Paper 2020/1559 Original: eprint.iacr.org/2020/1559 ↗

On Exploiting Message Leakage in (few) NIST PQC Candidates for Practical Message Recovery and Key Recovery Attacks

Abstract

With the NIST Post quantum cryptography competition in final round, the importance of implementation security is highlighted in the latest call. In this regard, we report practical side-channel assisted message recovery attacks over embedded implementations of several post-quantum public key encryption (PKE) and key encapsulation mechanisms (KEM) based on the Learning With Errors (LWE) and Learning With Rounding (LWR) problem, which include three finalists and three semi-finalist candidates of the NIST standardization process. The proposed attacks target storage of the decrypted message in memory, a basic operation found in all libraries and typically unavoidable in any embedded implementation. We also identify interesting ciphertext malleability properties for LWE/LWR-based PKEs and exploit them to generalise proposed attack to different implementation choices as well as implementations protected with side-channel countermeasures such as shuffling and masking. All proposed attacks are validated on ARM Cortex-M4 microcontroller, targeting optimized open source implementations of PQC schemes using electromagnetic side-channel measurements.