Built-in CD Protection

Overview

Low-end CD players are considerably less intellectual than PC CD-ROM drives. Most of them do not support multisession discs and tolerate incorrect TOCs, because they ignore most part of the TOC fields. Thus, by introducing minor errors into the TOC, it is possible to make the disc look OK for CD players, but, at the same time, unreadable for PC CD-ROM drives .

This idea has numerous applications. For example, instead of high-quality music, the vendor might try to palm off a data session created specially for PC CD-ROM and containing heavily compressed MP3 files. Another trick that developers of this kind of protection can play is correcting the pointer to the Lead-out area so as to force the PC CD-ROM to interrupt playback several seconds after it starts. A variant of this is to alter the starting address of the first track so that its LBA address takes a negative value. In all of the cases listed above, normal playback of the disc on a PC CD-ROM drive is impossible . However, an invalid TOC on a protected disc can be easily corrected (I ll show you how a little bit later).

Protection mechanisms based on the introduction of irrecoverable C1/C2-level errors are considerably harder to overcome in this respect. To crack this type of protection, you ll need a drive capable not only of detecting such errors, but also able to specify their location.