Single trace analysis against HyMES by exploitation of joint distributions of leakages

Beginning with the proposal of the McEliece cryptosystem in 1978, code-based cryptography has positioned itself as one of main categories in post-quantum cryptography (PQC). To date, the algebraic security of certain variants of McEliece cryptosystems has been challenged many times, although some of the variants have remained secure. However, recent studies on code-based cryptography have focused on the side-channel resistance since previous studies have indicated that the existing algorithms were vulnerable to side-channel analysis. In this paper, we propose the first side-channel attack on the Hybrid McEliece Scheme (HyMES) using only a single power consumption trace. HyMES is a variant of the McEliece system that provides smaller keys, along with faster encryption and decryption speed. By exploiting joint distributions of nonlinear functions in the decryption process, we were able to recover the private key of HyMES. To the best of our knowledge, this is the first work proposing a side-channel analysis based on a joint distribution of the leakages on the public-key system.