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Publications

Publications by Manuel Barbosa

2024

Formally Verifying Kyber Episode V: Machine-Checked IND-CCA Security and Correctness of ML-KEM in EasyCrypt

Authors
Almeida, JB; Olmos, SA; Barbosa, M; Barthe, G; Dupressoir, F; Grégoire, B; Laporte, V; Lechenet, JC; Low, C; Oliveira, T; Pacheco, H; Quaresma, M; Schwabe, P; Strub, PY;

Publication
ADVANCES IN CRYPTOLOGY - CRYPTO 2024, PT II

Abstract
We present a formally verified proof of the correctness and IND-CCA security of ML-KEM, the Kyber-based Key Encapsulation Mechanism (KEM) undergoing standardization by NIST. The proof is machine-checked in EasyCrypt and it includes: 1) A formalization of the correctness (decryption failure probability) and IND-CPA security of the Kyber base public-key encryption scheme, following Bos et al. at Euro S&P 2018; 2) A formalization of the relevant variant of the Fujisaki-Okamoto transform in the Random Oracle Model (ROM), which follows closely (but not exactly) Hofheinz, Hovelmanns and Kiltz at TCC 2017; 3) A proof that the IND-CCA security of the ML-KEM specification and its correctness as a KEM follows from the previous results; 4) Two formally verified implementations of ML-KEM written in Jasmin that are provably constant-time, functionally equivalent to the ML-KEM specification and, for this reason, inherit the provable security guarantees established in the previous points. The top-level theorems give self-contained concrete bounds for the correctness and security of ML-KEM down to (a variant of) Module-LWE. We discuss how they are built modularly by leveraging various EasyCrypt features.

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