Cryptanalysis of reduced QTL block cipher

Abstract

Recently, a new ultra lightweight block cipher called QTL has been proposed. The authors claim to achieve a fast diffusion in QTL by using a new variant of a generalized Feistel network structure that changes all block messages in one iterative round in contrast to traditional Feistel-type structures changing only half of block messages. In this paper, we evaluate the security claims of the designers and show that their claims are not valid as QTL is vulnerable to the standard statistical attacks on block ciphers.