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How Protection works

For the embattled music business, copyproof CDs are the killer app in the industry’s mounting war against digital piracy. The essential idea is to manufacture discs that can be played on stereo audio machines but cannot be copied onto computer hard drives.

A few systems now on the market provide such protection. The Cactus Data Shield, developed by Tel Aviv, Israel-based Midbar Tech, is embedded in more than 30 million CDs worldwide. Try to convert a Cactus-enabled CD into an MP3 file (a process known as “ripping”), you’ll get no sound at all. Sony has released 10 million CDs in Europe using its own key2audio copy-protection scheme. Such technologies are finally entering the United States as well. They debuted recently on two albums: the soundtrack More Fast and Furious, released by Universal Music Group, was protected by Midbar’s Cactus Data Shield. Charley Pride’s A Tribute to Jim Reeves, from Music City Records, used the MediaCloq encryption software developed by SunnComm in Phoenix.

Each technology works by exploiting the technical differences between traditional stereos and disc players inside computers. Stereo CDs must comply with what is known as the Red Book standard, a set of technological rules defined by Philips and Sony in 1980. The rules concern, in part, how a CD separates its tracks into different sectors on the disc. CD-ROMs, on the other hand, comply with a so-called Yellow Book standard.

Red Book and Yellow Book machines read audio in different ways. Red Book devices correct for slight defects, such as skips and scratches. And herein lies the science of copyproof CDs. When a traditional CD player encounters bad code, it skips over it and keeps playing. When a CD-ROM drive in a PC runs into such data, it loops back repeatedly until it gives up and refuses to play the disc. Midbar’s Cactus Data Shield modifies the way the tracks are encoded onto the disc in the Red Book format, rendering the audio invisible to a CD-ROM drive but still playable on a CD audio player.

While Cactus focuses on this high tech vanishing act, a competing technology developed by Macrovision in Santa Clara, CA, takes a different approach. Rather than strictly prohibiting copying, Macrovision’s SafeAudio software just makes the results close to worthless. SafeAudio employs several different methods to achieve this effect; one is based, according to product manager Steve Phillippo, “on the introduction of errors into the music.” This technique, called coding, embeds audio attributes that, when deciphered by a computer, produce a series of annoying crackles and pops. This degradation of sound quality doesn’t stop people from copying a CD, but it sure makes the results unsatisfying. Another SafeAudio technique, called timing, subverts the way in which a CD-ROM player reads audio from a spinning CD; by purposefully misleading the player into reading the data either too quickly or too slowly, it contaminates the music with unpleasant sounds or simply prevents copying.

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