We can still imagine a state actor spending the megadollars to research a reliable chip-cloning process, to bring parallel brute-forcing within reach.  I wonder if the NSA have been on a SEM&#x2F;FIB equipment buying spree lately.<p>The ultimate way to defeat physical or software attacks is to exploit intrinsic properties of the universe, which suggests finding a mathematical and&#x2F;or quantum structure impervious to both.