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Galileo

Copy Protection

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I think one valid form of copy protection are physical changes to the cd itself. The term weak-sector is the one most often used I believe. The software searches for things like this to verify that it has not been copied to another medium.

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I think one valid form of copy protection are physical changes to the cd itself. The term weak-sector is the one most often used I believe. The software searches for things like this to verify that it has not been copied to another medium.

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quote:
Original post by Galileo
How exactly do game makers do copy protection? Google searching just turned up Berman''s Bill...


Encryption seems to be effective. Sim Theme Park uses an encryption scheme to prevent people from copying there games, I believe it''s called Safedisc

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Hopefully this won''t descend into a piracy/anti piracy debate - it''s been done before, the same arguments & flames always arise (I''m develop commercial game titles myself so am acutely aware of the issues):


1) 99% of developers and publishers don''t do the protection themselves, instead using commercially available systems such as SafeDisc etc.

2) The essence of most protection schemes involves putting something (sectors/tracks) on the original CD which aren''t possible within the tolerances of CDRs using standard (low level) formats, sometimes even stuff which won''t work within the tolerance of pressed CDs. These usually require special glass master discs to be made and set up at with the duplication company.

3) The code side of the protection scheme wraps the main program executable in a layer of encryption and also checks for the presence of the "something" above. Usually that doesn''t contain any actual required data (due to how things like hardware error correction work it often can''t contain actual data).

4) Any protection system has to work within the tolerances of *every* CD-ROM drive on the market, so really has to be tested with a wide range. This wide range is also why PC protection schemes can never go as deep as those on platforms such as the Amiga which were able to fiddle with the lowest level (magnetic flux, screwed up MFM) stuff and still read data from them. The immense level of testing required is why most developers stay away from inventing their own schemes these days (some have been famously burnt for trying and had to deal with lots of returns since their game didn''t work on something like 40% of drives).

5) There are other higher level methods as well as the "intentionally wrong low level sector checksums/data" methods which abuse other error checking mechanisms in CDR drives and copy software. These include things such as dummy files in the catalogue which have sizes (in the catalogue, not the real data) which won''t fit on a copy, extremely short audio tracks etc.

6) On top of the actual disc protection checks, there is usually some amount of anti-cracking precaution. This stuff includes deliberately complex code, encryption, code to detect tools like SoftICE (though things like FrogsICE popped up as a countermeasure).

7) Since most protection systems are essentially "off the shelf", and often applied at the publishers, sometimes by the test departments (allegedly where most leaks occur), there''s very often absolutely no checks made by the game to see if the protection code itself is still intact.

8) Since many games have no code dependence on the actual protection system, the protection system itself can be removed/disabled by crackers leaving a fully working, unprotected game underneath. This is an area which IMO developers, publishers and software protection vendors need to collaborate on a lot more.

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