Yeah, that was just a search. There are 2^32 multipliers; call them m. For a bit in m*x to be useful, it must be zero for 16 symbols and one for 16 symbols.

Yeah, that was just a search. There are 2^32 multipliers; call them m. For a bit in m*x to be useful, it must be zero for 16 symbols and one for 16 symbols. Call those bits "useful bits." Try every multiplier; for each multiplier, compute all the useful bits (usually not many) and try all masks with 5 useful bits.