X · Coding theory
Cyclic redundancy check (CRC)
What it is
Treat the message as a binary polynomial; compute its remainder modulo a fixed generator polynomial. Detect any single burst of N consecutive bit errors.
Where it lives
Ethernet frames (CRC-32), TCP segments (with checksums on top), USB, ZIP archives, every DNS message.
The key insight
CRC is for detection only — it cannot correct errors. CRC-32 catches almost all random bit flips and any burst of ≤ 32 consecutive bit errors.