An Enhanced Two-Step CPA Side-Channel Analysis Attack on ML-KEM

This work presents an enhanced two-step Correlation Power Analysis (CPA) attack targeting the recently standardised ML-KEM on an ARM Cortex M4. Our enhancement exploits the knowledge of intermittent variables to identify sample points of interest and develop bespoke attack functions. Step one targets the odd coefficients of each Secret Key Polynomial Vector ( ˆ s), before step two targets the remaining even coefficients using more elaborate attack functions. After successfully demonstrating key recovery for the first set of ˆ s, we then characterise leakage behaviour, revealing a trend indicating recovery of each coefficient becomes more efficient with subsequent iterations of the internal doublebasemul operation. By applying our enhanced two step attack methodology, we successfully recovered the entire key using only 179 traces, without the need for elaborate preconditions or ciphertext manipulations. We obtain remarkable results in the initial stage of our attack, while the second phase achieves performance comparable to other recent studies.