Melting SNOW-V: improved lightweight architectures

SNOW-V is a stream cipher proposed by Ekdahl et al. at IACR ToSC 2019(3) with an objective to be deployed as the encryption primitive in 5G systems. The stream cipher offers 256-bit security and is ready for deployment in the post-quantum era, in which as a rule of thumb (due to Grover's algorithm), quantum security will vary as the square root of the classical security parameters. The authors further report good software performance figures in systems supporting the AES-NI instruction set. However, they only provide a theoretical analysis of the cipher's hardware efficiency. In this paper, we aim to fill this gap. We look at the three most important metrics of hardware efficiency: area, speed and power/energy, and propose circuits that optimize each of these metrics and validate our results using three different standard cell libraries. The smallest SNOW-V circuit we propose occupies only around 4776 gate equivalents of silicon area. Furthermore, we also report implementations which consume as little as 12.7 pJ per 128 bits of keystream and operate at a throughput rate of more than 1 Tbps.