Improved Cryptanalysis of GIFT-64

In this paper, we propose new differential attacks against the block cipher GIFT-64. First we demonstrate how the parallel matching algorithm proposed by Naya-Plasencia at CRYPTO’11 as an advanced list-merging algorithm can be leveraged to enhance differential attacks, overcoming a previously assumed bottleneck. By reducing the complexity of the pairs generation process whenever a non-linear filter is available, this approach enabled us to mount a new differential attack against 25-round GIFT-64 in the related-key setting.Then we use the differential Meet-in-the-Middle cryptanalysis technique introduced by Boura et al. at CRYPTO’23 to improve the differential attacks recently proposed by Chang et al. at CT-RSA’25, leading to the best known attacks against GIFT-64 in the single-key setting, both in term of number of rounds and of complexity.