def __rshift_rows(ciphertext):
    """
        Input: ciphertext - List of lists (4x4 Matrix)

        Output: ciphertext - List of lists (4x4 Matrix)

        Reversed ShiftRows step of the algorithm. This step rotates elements in rows each by different
        amount depending on the row. First row stays the same, second is rotated to the right
        by one, third is rotated to the right by two, and fourth is rotated to the right by three.
    """
    for i in range(4):
        ciphertext[i] = ciphertext[i][-i:] + ciphertext[i][:-i]
    return ciphertext
