International Association for Cryptologic Research

International Association
for Cryptologic Research


Cache-Timing Attack Against HQC

Senyang Huang , Lund University, Lund, Sweden
Rui Qi Sim , The University of Adelaide, Adelaide, Australia
Chitchanok Chuengsatiansup , The University of Melbourne, Melbourne, Australia
Qian Guo , Lund University, Lund, Sweden
Thomas Johansson , Lund University, Lund, Sweden
DOI: 10.46586/tches.v2023.i3.136-163
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Abstract: In this paper, we present the first chosen-ciphertext (CC) cache-timing attacks on the reference implementation of HQC. We build a cache-timing based distinguisher for implementing a plaintext-checking (PC) oracle. The PC oracle uses side-channel information to check if a given ciphertext decrypts to a given message. This is done by identifying a vulnerability during the generating process of two vectors in the reference implementation of HQC. We also propose a new method of using PC oracles for chosen-ciphertext side-channel attacks against HQC, which may have independent interest.We show a general proof-of-concept attack, where we use the Flush+Reload technique and also derive, in more detail, a practical attack on an HQC execution on Intel SGX, where the Prime+Probe technique is used. We show the exact path to do key recovery by explaining the detailed steps, using the PC oracle. In both scenarios, the new attack requires 53, 857 traces on average with much fewer PC oracle calls than the timing attack of Guo et al. CHES 2022 on an HQC implementation.
  title={Cache-Timing Attack Against HQC},
  journal={IACR Transactions on Cryptographic Hardware and Embedded Systems},
  publisher={Ruhr-Universit├Ąt Bochum},
  volume={2023, Issue 3},
  author={Senyang Huang and Rui Qi Sim and Chitchanok Chuengsatiansup and Qian Guo and Thomas Johansson},