Sega Saturn CD – Cracked after 20 years (2016) [video]

Simply not true. I own several Saturns and action replays since the 90's.

The Pseudo Saturn Action reply hack to circumvent disc checks was only within recent years released.

Part of the copy protection includes physical features of the disc that must be pressed into it when it's produced, meaning a BluRay writer has no way of replicating it.

BR is one part key exchange, one part manufacturing, one part firmware lockouts using that key. So if you mod a drive you probably could get raw data from the disc. The problem is getting that back out to a disc correctly that another unmoded player would like it. There are projects out there that are reading data right off the read head. But they are more focused on laserdisc items.

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.

So think of a block on a CD as some amount of data (like 512 bytes), and some amount of error correction bytes. When the CD is copied those blocks aren't copied exactly, but the data is read, corrected and the block is written with the corrected data and error correction data. Most formats don't record bad blocks, nor do consumer writes write invalid blocks.

One of the original methods used as copy protection used a special industrial writer write a invalid block, data was ok but the error correction would say it's something different, and check because the consumer hardware wouldn't read or write these blocks.

> Why can't you also make a copy at the block level?

I don't know about CDs / BluRays but similar to what user jaywalk answered: back in the floppy disks days some copy-protection relied on physical differences created on purpose on the original game. It could be something as "simple" as damaging a track on purpose, by punching a hole in it. Then the game would try to read the data, any data, from that track. And the read command had to fail. A dumb block level copy wouldn't work: it could of course not physically punch a hole in a floppy disk.

So pirate groups would crack the game and ship a version of the game without the copy protection and these could be copied at will.

Protection is at the physical level. I mean, it was for the CDs, but you can easily imagine stuff that you can press onto the disc that your burner can't do.

https://youtu.be/XUwSOfQ1D3c?t=481