Hardware Backed Credential

A credential stored in a file or a configuration store can be read by anyone who obtains the device or a copy of its storage, and then replayed from anywhere. For a fleet, that turns one compromised device into an impersonation of any device.

A hardware-backed credential is generated inside a secure element or trusted execution environment and cannot be extracted. The device proves identity by signing a challenge with a key it can use and cannot export. Physical possession becomes necessary, and cloning becomes hard rather than trivial.

The design decisions around it are where the work is. Provisioning: the key is generated on the device, and the corresponding public key must reach the backend through a trusted path — typically a manufacturing-time certificate or an attestation the device can produce. Rotation: certificates expire, and a fleet that cannot rotate has a hard expiry date on which every device stops working, which has happened to real deployments. Revocation: a compromised device must be excluded, which requires the backend to check status rather than merely validate a signature.

The constraint to design around is that the cheapest hardware may have no secure element, in which case the honest position is a software credential with compensating controls, not a claim of hardware backing.