HQC Post-Quantum Cryptography Decryption with Generalized Minimum-Distance Reed-Solomon Decoder

Computer Science > Cryptography and Security [Submitted on 20 Mar 2026] HQC Post-Quantum Cryptography Decryption with Generalized Minimum-Distance Reed-Solomon Decoder Jiaxuan Cai, Xinmiao Zhang Hamming Quasi-Cyclic (HQC) was chosen for the latest post-quantum cryptography standardization. A concatenated Reed-Muller (RM) and Reed-Solomon (RS) code is decoded during the HQC decryption. Soft-decision RS decoders achieve better error-correcting performance than hard-decision decoders and accordingly shorten the required codeword and key lengths. However, the only soft-decision decoder for HQC in prior works is an erasure-only decoder, which has limited coding gain. This paper analyzes other hardware-friendly soft-decision RS decoders and discovers that the generalized minimum-distance (GMD) decoder can better utilize the soft information available in HQC. Extending the Agrawal-Vardy bound for the scenario of HQC, it was found that the RS codeword length for HQC-128 can be reduced from 46 to 36. This paper also proposes efficient GMD decoder hardware architectures optimized for the short and low-rate RS codes used in HQC. The HQC-128 decryption utilizing the proposed GMD decoder achieves 20% and 15% reductions on the latency and area, respectively, compared to the decryption with hard-decision decoders. Subjects: Cryptography and Security (cs.CR); Information Theory (cs.IT) Cite as: arXiv:2603.20156 [cs.CR]   (or arXiv:2603.20156v1 [cs.CR] for this version)   https://doi.org/10.48550/arXiv.2603.20156 Focus to learn more Submission history From: Jiaxuan Cai [view email] [v1] Fri, 20 Mar 2026 17:29:20 UTC (295 KB) Access Paper: HTML (experimental) view license Current browse context: cs.CR < prev   |   next > new | recent | 2026-03 Change to browse by: cs cs.IT math math.IT References & Citations NASA ADS Google Scholar Semantic Scholar Export BibTeX Citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Demos Related Papers About arXivLabs Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)