{ if len(x) != len(y) { return 0 } var v byte for i := 0; i < len(x); i++ { v |= x[i] ^ y[i] } return ConstantTimeByteEq(v, 0) } // ConstantTimeSelect returns x if v == 1 and y if v == 0. // Its behavior is undefined if v takes any other value. func ConstantTimeSelect(v, x, y int) int { return ^(v-1)&x | (v-1)&y } // ConstantTimeByteEq returns 1 if x == y and 0 otherwise. func ConstantTimeByteEq(x, y uint8) int { return int((uint32(x^y) - 1) >> 31) } // ConstantTimeEq returns 1 if x == y and 0 otherwise....