At the time CDs debuted in late 1982, there was no worry from the industry about copying because CDs were read only and could be produced only by large-scale stamping equipment. Even more than 10 years later, CD recorders had become available but were extremely difficult to use and cost upwards of $10,000.

Even the blanks were about $35 each, often costing more than the originals you wanted to back up. Now that more than 20 years has elapsed, things have changed considerably and recording CDs is both easy and inexpensive. Unfortunately for the recording industry, the cat was already out of the bag so to speak, and adding copy protection late in the game has proven to be problematic.

It is because of this that DVDs were designed with integral copy protection from the start, which the entertainment industry had insisted on before it would allow material to be released in that format. Fortunately, though, every single type of copy protection system for CDs and DVDs has been broken, allowing users to exercise their right to make backups.

Worries about the public copying of software and music CDs has prompted the development of copy protection techniques that attempt to make these discs uncopyable. There are different methods of protecting software CDs versus music CDs, but the end result is the same: You are prevented from making normal copies, or the copies don't work properly.

In the case of music CDs, the copy protection can be quite obtrusive, adding noise to the recording, and in extreme cases preventing the disc from even playing in a PC drive. Several copy protection schemes are available for CD-DA (digital audio) discs, ranging from the simple to sophisticated.

The most popular protection scheme for digital audio discs is called SafeAudio by Macrovision. Macrovision won't explain exactly how SafeAudio works, but it purchased the technology from a company called TTR Technologies and patents filed by TTR describe the scheme in detail.

According to the patents, the disc is deliberately recorded with grossly erroneous values (bursts of noise) in both the audio data and the codes, which would typically be used to correct these errors. When reading the disc, the normal error correction scheme fails, leaving small gaps in the music.

When this happens on a standard audio CD player, the gaps are automatically bridged by circuitry or code in the player, which looks at the audio data on either side of the gap and interpolates (guesses) the missing values. The CD drive in a PC can do the same thing, so the interpolation occurs only when playing CDs in an audio player mode.

However, the drive in a PC does not perform this same interpolation when "ripping" the data—that is, copying it directly to a hard drive, another CD, or some other medium. In that case the unbridged gaps are heard as extremely loud clicks, pops, and noise.

Both TTR and Macrovision claim that the interpolation that occurs when playing a SafeAudio disc is not discernable to the human ear, but many audio experts disagree. To an audiophile, the addition of any distortion or noise to the audio signal is unconscionable.

Even more rigorous protection can be added that can render the audio disc unplayable on a PC and even cause problems on audio players. Of course, the final problem is that you can't make legal backups of your music—something that is allowed by law.

For software (rather than audio), several protection schemes are used, although most are similar to one another. Again the most popular is by Macrovision, but for CD-ROMs it is called SafeDisc. As with SafeAudio, Macrovision purchased the technology from another company; in this case it was a company called C-Dilla.

SafeDisc works by first encrypting all the software code on the disc and then adding a routine to the code that looks for a unique authentication signature (called a watermark) which would have been added to the disc during the mastering process.

When executed, the authentication code attempts to read the watermark on the disc. If the watermark is present, the main program code is unencrypted and executed. But if the watermark is not present, the program does not run. Because the watermark does not conform to the normal structures written to a CD, most CD burners can't duplicate it.

The authentication process basically requires that the original CD be present in the drive whenever the program is run. This, however, can be set up so that the original disc is required only during program installation, or it can be checked anytime the program is run, even if run from a hard disk.

The latter is quite inconvenient because it requires you to have the original CD with you at all times to run the program. To circumvent this type of protection, people have developed software that can fool the authentication code into believing the watermark is present. Some software even strips the authentication code from the software completely.

Others have found ways to copy the watermark such that it would appear on any copies of the original CD. As with other forms of copy protection, it has been easily defeated and represents more of a nuisance to the legitimate user rather than to the thief.

Unfortunately, in addition to violating my right to make backup copies, these forms of protection technically violate the original Red Book standards, rendering them unable to play on CD drives in computers or other devices. In my opinion, this cripples the software or music to the extent that I refuse to purchase any copy-protected discs.

My solution is to avoid the problem and purchase other software or music that is not encumbered by copy protection. Copy protection has been tried before (and failed) in the computer industry with floppies, and I feel we are going to see a repeat performance with CDs.

In the United States, the owner of a copyrighted work is allowed to copy that work for personal use under the 1976 doctrine of Fair Use. Because this appears to legalize making backups of both software and music, using specially designed software to copy any so-called uncopyable discs appears to also be completely legal.