indistinguishability under chosen-ciphertext attack (INDCCA) notion. We show that the PA2 notion is not sufficient to show the
above relation when targeting the IND-qCCA notion (Boneh-Zhandry
definition, Crypto 2013). However, our proposed post-quantum PA2 notion with superposition decryption queries fulfils this implication.
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