HQC (Hamming Quasi-Cyclic): standard, dates, parameters, and audit checklist
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HQC is the code-based KEM that NIST selected on 2025-03-11 (NIST IR 8545) as a backup to ML-KEM, so that a break of lattice cryptography does not leave the world without a standardized post-quantum KEM. NIST expects to publish a draft standard, anticipated as FIPS 207, in 2026 and a final standard in 2027.

Standard: FIPS 207 (expected designation, draft pending)
Standardized by: NIST
Date: Selected 2025-03-11; draft standard expected 2026, final 2027
Status: Selected, draft pending
Family: Code-based (quasi-cyclic codes)
Parameter sets: HQC-128 (cat 1, pk 2249 B, ciphertext 4433 B); HQC-192 (cat 3, pk 4522 B, ciphertext 8978 B); HQC-256 (cat 5, pk 7245 B, ciphertext 14421 B)
Audit focus: Constant-time decoding of the concatenated Reed-Muller / Reed-Solomon code | Decryption-failure rate and its impact on IND-CCA security | Quarkslab's 2025 work found correctness and security bugs in several HQC implementations; test against the latest specification | Parameter and encoding changes between Round 4 and the draft standard
Auditors: zkSecurity, Trail of Bits, NCC Group (Cryptography Services), Cryspen, Kudelski Security, Quarkslab, Least Authority, Galois, atsec information security, Riscure (Keysight), Cure53, X41 D-Sec
Sources: https://www.nist.gov/news-events/news/2025/03/nist-selects-hqc-fifth-algorithm-post-quantum-encryption | https://csrc.nist.gov/pubs/ir/8545/final | https://blog.quarkslab.com/finding-bugs-in-implementations-of-hqc-the-fifth-post-quantum-standard.html

Source page: https://pqaudit.org/algorithms/hqc/
Compiled by: PQC Audit Index editors (https://pqaudit.org/about/)
Last reviewed: 2026-09-12