Current copy-restriction methods

In the realm of copyright protection, technology is sought which will, as a function of the reproduction process (which is perceived as being the point where abuse occurs), detect that a specific work is copyrighted, and consequently disable the reproducing mechanism. It is further sought that such technology will be both automatic and secure, and that it will be appropriate for a broad range of media. Solutions not having the force of law have been implemented for computer software (copy-protection), analog audio recordings (bias modulation and difference tones), digital audio recordings (copy prohibit codes) and video recordings (vertical destabilization).

Such solutions have generally proved unsatisfactory, either because they are not very effective (bias modulation and difference tones), have little application (copy prohibit codes for current digital audio recordings), or are so ergonomically offensive and/or intrusive to non-copyrighted operations that they reduce the value of the treated product to an unacceptably low level for commercial viability (copy-protection and vertical destabilization).

Applications of technology to restrict copying

At the present time (1988) . . .

In the Analog Realm
Any technological system used to limit copyright in the analog realm must be specific for a given medium. Therefore, each medium will have to have its own copy-restricting technology, suitable for that particular medium, its tradition of usage and its abuse.

Suggested Criteria for Legally Mandated System Performance in the Analog Realm

Effect on copyrighted work
The copy-restricting technology should not alter the intellectual property beyond the commonly accepted "just-noticeable-difference" (jnd) or difference limen for any perceptual parameter of that intellectual property.

Comment
Particularly when we are dealing with works of art and cultural artifacts, we must restrain our engineering tendency to look for the most convenient, obvious and inexpensive method of indelibly marking a work to identify it as copyrighted. Therefore, I suggest a legal standard that should reasonably protect any work of art from perceivable tampering. (In music, for instance, what I suggest would essentially limit modification within the audible frequency, amplitude and time windows to changes of less than 1 decibel, .01% of frequency or 50 microseconds of time. It is unlikely that changes smaller than these thresholds would be perceivable.)

Effect on reproducing system
The copy-restricting technology should have a statistically insignificant effect on the reproducing system in terms of performance and reliability, i.e. it should not be possible to differentiate between a reproducing system fitted with the copy-restricting technology and a similar system without it, in terms of speed, quality, reliability, etc. of the system.

Comment
This standard requires that the functionality of the reproducing system not be compromised by the copy-restricting circuitry. The value of the reproducing system should not be reduced as a function of the copy-restriction circuitry. Operation of the copy-restriction system should be sufficiently effective in normal use that the operator cannot determine if the copy-restriction mechanism is in place and operation by performance comparison with other units. Further, the circuitry should be as statistically reliable in its intended restriction of reproducing copyrighted materials as the unit itself is in normal operation.