CA2422515C - Prevention of cd-audio piracy using sub-code channels - Google Patents
Prevention of cd-audio piracy using sub-code channels Download PDFInfo
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- CA2422515C CA2422515C CA2422515A CA2422515A CA2422515C CA 2422515 C CA2422515 C CA 2422515C CA 2422515 A CA2422515 A CA 2422515A CA 2422515 A CA2422515 A CA 2422515A CA 2422515 C CA2422515 C CA 2422515C
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/00086—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy
- G11B20/00188—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which result in a restriction to authorised devices recording or reproducing contents to/from a record carrier
- G11B20/00202—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which result in a restriction to authorised devices recording or reproducing contents to/from a record carrier wherein the copy protection scheme builds on multi-session recording, e.g. defective table of contents [TOC] in the 2nd session
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/00086—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy
- G11B20/00659—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving a control step which is implemented as an executable file stored on the record carrier
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/00086—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy
- G11B20/0092—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which are linked to media defects or read/write errors
- G11B20/00927—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which are linked to media defects or read/write errors wherein said defects or errors are generated on purpose, e.g. intended scratches
- G11B20/00956—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which are linked to media defects or read/write errors wherein said defects or errors are generated on purpose, e.g. intended scratches said intentional errors occurring due to an invalid TOC
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/10—Digital recording or reproducing
- G11B20/12—Formatting, e.g. arrangement of data block or words on the record carriers
- G11B2020/1264—Formatting, e.g. arrangement of data block or words on the record carriers wherein the formatting concerns a specific kind of data
- G11B2020/1265—Control data, system data or management information, i.e. data used to access or process user data
- G11B2020/1267—Address data
- G11B2020/1271—Address data the address data being stored in a subcode, e.g. in the Q channel of a CD
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/10—Digital recording or reproducing
- G11B20/14—Digital recording or reproducing using self-clocking codes
- G11B20/1403—Digital recording or reproducing using self-clocking codes characterised by the use of two levels
- G11B20/1423—Code representation depending on subsequent bits, e.g. delay modulation, double density code, Miller code
- G11B20/1426—Code representation depending on subsequent bits, e.g. delay modulation, double density code, Miller code conversion to or from block codes or representations thereof
- G11B2020/1461—8 to 14 modulation, e.g. the EFM code used on CDs or mini-discs
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B2220/00—Record carriers by type
- G11B2220/20—Disc-shaped record carriers
- G11B2220/25—Disc-shaped record carriers characterised in that the disc is based on a specific recording technology
- G11B2220/2537—Optical discs
- G11B2220/2545—CDs
Abstract
A method for protecting data recorded on an original storage medium (20) against copying using an unauthorized data readout device. The data are encoded in accordance with Standard 908 of the International Electrotechnical Commission. A portion of the encoded data is altered to introduce a modification in a sub-code Q channel of the data, such that the altered data are inconsistent with an implementation of Standard 908 used in the data readout device, but do not prevent playback of the data following recording thereof. The data, including the altered data, are recorded on the original storage medium, whereby an application which plays back the recorded data runs in a manner substantially unaffected by the alteration of the data, but a substantially unrecoverable error occurs in unauthorized copying of the original storage medium.
Description
PREVENTION OF CD-AUDIO PIRACY USING SUB-CODE CHANNELS
CROSS-REFERENCE TO RELATED APPLICATIONS.
This application corresponds to a continuation-in-part of U.S. Patent No.
6,988,206 filed April 14, 2000, which is a continuation-in-part of U.S. Patent No.
6,425,098 filed August 9, 1999, which is a continuation-in-part of U.S. Patent No.
6,256,738 filed October 20, 1998. All of these patents are assigned to the assignee of the present patent application.
FIELD OF THE INVENTION
The present invention relates generally to protection of intellectual property rights, and specifically to prevention of unauthorized copying of recorded audio, computer-readable media.
BACKGROUND OF THE INVENTION
Compact disk (CD) recordings are a preferred means for distributing both digital audio recordings and computer software. CD audio recordings are almost universally made in accordance with standard 908 of the International Electrotechnical Commission (IEC), entitled, "Compact Disc Digital Audio System" (Geneva, Switzerland, 1987). The 908 standard, also known as the Red Book, defines how audio data are to be encoded and recorded on the disk, enabling the data to be played back using standard -digital decoding chips. Different standards apply to other types of data, such as computer software, which may be recorded on CD, as well. For example, the Blue Book standard specifies multi-session recordings, that combine audio and other data on a single disk.
Original music CDs are produced by stamping plastic blanks with a master stamp piece, which is produced using costly, specialized equipment.
Alternatively, a recordable CD (CDR) may be created by authorized plants according to customer request. Because of the high cost of CD recording equipment, CD recordings were considered, until recently, to be relatively secure against unauthorized, copying. This situation has changed recently, as inexpensive CD recording devices and read/write media have become available to consumers. Thus, it is now easy, using a conventional personal computer with a read/write CD drive, or with one read drive and one write drive, to make exact, digital copies of all types of CDs. The CD content is read out by the computer, byte by byte, from one CD, typically a legitimately-purchased original CD, and then written to a blank CD so as to make a pirate copy.
Similar copying methods may be used with other media, such as Digital Video Disks (DVD).
Financial losses to the recording and software industries due to such pirate copying are estimated to be in the billions of dollars.
Another common method for pirate copying is via the digital audio output provided by many CD players, such as the S/PDIF (Sony/Philips Digital Interconnect Format) output. This output format is specified by IEC standard 958, entitled "Digital Audio Interface" (Geneva, Switzerland, 1993), which is incorporated herein by reference. The S/PDIF
output can be used legitimately to connect the CD player to high-quality converters, speakers and other audio components. On the other hand, since it reproduces the audio content of the CD
bit by bit, the S/PDIF output is also easy for pirates to use in making illegal copies. In addition to the audio content, the S/PDIF data includes a sub-code, known as the serial copying management system (SCMS) sub-code, that indicates whether the source of the data is an original recording or a copy. According to SCMS, commercially-available recording equipment is not supposed to allow users to record audio from a S/PDIF stream that is marked as a copy.
This protection, however, is easily circumvented by pirate copiers.
SUMMARY OF THE INVENTION
It is an object of some aspects of the present invention to provide improved methods and apparatus for preventing unauthorized copying of recorded, computer-readable media.
It is a further object of some aspects of the present invention to provide methods and apparatus for producing compact disks that are resistant to unauthorized copying.
It is still a further object of some aspects of the present invention to provide methods and apparatus for preventing unauthorized digital copying of audio disks.
In preferred embodiments of the present invention, signals recorded on an original storage medium are protected against unauthorized copying by changes made in a sub-code channel, preferably the Q-channel. For this purpose, a data-writing unit comprises an encoding block, which receives audio signals and encodes the signals in accordance with standard 908 of the International Electrotechnical Commission (IEC). A modification-insertion block of the data-writing unit alters the encoded signals, by introducing a modification in a sub-code Q
CROSS-REFERENCE TO RELATED APPLICATIONS.
This application corresponds to a continuation-in-part of U.S. Patent No.
6,988,206 filed April 14, 2000, which is a continuation-in-part of U.S. Patent No.
6,425,098 filed August 9, 1999, which is a continuation-in-part of U.S. Patent No.
