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ruv 29233db6d5 docs(adr-118): BFLD — Beamforming Feedback Layer for Detection (6 ADRs + research bundle)
Introduce the Beamforming Feedback Layer for Detection: the RuView safety layer
that ingests WiFi BFI, measures identity-leakage risk, and structurally prevents
identity-correlated data from leaving the node by default.

ADRs (6):
- ADR-118: umbrella decision, crate scaffolding, 6-phase rollout (~10.5 wk)
- ADR-119: BfldFrame wire format, magic 0xBF1D_0001, deterministic serialization
- ADR-120: 4 privacy classes, BLAKE3 keyed-hash rotation, #[must_classify] default-deny
- ADR-121: 9-feature identity-risk scoring, coherence gate with hysteresis
- ADR-122: 6 HA entities, 3 Matter clusters, mosquitto ACL, cognitum-v0 federation
- ADR-123: Pi 5 / Nexmon production capture, AX210 dev path, ESP32-S3 self-only fallback

Research bundle (docs/research/BFLD/, 13,544 words):
- SOTA survey covering BFId (KIT, ACM CCS 2025) and LeakyBeam (NDSS 2025)
- Architectural soul: defensive sensing primitive, not surveillance lens
- Six-adversary threat model with attack trees and mitigations
- Privacy-gating mechanics with structural cross-site isolation proof
- Automation/integration surface (HA, Matter, MQTT, federation)
- Concrete implementation plan with reuse map
- Evaluation strategy with red-team protocol on KIT BFId dataset
- Draft ADR, GitHub issue, and public gist

Three structural invariants enforced by the type system, not policy:
  I1 — Raw BFI never exits the node
  I2 — Identity embedding is in-RAM-only (no Serialize impl)
  I3 — Cross-site identity correlation is cryptographically impossible
       (per-site BLAKE3 keyed-hash with daily epoch rotation)

References:
  https://publikationen.bibliothek.kit.edu/1000185756 (BFId)
  https://www.ndss-symposium.org/wp-content/uploads/2025-5-paper.pdf (LeakyBeam)

Co-Authored-By: claude-flow <ruv@ruv.net>
2026-05-24 12:20:52 -04:00

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3.7 KiB
Markdown

# BFLD Research Bundle — Beamforming Feedback Layer for Detection
BFLD is the safety layer that detects when RF data becomes identifying. It sits between
raw 802.11 beamforming feedback (BFI) and every downstream consumer — home automation,
MQTT, Matter, cloud — measuring the identity-leakage potential of each frame and gating
what leaves the node. It does not produce identity; it guards against accidental or
adversarial exposure of identity.
---
## Table of Contents
| File | Purpose |
|------|---------|
| [01-sota-survey.md](01-sota-survey.md) | State-of-the-art literature: BFI vs CSI, attack tooling, identity-inference research, privacy-preserving techniques |
| [02-soul.md](02-soul.md) | Architectural intent, ethical stance, three non-negotiable invariants |
| [03-security-threat-model.md](03-security-threat-model.md) | Adversary classes, attack trees, mitigations, trust-boundary diagram, per-privacy-class analysis |
| [04-privacy-gating.md](04-privacy-gating.md) | privacy_class byte semantics, hash rotation algorithm, embedding lifecycle, wire-format diffs |
| [05-automation-integration.md](05-automation-integration.md) | Home Assistant entities, Matter clusters, MQTT ACLs, cognitum federation |
| [06-implementation-plan.md](06-implementation-plan.md) | New crate layout, reuse map, ESP32 additions, test plan, phased rollout |
| [07-benchmarks-and-evaluation.md](07-benchmarks-and-evaluation.md) | Datasets, metrics, red-team protocol, comparison baselines |
| [08-adr-draft.md](08-adr-draft.md) | Draft ADR-118 for formal project adoption |
| [09-github-issue.md](09-github-issue.md) | GitHub issue draft for tracking implementation |
| [10-gist.md](10-gist.md) | Public-facing one-pager / blog summary |
---
## Executive Summary
1. **Problem.** IEEE 802.11ac/ax beamforming feedback (BFI) — the compressed angle matrices
(Phi/Psi, Givens rotation) exchanged between client and AP — is transmitted unencrypted
on the management plane. Academic work (BFId at ACM CCS 2025, LeakyBeam at NDSS 2025)
demonstrates that a passive sniffer with commodity hardware can re-identify individuals
and infer occupancy through walls using only these frames. Existing CSI-based sensing
pipelines have no explicit layer to detect when their output crosses from "motion event"
into "identity record."
2. **Approach.** BFLD is a new crate (`wifi-densepose-bfld`) that wraps the BFI extraction
and normalization path in an identity-leakage estimator. Every output frame carries a
computed `identity_risk_score` and a `privacy_class` byte; downstream consumers decide
whether to act based on those tags rather than on raw measurements.
3. **Novel contribution.** BFLD does not try to suppress identity inference — it tries to
*measure* it continuously and make the measurement explicit in every event. This
transforms a latent, silent risk into an observable, auditable signal. The combination
of per-day per-site hash rotation and a local-only identity embedding creates structural
impossibility of cross-site re-identification — not merely a policy promise.
4. **Security posture.** Raw BFI never leaves the node. Identity embeddings live only in
an in-RAM ring buffer. The rf_signature_hash rotates daily using a per-site blake3
keyed-hash that is never transmitted. Matter and HA expose only presence, motion, and
person_count — never risk scores or embeddings.
5. **Integration plan.** Six phases: P1 frame format + extractor stub, P2 feature
extraction + identity_risk, P3 privacy gate + MQTT, P4 HA integration, P5 Matter
exposure, P6 cognitum federation. Each phase maps to a numbered acceptance criterion.
The crate slots into the existing workspace between `wifi-densepose-signal` and
`wifi-densepose-sensing-server`.