Regarding the copy protection process itself, there's an interesting interview at one of the links:
> The most common protection schemes were the ones that were productized and resold to hundreds of publishers. This was coordinated through the disk duplication houses, who offered copy protection as a “value add” on top of mastering the disks themselves. Publishers got the benefit of the latest and greatest copy protection without needing to play the cat-and-mouse game themselves.
> The E7 bitstream, a.k.a. “generic bit slip protection,” was the most common. It was a sequence of 1s and 0s, specially crafted so the first half could be read “in phase,” then the code would intentionally skip half a byte and read the second half “out of phase.” Bit copiers would drop bits due to hardware limitations, and the out-of-phase values would be wrong. It was brilliant.
> The most common protection schemes were the ones that were productized and resold to hundreds of publishers. This was coordinated through the disk duplication houses, who offered copy protection as a “value add” on top of mastering the disks themselves. Publishers got the benefit of the latest and greatest copy protection without needing to play the cat-and-mouse game themselves.
> The E7 bitstream, a.k.a. “generic bit slip protection,” was the most common. It was a sequence of 1s and 0s, specially crafted so the first half could be read “in phase,” then the code would intentionally skip half a byte and read the second half “out of phase.” Bit copiers would drop bits due to hardware limitations, and the out-of-phase values would be wrong. It was brilliant.
https://paleotronic.com/2018/06/15/confessions-of-a-disk-cra...