Until photonic processors become cheap, and then it’s a keccak-256 ASIC. Silicon wafers at 90nm quality are already quite cheap, but actually, a photonic waveguide can be made out of doped glass or grown on any substrate. Also, the 3D integration possibilities are nearly endless. If there was a real economic demand for these processors, the cost would go to nearly zero.<p>If you can figure out an actual hash with just the photonic part, then you have a strong case.