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api-docs/research/privacy-shield/05-experiment-protocol.md

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+# 05 — Experiment Protocol: Attacker vs. Protector
+
+This is the "start today" deliverable from the brief: **make one RuView node the
+attacker and one the protector, and measure whether protection drives identity
+recognition toward chance while keeping throughput above 95%.** It is realized as
+a deterministic, reproducible experiment in
+[`v2/crates/wifi-densepose-privshield`](../../../v2/crates/wifi-densepose-privshield).
+
+Because it runs on **SYNTHETIC** data (no radio is touched), its numbers describe
+the model, not real hardware — reproduced by `cargo test`, and to be
+re-established on silicon with a captured log before any deployment claim.
+
+---
+
+## 1. Setup
+
+- **Protector node.** Emits beamforming feedback shaped by the VEIL controls
+  (keyed per-session fine-subspace rotation + configured feedback resolution and
+  sounding overhead). Models a legitimate AP/STA protecting a room.
+- **Attacker node.** A passive sniffer that enrolls a template per candidate from
+  captured reports, then classifies fresh captures (nearest-centroid) — the
+  BFId-class re-identification threat.
+- **Scene.** `SceneConfig` default: 64-dim report, 8 comm dims, **16 candidate
+  identities** (chance = 1/16 = 6.25%), per-identity stable fine-block signature
+  + per-session environmental nuisance.
+
+Two runs of the attacker are compared: **shield off** (the attacker sees raw
+reports) and **shield on** (every captured report is VEIL-protected). The same
+attacker faces both.
+
+---
+
+## 2. Metrics and acceptance bar
+
+| Metric | Definition | Bar |
+|---|---|---|
+| **Re-ID accuracy, shield off** | Top-1 identity accuracy on unprotected traffic | Must be well above chance (threat is real) — bar ≥ 0.5 |
+| **Re-ID accuracy, shield on** | Top-1 identity accuracy on protected traffic | Must fall into the chance band `1/N · 2 + 0.03` |
+| **Throughput ratio** | Protected link capacity ÷ baseline capacity | **≥ 0.95** |
+| **Compliance** | Emission energy ratio ≈ 1 and non-interfering | `is_compliant == true` |
+
+Overall `passed()` requires all four.
+
+---
+
+## 3. Results (SYNTHETIC, hyper-optimized default configuration)
+
+Reproduce with `cargo test -p wifi-densepose-privshield` (all 35 tests + doctest
+pass). The default shield config is the `optimize` module's output — 96 Givens
+passes at 5-bit feedback resolution (see
+[08-optimization.md](08-optimization.md)). Salient values from the reference run:
+
+| Metric | Value |
+|---|---|
+| Candidate identities | 16 |
+| Chance level | 6.25% |
+| Chance band (acceptance) | ≤ 15.5% |
+| **Re-ID accuracy, shield OFF** | **100.0%** |
+| **Re-ID accuracy, shield ON** | **4.7%** |
+| **Throughput ratio** | **97.60%** |
+| Emission energy ratio | 1.000000 |
+| Overall verdict | **PASS** |
+
+Reading the result: the attacker is a *perfect* re-identifier without protection
+(the synthetic signatures are cleanly separable), and VEIL drives it *to the
+chance floor* (4.7% sits just below the ideal 6.25%, i.e. no better than
+guessing) — while the modeled link keeps 97.6% of its throughput and the
+emission conserves energy exactly (compliant, not jamming). The same collapse
+holds under a Cosine-metric attacker and at N=32, confirming it is a property of
+the signal, not the classifier.
+
+---
+
+## 4. Determinism and the witness
+
+The experiment is byte-reproducible: no OS entropy, no wall-clock, no threads.
+`proof::Proof` folds the salient outputs (quantized to avoid last-bit f32
+round-off) into an FNV-1a witness pinned as `EXPECTED_WITNESS`. Any drift in the
+PRNG stream, rotation schedule, throughput formula, or scene geometry changes the
+witness and fails `witness_matches_pinned`. This is the same
+deterministic-proof discipline as `nvsim` and the Python `verify.py`.
+
+---
+
+## 5. Sensitivity and what to vary next
+
+`ExperimentConfig` exposes the levers for a fuller study:
+
+- **`scene.identities`** — larger N lowers the chance floor; confirm collapse
+  holds as candidates grow.
+- **`scene.env_sigma` / `beam_amplitude`** — nuisance and comm energy; stress the
+  separability assumption.
+- **`shield.feedback_bits`** — trace the privacy–throughput curve (the
+  `throughput` tests already show coarse resolution costs more).
+- **`shield.givens_passes`** — mixing strength; fewer passes should degrade the
+  collapse gracefully.
+- **Stronger attacker** — swap in a learned classifier to confirm the collapse is
+  signal-level, not classifier-level (the argument says it must be, but a
+  hardware study should verify).
+
+---
+
+## 6. Path to a real two-node measurement
+
+The synthetic experiment is the design proof. The hardware path (per CLAUDE.md,
+requires a captured log to claim MEASURED):
+
+1. Two ESP32-S3/C6 or Nexmon-capable nodes: one runs Wi-BFI capture (attacker),
+   one runs a VEIL-shaped feedback profile (protector).
+2. Enroll and test the same BFId-style classifier on captured BFI, shield off vs.
+   on; log throughput via iperf across the legitimate link.
+3. Success = the same shape as §3 on real captures, with the boot/runtime log as
+   the witness. Until then, all defense numbers remain SYNTHETIC.