Paper 2011/500

Biclique Cryptanalysis of the Block Cipher SQUARE

Hamid Mala

Abstract

SQUARE, an 8-round substitution-permutation block cipher, is considered as the predecessor of the AES. In this paper, inspired from the recent biclique attack on the AES by Bogdanov et al., we present the first single-key attack on full SQUARE. First, we introduce a biclique for 3 rounds of SQUARE using the independent related-key differentials. Then, we present an attack on the full round of this cipher with a data complexity of about 2^48 chosen plaintexts and a time complexity of about 2^126 encryptions.