Protection Mechanisms Based on Non-Standard Disc Formats

Audio Overlapped by Data

Let s consider a multisession CD containing two sessions ”an audio session and a data session. When browsing such disc using built-in Windows tools, we ll see only the data session. On the other hand, low-end audio players will play back the audio session, without even picking up that the data session exists (for compatibility with CD players, the session containing audio tracks must come first). Theoretically, it is possible to play back audio tracks by manually starting the CD-player application. However, in practice, attempts to do this usually fail, because the protection mechanism uses additional levels of defence (for instance, a castrated Lead-in, the introduction of irrecoverable CIRC errors, etc.), which prevent such an easy method of cracking.

Visually, these discs can be recognized by their characteristic Lead-out area located near the outside disc edge (Fig. 7.1). This is the barrier that separates the audio session from the data session. Naturally, the presence of an extra Lead-out area in itself is not an evidence of the presence of protection. This can also be found on so-called CD-Enhanced discs, i.e., mixed-type discs (audio plus data), which are compatible with contemporary drives and operating systems. However, its presence is, all the same, a disturbing symptom. Unless it is necessary for some reason, it is better not to purchase this type of disc (don t worry if you have, however, as that protection can be easily bypassed). The glittering ring of a Lead-out area near the external edge of a disc, easily noticeable in reflected light, isn t yet evidence of the presence of protection against playback. However, the probability that it is present is pretty high.

image from book
Fig. 7.1: Disc displayed in this photo is protected by Cactus Shield 2.00, which currently is the most popular protection against the digital copying of audio discs

The data session can include practically anything (it can even be, sometimes, absolutely empty). As a rule, however, it contains heavily compressed audio in the MP3 format. At the same time, this MP3 audio is not recorded as individual files that can be copied from the disc and uploaded onto the Internet. Instead, this audio information is usually rolled up into an executable shell that can be started only from the original CD! Naturally, this executable file can only run under Windows, so the only thing that remains to UNIX/Mac users is either to lick their lips or crack this protection! By the way, the procedure of recovering an incorrectly written CD by a user on their own and at their own expense must not be considered cracking .

If no provision for additional levels of protection has been made, the content of the audio session can easily be grabbed into MP3/WMA format. Most end-user programs for burning CD-R/RWs allow you to view the contents of all disc sessions, including the first one. You can use Roxio Easy CD Creator, Stomp Record Now!, or any similar program. To do this using Easy CD Creator, select the CD Information command from the CD menu, and choose one or more audio tracks from the first session. Then, click Convert Audio and enjoy high-quality music grabbed into your favorite format (the Easy CD Creator version supplied with the PHILIPS recorder provides only two variants, from which the user can choose: WMA and WAV, and doesn t support MP3).

Another variation is to create a corrected copy of the protected disc by removing a data session. The Clone CD program can do this automatically. To achieve this, find the Audio read parameters tab in the Profile parameters window, set the Read first session only checkbox, and click OK . Disc copying will proceed in a normal mode. As a result, you ll get a normal audio CD with all of the garbage thrown out.

Alcohol 120% doesn t support this capability. It does, however, allow you to achieve the same result manually. This can be done as follows : First, create the disc image recorded in the Clone CD format (Alcohol 120% allows you to do this). Then, edit the CCD file by removing from it any references to the data session(s). Second, it is necessary to decrease the value of the Sessions field from 2 to 1. Then, remove from the file all entries, for which the Session value is more than 1. Next, decrease the value of the TocEntries field by the number of removed entries. Now, all that remains is to delete the one or more data tracks that go last. Pass-through numbering of tracks slightly complicates this task, which, at first glance, appears to be an easy one. The difficulty is that we cannot easily discover, which track belongs to which session. Therefore, we have to either calculate the number of tracks manually (this corresponds to the number of Point fields having a value greater than 0, but smaller than 0x64 ), or remove all tracks, for which the Mode value is not zero. An example of practical work with the CCD file is shown in Listing 7.1.

Listing 7.1: Correcting the CCD to crack a protected disc
image from book
 [CloneCD]                    [CloneCD]  Version=3                    Version=3  [Disc]                       [Disc]  TocEntries=24                   TocEntries=20  Sessions=2                   Sessions=1  DataTracksScrambled=0               DataTracksScrambled=0  CDTextLength=0                   CDTextLength=0  [Session 1]                  CDTextLength=0  PreGapMode=0                     PreGapMode=0  PreGapSubC=0                     PreGapSubC=0  [Session 2]  [Session 2]  PreGapMode=2  PreGapMode=2  PreGapSubC=0  PreGapSubC=0  [Entry 0]                    [Entry 0]  Session=1                    Session=1  Point=0xa0                   Point=0xa0  ADR=0x01                     ADR=0x01  Control=0x00                     Control=0x00  TrackNo=0                    TrackNo=0  AMin=97                      AMin=97  ASec=26                      ASec=2  6  AFrame=66                    AFrame=66  ALBA=   11634                  ALBA=   11634  Zero=0                       Zero=0  PMin=1                       PMin=1  PSec=32                      PSec=32  PFrame=0                     PFrame=0  PLBA=6750                    PLBA=6750  ...  [Entry 20]  [Entry 20]  Session=2  Session=2  Point=0xa0  Point=0xa0  ADR=0x01  ADR=0x01  Control=0x04  Control=0x04  TrackNo=0  TrackNo=0  AMin=72  AMin=72  ASec=22  ASec=2 2  AFrame=38  AFrame=38  ALBA=325538  ALBA=325538  Zero=0  Zero=0  PMin=16P  Min=16  PSec=32  PSec=32  PFrame=0  PFrame=0  PLBA=74250  PLMA=74250  ...  [Entry 23]  [Entry 23]  Session=2  Session=2  Point=0x10  Point=0x10  ADR=0x01  ADR=0x01  Control=0x04  Control=0x04  TrackNo=0  TrackNo=0  AMin=72  AMin=72  ASec=23  ASec=23  AFrame=17  AFrame=17  ALBA=325592  ALBA=325592  Zero=0  Zero=0  PMin=73  PMin=73  PSec=54  Psec=54  PFrame=38  PFrame=38  PLBA=332438  PLBA=332438  [TRACK 1]                    [TRACK 1]  MODE=0                       MODE=0  FLAGS=DCP                    FLAGS=DCP  INDEX 1=0                    INDEX 1=0  [TRACK 2]                    [TRACK 2]  MODE=0                       MODE=0  FLAGS= DCP                   FLAGS= DCP  INDEX 1=19173                    INDEX 1=19173  ...  [TRACK 16]                   [TRACK 16]  MODE=2                       MODE=2  INDEX 1=0                    INDEX 1=0 
image from book
 

Some discs contain a nasty program that starts automatically when the disc is loaded into the drive and secretly loads itself into the RAM. Its main goal is to protect audio tracks against digital grabbing . The specific approaches of this kind of guard may differ . For example, it is possible to scan the list of top-level windows periodically (see descriptions of FindWindows or EnumWindows function in Platform SDK) to search for the headers of the most popular grabbers. Really good programs for working with digital audio are few. Therefore, being able to recognize them all is not unrealistic . If a window of one of these programs is found, the protection mechanism can do whatever it likes to this window. For instance, in order to forcibly close the application, it is enough to send it the WM_DESTROY message.



CD Cracking Uncovered. Protection against Unsanctioned CD Copying
CD Cracking Uncovered: Protection Against Unsanctioned CD Copying (Uncovered series)
ISBN: 1931769338
EAN: 2147483647
Year: 2003
Pages: 60

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net