We use an int instead of bool in order to make decisions in // constant time by turning it into a mask. type choice uint func not(c choice) choice { return 1 ^ c } const yes = choice(1) const no = choice(0) // ctMask is all 1s if on is yes, and all 0s otherwise. func ctMask(on choice) uint { return -uint(on) } // ctEq returns 1 if x == y, and 0 otherwise. The execution time of this // function does not depend on its inputs. func ctEq(x, y uint) choice { // If x != y, then either x - y or y - x will...