6,256,738 filed October 20, 1998. All of these patents are assigned to the assignee of the present patent application.
FIELD OF THE INVENTION
The present invention relates generally to protection of intellectual property rights, and specifically to prevention of unauthorized copying of recorded audio, computer-readable media.
BACKGROUND OF THE INVENTION
Compact disk (CD) recordings are a preferred means for distributing both digital audio recordings and computer software. CD audio recordings are almost universally made in accordance with standard 908 of the International Electrotechnical Commission (IEC), entitled, "Compact Disc Digital Audio System" (Geneva, Switzerland, 1987). The 908 standard, also known as the Red Book, defines how audio data are to be encoded and recorded on the disk, enabling the data to be played back using standard -digital decoding chips. Different standards apply to other types of data, such as computer software, which may be recorded on CD, as well. For example, the Blue Book standard specifies multi-session recordings, that combine audio and other data on a single disk.
Original music CDs are produced by stamping plastic blanks with a master stamp piece, which is produced using costly, specialized equipment.
Alternatively, a recordable CD (CDR) may be created by authorized plants according to customer request. Because of the high cost of CD recording equipment, CD recordings were considered, until recently, to be relatively secure against unauthorized, copying. This situation has changed recently, as inexpensive CD recording devices and read/write media have become available to consumers. Thus, it is now easy, using a conventional personal computer with a read/write CD drive, or with one read drive and one write drive, to make exact, digital copies of all types of CDs. The CD content is read out by the computer, byte by byte, from one CD, typically a legitimately-purchased original CD, and then written to a blank CD so as to make a pirate copy.
Similar copying methods may be used with other media, such as Digital Video Disks (DVD).
Financial losses to the recording and software industries due to such pirate copying are estimated to be in the billions of dollars.
Another common method for pirate copying is via the digital audio output provided by many CD players, such as the S/PDIF (Sony/Philips Digital Interconnect Format) output. This output format is specified by IEC standard 958, entitled "Digital Audio Interface" (Geneva, Switzerland, 1993), which is incorporated herein by reference. The S/PDIF
output can be used legitimately to connect the CD player to high-quality converters, speakers and other audio components. On the other hand, since it reproduces the audio content of the CD
bit by bit, the S/PDIF output is also easy for pirates to use in making illegal copies. In addition to the audio content, the S/PDIF data includes a sub-code, known as the serial copying management system (SCMS) sub-code, that indicates whether the source of the data is an original recording or a copy. According to SCMS, commercially-available recording equipment is not supposed to allow users to record audio from a S/PDIF stream that is marked as a copy.
This protection, however, is easily circumvented by pirate copiers.
SUMMARY OF THE INVENTION
It is an object of some aspects of the present invention to provide improved methods and apparatus for preventing unauthorized copying of recorded, computer-readable media.
It is a further object of some aspects of the present invention to provide methods and apparatus for producing compact disks that are resistant to unauthorized copying.
It is still a further object of some aspects of the present invention to provide methods and apparatus for preventing unauthorized digital copying of audio disks.
In preferred embodiments of the present invention, signals recorded on an original storage medium are protected against unauthorized copying by changes made in a sub-code channel, preferably the Q-channel. For this purpose, a data-writing unit comprises an encoding block, which receives audio signals and encodes the signals in accordance with standard 908 of the International Electrotechnical Commission (IEC). A modification-insertion block of the data-writing unit alters the encoded signals, by introducing a modification in a sub-code Q
channel of the encoded signals. A recording block of the data-writing unit subsequently records the altered signals on the storage medium, which typically comprises a compact disk (CD).
Preferably, the altered signals are erroneous according to standard 908, or according to implementations of the standard used in CD-ROM drives, but nevertheless do not prevent playback of the audio signals from the original medium following recording.
Thus, the original CD is able to perform in a manner substantially unaffected by the alteration. By contrast, the alteration causes a substantially-unrecoverable error when an attempt is made to create an unauthorized copy of the CD. The error manifests itself in that either the unauthorized copy cannot be produced at all, or the copy is corrupted in such a way as to render it substantially unusable. Preferably, authorized software residing in the data-writing unit or in other hardware is enabled to duplicate the CD, such that authorized copies also can be played back, unaffected by the alteration.
In some preferred embodiments of the present invention, the modification-insertion block inserts the modification in the sub-code Q channel by specifying a modified absolute or relative track time of the audio signals recorded on the CD. CD copying algorithms known in the art rely on non-corrupted track times, and are therefore unable to make unauthorized copies of CDs which are prepared using these embodiments of the present invention.
Optionally, the original track time is stored on the original CD in reserved bits of the sub-code channels that are defined by standard 908. Authorized copying software retrieves the original track time from the reserved bits, and is thereby enabled to make fully-functioning copies of the original CD.
Alternatively or additionally, the modification is introduced by adding one or more additional sessions on the disk, with a lead-in that point to tracks in the program area of the first session and includes special modes to block an unauthorized computer from reading the session.
Further alternatively or additionally, the modification-insertion block inserts the modification in the sub-code Q channel by specifying a modified index number of a track of the audio signals recorded on the CD. CD copying algorithms known in the art rely on the non-corrupted index number of the track, and are therefore unable to make unauthorized copies of CDs which are prepared using these embodiments of the present invention.
Optionally, the original index number of a track is stored on the original CD
in reserved bits of the sub-code channels that are defined by standard 908. Authorized copying software retrieves the original index number of the track from the reserved bits or from a second session on the disk, and is thereby enabled to make fully-functioning copies of the original CD.
Preferably, in order to allow an authorized personal computer (PC) to play the contents of the protected disk, the original contents are protected by digital rights management (DRM) technology, typically by compressing (using any suitable format known in the art, such as MP3 or VQF) and encrypting the contents. These encrypted data are stored in a manner that is hidden to conventional CD driver software, for example in reserved sub-code channel bits, in the pause area or lead-but area, or in a second session on the CD. The data can be decrypted and played back only by using authorized software, which is preferably stored in the second session.
Further preferably, the modifications introduced in the CD are such as to cause changes in a S/PDIF output or other digital output generated by a CD player in which the protected CD is played. The changes in the digital output do not interfere with audio playback of the CD recording by compatible equipment, such as audio speakers with a digital/analog converter. The changes do, however, prevent unauthorized copying of the CD content using the digital output, for example, as a digital input to a recorder.
Optionally, in addition to the modifications introduced in the sub-code channel, further modifications are intentionally introduced in the audio data as an added impediment to unauthorized copying. The modifications are introduced in such a way that ancillary data on the disk, such as error detection codes, which are provided by the 908 standard (or other applicable standard), enable a CD player either to correct or conceal the modifications during playback or to ignore them altogether. When an unauthorized copy is made of the medium, however, the ancillary data are ineffective in overcoming the intentional modifications in the original medium, with the result that faults occur in the copy that are substantially unrecoverable. Methods for introducing such modifications are described in U.S. Patents 6,256,738 and 6,425,098.
