RSM protection of the present lightweight cipher as a RISC-V extension

Embedded technologies such as IoTs, connected cars or medical equipment are often executed in constrained environment with limited resources. The high demand of security makes cryptography essential. Moreover, the security must consider physical attacks as these objects are physically accessible and can be tampered with. Lightweight Cryptography (LWC) proposes interesting candidates for securing the communications in constrained environments. As many lightweight cryptographic algorithms have been proposed with closed architectures, the features of agility and genericity could be considered. Moreover, a high robustness against side-channel analysis (SCA) is required when the connected object executes sensitive applications or manipulates private data. In this work, we propose the use of Rotating SBox Masking (RSM) protection as a generic protection that would fit most lightweight block cipher, more specifically those using 4×4 substitution boxes. This protection is developed as an extension to the RISC-V ISA through the use of additional generic instructions. This specific instruction set was implemented on the VexRisc core processor and tested with a protected implementation of the PRESENT cipher. It is easily portable to most nibble-based LWC cipher types. The security analysis of this secure RISC-V processor showed that SCA were impossible with up to 1 million traces.