julian
8a8e74561d
Pivot from the hardware/integrity layer to the parking operation. All wiki-only; no code yet. Core principle throughout: business entities are projections over the signed append-only event log, never mutable tables. New concepts: parking-session, tariff (composable/versioned, FX-ready), shift (manned-only Z-report), capacity-occupancy, validation-discounts, reporting-analytics, clock-integrity, ticket-encoding, anti-passback. New entities: permit, opencv-anpr-service, blocklist. Decisions: session-model, vision-service (host-side ANPR + vehicle verification; scoped AGPL exception for the isolated service). Updates: append-only-event-chain (new event types + vision witness), local-jwt-auth (drop 8h expiry -> until logout; code change pending), lpr-camera (host-side recognition supersedes edge-AI), standing-decisions (AGPL exception), open-questions (+FX, +pay-station money corners, backup). Deferred + flagged: intercom/help-call, receipts/refunds/change, FX engine, lane topology (#1).
59 lines
4.1 KiB
Markdown
59 lines
4.1 KiB
Markdown
---
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type: decision
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tags: [parking, decisions, open]
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sources: [parking-system-architecture]
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updated: 2026-06-15
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status: open
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---
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# Open Questions / Next Steps
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**Not yet decided**, and they drive everything else — settle before procurement. (See
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[[parking-system-architecture]] §10.)
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1. **Lane topology.** One host per lane, or one central host driving networked devices in each
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lane? Decides how many controllers, printers, UPSs, and [[sqlite]] instances exist, and the
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failure blast radius. (A single central host is a single point of failure for *all* lanes.)
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2. **Failure modes.** Define per direction what happens to barriers on host/power/network loss —
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particularly **fail-open on exit** for egress safety. Currently unaddressed. See
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[[fail-state-safety]].
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3. **Payment subsystem.** Manned booth (P2PE terminal + cash drawer) vs unmanned pay station;
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confirm **PCI scope is kept out of the application** via a standalone certified terminal
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(see [[bom]]).
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4. **Reconciliation channel.** Even if "offline," establish *some* periodic path (USB, hotspot,
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manager visit) to reconcile the signed log against an external authority — the real anti-fraud
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control. See [[reconciliation]].
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5. **Durability / backup.** Backup strategy for the [[sqlite]] database + recovery plan; "sync
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later" currently leaves a disk failure as **total revenue-history loss**. _(Confirmed in-scope
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to design, 2026-06-15.)_ Because the DB is the signed [[append-only-event-chain]], a backup must
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preserve the chain intact (a restored copy must still `verifyChain`); options include SQLite
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WAL/online-backup snapshots to a second disk/USB + the periodic external export that doubles as
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the [[reconciliation]] channel (#4). Encryption at rest already applies ([[disk-os-hardening]]).
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Design TBD.
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6. **Secure-element integration.** Confirm [[atecc608]] wiring/usage on the host (event
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signing). The [[esp32-custom-controller]] command-authentication use is **deferred — not
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being implemented for now** (access control is the [[dingtian-relay]] behind
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[[network-isolation]]); revisit only if prevention-grade device auth becomes a requirement.
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7. **JWT signing: symmetric vs. asymmetric key.** _(Raised by the commit security review, not the
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source doc.)_ Auth currently uses a symmetric HMAC secret (`@fastify/jwt`, see
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[[local-jwt-auth]]) — the same secret signs *and* verifies, so it must live on every host that
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validates tokens. Consider rotating to an **asymmetric key (RS256 / EdDSA)** so the server
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holds only the **public key** to verify; the private signing key can then live in the
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[[atecc608]] or a key-management step. This mirrors the "store only the public key" property
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already used for [[atecc608]] event signing and the [[challenge-response-auth]] scheme —
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compromising a verifying host yields nothing that can forge a token. Decide before
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multi-host / multi-lane deployment (see #1 lane topology), since that's when shared-secret
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distribution becomes the liability.
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8. **Exchange-rate (FX) system.** _(Raised by the [[tariff]] design, 2026-06-15.)_ Currency is
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selectable per tariff version and the money model is FX-ready (`payment` stores currency + a
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reserved `fxRate`), but **no conversion is built**. If multi-currency pricing/charging is ever
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needed, it requires an **offline** rate source (rates can't depend on the network —
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[[offline-first]]), a base currency, and a rounding policy. Deferred; nothing blocks adding it
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later without migrating stored amounts.
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9. **Pay-station money corners — receipts & refunds/change.** _(Raised by the scope sweep,
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2026-06-15; deferred until pay-station hardware is chosen.)_ Not yet designed: **receipts / VAT
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invoices** (fiscal receipt with tax number + sequential numbering may be legally required — could
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change what the `payment` event must store) and **refunds / overpayment / change** (cash change,
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"exact change only", a refund as a signed reversal event). Both depend on the unmanned-vs-manned
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payment subsystem (#3) and the note/coin/card acceptor hardware. Revisit at procurement.
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