There is therefore provided, in accordance with a preferred embodiment of the present invention, a method for protecting data recorded on an original storage medium against copying using an unauthorized data readout device, the method, including:
receiving data encoded in accordance with Standard 908 of the International Electrotechnical Commission;
altering a portion of the encoded data to introduce a modification in a sub-code Q
channel of the data, such that the altered data are inconsistent with an implementation of Standard 908 used in the data readout device, but do not prevent playback of the data following recording thereof; and recording the data, including the altered data, on the original storage medium, whereby an application which plays back the recorded data runs in a manner substantially unaffected by the alteration of the data, but a substantially unrecoverable error occurs in unauthorized copying of the original storage medium.
Preferably, the medium includes a compact disk, and the data include digital audio data.
In a preferred embodiment, altering the data includes modifying an absolute time in the data to be recorded on the medium. Preferably, a correct absolute time is stored in reserved sub-code bits on the medium. Most preferably, modifying the absolute time includes altering absolute times recorded in a plurality of consecutive blocks of a selected track.
In another preferred embodiment, altering the data includes duplicating one or more blocks of the data to a new location on the storage medium, without changing the absolute time recorded in the sub-code Q channel of the one or more blocks.
In still another preferred embodiment, altering the data includes modifying a point index number in a track of the data to be recorded on the medium. Preferably, the method includes storing a correct index number in reserved sub-code bits on the medium.
In yet another preferred embodiment, altering the data includes generating a multiple-session recording, including one or more audio and data sessions, wherein the modification in the sub-code Q channel is introduced in one or more of the data and audio sessions. Preferably, generating the multiple-session recording includes creating a lead-in to one of the sessions that points to one or more tracks located in a first audio session on the medium. Alternatively or additionally, generating the multiple-session recording includes creating a lead-in to one of the sessions that includes a larger number of tracks than is specified by the standard. Further alternatively or additionally, generating the multiple-session recording includes creating a lead-in to one of the sessions that indicates that the recording medium is shorter than it is in actuality. Still further alternatively or additionally, generating the multiple-session recording includes inserting a modified absolute time at a start of one of the sessions. Yet further alternatively or additionally, generating the multiple-session recording includes creating multiple sessions at least two of which are identified as audio sessions.
In a preferred embodiment, recording the data includes compressing and storing the data in a data session on the medium, for use in making an authorized copy of the medium.
In a further preferred embodiment, the encoded data include encoded audio data, and the method includes altering a portion of the encoded audio data such that the altered data are inconsistent with the implementation of Standard 908 used in the data readout device, wherein recording the data on the medium includes recording ancillary data which are used by a processor in the application to operate upon the altered portion of the encoded audio data such that the application plays back the data in a manner substantially unaffected by the alteration of the encoded audio data, but which ancillary data are ineffective in correcting the altered portion of the encoded audio data upon copying of the data, so that the alteration causes a further substantially unrecoverable error in the unauthorized copying of the original medium.
Preferably, the ancillary data include error detection codes.
There is further provided, in accordance with a preferred embodiment of the present invention, a method for protecting data recorded on an original storage medium against unauthorized copying, including:
receiving data encoded in accordance with Standard 908 of the International Electrotechnical Commission;
altering a portion of the encoded data to introduce a modification in the data, so that a digital output of the altered data will be inconsistent with an implementation of a digital output standard, such as Standard 958 of the International Electrotechnical Commission, but the modification will not prevent playback of the data following recording thereof, and recording the data, including the altered data, on the original storage medium, whereby an application which plays back the recorded data runs in a manner substantially unaffected by the modification in the data, but a substantially unrecoverable error occurs in unauthorized copying of the original storage medium based on the digital output.
Preferably, altering the portion of the encoded data includes altering one or more control bits in the encoded data, which control bits are reproduced in the digital output.
Additionally or alternatively, altering the portion of the encoded data includes manipulating bits of audio data within a frame of the encoded data.
There is also provided, in accordance with a preferred embodiment of the present invention, apparatus for protecting data recorded on an original data storage medium against copying using an unauthorized data readout device, including:
an encoder, adapted to receive a stream of data for recording on the medium and encodes the data in accordance with Standard 908 of the International Electrotechnical Commission;
a sub-code generator, operative to alter a portion of the encoded data by introducing a modification in a sub-code Q channel of the data, such that the altered data are inconsistent with an implementation of Standard 908 used in the data readout device, but do not prevent playback of the data following recording thereof; and an eight-to-fourteen bit (EFM) modulator, coupled to modulate the altered data for recording on the original storage medium, whereby an application which plays back the recorded data runs in a manner substantially unaffected by the alteration of the data, but a substantially unrecoverable error occurs in unauthorized copying of the original storage medium.
In a preferred embodiment, the apparatus includes a data session generator, operative to provide a data session to the EFM for recording on the original storage medium, so that the data recorded on the medium include multiple-session data, and the defect in the sub-code Q
channel is introduced in at least one of the multiple sessions.
There is additionally provided, in accordance with a preferred embodiment of the present invention, a data storage medium that is resistant to copying using an unauthorized readout device, on which medium data encoded in accordance with Standard 908 of the International Electrotechnical Commission are stored, a portion of which encoded data is altered by introducing a modification in a sub-code Q channel of the data, such that the altered data are identified as inconsistent with an implementation of Standard 908 used in the data readout device, but do not prevent playback of the data following recording thereof, whereby an application which plays back the recorded data runs in a manner substantially unaffected by the alteration of the data, but a substantially unrecoverable error occurs in unauthorized copying of the original storage medium.
The present invention will be more fully understood from the following detailed description of the preferred embodiments thereof, taken together with the drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic, sectional view of a compact disk (CD), in accordance with recording practice known in the art;
Fig. 2 is a schematic block diagram that illustrates apparatus for producing a copy-resistant CD, in accordance with a preferred embodiment of the present invention;
Fig. 3 is a schematic illustration of details of a data structure written to a CD, in accordance with recording practice known in the art; and Fig. 4 is a block diagram that schematically illustrates duplication of data on a CD for the purpose of preventing unauthorized copying, in accordance with a preferred embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Reference is now made to Fig. 1, which is a schematic sectional view of an audio compact disk (CD) 20, showing the overall layout of the disk, in accordance with recording practice known in the art. An information area 22 includes a lead-in (LI) area 24, a program area (PA) 26 and a lead-out (LO) area 28. Information area 22 progresses outwards in a widening spiral, and contains all of the recorded contents of CD 20. Lead-in area 24 and lead-out area 28 both contain P and Q channels, which include timing and track information used during playback of the CD. Program area 26 consists of up to 99 tracks of audio information (e.g., music), as well as accompanying sub-code information.
Preferably, the altered signals are erroneous according to standard 908, or according to implementations of the standard used in CD-ROM drives, but nevertheless do not prevent playback of the audio signals from the original medium following recording.
Thus, the original CD is able to perform in a manner substantially unaffected by the alteration. By contrast, the alteration causes a substantially-unrecoverable error when an attempt is made to create an unauthorized copy of the CD. The error manifests itself in that either the unauthorized copy cannot be produced at all, or the copy is corrupted in such a way as to render it substantially unusable. Preferably, authorized software residing in the data-writing unit or in other hardware is enabled to duplicate the CD, such that authorized copies also can be played back, unaffected by the alteration.
In some preferred embodiments of the present invention, the modification-insertion block inserts the modification in the sub-code Q channel by specifying a modified absolute or relative track time of the audio signals recorded on the CD. CD copying algorithms known in the art rely on non-corrupted track times, and are therefore unable to make unauthorized copies of CDs which are prepared using these embodiments of the present invention.
