On the Security of Piccolo Lightweight Block Cipher against Related-Key Impossible Differentials

摘要

Piccolo is a new lightweight block cipher proposed at CHES 2011. It ciphers plaintext blocks of length 64 bits under keys of lengths 80 or 128 bits. It is based on a modified Feistel structure with a variable number of rounds. In this paper, we present two related key impossible differential attacks against 14 rounds of Piccolo-80 and 21 rounds of Piccolo-128 without the whitening layers. The attack against Piccolo-80 has a time and data complexity of 2~(68.19) whereas the time/data complexity of the attack against Piccolo-128 is 2~(117.77).