Abstract: An apparatus for combined digital and optical processing of a cryptocurrency data block includes a digital processor that computes a hash vector from the cryptocurrency data block; a laser and splitter that produces optical input signals; optical modulators that binary phase-shift key modulate the optical input signals based on the hash vector; a photonic matrix multiplier circuit that performs an optically perform a discrete matrix-vector product operation on the modulated optical input signals to produce optical output signals, where the discrete matrix-vector product operation is defined by matrix elements limited to K discrete values, where 2?K?17; and photodetectors and comparators that perform optoelectronic conversions of the optical output signals to produce corresponding digital electronic output signals. The digital processor performs a second hash computation on an XOR result between the digital electronic output signals and the hash vector to produce a proof of work result.