Paper 2026/764 Original: eprint.iacr.org/2026/764 ↗

CEDAR: A Compact and Efficient Decoder Architecture for RS-RM Code in HQC

Abstract

The rapid development of quantum computing has driven a new wave of cryptographic innovation: Post-Quantum Cryptography (PQC), a class of algorithms that resist quantum attacks. In particular, the National Institute of Standards and Technology (NIST) has initiated the PQC standardization process, selecting five algorithms. Notably, HQC (the newest selection) is a code-based PQC scheme that has not been widely studied in the literature, especially with respect to its hardware acceleration. This paper follows the current trend to design CEDAR, a Compact and Efficient Decoder Architecture for Reed-Solomon Reed-Muller (RS-RM) code in HQC. We have proposed three layers of contributions in total: (i) an optimized RM decoder is designed; (ii) an efficient low-complexity RS decoder is also presented; (iii) a complete HQC decoder is implemented, along with a comprehensive evaluation (it is shown that CEDAR outperforms the existing approach). We hope this outcome will facilitate a more efficient hardware acceleration of HQC and impact the ongoing NIST PQC standardization process.