Towards an Energy-Efficient Hash-based Message Authentication Code (HMAC)

Hash-based message authentication code (HMAC) involves a secret cryptographic key and an underlying crypto-graphic hash function. HMAC is used to simultaneously verify both integrity and authenticity of messages and, in turn, plays a significant role in secure communication protocols e.g., Transport Layer Security (TLS). The high energy consumption of HMAC is well-known as is the trade-off between security, energy consumption, and performance. Previous research in reducing energy consumption in HMAC has approached the problem primarily at the system software level (e.g. scheduling algorithms). This paper attempts to reduce energy consumption in HMAC by applying an energy-reducing algorithmic engineering technique to the underlying hash function of HMAC, as a means to preserve the promised security benefits. Using pyRAPL, a python library to measure computational energy, we experiment with both the standard and energy-reduced implementations of HMAC for different input sizes (in bytes). Our results show up to 17% reduction in energy consumption by HMAC, while preserving function. Such energy savings in HMAC, by virtue of HMAC's prevalent use in existing network protocols, extrapolate to lighter-weight network operations with respect to total energy consumption.