Technique for preventing unauthorized copying of information recorded on a recording medium and a protected recording medium

A method for prevention of usage of unauthorized copies of information recording media, such as diskettes, comprising the steps of:

• producing a variable signature on the information recording medium, which variable signature provides a different signal output upon multiple readings:
• analyzing the information recording media after producing the variable signature to provide a storable indication of the precise locations of the variable signature;
• recording onto the signature bearing recording media information the copying of which is to be resisted, the information thus recorded including said storable indication of the precise location of the variable signature;
• and
• embedding onto the signature bearing recording medium instructions requiring:
• reading the information recording medium at the location of the variable signature a plurality of times;
• comparing the read signatures obtained upon said plurality of readings to determine whether variation is present therebetween;
• and
• providing an output indication permitting usage of information stored on said information recording medium only in response to sensed variation in the read signatures upon said plurality of readings.