A simpler explanation than some of the below: imagine a damaged CD (or floppy) where one of the “blocks” returned inconsistent data.

    for x = 1 to 10:
         total += (read $DAMAGED_BLOCK) mod 2
    assert total > 2 and total < 8

Basically you’d need extra metadata to go along with your block-copy and a custom driver to know which blocks should return inconsistent data.

Plain English explanation of the above code would be read a sector multiple times, make sure it is never always just even or just odd, but instead varies.

Usually perfection in digital media is what you strive for, but strategically introducing imperfections has a long history in authenticating “genuine” products.