Optionally, the original track time is stored on the original CD in reserved bits of the sub-code channels that are defined by standard 908. Authorized copying software retrieves the original track time from the reserved bits, and is thereby enabled to make fully-functioning copies of the original CD.
Alternatively or additionally, the modification is introduced by adding one or more additional sessions on the disk, with a lead-in that point to tracks in the program area of the first session and includes special modes to block an unauthorized computer from reading the session.
Further alternatively or additionally, the modification-insertion block inserts the modification in the sub-code Q channel by specifying a modified index number of a track of the audio signals recorded on the CD. CD copying algorithms known in the art rely on the non-corrupted index number of the track, and are therefore unable to make unauthorized copies of CDs which are prepared using these embodiments of the present invention.
Optionally, the original index number of a track is stored on the original CD
in reserved bits of the sub-code channels that are defined by standard 908. Authorized copying software retrieves the original index number of the track from the reserved bits or from a second session on the disk, and is thereby enabled to make fully-functioning copies of the original CD.
Preferably, in order to allow an authorized personal computer (PC) to play the contents of the protected disk, the original contents are protected by digital rights management (DRM) technology, typically by compressing (using any suitable format known in the art, such as MP3 or VQF) and encrypting the contents. These encrypted data are stored in a manner that is hidden to conventional CD driver software, for example in reserved sub-code channel bits, in the pause area or lead-but area, or in a second session on the CD. The data can be decrypted and played back only by using authorized software, which is preferably stored in the second session.
Further preferably, the modifications introduced in the CD are such as to cause changes in a S/PDIF output or other digital output generated by a CD player in which the protected CD is played. The changes in the digital output do not interfere with audio playback of the CD recording by compatible equipment, such as audio speakers with a digital/analog converter. The changes do, however, prevent unauthorized copying of the CD content using the digital output, for example, as a digital input to a recorder.
Optionally, in addition to the modifications introduced in the sub-code channel, further modifications are intentionally introduced in the audio data as an added impediment to unauthorized copying. The modifications are introduced in such a way that ancillary data on the disk, such as error detection codes, which are provided by the 908 standard (or other applicable standard), enable a CD player either to correct or conceal the modifications during playback or to ignore them altogether. When an unauthorized copy is made of the medium, however, the ancillary data are ineffective in overcoming the intentional modifications in the original medium, with the result that faults occur in the copy that are substantially unrecoverable. Methods for introducing such modifications are described in U.S. Patents 6,256,738 and 6,425,098.
There is therefore provided, in accordance with a preferred embodiment of the present invention, a method for protecting data recorded on an original storage medium against copying using an unauthorized data readout device, the method, including:
receiving data encoded in accordance with Standard 908 of the International Electrotechnical Commission;
altering a portion of the encoded data to introduce a modification in a sub-code Q
channel of the data, such that the altered data are inconsistent with an implementation of Standard 908 used in the data readout device, but do not prevent playback of the data following recording thereof; and recording the data, including the altered data, on the original storage medium, whereby an application which plays back the recorded data runs in a manner substantially unaffected by the alteration of the data, but a substantially unrecoverable error occurs in unauthorized copying of the original storage medium.
Preferably, the medium includes a compact disk, and the data include digital audio data.
In a preferred embodiment, altering the data includes modifying an absolute time in the data to be recorded on the medium. Preferably, a correct absolute time is stored in reserved sub-code bits on the medium. Most preferably, modifying the absolute time includes altering absolute times recorded in a plurality of consecutive blocks of a selected track.
In another preferred embodiment, altering the data includes duplicating one or more blocks of the data to a new location on the storage medium, without changing the absolute time recorded in the sub-code Q channel of the one or more blocks.
In still another preferred embodiment, altering the data includes modifying a point index number in a track of the data to be recorded on the medium. Preferably, the method includes storing a correct index number in reserved sub-code bits on the medium.
In yet another preferred embodiment, altering the data includes generating a multiple-session recording, including one or more audio and data sessions, wherein the modification in the sub-code Q channel is introduced in one or more of the data and audio sessions. Preferably, generating the multiple-session recording includes creating a lead-in to one of the sessions that points to one or more tracks located in a first audio session on the medium. Alternatively or additionally, generating the multiple-session recording includes creating a lead-in to one of the sessions that includes a larger number of tracks than is specified by the standard. Further alternatively or additionally, generating the multiple-session recording includes creating a lead-in to one of the sessions that indicates that the recording medium is shorter than it is in actuality. Still further alternatively or additionally, generating the multiple-session recording includes inserting a modified absolute time at a start of one of the sessions. Yet further alternatively or additionally, generating the multiple-session recording includes creating multiple sessions at least two of which are identified as audio sessions.
In a preferred embodiment, recording the data includes compressing and storing the data in a data session on the medium, for use in making an authorized copy of the medium.
In a further preferred embodiment, the encoded data include encoded audio data, and the method includes altering a portion of the encoded audio data such that the altered data are inconsistent with the implementation of Standard 908 used in the data readout device, wherein recording the data on the medium includes recording ancillary data which are used by a processor in the application to operate upon the altered portion of the encoded audio data such that the application plays back the data in a manner substantially unaffected by the alteration of the encoded audio data, but which ancillary data are ineffective in correcting the altered portion of the encoded audio data upon copying of the data, so that the alteration causes a further substantially unrecoverable error in the unauthorized copying of the original medium.
Preferably, the ancillary data include error detection codes.
There is further provided, in accordance with a preferred embodiment of the present invention, a method for protecting data recorded on an original storage medium against unauthorized copying, including:
receiving data encoded in accordance with Standard 908 of the International Electrotechnical Commission;
altering a portion of the encoded data to introduce a modification in the data, so that a digital output of the altered data will be inconsistent with an implementation of a digital output standard, such as Standard 958 of the International Electrotechnical Commission, but the modification will not prevent playback of the data following recording thereof, and recording the data, including the altered data, on the original storage medium, whereby an application which plays back the recorded data runs in a manner substantially unaffected by the modification in the data, but a substantially unrecoverable error occurs in unauthorized copying of the original storage medium based on the digital output.
Preferably, altering the portion of the encoded data includes altering one or more control bits in the encoded data, which control bits are reproduced in the digital output.
Additionally or alternatively, altering the portion of the encoded data includes manipulating bits of audio data within a frame of the encoded data.
There is also provided, in accordance with a preferred embodiment of the present invention, apparatus for protecting data recorded on an original data storage medium against copying using an unauthorized data readout device, including:
an encoder, adapted to receive a stream of data for recording on the medium and encodes the data in accordance with Standard 908 of the International Electrotechnical Commission;
a sub-code generator, operative to alter a portion of the encoded data by introducing a modification in a sub-code Q channel of the data, such that the altered data are inconsistent with an implementation of Standard 908 used in the data readout device, but do not prevent playback of the data following recording thereof; and an eight-to-fourteen bit (EFM) modulator, coupled to modulate the altered data for recording on the original storage medium, whereby an application which plays back the recorded data runs in a manner substantially unaffected by the alteration of the data, but a substantially unrecoverable error occurs in unauthorized copying of the original storage medium.
