Analyzing the Leakage Resistance of the NIST’s Lightweight Crypto Competition’s Finalists

We investigate the security of the NIST Lightweight Crypto Competition’s Finalists against side-channel attacks. We start with a mode-level analysis that allows us to put forward three candidates (Ascon, ISAP and Romulus-T) that stand out for their leakage properties and do not require a uniform protection of all their computations thanks to (expensive) implementation-level countermeasures. We then implement these finalists and evaluate their respective performances. Our results confirm the interest of so-called leveled implementations (where only the key derivation and tag generation require security against differential power analysis). They also suggest that these algorithms differ more by their qualitative features (e.g., two-pass designs to improve confidentiality with decryption leakage vs. one-pass designs, flexible overheads thanks to masking vs. fully mode-level, easier to implement, schemes) than by their quantitative features, which all improve over the AES and are quite sensitive to security margins against cryptanalysis.