International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Quantum Collision Attacks on Reduced SHA-256 and SHA-512

Akinori Hosoyamada , NTT Corporation and Nagoya University
Yu Sasaki , NTT Corporation
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Presentation: Slides
Conference: CRYPTO 2021
Abstract: In this paper, we study dedicated quantum collision attacks on SHA-256 and SHA-512 for the first time. The attacks reach 38 and 39 steps, respectively, which significantly improve the classical attacks for 31 and 27 steps. Both attacks adopt the framework of the previous work that converts many semi-free-start collisions into a 2-block collision, and are faster than the generic attack in the cost metric of time-space tradeoff. We observe that the number of required semi-free-start collisions can be reduced in the quantum setting, which allows us to convert the previous classical 38 and 39 step semi-free-start collisions into a collision. The idea behind our attacks is simple and will also be applicable to other cryptographic hash functions.
Video from CRYPTO 2021
  title={Quantum Collision Attacks on Reduced SHA-256 and SHA-512},
  author={Akinori Hosoyamada and Yu Sasaki},