Cryptology ePrint Archive: Report 2021/237

Post-quantum Security of OAEP Transform

Ehsan Ebrahimi

Abstract: In this paper, we show that OAEP transform is indistinguishable under chosen ciphertext attack in the quantum random oracle model if the underlying trapdoor permutation is quantum partial-domain one-way. The existing post-quantum security of OAEP (TCC 2016-B ) requires a modification to the OAEP transform using an extra hash function. We prove the security of the OAEP transform without any modification and this answers an open question in one of the finalists of NIST competition, NTRU submission, affirmatively.

Category / Keywords: public-key cryptography / Post-quantum Security, OAEP, Quantum Random Oracle Model

Date: received 1 Mar 2021

Contact author: ehsan ebrahimi at uni lu

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Version: 20210302:203806 (All versions of this report)

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