Improving Integral Cryptanalysis against Rijndael with Large Blocks

TL;DR

This paper introduces new four-round integral properties and extended attacks on Rijndael variants with larger blocks, achieving up to 8-round attacks with practical complexities.

Contribution

It presents novel integral properties and higher-order distinguishers for Rijndael with large blocks, extending the number of rounds vulnerable to integral cryptanalysis.

Findings

7-round attack on Rijndael-224 with $2^{80}$ complexity

Attacks extend to 8 rounds for larger block sizes

New integral properties improve cryptanalysis of Rijndael variants

Abstract

This report presents new four-round integral properties against the Rijndael cipher with block sizes larger than 128 bits. Using higher-order multiset distinguishers and other well-known extensions of those properties, the deduced attacks reach up to 7 and 8 rounds of Rijndael variants with 160 up to 256-bit blocks. For example, a 7-rounds attack against Rijndael-224 has a time complexity equal to $2^{80}$.