BIKE

Bit Flipping Key Encapsulation — code-based KEM using quasi-cyclic moderate-density parity-check codes, a NIST fourth-round alternate.

Core Principles & Analysis

• Achieves far smaller keys than Classic McEliece by imposing quasi-cyclic structure on the code.
• Its iterative bit-flipping decoder has a small failure rate, which complicated security proofs.
• Lost the backup-KEM slot to HQC in 2025, largely over that decoding-failure analysis.

Specifications & Metrics

• FAMILY: Code-based (QC-MDPC)
• STATUS: Not selected
• YEAR: 2017