Paper 2026/756

Integral Attack on Reduced-Round Kalyna

Ranit Dutta, Indian Institute of Technology Jodhpur

Bimal Mandal, Indian Institute of Technology Jodhpur

Abstract

We study integral cryptanalysis of the Ukrainian block cipher Kalyna and focus on constructing reduced-round distinguishers and key-recovery attacks with low data, time, and memory complexities. Although Kalyna has an SPN-type round structure, its pre-whitening and post-whitening layers use column-wise addition modulo $2^{64}$, which makes the propagation of integral properties more delicate than in XOR-only designs. By combining carefully chosen input multisets with backward extension through inverse round transformations, we obtain integral distinguishers for Kalyna-128, Kalyna-256, and Kalyna-512 in the standard setting, under weak-key assumptions, and in variants without pre-whitening. These distinguishers require as few as $2^8$ or $2^{16}$ chosen texts, substantially improving the data complexity of previously reported public integral results on Kalyna. We further extend them to key-recovery attacks on reduced-round Kalyna by partial decryption and balancedness tests on suitable intermediate states. For example, we obtain a $5$-round key-recovery attack on Kalyna-128/128 with data complexity $2^9$ chosen plaintexts, time complexity $2^{74}$ encryptions, and negligible memory. To the best of our knowledge, this is the first work to provide integral cryptanalysis of Kalyna-256/256 and Kalyna-512/512. Overall, our results give a unified integral analysis of Kalyna across its standard block sizes and clarify the effect of modular whitening on reduced-round distinguishers and key-recovery attacks.

@misc{cryptoeprint:2026/756,
      author = {Nitish Kumar and Ranit Dutta and Bimal Mandal},
      title = {Integral Attack on Reduced-Round Kalyna},
      howpublished = {Cryptology {ePrint} Archive, Paper 2026/756},
      year = {2026},
      url = {https://eprint.iacr.org/2026/756}
}