Invalid File Sizes

Overview

That a properly produced digital copy is absolutely identical to the original seems to be a broadly held view at present, thanks to which consumers are often of the opinion that the only difference between the two options lies in the question of their price. In actuality, this isn t the case, as no two CDs are absolutely identical to each other. In fact, each CD is characterized by a set of unique parameters that differentiate it from all other CDs. These unique characteristics (later on, we ll call them marks ) can be used by protection mechanisms for the identification of original media and weeding out unauthorized copies.

Professional ethics oblige protection developers to use only the marks that satisfy the following (rather stringent) requirements as means for this type of identification:

• The mark must be detected without errors by all existing drives .

• The mark mustn t be reproducible by any copier .

• The mark stability against any external influence (scratches or the natural aging of the disc) mustn t be lower than that of other data written using a standard method.

Unfortunately, a protection mechanism that can satisfy all of the above-listed requirements has yet to be invented. Quite often, customers encounter the situation where a program legally purchased erroneously considers itself to be a counterfeit copy and refuses to run. What are chosen as the key characteristics by protection developers? An analysis of existing protection mechanisms shows that they include, first, physical media flaws (both natural and those purposely introduced); second, the timing characteristics for reading sector groups; third, reading stability; and finally, the information reported by the storage medium itself ( ATIP , in particular).