The researchers realized that apparently identical graphics processors are actually different in subtle, unforgeable ways. A piece of software developed by the researchers is capable of discerning these fine differences. The order of magnitude of these differences is so minute, in fact, that manufacturing equipment is incapable of manipulating or replicating them. Thus, the fine-grained manufacturing differences can act as a sort of a key to reliably distinguish each of the processors from one another.
The implication of this discovery is that such differences can be used as PUFs to securely link the graphics cards, and by extension, the computers in which they reside and the persons using them, to specific online accounts.