HbAya

HbAya is a lightweight cryptographic hash algorithm developed for embedded systems to provide fast, secure data integrity checks. The algorithm was introduced in 2015 by the research group at the Institute of Cybersecurity and Communications in Tokyo. It produces a 256‑bit hash value and is intentionally designed to work efficiently on microcontrollers with limited memory and processing power. HbAya’s design uses a series of permutation, substitution, and linear mixing operations that are computationally inexpensive while retaining strong diffusion and confusion properties.

The motivation behind HbAya was to deliver a hash function that could be implemented in hardware as well as software without requiring large state sizes or complex arithmetic. The algorithm’s internal state consists of eight 32‑bit words and the rounds are structured to allow speculatively pipelined execution. In 2017, the National Institute of Standards and Technology (NIST) reviewed HbAya as part of its hash function family evaluation process, however it was not selected for standardization. Nevertheless, HbAya has been adopted by a number of commercial Internet of Things (IoT) vendors for firmware integrity verification and by some academic projects that require a small cryptographic footprint.

Key characteristics of HbAya include a key‑dependent initialization vector, resistance to collision attacks—its best known collision is that of the underlying compression function shifted by 56 bits, and easy verifiability of implementation errors through built‑in test vectors. The algorithm’s source code is publicly available under the BSD 2‑Clause license, fostering its use in both open‑source and proprietary projects.