Improved biclique cryptanalysis of the lightweight block cipher piccolo

Abstract

Biclique cryptanalysis is a typical attack through finding a biclique which is a type of bipartite diagram to reduce the computational complexity. By investigating the subkey distribution and the encryption structure, we find out a weakness in the key schedule of Piccolo-80. A 6-round biclique is constructed for Piccolo-80 and a 7-round biclique for Piccolo-128. Then a full round biclique cryptanalysis of Piccolo is presented. The results of the attacks are with data complexity of240 and 224 chosen ciphertexts and with computational complexity of 279.22 and 2127.14respectively. They are superior to other known results of biclique cryptanalytic on Piccolo.