A 10-Round Attack on Midori-64

Abstract

Midori is a lightweight block cipher introduced by Banik et al. at ASIACRYPT 2015. It comes in two variants: Midori-64, which has a 64-bit state with 16 rounds, and Midori128, which has a 128 -bit state with 20 rounds. Both use a 128 -bit key. In this work, we present the first truncated differential attack on Midori-64. We construct a 6-round truncated differential by precisely computing the propagation probabilities of specific truncated differences through the cipher's matrix multiplication layer, as well as identifying the positions they may occupy. We also determine its exact probability, with a ratio of approximately 1.85 compared to a random permutation. Using this distinguisher, we mount the first known truncated differential attack on 10 -round Midori-64. Although our attack does not compromise the fullround cipher, it ranks among the most effective known attacks on reduced-round Midori. © 2025 IEEE.