Tower field construction of power attack resistant 4 × 4 substitutions in lightweight SPN ciphers for implantable medical devices
VK Ashwin Karthik, GC Kamaleshwar, A Saravana Kumar, Sandeep Krishna V, Sanjith Ram V, Yogesh P, SM Verappan, A. Prathiba · Alexandria Engineering Journal · 2025
This paper introduces the design of a masked 4 × 4 S-box over a finite field using a polynomial basis to enhance resilience against Power Analysis Attacks (PAA). It unveils an additive-masked lightweight S-box tailored for the SPN-64/128 cipher engine, specifically designed to counteract side-channel power attacks. The proposed design represents the first masked nibble-sized finite field S-box, incorporating an optimized affine transformation that minimizes the XOR gate count for a compact design and low Transparency Order (TO), thereby enhancing resistance to PAA. The masking technique employed strengthens security by randomizing power consumption patterns of the non-linear inverse operations. This innovative S-box design achieves reduced area occupancy, ranging from 2 × to 11 × less than existing masked lightweight S-box implementations. Further, it reduces area overhead by 40 % compared to round-based lightweight cipher architectures employing multi-share Threshold Implementation (TI) techniques. The paper also details a streamlined mask removal process for efficient decryption, enabling secure encryption and decryption. This work sets a new benchmark for integrating effective masking techniques in real-world applications including sensitive systems like Implantable Medical Devices (e.g., pacemakers) which are particularly vulnerable to PAA, a cost-effective and non-invasive threat to Integrated Circuits (ICs).