---
type: entity
tags: [parking, hardware, security, crypto]
sources: [parking-system-architecture]
updated: 2026-06-14
---

# ATECC608 (secure element)

An inexpensive **secure element** holding a signing key that **cannot be extracted, even by
someone who owns the machine**. The keystone of integrity in this system. (See
[[parking-system-architecture]] §3, §7.)

Two distinct uses:

1. **Host-side event signing.** Each event in the [[append-only-event-chain]] is signed by the
   ATECC608 on the host machine. This is what makes the hash chain **unforgeable** rather than
   merely self-consistent.
2. **Custom controller command authentication.** On the [[esp32-custom-controller]], it holds
   the key(s) for [[challenge-response-auth]] — generated on-chip, non-extractable, so popping
   the cabinet and dumping flash yields nothing usable.

Confirming ATECC608 wiring/usage on both ends is [[open-questions]] #6. Listed in the [[bom]]
on the host machine.

> **Platform caveat (2026-06-21):** the ATECC608 is **not a PC component** — it's an external I²C
> secure element you add/solder, native to embedded boards (the [[esp32-custom-controller]]), not to
> an off-the-shelf host PC. For a **PC-based appliance** the realistic host secure-element for the
> non-extractable event-signing key is the **[[tpm|TPM 2.0]]** the machine likely already has; reserve
> the ATECC608 for the embedded controller. Both give the same non-extractable property — see [[tpm]]
> "TPM vs. ATECC608". So use #1 (host event signing) is **TPM on a PC, ATECC608 on embedded**; use #2
> (controller command auth) stays ATECC608.