Bridge layer — how to use this section

Prereqs: finish Fundamentals (or the first six); Orientation if you skipped the story
Next: work through the ordered list below, then Concepts

Why bridge exists

Fundamentals = math and crypto intuition from scratch.
Concepts = compact PQC vocabulary cards.

The jump can feel steep (codes, syndromes, DFR, independence, LWE). Bridge pages are longer, story-first explainers that sit in the middle on purpose. More files and more wording are intentional — written so newcomers can follow with patience.

Study tip: do every tiny table on paper. Reading alone is not enough on decoding and McEliece pages.

Suggested order (code-based core)

1. From bits to codes — redundancy, repeat-3, distance
2. Noisy channel story — BSC, DFR cousin, crypto twist
3. Generator and parity-check matrices — \(G\), \(H\), syndrome
4. Decoding as a puzzle — sparse search, trapdoor gap
5. McEliece in plain words — public scramble + intentional error
6. From KEM API to noise — Encaps ↔ noise ↔ DFR
7. Finite fields beyond \(\mathbb{F}_2\) — \(\mathbb{F}_q\) postcard
8. Security bits and attack work — \(2^{128}\) work vs \(2^{-128}\) failure

Rank-metric fork (after finite fields + linear-code intuition):

1. From Hamming to rank → Rank metric track

Lattice / LWE fork (after vectors + modular arithmetic + Lattices (gentle)):

1. Noisy linear equations (LWE story) → Lattice / LWE track

PQC hardware fork (after modular arithmetic + bits; Module-LWE helpful before NTT/accelerator pages):

1. Clocks, registers, and latency
2. Area, time, power honesty → PQC hardware track

Then enter Concepts starting at Error-correcting codes (code track), LWE (lattice track), or Modular multiplier (hardware track) — they should read as summaries of ideas you already met slowly.

Already comfortable?

If a bridge page feels easy, still skim the “crypto twist” / “common confusions” sections — those prevent the usual mix-ups before concepts.