Paper 2020/467

Automatic Search of Meet-in-the-Middle Preimage Attacks on AES-like Hashing

Zhenzhen Bao, Xiaoyang Dong, Jian Guo, Zheng Li, Danping Shi, Siwei Sun, and Xiaoyun Wang


The Meet-in-the-Middle (MITM) preimage attack is highly effective in breaking the preimage resistance of many hash functions, including but not limited to the full MD5, HAVAL, and Tiger, and reduced SHA-0/1/2. It was also shown to be a threat to hash functions built on block ciphers like AES by Sasaki in 2011. Recently, such attacks on AES hashing modes evolved from merely using the freedom of choosing the internal state to also exploiting the freedom of choosing the message state. However, detecting such attacks especially those evolved variants is difficult. In previous works, the search space of the configurations of such attacks is limited, such that manual analysis is practical, which results in sub-optimal solutions. In this paper, we remove artificial limitations in previous works, formulate the essential ideas of the construction of the attack in well-defined ways, and translate the problem of searching for the best attacks into optimization problems under constraints in Mixed-Integer-Linear-Programming (MILP) models. The MILP models capture a large solution space of valid attacks; and the objectives of the MILP models are attack configurations with the minimized computational complexity. With such MILP models and using the off-the-shelf solver, it is efficient to search for the best attacks exhaustively. As a result, we obtain the first attacks against the full (5-round) and an extended (5.5-round) version of Haraka-512 v2, and 8-round AES-128 hashing modes, as well as improved attacks covering more rounds of Haraka-256 v2 and other members of AES and Rijndael hashing modes.

Note: Full version of the original publication.

Available format(s)
Secret-key cryptography
Publication info
A major revision of an IACR publication in EUROCRYPT 2021
AESRijndaelHaraka v2HashMITMPreimageAutomatic searchMILP
Contact author(s)
zzbao @ ntu edu sg
xiaoyangdong @ tsinghua edu cn
guojian @ ntu edu sg
lizhengcn @ bjut edu cn
shidanping @ iie ac cn
sunsiwei @ iie ac cn
xiaoyunwang @ tsinghua edu cn
2021-03-17: last of 2 revisions
2020-04-24: received
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      author = {Zhenzhen Bao and Xiaoyang Dong and Jian Guo and Zheng Li and Danping Shi and Siwei Sun and Xiaoyun Wang},
      title = {Automatic Search of Meet-in-the-Middle Preimage Attacks on AES-like Hashing},
      howpublished = {Cryptology ePrint Archive, Paper 2020/467},
      year = {2020},
      note = {\url{}},
      url = {}
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