key2audio is a

copy restriction Copy protection, also known as content protection, copy prevention and copy restriction, describes measures to enforce copyright by preventing the reproduction of software, films, music, and other media. Copy protection is most commonly found on ...

system for

Audio CD Compact Disc Digital Audio (CDDA or CD-DA), also known as Digital Audio Compact Disc or simply as Audio CD, is the standard format for audio compact discs. The standard is defined in the ''Red Book'', one of a series of Rainbow Books (named ...

s, developed by

Sony DADC Sony Digital Audio Disc Corporation (Sony DADC) is a manufacturer of CDs, DVDs, UMDs, and Blu-ray Discs. The company has many plants worldwide. Although it primarily services Sony Music Entertainment-owned record labels, Sony Pictures Home En ...

. The system gained notoriety after it was discovered that one can effectively disable the system by tracing the outer edge of a CD with a felt-tip marker. The system works by applying a bogus data track onto the disc during glass master manufacturing. Since computers are designed to read data before music, this prevents playback on a PC and thereby prevents

ripping Ripping is extracting all or parts of digital content from a container. Originally, it meant to rip music out of Commodore 64 games. Later, the term was used to extract WAV or MP3 format files from digital audio CDs, but got applied as well to ...

as well as ordinary listening using a computer. CD players ignore any non-audio tracks on a disc, and can therefore play the CD unimpeded -

Enhanced CD Enhanced CD is a certification mark of the Recording Industry Association of America for various technologies that combine audio and computer data for use in both Compact Disc and CD-ROM players. Formats that fall under the "enhanced CD" ...

s also take advantage of this factor. Currently there are two major versions of the key2Audio protection: the original key2Audio, and key2AudioXS.

key2Audio

key2audio products are highly compatible because the audio session is not modified. Since additional data sessions are used, the CD is not Red Book compliant and should not use the "

Compact Disc The compact disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then released in Octo ...

" logo. As with any passive DRM technology some players are unable to play the non-standard disc. Since optical computer CD/DVD drives are also capable of reading Red Book audio CDs, a lot of player manufacturers use these same CD/DVD ROM drives instead of specialized Audio CD / Video DVD only drives in order to reduce costs. DVD players and car stereo systems seem to have most problems with incompatibilities of key2Audio protected CDs. A protected CD still achieves a maximum recording time of 77 minutes and supports full

ISRC The International Standard Recording Code (ISRC) is an international standard code for uniquely identifying sound recordings and music video recordings. The code was developed by the recording industry in conjunction with the ISO technical commit ...

, UPC and

CD-Text CD-Text is an extension of the Red Book Compact Disc specifications standard for audio CDs. It allows storage of additional information (e.g. album name, song name, and artist name) on a standards-compliant audio CD. The specification for CD- ...

capabilities. Early versions of this copy protection were infamous for being easily circumvented with a

marker pen A marker pen, fine liner, marking pen, felt-tip pen, felt pen, flow marker, sign pen (in South Korea), vivid (in New Zealand), texta (in Australia), sketch pen (in South Asia) or koki (in South Africa), is a pen which has its own ink sourc ...

, by drawing a circle on the rim of the visible edge of audio data.

Technical background

It appears that key2Audio protected disc TOC contains three sessions written on the disc. Two of them contain small data tracks, and one contains the audio tracks. The regular CD players pick the audio tracks outright, while the computer CD and DVD players get confused by the corrupted TOC information. CD players and drives that do not support multisession discs are immune to this confusion. It can be worked around by e.g.

CloneCD CloneCD is proprietary optical disc authoring software that makes exact, 1:1 copies of music and data CDs and DVDs, regardless of any Digital Rights Management (DRM) restrictions. It was originally written by Oliver Kastl and offered by Swiss ...

Exact Audio Copy Exact Audio Copy (EAC) is a CD ripping program for Microsoft Windows. The program has been developed by Andre Wiethoff since 1998. Wiethoff's motivation for creating the program was that other such software only performed jitter correction while ...

key2AudioXS

key2audioXS combines a PC playback and a clone-proof Multimedia session for CD-Extra and Web Links. The new version of this protection allows the listener the right to play the CD on a PC, and allows controlled burning the audio to CD. This solution allows consumers a limited amount of private copies. The record labels can individually define the burn count. These copies are then also fully protected and offer the same efficiency and compatibility as the original disc. The audio sessions are being encoded to

Windows Media Audio Windows Media Audio (WMA) is a series of audio codecs and their corresponding audio coding formats developed by Microsoft. It is a proprietary technology that forms part of the Windows Media framework. WMA consists of four distinct codecs. The ...

DRM DRM may refer to: Government, military and politics * Defense reform movement, U.S. campaign inspired by Col. John Boyd * Democratic Republic of Madagascar, a former socialist state (1975–1992) on Madagascar * Direction du renseignement militai ...

-protected files, so that some portable devices are supported and online distribution prevented. Furthermore, with key2audioXS the user can now pick and send audio tracks via email. With a usability period defined by the record label, users can share music, facilitating promotion activities for labels. Additionally, some discs feature "n-CD", which lets the user access bonus features such as videos, ringtones, lotteries and the like. The original n-CD is a unique key reserved for just their owners. For this purpose, the user interface for key2Audio on PC allows for navigation and includes a copying and burning tool, as well as additional content such as bonus pictures and lyrics. The audio part can hold up to 75 minutes.

Notes

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External links

Key2Audio explained and should we fear it?
Compact Disc and DVD copy protection