What is device-attested location

Definition

What is device-attested location?

Device-attested location is a location result signed by a key held in the device’s secure hardware, accompanied by a platform attestation that the hardware is genuine, the operating system is unmodified, and the app that produced the result is the build that shipped.

Two separate guarantees

Device attestation combines two guarantees that are often confused.

A signing key the software cannot reach. On iPhone the key is held in the Secure Enclave. On Android it is held in the trusted execution environment or, where present, StrongBox. The private key never leaves the chip. The app can ask the chip for a signature but cannot copy the key.
A statement from the platform about the device. Apple App Attest and Google’s Play Integrity and key attestation let Apple or Google certify that the key lives in genuine hardware and that the app asking for signatures is the unmodified build from the store.

Together they let a relying party verify where a signature came from, as well as that it is valid.

Attest once, sign each result

The platform attestation is the expensive step, and it happens once, at enrolment. After that, each location result needs one signature from the enrolled key. That keeps the cost of each check low. The proof carries the keys and attestation chain needed to verify it, so it verifies offline.

What attestation does not do

Attestation shows that the measuring code is genuine. It does not show that the measurement is right. A genuine app on a genuine phone can still read misleading signals, so the location result must come from many signals that are hard to fake together. See proof of location for how Octet builds it, and GPS, Wi-Fi, GSM and IP for what each signal can show. Attestation also makes Apple and Google part of the trust model, and it requires an installed app.

What this does not establish

A verdict answers for a device, not a person. It says an enrolled device was inside or outside a region at a time. It does not say who was holding it. Use it alongside identity verification, never instead of it. It does raise the cost of cheating: instead of a VPN subscription, a cheater needs real devices and a person in the permitted place for every transaction.