IoT Security
What the exam tests
IoT security across device, network, platform, and application: identity, authentication, encryption, integrity, and privacy.
Core rules
- Device identity: unique ID plus secret or X.509 certificate; bootstrap should not ship shared default keys.
- Transport security: TLS for MQTT/HTTP, DTLS for CoAP/UDP; verify server certificates and pin where appropriate.
- Secure boot and firmware integrity prevent tampered images; OTA must be signed and rollback-safe.
- Least privilege: per-device credentials, scoped tokens, and command authorization.
- Privacy: minimize collected data, encrypt at rest, and define retention.
Worked example
A smart lock connects over NB-IoT. Threat model: stolen device, replay of unlock command, fake server. Controls: per-device certificate, TLS with server verification, monotonically increasing command nonce to block replay, secure element for key storage, signed OTA, and audit logs in the platform. Reasoning: each control maps to a threat; a shared password would fail device compromise and replay.
Traps
- Treating a custom protocol as security by obscurity; attackers can reverse it.
- Using TLS without certificate validation, which allows man-in-the-middle.
- Forgetting physical attack and key extraction on exposed devices.