---
type: concept
tags: [parking, security, foundational]
sources: [parking-system-architecture]
updated: 2026-06-14
---

# Threat Model

The **second foundational force** (with [[offline-first]]). The central insight is a
**reframing of who the adversary is**. (See [[parking-system-architecture]] §3.)

## The key reframing

Early thinking focused on protecting the database **at rest** — SQLCipher, LUKS, BitLocker,
TPM-sealed keys. All of that defends against **an outsider who steals the machine or boots from
external media**.

That is the **wrong primary threat**. The most likely adversary is the **legitimate operator at
the booth**. While the app runs, the database is decrypted in memory and the operator has full
authorised access *through the app*. Encryption does nothing against the classic parking fraud:
**take the cash, then void/delete the entry/exit record so the books balance.**

## Consequences

The controls that actually address insider/operator fraud are different in kind:

- **[[append-only-event-chain]]** — events appended, never edited/deleted; a "void" is itself a
  recorded event, hash-chained, and **[[atecc608]]-signed** (unforgeable).
- **[[reconciliation]]** against an authority the operator can't alter — *this is what remote
  sync really is*: a fraud-control mechanism, not just a backup.
- **[[disk-os-hardening]]** still worthwhile (defeats boot-from-USB) but **not the main event**;
  with LUKS in place, SQLCipher is optional defence-in-depth.

The same reframing recurs at the device layer: the [[uhppote-controller]]'s real problem is
unauthenticated commands ([[uhppote-udp-protocol]]), addressed by detection
([[event-log-ingestion]]) or prevention ([[esp32-custom-controller]]).