Paper 2021/292

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

Akinori Hosoyamada and Yu Sasaki


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.

Note: Minor revision. Some errors in Section 7 are corrected. Complexity analysis is slightly changed.

Available format(s)
Secret-key cryptography
Publication info
A major revision of an IACR publication in CRYPTO 2021
hash functionSHA-256SHA-512collision attackquantum attackconversion from semi-free-start collisions
Contact author(s)
akinori hosoyamada bh @ hco ntt co jp
2021-06-25: revised
2021-03-07: received
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Creative Commons Attribution


      author = {Akinori Hosoyamada and Yu Sasaki},
      title = {Quantum Collision Attacks on Reduced SHA-256 and SHA-512},
      howpublished = {Cryptology ePrint Archive, Paper 2021/292},
      year = {2021},
      note = {\url{}},
      url = {}
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