copy(xb[8-len(x):], x) copy(yb[8-len(y):], y) x0 := byteorder.BEUint64(xb) y0 := byteorder.BEUint64(yb) _, b = bits.Sub64(y0, x0, b) } return int(b ^ 1) } // ConstantTimeCopy copies the contents of y into x (a slice of equal length) // if v == 1. If v == 0, x is left unchanged. Its behavior is undefined if v // takes any other value. func ConstantTimeCopy(v int, x, y []byte) { if len(x) != len(y) { panic("subtle: slices have different lengths") } xmask := byte(v - 1) ymask := byte(^(v - 1)) for i := 0; i...