Abstract

This paper investigates a new framework to analyze symmetric ciphers by guessing intermediate states and dividing algorithms into consecutive sub-ciphers. It is suitable for lightweight ciphers with simple key schedules and block sizes smaller than key lengths. New attacks on the block cipher family KATAN are proposed by adopting this framework. Our new attacks can recover the master keys of 175-round KATAN32, 130-round KATAN48 and 112-round KATAN64 faster than exhaustive search, and thus reach many more rounds than previous attacks. We also provide new attacks on 115-round KATAN32 and 100-round KATAN48 in order to demonstrate this new kind of attacks can be more time-efficient and memory-efficient than existing attacks.