> The second limitation is that it is impractical to audit the hardware to determine whether you have actually received the unmodified open source design. For software this can be achieved using reproducible builds or just by compiling it for yourself.
Mostly too expensive AFAIK. I'm fuzzy on the details, but it should be possible to create high-resolution (e.g. X-ray) scans of the chips (as is done by chip design pirates) and compare them to known-good implementations, or images generated based off the chip's open-source design.
I'm looking forward to a future where PC auditing shops are a thing. Take in your machine, and let them verify the contents of every chip and storage unit on your device.
Is there really an imaging technology that is high enough resolution to capture the detail of a modern CPU?
And if so, would that be sufficient for an audit? Aren't CPUs dependent not just on the layout of circuits but also on the material properties of the components, which might not be apparent just from images?
This is true, imaging a die can help but it's not enough for full assurance. See e.g. this work on inserting hardware trojans through changing the dopant levels on transistors http://sharps.org/wp-content/uploads/BECKER-CHES.pdf
That just increases the verification costs: order ten chips, verify five randomly chosen ones. If all five are clean, the other five are probably also clean. Modify numbers for the desired cost/risk trade-off.
Mostly too expensive AFAIK. I'm fuzzy on the details, but it should be possible to create high-resolution (e.g. X-ray) scans of the chips (as is done by chip design pirates) and compare them to known-good implementations, or images generated based off the chip's open-source design.
I'm looking forward to a future where PC auditing shops are a thing. Take in your machine, and let them verify the contents of every chip and storage unit on your device.