Side-channel attack on Rainbow post-quantum signature

Rainbow, a layered multivariate quadratic digital signature, is a candidate for standardization in a competition-like process organized by NIST. In this paper, we present a CPA side-channel attack on the submitted 32-bit reference implementation. We evaluate the attack on an STM32F3 ARM microcontroller, successfully revealing the full private key. Furthermore, we propose a simple masking scheme with minimum overhead.