{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,15]],"date-time":"2026-08-15T20:36:03Z","timestamp":1786826163239,"version":"build-2736575974"},"reference-count":0,"publisher":"Universitatsbibliothek der Ruhr-Universitat Bochum","issue":"4","license":[{"start":{"date-parts":[[2025,9,5]],"date-time":"2025-09-05T00:00:00Z","timestamp":1757030400000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["TCHES"],"abstract":"<jats:p>The Hamming Quasi-Cyclic (HQC) key encapsulation mechanism (KEM), recently selected by NIST for standardization in the Post-Quantum Cryptography (PQC) process, distinguishes itself through its efficiency, robust design based on hard decoding problems in coding theory, and well-characterized decryption failure rates. Despite its selection, practical security concerns arise from implementation threats, particularly those exploiting plaintext-checking (PC) oracles. While multi-value PC (MV-PC) and full decryption (FD) oracle attacks have been extensively studied in the context of lattice-based cryptography, their applicability to code-based schemes like HQC has remained relatively unexplored.In this work, we present the first MV-PC and FD oracle attacks targeting codebased KEMs, specifically on HQC. Our MV-PC attack significantly reduces the required oracle queries compared to previous PC oracle-based methods and holds implications for side-channel, key-mismatch, and fault-injection attacks. Our FD attack exhibits remarkable efficiency in trace complexity, achieving secret key recovery for hqc-128 with just two queries to a perfect oracle, and four queries for hqc-192 and hqc-256. Simulations further demonstrate the robustness of our MV-PC and FD oracle attacks against imperfect oracle responses. We experimentally validate the new attacks on an ARM Cortex-M4 microcontroller, highlighting the critical need for robust countermeasures. In particular, on such a platform, substantial leakage during operations like syndrome computation poses significant challenges to the efficiency of masking techniques in mitigating FD oracle attacks.<\/jats:p>","DOI":"10.46586\/tches.v2025.i4.254-289","type":"journal-article","created":{"date-parts":[[2025,9,5]],"date-time":"2025-09-05T13:10:38Z","timestamp":1757077838000},"page":"254-289","source":"Crossref","is-referenced-by-count":5,"title":["Multi-Value Plaintext-Checking and Full-Decryption Oracle-Based Attacks on HQC from Offline Templates"],"prefix":"10.46586","volume":"2025","author":[{"given":"Haiyue","family":"Dong","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Qian","family":"Guo","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"25480","published-online":{"date-parts":[[2025,9,5]]},"container-title":["IACR Transactions on Cryptographic Hardware and Embedded Systems"],"original-title":[],"link":[{"URL":"https:\/\/tches.iacr.org\/index.php\/TCHES\/article\/download\/12410\/12139","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/tches.iacr.org\/index.php\/TCHES\/article\/download\/12410\/12139","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,9,5]],"date-time":"2025-09-05T13:10:38Z","timestamp":1757077838000},"score":1,"resource":{"primary":{"URL":"https:\/\/tches.iacr.org\/index.php\/TCHES\/article\/view\/12410"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,9,5]]},"references-count":0,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2025,9,5]]}},"URL":"https:\/\/doi.org\/10.46586\/tches.v2025.i4.254-289","relation":{},"ISSN":["2569-2925"],"issn-type":[{"value":"2569-2925","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,9,5]]}}}