How disks are `padlocked'

Abstract

Copy protection uses special techniques to write information on a floppy disk, that the disk drive of an ordinary personal computer can read but cannot write. When a user makes a copy of this disk, that information will thus be lost. Software embedded in the application program can check for this unique data. If it is there, the disk is legitimate; if it is not, the disk is a copy, and the program terminates. The methods described for protecting a disk against copying are: bad sectoring; the use of spiral tracks and offset tracks which depend intimately on the hardware characteristics of the system involved; extra sectors slipped into the outer tracks of some disks; fake sectors; super sectors (write-splicing); sector alignment; wide tracks; and weak bit encoding. The legal, technical, and ethical questions that arise are explored.