RuView/firmware/privshield/README.md

VEIL privacy shield — end-to-end hardware implementation

This tree is the hardware/firmware realization of the VEIL compliant-waveform privacy shield (crate wifi-densepose-privshield, ADR-288; hardware program ADR-290). It takes VEIL from a synthetic reference model toward real silicon across multiple hardware providers.

Evidence discipline (read this first). Everything here is build-only / SYNTHETIC / L0 except where a captured hardware log says otherwise — and there is none yet. Per CLAUDE.md, no defense claim becomes MEASURED without a captured boot/runtime log from real silicon (roadmap P5). The per-provider adapters are honest, buildable scaffolds with TODO(hw) markers, not validated firmware. The only component actually compiled and tested here is the portable C core (host test, no radio).

Compliant waveform controls only — never jamming. Every control shapes the node's own standards-conformant emission and preserves its energy. Nothing here transmits to interfere with another station.

Architecture

        ┌────────────────────────────────────────────────────────┐
        │  core/  — portable C shield  (validated, host-tested)   │
        │  keyed Givens rotation over the fine subspace;          │
        │  SplitMix64 key schedule byte-consistent with the Rust  │
        │  crate; orthogonal ⇒ energy-preserving (not jamming)    │
        └───────────────┬───────────────────────────┬────────────┘
                        │ links against              │
        ┌───────────────▼───────┐   ┌────────────────▼───────────┐
        │ protector adapters    │   │ supporting roles           │
        │ (shape TX feedback)   │   │                            │
        │  • openwifi/ (SDR)    │   │  • esp32/ sensing detector │
        │  • openwrt/  (mac80211)│  │    → trigger the shield     │
        │  • nexmon/   (Broadcom)│  │  • esp32/ RIS controller    │
        └───────────────────────┘   │    → external scramble     │
                                     └────────────────────────────┘

• core/ — the shared, hardware-agnostic keyed-rotation implementation. Pure C99, no malloc, no libc I/O, only <math.h>. Validated here: cd core && make test (energy conservation, reversibility, wrong-key-fails, and a PRNG stream that matches the Rust crate exactly). This is what makes the on-air behavior identical across every provider and consistent with the reference crate.
• Protector adapters apply the core's rotation to the transmitted beamforming feedback / spatial mapping. Feasibility differs sharply by platform (see the matrix) — full control needs an open PHY (openwifi); commodity paths are partial and firmware-deep.
• Supporting roles are where cheap commodity hardware (ESP32) genuinely helps without being able to shape its own feedback: detecting sensing to trigger the shield, or driving an external reconfigurable surface (RIS).

Layout

Path	Provider	Role
core/	portable C	keyed-rotation shield core (validated host test)
openwifi/	Xilinx Zynq + AD9361 (open PHY/MAC)	full protector + the P5 measurement path
openwrt/	Linux mac80211 (mt76 / ath9k…)	commodity protector (partial; sounding/MU control feasible)
nexmon/	Broadcom/Cypress (RPi)	C-firmware-patch protector (research-grade, partial)
esp32/	Espressif ESP-IDF	sensing detector + RIS controller (NOT a feedback protector)

Feasibility matrix

Grades reflect capability to actually shape the beamforming-feedback surface (the waveform VEIL must touch), not effort. Each grade is taken from that provider's own README, produced by a hardware research agent; the effort/blocker reality is in the "Why" column. All rows are SYNTHETIC / L0 — build-only, no silicon, no captured log.

Provider	Grade	Can it shape the BF-feedback surface?	Why
openwifi (Zynq + AD9361, open PHY/MAC)	B	Yes — the only full path. Capability ceiling A; graded B for effort D.	Only platform exposing the whole PHY/MAC on FPGA, so a keyed rotation and its inverse are physically reachable. But it ships SISO 802.11a/g/n with no native explicit beamforming (no NDP sounding, no SVD V, no compressed report), so VEIL is realized as the client-transparent per-packet keyed unitary on the TX spatial-mapping stage — which requires new HDL + a 2nd TX chain + a Vivado rebuild. Carries the P5 measurement protocol.
openwrt (Linux mac80211; mt76 / ath9k / ath1x)	C	Partial — coarse compliant knobs only.	The per-packet keyed unitary on the compressed-BF angles / LTF precoder is generated inside the WiFi MCU firmware blob on every mainstream AP part (Qualcomm ath10k/11k/12k, MediaTek mt76/mt7915) — userspace never touches the pre-TX V. Reachable from userspace: TX antenna-map perturbation, hostapd sounding-cadence jitter, beamformer-capability toggles. ath9k (802.11n, register-open) is the one credible driver-patch route toward B.
nexmon (Broadcom/Cypress C-firmware patch; e.g. BCM43455c0)	C	Read = A (solved); write = C/C-.	Reading the compressed-BF angles is already solved (nexmon_csi + Wi-BFI, no firmware change). Shaping the transmitted report is graded C: the report is emitted by the proprietary D11 real-time core ~10 µs after the NDP, from hardware-updated internal memory — below the ARM firmware where Nexmon's C hooks live. Plausible, deep, firmware-version-specific, unproven here.
esp32 (Espressif ESP-IDF)	F / B	F as a self-protecting node; B as a supporting device.	The BF-report is emitted by the closed esp-phy-lib blob with no ESP-IDF hook to intercept or rotate it (esp_wifi_80211_tx won't hand-craft sounding feedback) — so F (infeasible) for shaping its own feedback. It earns B (build-only) in three legitimate, compliance-only supporting roles: sensing detector (CSI-rate trigger for the AP-side shield) and RIS controller (drive an external passive reconfigurable surface — the honest way ESP32 "helps scramble", via an external surface, never its own PHY).

Reading the grades. Only openwifi can host the full keyed-reversible VEIL design end-to-end (and only after real HDL work). openwrt and nexmon are partial: the exact angles are blob-/ucode-locked on commodity silicon, leaving either coarse compliant perturbations (openwrt) or a deep, unproven ucode-adjacent hook (nexmon). esp32 cannot shield its own feedback at all — it contributes as a detector or an external-RIS driver. The direct answer to "can OpenWRT/open WiFi software implement this, and can ESP32 scramble signals?" is: partially via OpenWRT (full only on an open PHY like openwifi), and ESP32 only indirectly via an external surface — never by shaping its own transmission.

Two firmware variants

• Keyed-reversible (VEIL's ~98%-throughput design): the protector rotates and the associated receiver undoes it with the shared key — needs changes on both ends + key agreement. Best result; needs an open PHY (openwifi) for a true demo, or the client-transparent AP-side variant below.
• Client-transparent per-packet unitary (LeakyBeam family): only the AP changes; clients are unmodified. Rides the 802.11 spatial-mapping mechanism the standard marks "not restricted".

Roadmap position

This tree is roadmap P4 (firmware feedback shaping — build). P5 is the two-node hardware measurement that produces the first MEASURED numbers with a captured log; the openwifi MEASUREMENT.md defines that protocol. See docs/research/privacy-shield/07-implementation-and-roadmap.md.