often did not even need to inspect the encoded Copylock routines, because the check for disk authenticity was implemented in such a way that they could clearly see what the serial key was from the code that checked for it. Therefore, whilst many people understood how Copylock worked, very few had taken the time to work out how to actually decode one. By now, however, Copylock had evolved to allow parameters to be passed to it before execution, which meant that Copylock could now write not only the serial key, but also specific game-related values into the contents of registers passed to Copylock, or simply write values to a list of predefined addresses, which would make the game operate correctly. The typical, generally incorrect way of cracking a Copylocked game was to get the serial key, modify the header of the Copylock to put the correct serial key into register D0, and then bypass all the reading and decoding process. This would mean the "special case" code in the Copylock would never be executed, which would mean the game would not work by using the serial key alone. PC version It was possible to port Copylock to the PC because the x86 microprocessor supports the trace vector the same as the 68000 processor does, through a single-step interrupt or INT 1. It manifested itself in a slightly different way in that the game's executable code was encrypted and "wrapped" by the Copylock loader. At runtime this loader would read 4 sectors from the floppy, and generate checksums from them. These in turn would be used as the keys to decrypt the game code. Once the decryption was done, the loader transferred control to the game program. The PC version was easy to circumvent, as the original game executable code was just stored inside the loader. Once you got past the disk checks, and encryption code, dumping the unencrypted executable was just a matter of performing 2 disk writes. The first would dump the unmodified "MZ" header, and the 2nd write would finish the job by saving the actual game code. Fabulous Furlough of The Humble Guys wrote a tool that did just that, and could "crack" a game in less than a minute. References External links Interview with Rob Northen about his copy-protection systems Rob Northen on MobyGames Example of a Series 1 Copylock 'Wrapper' type: Barbarian II for Atari