The 12th-Order Differential Attack on the 10-Round Variants of Midori64 Block Cipher

Abstract

Midori64 proposed by Banik et al. in 2015 is an SPN-type block cipher with 128-bit secret key. The designers have evaluated the security of Midori64 against differential attack, linear attack, boomerang-type attack, impossible differential attacks, and meet-in-the-middle attack by themselves. In this paper, we discuss higher-order differential attack on Midori64, which has not been analyzed yet. Higher-order differential attack proposed by Lai is one of the generic cryptanalysis technique focusing on degree of boolean polynomial of encryption function. As a result, we show the 12th-order differential attack on the 10-round variant of Midori64 where we exploit partial-sum technique proposed by Ferguson and the first-round key assumption called a round-elimination technique. The original Midori64 is secure against our attack because it consists of 16 round functions.