CHX-128: A Lightweight ARX-Based Hash for Resource-Constrained IoT Devices
Amal P · 2025
Billions of Internet-of-Things (IoT) devices operate under tight compute, memory, and energy budgets, which complicates deploying general-purpose cryptographic hashes such as SHA-256 and SHA-3. This article presents CHX-128, a compact, software-oriented hash based on an Addition-Rotation-XOR (ARX) permutation used inside a sponge construction. The design targets small microcontrollers while avoiding table lookups and datadependent branches. The article describes the permutation structure, padding and absorbing/squeezing procedure, and reference implementation choices, and we outline a measurement methodology suitable for reproducible diffusion, balance, and microbenchmark studies on IoT-class hardware. Using the prototype, CHX-128 exhibits near-ideal avalanche and balanced per-bit flip rates on synthetic tests and stable throughput for short messages common in telemetry paths. The article discusses security considerations in light of sponge security bounds and rotational cryptanalysis of ARX designs, and recommends parameters that meet conservative bounds for a 128-bit digest. CHX-128 is not a replacement for standardized primitives; rather, it explores the trade-off space for software-minimal ARX sponges on constrained devices and provides an implementation and evaluation framework aligned with best practices for reproducibility.