HQC

Code-based key encapsulation mechanism selected by NIST in March 2025 as the official backup to ML-KEM, built on entirely different mathematics.

Core Principles & Analysis

• Chosen precisely because it does not rely on lattices — insurance against a mathematical break of Module-LWE.
• Beat out BIKE and Classic McEliece in NIST's fourth-round evaluation of code-based alternates.
• Trades larger keys and ciphertexts for that independence — a few kilobytes versus ML-KEM's ~1 KB.

Specifications & Metrics

• FAMILY: Code-based (Hamming Quasi-Cyclic)
• STATUS: Backup standard
• STANDARD: Draft expected 2026–2027
• YEAR: 2025