I have the exe for “Super Alpha” - Definately CD-COPS protected, but not the original CD.
I guess, and this is only a theory, that
CD-COPS might do this:
If say we have two sectors on the outer edge of the CD which are in the same “line” and are quite close to each other, CD-COPS reads from the first to the second (a short distance - eg 50 degrees), giving a value for the seek. Given that the CD always spins in the same direction, when CD-COPS next seeks from the second to the first, the CD reader has to spin the CD right round (eg 310 degrees).
By adding together the values or getting a value from seeking the first then seeking the first again (in someway that the reader has to spin the CD round completely) - CD-COPS gets the time to seek 360 degrees.
By dividing the values for “first to second” and “second to first” by this value, it can get the precise angles (eg: 51.9812 degrees and 308.1298 degrees)
It then converts these measurements into a key via a series of encryption algorithms.
This angle will be the same for every CD produced from one glass master.
I have tried to implement this method, but given that it is not hugely reliable, CD-COPS must have a lot of rechecks and averaging of measurements as well.
The person who can really explain this though is Venom386 (The DT developer) - because DT 3.17 can emulate CD-COPS so I presume that he obviously has a pretty good understanding of how it works.