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Provision of Hardware Keys on Floppy Diskettes for Copy Protection

IP.com Disclosure Number: IPCOM000042013D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 3 page(s) / 44K

Publishing Venue

IBM

Related People

Comerford, LD: AUTHOR [+2]

Abstract

To provide copy protection for software written on floppy diskettes, hardware keys represented by variably spaced code holes are formed in the diskettes, each set of such holes having a pattern of relative angular spacings which is unique to its diskette. This type of key is transparent to the software user and can be used to prevent unauthorized copying of the program on the diskette. Copy-protection methods which use hardware keys are more effective than those which are software-based, because hardware keys are more costly to duplicate than software. Hardware keys customarily reside in the machine hardware and are interrogated by the programs which are to be protected. The present copy-protection method takes a more convenient approach by encoding the hardware key directly onto the diskette carrying the protected software.

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Provision of Hardware Keys on Floppy Diskettes for Copy Protection

To provide copy protection for software written on floppy diskettes, hardware keys represented by variably spaced code holes are formed in the diskettes, each set of such holes having a pattern of relative angular spacings which is unique to its diskette. This type of key is transparent to the software user and can be used to prevent unauthorized copying of the program on the diskette. Copy-protection methods which use hardware keys are more effective than those which are software-based, because hardware keys are more costly to duplicate than software. Hardware keys customarily reside in the machine hardware and are interrogated by the programs which are to be protected. The present copy- protection method takes a more convenient approach by encoding the hardware key directly onto the diskette carrying the protected software. This is accomplished by forming in the diskette a set of optically readable holes which are coded by variations of their relative angular positions. Two applications of this principle will be described, one for hard-sectored diskettes and the other for soft-sectored diskettes. Hard-sectored diskettes, as illustrated in Fig. 1, contain holes which mark locations at the beginning of the track and the beginning of each sector. As the diskette rotates in the drive, these holes are detected by sensing when a light positioned on one side of the diskette shines through the diskette onto a light detector on the opposite side. Each time this occurs, the drive sends a hole-detection signal to the diskette controller. After a hole has been detected at the beginning of a sector, a short time is allowed to elapse before information is read from or written onto the diskette this unused interval is called the inter-sector gap. The present method of copy protection utilizes the inter-sector gaps for coding purposes to provide a hardware key. The diskettes are manufactured in such a way that the angular positions of the holes are varied from diskette to diskette, so that each diskette is identified by a unique set of hole positions. The variation in hole position is limited only by the length of the inter- sector gap. The angular positions of the holes are communicated to the computer by measuring the amounts of time that elapse between successive "ho...