In a preferred embodiment, the apparatus includes a data session generator, operative to provide a data session to the EFM for recording on the original storage medium, so that the data recorded on the medium include multiple-session data, and the defect in the sub-code Q
channel is introduced in at least one of the multiple sessions.
There is additionally provided, in accordance with a preferred embodiment of the present invention, a data storage medium that is resistant to copying using an unauthorized readout device, on which medium data encoded in accordance with Standard 908 of the International Electrotechnical Commission are stored, a portion of which encoded data is altered by introducing a modification in a sub-code Q channel of the data, such that the altered data are identified as inconsistent with an implementation of Standard 908 used in the data readout device, but do not prevent playback of the data following recording thereof, whereby an application which plays back the recorded data runs in a manner substantially unaffected by the alteration of the data, but a substantially unrecoverable error occurs in unauthorized copying of the original storage medium.
The present invention will be more fully understood from the following detailed description of the preferred embodiments thereof, taken together with the drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic, sectional view of a compact disk (CD), in accordance with recording practice known in the art;
Fig. 2 is a schematic block diagram that illustrates apparatus for producing a copy-resistant CD, in accordance with a preferred embodiment of the present invention;
Fig. 3 is a schematic illustration of details of a data structure written to a CD, in accordance with recording practice known in the art; and Fig. 4 is a block diagram that schematically illustrates duplication of data on a CD for the purpose of preventing unauthorized copying, in accordance with a preferred embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Reference is now made to Fig. 1, which is a schematic sectional view of an audio compact disk (CD) 20, showing the overall layout of the disk, in accordance with recording practice known in the art. An information area 22 includes a lead-in (LI) area 24, a program area (PA) 26 and a lead-out (LO) area 28. Information area 22 progresses outwards in a widening spiral, and contains all of the recorded contents of CD 20. Lead-in area 24 and lead-out area 28 both contain P and Q channels, which include timing and track information used during playback of the CD. Program area 26 consists of up to 99 tracks of audio information (e.g., music), as well as accompanying sub-code information.
Preferred embodiments of the present invention provide a number of different, complementary techniques for modifying the data in CD 20 in order to frustrate pirate copiers.
A number of these embodiments are described in detail hereinbelow. Generally speaking, the modifications fall into the following categories:
= General disk layout modifications - for example, recording several sessions on an audio CD. The second session can be used to mislead personal computers (PCs) that are commonly used in pirate copying, typically by adding conflicting pointers in the lead-in of the second session. Preferably, the last session on the CD is a data session that contains the music in compressed form. Most preferably, the music is encrypted so as to enable playback directly from the disk and/or encoded using digital wrapper technology (also known as digital rights management - DRM) to enable download and playback through secure software from the disk of an authorized user.
= Modifications of the audio data, by insertion of noise, preferably as described in the above-mentioned U.S. 6,425,098, = Modifications of the subcode information, particularly in the Q channel.
These modifications may include, for example, changing the absolute or relative time, index pointers, table of contents (TOC) information (listing too many or too few tracks, or misleading pointers between multiple sessions), control, byte modifications, pregap length manipulation. Other such modifications will be apparent to those skilled in the art.
= Low-level modifications to the structure of the bits recorded on the CD.
Such modifications are described in detail in the above-mentioned U.S. Patents Nos.
6,256,738 and 6,425,098,.- They typically involve recording sequences of bits on the CD that cause hardware errors in some CD-ROM drives used in PCs, or prevent them from interpolating over erroneous audio data. Alternatively or additionally, bit sequences may be recorded on the CD that do not appear in the conventional eight-to-fourteen bit (EFM) lookup table specified by the 908 standard.
These modifications may be used in CD 20 in different combinations, depending on application needs.
A number of these embodiments are described in detail hereinbelow. Generally speaking, the modifications fall into the following categories:
= General disk layout modifications - for example, recording several sessions on an audio CD. The second session can be used to mislead personal computers (PCs) that are commonly used in pirate copying, typically by adding conflicting pointers in the lead-in of the second session. Preferably, the last session on the CD is a data session that contains the music in compressed form. Most preferably, the music is encrypted so as to enable playback directly from the disk and/or encoded using digital wrapper technology (also known as digital rights management - DRM) to enable download and playback through secure software from the disk of an authorized user.
= Modifications of the audio data, by insertion of noise, preferably as described in the above-mentioned U.S. 6,425,098, = Modifications of the subcode information, particularly in the Q channel.
These modifications may include, for example, changing the absolute or relative time, index pointers, table of contents (TOC) information (listing too many or too few tracks, or misleading pointers between multiple sessions), control, byte modifications, pregap length manipulation. Other such modifications will be apparent to those skilled in the art.
= Low-level modifications to the structure of the bits recorded on the CD.
Such modifications are described in detail in the above-mentioned U.S. Patents Nos.
6,256,738 and 6,425,098,.- They typically involve recording sequences of bits on the CD that cause hardware errors in some CD-ROM drives used in PCs, or prevent them from interpolating over erroneous audio data. Alternatively or additionally, bit sequences may be recorded on the CD that do not appear in the conventional eight-to-fourteen bit (EFM) lookup table specified by the 908 standard.
These modifications may be used in CD 20 in different combinations, depending on application needs.
Fig. 2 is a schematic block diagram that illustrates apparatus 40 for producing a copy-resistant CD, in accordance with a preferred embodiment of the present invention. The original sound, or analog audio, is converted to digital format suitable for encoding on a disk, such that the information can subsequently be played back (decoded) by a standard player of audio CD 20. In a first stage of encoding, a digital bit stream is generated which represents the continuous analog sound signal. The analog signal is converted into discrete digital samples by an analog-to-digital (AID) converter 30.
To enable detection and correction of errors during playback, parity bits are added to the bit stream. An error-correction encoder 32 employs the commonly used Cross-Interleaved Reed-Solomon Code (CIRC) to reorder the digital data. A sub-code generator 36 adds a byte of sub-code for every thirty-two bytes of error-corrected audio. The 908 standard prescribes the contents of the sub-code channels to be added at this stage. Sub-code generator 36, however, alters the standard sub-codes in such a manner that ordinary playback of the CD is substantially unaffected, but unauthorized copying is prevented. In particular, the alterations do not compromise the integrity of the bit stream and do not generate CIRC errors on the disk.
Methods of such alteration are described hereinbelow.
Apparatus 40 is also shown to include an optional data session generator 37, for use in producing multiple-session disks that include both audio and data sessions. As described hereinbelow, the data session is configured so as to prevent an unauthorized computer from reading the CD. An audio compressor 35 is optionally provided to compress the audio input for inclusion in such a multiple-session disk in an encoded form.
It is known in the art to map a standard sixteen-bit word of sound data into two fourteen-bit "optical" symbols, and to include in the recording additional information, such as playback control and display functions. An eight-to-fourteen modulator (EFM) 34 combines the output of error-correction encoder 32 with the output of sub-code generator 36 and data session generator 37. Each bit of encoded data is preferably physically inscribed onto a master for producing CD 20, using a laser beam recorder (LBR) 38 to create a series of microscopic pits on the master. Alternatively, a dedicated burner 39 is used to produce CD
20 directly on a recordable CD (CDR).
