Why only Macs? If we think of all PCs and mobile phones running idle, the potential is much larger.
They use the Apple TEE which they claim also protects GPU memory (I wasn't aware of this).
NVidia data center GPUs have a similar path, but not their consumer ones. Not sure about the NVidia Spark.
It's possible AMD Strix Halo can do this, but unlikely for any other PC based GPU environments.
simple first target, PCs have more variability
From the paper: https://github.com/Layr-Labs/d-inference/blob/master/papers/...
> Apple’s attestation servers will only generate the FreshnessCode for a genuine device that checks in via APNs. A software-only adversary cannot forge the MDA certificate chain (Assumption 3). Com- bined with SIP enforcement (preventing binary replace- ment) and Secure Boot (preventing bootloader tampering), this provides strong evidence that the signing key resides in genuine Apple hardware.