eli5: If game console CDs just tell the game console “yeah they own this game” what was stopping people from just copying the data to other CDs and giving it to people?

Question

(besides legally)

In: 6

Answer 1

Each console has a slightly different way of constructing a disc that is impossible to be replicated with fidelity with consumer equipment, sometimes even professional replication towers.

Taking Xbox DVDs for example.

The disc have decoy information in the inner rim lead-in section and first few megabytes of the data section, pretending to be a DVD-9 movie of a few megabytes. The real metadata for the disc is at the outer rim.

There are gaps of absolutely nothing between the DVD movie partition and real game data partition.

The above two prevents any consumer DVD drives, which respects limitation parameters in the lead-in section, from moving the laser past the gap, therefore not possible to read any actual game data.

The lead-in information of a burnable disc already contained something else, therefore it is not possible to pose a burnable disc as a genuine game disc without hacking the drive.

Then there are various security sectors created in a way to be non-compliant according to official DVD standards, like altered pit length modulation, altered error correction scheme, wrong physical sector numbers, specifically crafted tracks with wobbles, overlapping destroyed tracks by burning the area twice.

These sectors will either be unreadable or be read as something else according to error correction schemes of a standard DVD, or impossible to be recreated even with industrial grade mastering equipment because physical tolerances always create a unique result each time a disc is mastered.

Then the angular distance of certain data sectors will be measured and compared, because consumer burners and even professional mastering equipment will not be able to accurately reproduce this feature either. Consumer burnable discs are already pre-indexed and will have a different angle, professionally mastered discs will always have a slightly different angle due to speed variances when mastering.

Create, measure and record those parameters to create a unique disc signature, which can easily be measured by console drives, but impossible to fake, therefore the discs can never be faked without hacking the drive to lie about the measurement results.