Fig. 3 is a schematic illustration of details of the data structure received by EFM
modulator 34, in accordance with the 908 standard. A block 58 of data for recording on a CD
contains 98 frames, each frame made up of 32 bytes of data, or symbols, received from encoder 32 (or from the data session generator 37) and one eight-bit "sub-code" word. The eight bits in each sub-code word are respectively called P, Q, R, S, T, U, V, and W.
The Q bits from 98 consecutive frames are collectively called a sub-code Q
channel 64.
The sub-code Q channel contains program and timing information, including synchronization bits SO and Si, 4 control bits, 4 address bits, 72 data bits, and a 16-bit cyclic redundancy check code (CRCC). In lead-in area 24, the 72 data bits include relative time (R-Time, or track time) data 74 and track position, while in program area 26, relative time and absolute time (A-Time, or disk time) data are stored. The relative time for each block indicates the length of time from the beginning of a current track to the beginning of the block. The absolute time indicates the length of time from the beginning of program area 26 to the beginning of the block. Time is measured in units of minutes, seconds and frames (different from the 98 data frames in a block), with 75 time frames in a second. The Q channel also includes a track number (TNO) and in-track indices, also referred to as point indices. In lead-in area 24, the Q channel carries a table of contents (TOC).
Table I below schematically illustrates alteration of absolute time values of sub-code Q
channel 64, in accordance with a preferred embodiment of the present invention. In typical encoding of CD 20 according to standard 908, absolute time starts at the beginning of program area 26 and increases linearly to the end of lead-out area 28. Copying software known in the art uses the absolute time as a pointer, in order to ensure smooth reproduction of the original audio and synchronicity of timing between recorded frames and played-back frames.
Preferably embodied, a modification is introduced into the absolute time values of the sub-code Q channel, as shown in the "altered" column in the table, thereby increasing the speed at which time appears to pass in this track.
TABLE I
Original time Altered time Min Sec Frame Min Sec Frame 0 (start 0 0 0 0 0 track) ... ... ... ... ... ...
(end 30 42 5 36 20 track) 5 (pause) 30 43 5 30 43 So as not to adversely affect stereo play-back of the audio, the absolute time for original CD 20 is preferably increased in several consecutive blocks out of every 150 consecutive blocks, and returned to normal in a pause area between tracks, as shown in the 5 table above. A standard CD player will be unaffected by these intentional distortions of the absolute time. An unauthorized copy of CD 20, however, will contain discontinuities in the music, for example, where absolute time jumps from frame 2 to frame 4 to frame 6, in the table above. The resulting signal on the CD copy will have a series of constant-amplitude, audible, distorted and generally unmelodious sounds.
Optionally, the original, correct absolute time information is stored in the reserved bits of the sub-code R-W channels (Fig. 3), which are currently unassigned according to standard 908. Authorized software is enabled to make copies of original CD 20 by accessing the data stored in the R-W channels.
Alternatively, rather than introducing modifications in the absolute time, modifications that produce audible effects in unauthorized copies are introduced in sub-code Q channel 64 by changing point index and/or mode values. Like the absolute track time, the point index provides a series of "checkpoints" within a track. A modified series of point indices will cause mute areas in an unauthorized copy of CD 20, but will not affect the playback of the original CD. Optionally, as described above, the correct indices are stored in the R-W
channels, and authorized software is enabled to copy the original CD by retrieving the indices from these channels.
Preferably, modifications introduced in the CD are such as to cause changes in a digital output, such as a S/PDIF output, generated by a CD player in which the protected CD is played. The digital output data stream comprises a sequence of 32-bit words, known as sub-frames, each carrying between 16 and 24 bits of audio data, along with preamble and control bits. One of the control bits in each sub-frame is a sub-code bit, similar to the sub-code bits in each frame of data on the CD. The sub-code bits in a block of 192 frames (typically 384 sub-frames) in the S/PDIF data stream carry most of the contents of the sub-code Q
channel being played on the CD, including control bytes, the track number and the time.
Preferably, the modifications that are introduced in the Q channel on the disk are such as to be carried over to the S/PDIF data. Although these modifications do not interfere with audio playback of the CD recording by speakers and other compatible equipment, they do impede unauthorized copying of the CD content using the digital output.
As specified by the above-mentioned IEC 958 standard, the S/PDIF signal contains four control bytes copied from the CD. Therefore, in an alternative embodiment of the present invention, these control bytes are used to frustrate illegal copying of the audio contents. For this purpose, in recording the control bytes on the CD, in accordance with the Red Book standard, the track mode is set to "data" for a number of blocks, typically between one and ten blocks, in a repetitive cycle. The CRCC is then recalculated so that this control byte is valid from the standpoint of data accuracy. When a recording is made from the S/PDIF
output of the CD player, however, this control byte setting will typically cause mutes or clicks to appear in the resulting audio stream.
In a further alternative embodiment, the bits in the S/PDIF envelope are shifted or otherwise manipulated in order to confound unauthorized recording of the CD
contents. When the 32 bits in a S/PDIF sub-frame are fed to a digital/analog converter for audio playback, the converter takes all 32 bits and plays back the audio irrespective of the shift. A digital recorder, however, will seek the audio data in a given subset of the bits of the sub-frame, and the control data in another subset, disjoint from the audio data, where these data are supposed to be according to the standard. Therefore, manipulating the bit order can block recorders while still enabling audio playback.
Fig. 4 is a block diagram that schematically illustrates another method for preventing unauthorized copying of a CD, using data session generator 37, in accordance with a preferred embodiment of the present invention. Whereas an audio CD has only a single session 90, apparatus 40 with session generator 37 can produce CDs having multiple sessions, including, for example, one or more audio sessions 100 and at least one data session 102.
Audio CD
players read only the first session on a multiple-session CD, in this case session 100 and ignore the rest. DVD players read and are "aware" of data session 102, as well, but still play back audio session 100. When the CD is inserted into a CD-ROM drive, however, the computer can access any of the sessions and therefore will be confused by the modifications embedded in the second or subsequent sessions. The present embodiment therefore operates by introducing conflicting data into the sub-code Q channel of data session 102 or of additional audio sessions, subsequent to the first audio session. Most preferably, there are at least two audio sessions out of a total of three or more sessions on the disk.
Preferably, modified data are introduced into audio session 100, as well. The modifications are introduced in such a way that ancillary data on the disk, such as Cross Interleave Reed Solomon Code (CIRC) error detection codes, which are provided by the 908 standard (or other applicable standard), enable a CD player either to correct or conceal the modifications during playback or to ignore them altogether. When an unauthorized copy is made of the medium, however, the ancillary data are ineffective in overcoming the intentional modifications in the original medium, with the result that faults occur in the copy that are substantially unrecoverable. Methods for introducing such modifications are described in the above-mentioned U.S. Patents 6,256,738 and 6,425,098.
Despite the modifications in the sub-code channels and/or audio data, an audio CD
player will reproduce the audio signals on the disk without difficulty. A
computer CD drive, however, will be confused by either the multiple sessions on the CD or the modified data in audio session 100 (or by both) and will not be able to load or play the disk, let alone copy it.
Modifications in the added audio and/or data sessions are preferably introduced by one or more of the following mechanisms:
= Generating a lead-in that points to tracks located in the program area of the first session.
= Generating a lead-in with a larger number of tracks than is allowed by the standard.
