{
  "slug": "hqc",
  "name": "HQC",
  "aka": "Hamming Quasi-Cyclic",
  "kind": "Key-encapsulation mechanism (KEM)",
  "family": "Code-based (quasi-cyclic codes)",
  "standard": "FIPS 207 (expected designation, draft pending)",
  "standard_url": "https://www.nist.gov/news-events/news/2025/03/nist-selects-hqc-fifth-algorithm-post-quantum-encryption",
  "body": "NIST",
  "date": "Selected 2025-03-11; draft standard expected 2026, final 2027",
  "status": "Selected, draft pending",
  "summary": "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.",
  "parameter_sets": [
    {
      "name": "HQC-128",
      "category": 1,
      "pk": 2249,
      "sk": 2305,
      "ct_or_sig": 4433
    },
    {
      "name": "HQC-192",
      "category": 3,
      "pk": 4522,
      "sk": 4586,
      "ct_or_sig": 8978
    },
    {
      "name": "HQC-256",
      "category": 5,
      "pk": 7245,
      "sk": 7317,
      "ct_or_sig": 14421
    }
  ],
  "size_label": "Ciphertext (Round 4 submission sizes)",
  "deployments": [
    "No production deployments expected before the draft standard; available in liboqs and reference code"
  ],
  "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"
  ],
  "references": [
    [
      "NIST selects HQC as fifth algorithm (2025-03-11)",
      "https://www.nist.gov/news-events/news/2025/03/nist-selects-hqc-fifth-algorithm-post-quantum-encryption"
    ],
    [
      "NIST IR 8545, Status report on the fourth round",
      "https://csrc.nist.gov/pubs/ir/8545/final"
    ],
    [
      "Quarkslab: Finding bugs in implementations of HQC",
      "https://blog.quarkslab.com/finding-bugs-in-implementations-of-hqc-the-fifth-post-quantum-standard.html"
    ]
  ],
  "url": "https://pqaudit.org/algorithms/hqc/",
  "updated": "2026-09-12"
}