Question

A manufacturer is designing an IoT smart-thermostat that receives over-the-air firmware updates from a cloud server. The security team must ensure devices install only authentic, unmodified firmware, even though the devices have limited compute power and no secure display for user verification. Which control BEST achieves this goal?

Accepted Answer

Verify a digital signature on each firmware image using the manufacturer's public key stored in the device's read-only memory

Answer

Encrypt firmware images with a symmetric AES key shared by all devices before transmission

Answer

Transmit firmware over a TLS-protected channel and reject any download that fails certificate validation

Answer

Require the user to enter a one-time PIN in the mobile app before an update is applied