= Modifying the lead-in to simulate a shorter CD.
= Modifying the absolute time at the beginning of the session.
Following these methods, Table II below describes changes made in the sub-code Q
channel of a multiple-session CD, in order to prevent computer copying of the audio content without interfering with audio playback. The first session on the CD is an audio session, based on the Red Book standard, while the second and subsequent sessions may be audio or data sessions, based on the Blue Book, as described above.
TABLE II
Session Standard Modification 1 Lead-in (2'/2-3 Add pointers BO and CO to the second and third min) sessions, per Blue Book format.
Pause length 2 Use different pregap length, per Blue Book format, sec preferably set to value between 1 and 3 sec.
Accurate Start A-Time at non-zero value, e.g., 10 sec, to mask A-Time beginning of disk for computer CD drive.
2 Audio track Audio track length 4 sec (minimum time per Red Book).
3 Lead-in (1 TOC points to 99 non-existent data tracks at time min) 00:02.
Modify lead-out pointer (A2) to a value between 00:01 and 00:07.
Audio track Data track length 4 see, plus fill to a total CD length.
As a result of these changes, a computer CD-ROM or DVD-ROM drive, upon reading the sub-code Q channel data in session 3, will either fail to mount the CD
entirely, or will go into an endless loop looking for the non-existent data tracks listed in the TOC. If the drive does succeed in accessing session 1, which holds the normal audio content, it is still likely to be confused by the 1 sec pregap (which is outside the Red Book specification) and/or by the distorted A-time. CD audio and DVD players, however, will be largely unaffected by these changes. In this regard, session 2 is important, since without it, some Blue Book-compliant DVD players might refuse to mount the CD. It will be understood that the specific modifications noted in the table are listed by way of example. Alternative combinations of modifications and settings of the time values and other parameters will be apparent to those skilled in the art.
Preferably, in order to allow an authorized personal computer (PC) to play the contents of the protected disk, the original contents are compressed (using any suitable format known in the art, such as MP3 or VQF) and encrypted, by audio compressor 35 (Fig. 2).
These encrypted data are stored using a "digital wrapper" technique, so that the data are hidden from conventional CD driver software. For example, the data may be stored in the reserved sub-code channel bits, as described above, or in one of the data sessions on the CD, or in a lead-in, lead-out or pause area. The data can be decrypted and played back only by using authorized software, which is also preferably stored in the second session and is made available only to appropriately-licensed users and/or equipment. The authorized software will prevent the decryption of the data if its source is not the original CD or if the rules for distributing and using the data are otherwise violated.
It will be appreciated that the preferred embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.
To enable detection and correction of errors during playback, parity bits are added to the bit stream. An error-correction encoder 32 employs the commonly used Cross-Interleaved Reed-Solomon Code (CIRC) to reorder the digital data. A sub-code generator 36 adds a byte of sub-code for every thirty-two bytes of error-corrected audio. The 908 standard prescribes the contents of the sub-code channels to be added at this stage. Sub-code generator 36, however, alters the standard sub-codes in such a manner that ordinary playback of the CD is substantially unaffected, but unauthorized copying is prevented. In particular, the alterations do not compromise the integrity of the bit stream and do not generate CIRC errors on the disk.
Methods of such alteration are described hereinbelow.
Apparatus 40 is also shown to include an optional data session generator 37, for use in producing multiple-session disks that include both audio and data sessions. As described hereinbelow, the data session is configured so as to prevent an unauthorized computer from reading the CD. An audio compressor 35 is optionally provided to compress the audio input for inclusion in such a multiple-session disk in an encoded form.
It is known in the art to map a standard sixteen-bit word of sound data into two fourteen-bit "optical" symbols, and to include in the recording additional information, such as playback control and display functions. An eight-to-fourteen modulator (EFM) 34 combines the output of error-correction encoder 32 with the output of sub-code generator 36 and data session generator 37. Each bit of encoded data is preferably physically inscribed onto a master for producing CD 20, using a laser beam recorder (LBR) 38 to create a series of microscopic pits on the master. Alternatively, a dedicated burner 39 is used to produce CD
20 directly on a recordable CD (CDR).
Fig. 3 is a schematic illustration of details of the data structure received by EFM
modulator 34, in accordance with the 908 standard. A block 58 of data for recording on a CD
contains 98 frames, each frame made up of 32 bytes of data, or symbols, received from encoder 32 (or from the data session generator 37) and one eight-bit "sub-code" word. The eight bits in each sub-code word are respectively called P, Q, R, S, T, U, V, and W.
The Q bits from 98 consecutive frames are collectively called a sub-code Q
channel 64.
The sub-code Q channel contains program and timing information, including synchronization bits SO and Si, 4 control bits, 4 address bits, 72 data bits, and a 16-bit cyclic redundancy check code (CRCC). In lead-in area 24, the 72 data bits include relative time (R-Time, or track time) data 74 and track position, while in program area 26, relative time and absolute time (A-Time, or disk time) data are stored. The relative time for each block indicates the length of time from the beginning of a current track to the beginning of the block. The absolute time indicates the length of time from the beginning of program area 26 to the beginning of the block. Time is measured in units of minutes, seconds and frames (different from the 98 data frames in a block), with 75 time frames in a second. The Q channel also includes a track number (TNO) and in-track indices, also referred to as point indices. In lead-in area 24, the Q channel carries a table of contents (TOC).
Table I below schematically illustrates alteration of absolute time values of sub-code Q
channel 64, in accordance with a preferred embodiment of the present invention. In typical encoding of CD 20 according to standard 908, absolute time starts at the beginning of program area 26 and increases linearly to the end of lead-out area 28. Copying software known in the art uses the absolute time as a pointer, in order to ensure smooth reproduction of the original audio and synchronicity of timing between recorded frames and played-back frames.
Preferably embodied, a modification is introduced into the absolute time values of the sub-code Q channel, as shown in the "altered" column in the table, thereby increasing the speed at which time appears to pass in this track.
TABLE I
Original time Altered time Min Sec Frame Min Sec Frame 0 (start 0 0 0 0 0 track) ... ... ... ... ... ...
(end 30 42 5 36 20 track) 5 (pause) 30 43 5 30 43 So as not to adversely affect stereo play-back of the audio, the absolute time for original CD 20 is preferably increased in several consecutive blocks out of every 150 consecutive blocks, and returned to normal in a pause area between tracks, as shown in the 5 table above. A standard CD player will be unaffected by these intentional distortions of the absolute time. An unauthorized copy of CD 20, however, will contain discontinuities in the music, for example, where absolute time jumps from frame 2 to frame 4 to frame 6, in the table above. The resulting signal on the CD copy will have a series of constant-amplitude, audible, distorted and generally unmelodious sounds.
Optionally, the original, correct absolute time information is stored in the reserved bits of the sub-code R-W channels (Fig. 3), which are currently unassigned according to standard 908. Authorized software is enabled to make copies of original CD 20 by accessing the data stored in the R-W channels.
Alternatively, rather than introducing modifications in the absolute time, modifications that produce audible effects in unauthorized copies are introduced in sub-code Q channel 64 by changing point index and/or mode values. Like the absolute track time, the point index provides a series of "checkpoints" within a track. A modified series of point indices will cause mute areas in an unauthorized copy of CD 20, but will not affect the playback of the original CD. Optionally, as described above, the correct indices are stored in the R-W
channels, and authorized software is enabled to copy the original CD by retrieving the indices from these channels.
