Tech Roms Copy Protection Mechanisms
|While ROM images are often used as a means of preserving the history of computer games, they are also often used to facilitate the unauthorized copying of modern games which are still commercially viable. Seeing this as potentially reducing sales of their products, many game distributors have incorporated features into newer games which are designed to prevent copying, while still allowing the original game to be played. For instance, the Nintendo GameCube used a non-standard 8 cm DVD-like optical media which for a long time prevented games from being copied to PCs. It was not until a security hole was found in Phantasy Star Online Episode I & II that GameCube games could be successfully copied to a PC.|
SNK (now known as SNK Playmore) also employed a protection on their Neo Geo games (because of bootlegs flooding the market) starting with The King of Fighters 1999 which used an encryption algorithm on the graphics ROMs that prevented them to be played in an emulator. Many thought that this was the end of NeoGeo emulation but the protection didn't last long because soon enough emulation gurus found a way to decrypt the ROMs (as early as 2000), dump them successfully and make them playable in any given NeoGeo emulator.
Another company that used to protect their arcade games was Capcom which is known for its CPS-2 arcade board (Capcom Play System II) that has a heavy protection algorithm that was broken 7 years after the system's release in 1993 by CPS2Shock Team but even this wasn't a true emulation of the protection because it used XOR tables to trick the game to decrypt and play in an emulator. Their stated intent was to wait until CPS-2 games were no longer profitable to release the decryption method (three years after the last game release). The full decryption algorithm was worked out by Nicola Salmoria, Andreas Naive, and Charles MacDonald (of MAME Dev) in 2007.
Capcom's latest arcade board to date is the CPS-3, whose encrypted ROMs have resisted emulation attempts until June 2007, when the encryption method was reverse-engineered by Andreas Naive. MAME and a variant of the CPS-2 emulator Nebula currently emulate CPS-3 games.