Zero-correlation Linear Cryptanalysis on Full-round Shadow

The rapid development of the Internet of Things (IoT) has led to an increasing demand for symmetric ciphers in IoT devices. Shadow is a lightweight block cipher proposed in 2021. In previous research, the security evaluations on Shadow against differential attack, impossible differential cryptanalysis and linear cryptanalysis were proposed. However, the security level on Shadow for zero-correlation linear cryptanalysis is still missing. In this paper, we fill this gap and propose the security evaluation on Shadow against zero-correlation linear cryptanalysis. To make thorough security analysis, two different approaches are adopted to construct zero-correlation linear distinguishers on Shadow. Based on the method of traceable pattern, 128 6-round zero-correlation linear distinguishers are constructed for Shadow-32, and 256 8-round distinguishers for Shadow-64 are constructed with similar approach. Based on the detailed linear property of the round function, 56 and 240 full-round zero-correlation linear distinguishers are constructed for Shadow-32 and Shadow-64 respectively. To validate the correctness of our theoretical analysis, a series of experiments are conducted, which matches our results well. The result in this paper implies Shadow cannot meet the expected security level in terms of zero-correlation linear cryptanalysis.