H₂B: Crypto Hash Functions Based on Hybrid Ring Generators

Protection of integrated circuits (ICs) against hardware security threats has been tackled by many schemes proposed to mitigate risks associated with an unauthorized access and usage of ICs in general, and intellectual property (IP) cores in particular. Typically, this is accomplished by virtue of hardware roots of trust whose crucial security primitives entail cryptographic hash functions. They provide data integrity services and thus can support the IC authentication protocols employed to counteract potential threats such as untrusted users accessing ICs. However, IC vendors raise concerns regarding the complexity of certain hash functions in terms of area overhead, the impact on the design flow, and testability. These concerns have motivated this work presenting a simple, yet effective, lightweight, scalable cryptographic hash function H2B. It builds on a hybrid ring generator, i.e., an area and time-optimized version of a linearfeedback shift register, which works in tandem with a nonlinear sequential circuitry whose feedback network comprises bent-like functions. A comprehensive evaluation, including test suits from the National Institute of Standards and Technology, shows the feasibility and efficiency of the proposed scheme and is reported herein.