[NoxiousPluK]

I remember reading an article about this years ago - a non-transferable FPGA configuration which had some logic that should be unreachable but didn't work without it. Very faschinating but I've not been able to find it since.

[nick__m]

I think you want that paper "An Evolved Circuit, Intrinsic in Silicon, Entwined with Physics" available there https://cgi.cse.unsw.edu.au/~cs4601/refs/papers/es97thompson...