swapN(0x33333333, 0xCCCCCCCC, 2, $x, $y);
    }

    /**
     * @param int $x index 1
     * @param int $y index 2
     * @return self
     */
    public function swap8($x, $y)
    {
        return $this->swapN(0x0F0F0F0F, 0xF0F0F0F0, 4, $x, $y);
    }

    /**
     * @return self
     */
    public function orthogonalize()
    {
        return $this
            ->swap2(0, 1)
            ->swap2(2, 3)
            ->swap2(4, 5)
            ->swap2(6, 7)

            ->swap4(0, 2)
            ->swap4(1, 3)
            ->swap4(4, 6)
            ->swap4(5, 7)

            ->swap8(0, 4)
            ->swap8(1, 5)
            ->swap8(2, 6)
            ->swap8(3, 7);
    }

    /**
     * @return self
     */
    public function shiftRows()
    {
        for ($i = 0; $i < 8; ++$i) {
            $x = $this->values[$i] & P