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

# UHPPOTE vs. Custom ESP32 — Detection vs. Prevention

A head-to-head on the [[trust-boundary]] fork: the off-the-shelf [[uhppote-controller]] versus
the [[esp32-custom-controller]]. (Synthesized from [[parking-system-architecture]] §6–7.)

| | [[uhppote-controller]] | [[esp32-custom-controller]] |
| --- | --- | --- |
| **Trust boundary** | The network | The device |
| **Security posture** | Tamper-**evident** (detection) | Tamper-**proof** (prevention) |
| **Command auth** | None — [[uhppote-udp-protocol]] is open UDP | [[challenge-response-auth]] (asymmetric sigs) |
| **Key mitigation** | [[network-isolation]] (mandatory) + [[event-log-ingestion]] | [[atecc608]] holds non-extractable key; controller stores only a public key |
| **Firmware** | Manufacturer-only; not customizable | You own it (tiny + auditable) |
| **Cost / effort** | Cheap, off-the-shelf, available now | Build + firmware reliability, EMC/surge, field maintenance |
| **Replay/forgery on the wire** | Possible — contained only by isolation | Defeated by fresh per-command nonce |
| **Safety** | Barrier operator owns it ([[barrier-not-a-door]]) | Same + explicit [[fail-state-safety]] |

## Bottom line

- The UHPPOTE is the **current choice**: good enough as a detection/audit layer **when only the
  host can reach it** (isolation) and every event lands in the [[append-only-event-chain]].
- The ESP32 is the **documented upgrade** when you need a control path that holds even against an
  attacker on the wire. They're **mixable per lane**.
- Both still rely on host-side integrity ([[append-only-event-chain]]) and external
  [[reconciliation]] as the ultimate anti-fraud control.