Optical Technique Tells Fake CDs from the Originals

Pirated CDs and DVDs are a major dent in profits for large companies, considering the fact that some countries use stolen software on 70 to 80 percent of its market. This means that no revenues enter the pockets of the manufacturer, while its products are widely used. Now, scientists at the University of Granada (UG) came up with an ingenious way of detecting which CDs were fake, and which were genuine.

Most print runs record data on optical storage devices via a process called “printing,” which decreases per unit costs if the number of CDs or DVDs is very large. These runs are usually employed by artists or movie studios to release their productions, in large numbers, for international distribution and sales. This process leaves an unmistakable signature on the face of the disc itself, one that cannot be counterfeited, if software pirates do not own industrial-scale machines.

Most duplicators use CD/DVD-ROMs to multiply the software they've stolen or cracked. These devices do not “print” on the disc, but rather burn holes of different size on its surface. Identifying the type of holes left behind by these writers is very easy, and their signatures thoroughly differ from those left behind by large-scale printing.

Scientists from the Department of Optics at UG developed a fast, economic, and effective technique of identifying the type of inscription with each disc made, which helped them detect if the CD or DVD was genuine or counterfeited. The device analyzes the light reflection given off by the discs, and runs it through its decoding software. Light diffraction, specific to every disk, provides investigators with the information they need, regarding its origin.