Efficient Implementation of AES and CTR_DRBG on 8-Bit AVR-Based Sensor Nodes

Since Rijndael algorithm was selected as the Advanced Encryption Standard (AES) by NIST, optimization research for the AES has been actively conducted on various IoT-based processors. In an 8-bit AVR environment, LIGHT version of Fast AES CTR-mode Encryption (FACE-LIGHT) was proposed at ICISC'2019 conference. However, in a Wireless Sensor Network environment, where sessions are frequently changed, FACE-LIGHT seems not efficient in terms of available memory and generating a pre-computation table. In this article, we present a new column-wise fashion implementation. Unlike previous best AES implementations, our proposed implementation in an 8-bit AVR microcontroller combines SubBytes, ShiftRows, and MixColums operations and optimizes the operation speed through efficient register scheduling. Our constant-time implementation uses a significantly less table than FACE-LIGHT in an 8-bit AVR microcontroller, achieving 2,251, 2,706, and 3,160 clock cycles when encrypting 128-bit data for each of three security levels. In particular, our 256-bit security level AES implementation is the fastest AES implementation as far as we know in 8-bit AVR microcontroller. Finally, we apply our implementation in CounTeR-mode_Deterministic Random Bit Generator (CTR_DRBG), one of the upper algorithms of a symmetric-key algorithm, to prove the generality of our optimization technology in various operating modes of AES.