5 ms·

If like me, you are curious about the copy protection mentioned in the article, here is the patent that was filed about it: http://www.google.com/patents/US484

If like me, you are curious about the copy protection mentioned in the article, here is the patent that was filed about it: http://www.google.com/patents/US4849836 http://www.google.com/patents/US4849836 It relies on "fuzzy bits" which were stored on a specific track. Reading this track repeatedly should yield different values. If the same value is found multiple times, the disk is a copy. The devious aspect of this scheme is that if the program detected an illegal copy, it wouldn't abort right away but later, in various ways (system errors, killing your entire party, etc...). The check was also performed multiple times during the game (e.g. changing levels). All these reasons combined explain why it took more than a year for the first real cracks to appear.

Udo 11y ago
I'd imagine the rate of false positives was also quite high.
- incepted 11y ago
  Apparently not. The fuzzy bits created on the master discs were extremely reliable (and by that I mean "unreliable"): every time you read the track, you would get different values. Remember that a track contains a lot of bytes. The copy protection was only checking one fuzzy bit to declare the disk genuine. And these fuzzy bits were by design impossible to create on regular disk drives (thankfully!). The hardware required to create these tracks was extremely expensive and sometimes even out of stock, leaving hackers no other solution than to actually remove the protection if they wanted to produce a crack. Years later, a disk copier appeared that was able to preserve these fuzzy bits but it was way after there was any commercial interest left in the Dungeon Master titles.
  - TeMPOraL 11y ago
    > Years later, a disk copier appeared that was able to preserve these fuzzy bits but it was way after there was any commercial interest left in the Dungeon Master titles. I wonder what's the story behind that copier. Was its ability a side effect of the method they used? Or was there a legitimate commercial interest in preserving those fuzzy bits in copies? Or was actually built with pirates in mind?
jjbinx007 11y ago
The history of copy protection would make for a fantastic article in itself. The only sad thing about the copy protection in Dungeon Master is it's difficult to play the game using an emulator as you don't know if the version you're playing is a fully working crack until you get to the later levels.
MereInterest 11y ago
Wasn't that the same technique that caused StarForce DRM to destroy the CD drive? When reading the fuzzy bits, the drive's firmware notices that it is getting different values each time, and slows down its read speed to compensate. This happens many times, with no way in the firmware to reset the read speed, resulting in a useless drive.

Udo 11y ago

I'd imagine the rate of false positives was also quite high.

incepted 11y ago
Apparently not. The fuzzy bits created on the master discs were extremely reliable (and by that I mean "unreliable"): every time you read the track, you would get different values. Remember that a track contains a lot of bytes. The copy protection was only checking one fuzzy bit to declare the disk genuine. And these fuzzy bits were by design impossible to create on regular disk drives (thankfully!). The hardware required to create these tracks was extremely expensive and sometimes even out of stock, leaving hackers no other solution than to actually remove the protection if they wanted to produce a crack. Years later, a disk copier appeared that was able to preserve these fuzzy bits but it was way after there was any commercial interest left in the Dungeon Master titles.
- TeMPOraL 11y ago
  > Years later, a disk copier appeared that was able to preserve these fuzzy bits but it was way after there was any commercial interest left in the Dungeon Master titles. I wonder what's the story behind that copier. Was its ability a side effect of the method they used? Or was there a legitimate commercial interest in preserving those fuzzy bits in copies? Or was actually built with pirates in mind?

jjbinx007 11y ago

The history of copy protection would make for a fantastic article in itself. The only sad thing about the copy protection in Dungeon Master is it's difficult to play the game using an emulator as you don't know if the version you're playing is a fully working crack until you get to the later levels.

MereInterest 11y ago

Wasn't that the same technique that caused StarForce DRM to destroy the CD drive? When reading the fuzzy bits, the drive's firmware notices that it is getting different values each time, and slows down its read speed to compensate. This happens many times, with no way in the firmware to reset the read speed, resulting in a useless drive.