Rob Northen Copylock (also known simply as Copylock) is a copy-protection system designed to prevent disk duplication with standard floppy disk drives on the Amiga, Atari ST and MS-DOS platforms. It was created by British programmer Rob Northen after founding his own company Copylock Software. It was used mainly to prevent games from being copied by regular users. History In 1984, Rob Northen was hired by Acornsoft to write copy protection routines for their published software, such as the original Elite for the BBC Micro. Northen left the company six months later and started his own company Copylock Software, while still working part-time for Acornsoft to write copy protection routines, file systems and disk utilities. Northen's first copy-protected software under the Copylock name came in 1987 on the Atari ST. The first version of the Copylock software was used to protect those early Commodore Amiga and Atari ST games that had no multi-load, hence had to reside on a single floppy disk. Initially, publishers would send the unprotected master disk to Northen, who would then replace the loader program with his own encrypted loader and ship the protected master disk out for duplication. Following requests from game developers, such as The Bitmap Brothers, who were keen to implement more complex protection checks, Northen wrote subroutines that developers could implement to their own liking. In 1990, he purchased a disk duplicator and used it to create floppies with Copylock serial numbers embedded in them, which he would then send to developers in lieu of the protected master disks, along with the Copylock routines for them to include in their games. This Copylock series could accommodate more recent games with multi-load or spanning across multiple floppies. It also allowed for protection checks to be included at arbitrary points in the game code: one example of this was the Hook computer game by Ocean Software, which included an in-game protection check that if failed would cause a key item, namely a mug, to disappear from the game. In 1990, Copylock was also ported to MS-DOS-based systems. By the end of its run in 1996, around 500 commercial Amiga games had reportedly been protected with Copylock. Technical details A Copylock-protected floppy disk contains one long track, known as the Copylock Serial Track, which can be read on a standard floppy drive but is impossible to write without a sophisticated disk duplication machine. The disk