Research for Speed Improvement Method of Lightweight Block Cipher CHAM using NEON SIMD

Sujin Lee, Junyoung Kang, Dowon Hong, Changho Seo

http://doi.org/10.5626/JOK.2019.46.5.485

As embedded devices and IoT devices are being developed, lightweight block ciphers have been proposed to achieve confidentiality on low-end devices. Recently, a lightweight block cipher algorithm, called CHAM, with 4-branch Feistel structure was proposed in Korea. It is consists of CHAM-64/128, CHAM-128/128, and CHAM-128/256 depending on the size of plaintext and secret key. CHAM, which is based on ‘stateless on the fly’ key schedule and ARX operations, is efficient on embedded devices, especially on low-end devices. In this paper, we analyze the lightweight block cipher CHAM and study an optimization method on a high-end IoT device. We implemented a serial code by independently generating round keys and leveraging 4-branch Feistel structure, and optimized CHAM using NEON-SIMD on ARM Cortex-A53.