Optimized Software Implementations for the Lightweight Encryption Scheme ForkAE

In this work we develop optimized software implementations for ForkAE, a second round candidate in the ongoing NIST lightweight cryptography standardization process. Moreover, we analyze the performance and efficiency of different ForkAE implementations on two embedded platforms: ARM Cortex-A9 and ARM Cortex-M0. First, we study portable ForkAE implementations. We apply a decryption optimization technique which allows us to accelerate decryption by up to 35%. Second, we go on to explore platform-specific software optimizations. In platforms where cache-timing attacks are not a risk, we present a novel table-based approach to compute the SKINNY round function. Compared to the existing portable implementations, this technique speeds up encryption and decryption by 20% and 25%, respectively. Additionally, we propose a set of platform-specific optimizations for processors with parallel hardware extensions such as ARM NEON. Without relying on parallelism provided by long messages (cf. bit-sliced implementations), we focus on the primitive-level ForkSkinny parallelism provided by ForkAE to reduce encryption and decryption latency by up to 30%. We benchmark the performance of our implementations on the ARM Cortex-M0 and ARM Cortex-A9 processors and give a comparison with the other SKINNY-based schemes in the NIST lightweight competition – SKINNY-AEAD and Romulus.