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Unspoofable Device Identity Using Flash Memory
wiredmikey writes with a story from Security Week that describes a security silver lining to the inevitable errors that arise in NAND flash chips. By seeking out (or intentionally causing) defects in a given part of the chip, a unique profile can be created for any device using NAND flash which the author says may be obscured, but not reproduced: "[W]e recognize devices (or rather: their flash memory) by their defects. Very much like humans recognize faces: by their defects (or deviations from the 'norm') a bigger nose, a bit too bushy eyebrows, bigger cheeks. The nice twist is that if an attacker manages to read your device identity, he cannot inscribe it into his own device. Yes, he can create errors — like we did. But he cannot control where in the block they occur as this relies solely on microscopic manufacturing defects in the silicon."
you mean I can't create a simple device [...] by using any low-cost prototyping board to spoof a USB interface? Or SATA interface?
Markus Jakobsson wrote in the article:
No need for error-correcting codes; in fact, we will read and write "raw", which is possible since all of this will be done on OS level.
He's talking about using raw NAND flash without a (hardware) controller, which is more than likely soldered to the motherboard. All USB flash drives have a controller performing error correction, as do all CompactFlash, SD, and Memory Stick memory cards. The only popular consumer flash storage devices that don't have a built-in controller are SmartMedia and xD-Picture cards; the controller for these is inside the camera or the USB card reader.
This sounds like an early 80s copy-protection scheme that depended on the bad-sector map of the installed hard drive to identify it. It was reliable because only a low-level format would change the pattern, and very few people ever did a low-level format to their drives. The scheme failed when production improved and most drives could be manufactured error-free.