Integral Cryptanalysis of Lightweight Block Cipher PIPO

PIPO is a lightweight block cipher proposed at ICISC 2020, which has a byte-oriented structure suitable for bit-sliced implementation and allows for efficient higher-order masking implementations. In this study, we use bit-based division property techniques to construct 6-round integral distinguishers, and propose key-recovery attacks on 8 rounds of PIPO-64/128 and 10 rounds of PIPO-64/256. The data complexity of both attacks is 263 chosen plaintexts and the time complexities are 2125 and
$2^{253.8}$
respectively. Our results complement the security analysis of PIPO, and show that the PIPO structure is resistant to recently researched cryptanalysis methods. Because only differential and linear attacks were carefully considered to determine the number of rounds of PIPO, our work, based on division property, is important for verifying the security margin.