Integral Cryptanalysis of Round-Reduced Shadow-32 for IoT Nodes

The increasing prominence of the Internet of Things (IoT) necessitates a thorough examination of IoT nodes, as they play a critical role in transmitting, processing, and storing private data. To address the security concerns associated with IoT nodes, researchers have proposed various methods for safeguarding sensitive information and ensuring secure communication. However, existing privacy protection approaches may not cater specifically to the IoT perception layer, rendering IoT devices vulnerable to security attacks. In response to this challenge, lightweight block ciphers, such as Shadow, have emerged as a potential solution. Shadow employs a novel combination technique of generalized Feistel structure and AND-RX operations, offering improved diffusion, stability, and resistance against attacks. In this article, we leverage integral cryptanalysis, particularly the mixed integral linear programming-aided method introduced by Xiang et al., to propose a 10-round integral distinguisher for Shadow-32. By extending this characteristic to 11 rounds with a novel approach, we propose the best integral distinguisher to date, featuring 16 balanced bits. In addition, we present a comprehensive integral attack on 14 rounds of Shadow-32, which exhibits a data complexity of 2(31), a time complexity of 2(56.429), and a memory complexity of 2(24) bytes. Although our proposed attack only targets 14 out of the 16 rounds of Shadow-32, it raises concerns about the practical security of the full-round Shadow-32. Consequently, further analysis is essential to ensure the security of IoT nodes, given their significance.