Preferably, modifications introduced in the CD are such as to cause changes in a digital output, such as a S/PDIF output, generated by a CD player in which the protected CD is played. The digital output data stream comprises a sequence of 32-bit words, known as sub-frames, each carrying between 16 and 24 bits of audio data, along with preamble and control bits. One of the control bits in each sub-frame is a sub-code bit, similar to the sub-code bits in each frame of data on the CD. The sub-code bits in a block of 192 frames (typically 384 sub-frames) in the S/PDIF data stream carry most of the contents of the sub-code Q
channel being played on the CD, including control bytes, the track number and the time.
Preferably, the modifications that are introduced in the Q channel on the disk are such as to be carried over to the S/PDIF data. Although these modifications do not interfere with audio playback of the CD recording by speakers and other compatible equipment, they do impede unauthorized copying of the CD content using the digital output.
As specified by the above-mentioned IEC 958 standard, the S/PDIF signal contains four control bytes copied from the CD. Therefore, in an alternative embodiment of the present invention, these control bytes are used to frustrate illegal copying of the audio contents. For this purpose, in recording the control bytes on the CD, in accordance with the Red Book standard, the track mode is set to "data" for a number of blocks, typically between one and ten blocks, in a repetitive cycle. The CRCC is then recalculated so that this control byte is valid from the standpoint of data accuracy. When a recording is made from the S/PDIF
output of the CD player, however, this control byte setting will typically cause mutes or clicks to appear in the resulting audio stream.
In a further alternative embodiment, the bits in the S/PDIF envelope are shifted or otherwise manipulated in order to confound unauthorized recording of the CD
contents. When the 32 bits in a S/PDIF sub-frame are fed to a digital/analog converter for audio playback, the converter takes all 32 bits and plays back the audio irrespective of the shift. A digital recorder, however, will seek the audio data in a given subset of the bits of the sub-frame, and the control data in another subset, disjoint from the audio data, where these data are supposed to be according to the standard. Therefore, manipulating the bit order can block recorders while still enabling audio playback.
Fig. 4 is a block diagram that schematically illustrates another method for preventing unauthorized copying of a CD, using data session generator 37, in accordance with a preferred embodiment of the present invention. Whereas an audio CD has only a single session 90, apparatus 40 with session generator 37 can produce CDs having multiple sessions, including, for example, one or more audio sessions 100 and at least one data session 102.
Audio CD
players read only the first session on a multiple-session CD, in this case session 100 and ignore the rest. DVD players read and are "aware" of data session 102, as well, but still play back audio session 100. When the CD is inserted into a CD-ROM drive, however, the computer can access any of the sessions and therefore will be confused by the modifications embedded in the second or subsequent sessions. The present embodiment therefore operates by introducing conflicting data into the sub-code Q channel of data session 102 or of additional audio sessions, subsequent to the first audio session. Most preferably, there are at least two audio sessions out of a total of three or more sessions on the disk.
Preferably, modified data are introduced into audio session 100, as well. The modifications are introduced in such a way that ancillary data on the disk, such as Cross Interleave Reed Solomon Code (CIRC) error detection codes, which are provided by the 908 standard (or other applicable standard), enable a CD player either to correct or conceal the modifications during playback or to ignore them altogether. When an unauthorized copy is made of the medium, however, the ancillary data are ineffective in overcoming the intentional modifications in the original medium, with the result that faults occur in the copy that are substantially unrecoverable. Methods for introducing such modifications are described in the above-mentioned U.S. Patents 6,256,738 and 6,425,098.
Despite the modifications in the sub-code channels and/or audio data, an audio CD
player will reproduce the audio signals on the disk without difficulty. A
computer CD drive, however, will be confused by either the multiple sessions on the CD or the modified data in audio session 100 (or by both) and will not be able to load or play the disk, let alone copy it.
Modifications in the added audio and/or data sessions are preferably introduced by one or more of the following mechanisms:
= Generating a lead-in that points to tracks located in the program area of the first session.
= Generating a lead-in with a larger number of tracks than is allowed by the standard.
= Modifying the lead-in to simulate a shorter CD.
= Modifying the absolute time at the beginning of the session.
Following these methods, Table II below describes changes made in the sub-code Q
channel of a multiple-session CD, in order to prevent computer copying of the audio content without interfering with audio playback. The first session on the CD is an audio session, based on the Red Book standard, while the second and subsequent sessions may be audio or data sessions, based on the Blue Book, as described above.
TABLE II
Session Standard Modification 1 Lead-in (2'/2-3 Add pointers BO and CO to the second and third min) sessions, per Blue Book format.
Pause length 2 Use different pregap length, per Blue Book format, sec preferably set to value between 1 and 3 sec.
Accurate Start A-Time at non-zero value, e.g., 10 sec, to mask A-Time beginning of disk for computer CD drive.
2 Audio track Audio track length 4 sec (minimum time per Red Book).
3 Lead-in (1 TOC points to 99 non-existent data tracks at time min) 00:02.
Modify lead-out pointer (A2) to a value between 00:01 and 00:07.
Audio track Data track length 4 see, plus fill to a total CD length.
As a result of these changes, a computer CD-ROM or DVD-ROM drive, upon reading the sub-code Q channel data in session 3, will either fail to mount the CD
entirely, or will go into an endless loop looking for the non-existent data tracks listed in the TOC. If the drive does succeed in accessing session 1, which holds the normal audio content, it is still likely to be confused by the 1 sec pregap (which is outside the Red Book specification) and/or by the distorted A-time. CD audio and DVD players, however, will be largely unaffected by these changes. In this regard, session 2 is important, since without it, some Blue Book-compliant DVD players might refuse to mount the CD. It will be understood that the specific modifications noted in the table are listed by way of example. Alternative combinations of modifications and settings of the time values and other parameters will be apparent to those skilled in the art.
Preferably, in order to allow an authorized personal computer (PC) to play the contents of the protected disk, the original contents are compressed (using any suitable format known in the art, such as MP3 or VQF) and encrypted, by audio compressor 35 (Fig. 2).
These encrypted data are stored using a "digital wrapper" technique, so that the data are hidden from conventional CD driver software. For example, the data may be stored in the reserved sub-code channel bits, as described above, or in one of the data sessions on the CD, or in a lead-in, lead-out or pause area. The data can be decrypted and played back only by using authorized software, which is also preferably stored in the second session and is made available only to appropriately-licensed users and/or equipment. The authorized software will prevent the decryption of the data if its source is not the original CD or if the rules for distributing and using the data are otherwise violated.
It will be appreciated that the preferred embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.
Claims (36)
1. A method for protecting data recorded on an original storage medium against unauthorized use, comprising:
receiving digital audio data encoded in accordance with Standard 908 of the International Electrotechnical Commission;
incorporating the digital audio data in a audio session of a multi-session recording, which further comprises a data session;
introducing an error in a sub-code Q channel of the data session, so as to prevent a computer from reproducing the recording, without preventing playback of the audio data by an audio player; and recording the audio and data sessions, including the error in the sub-code Q
channel, on the original storage medium.
receiving digital audio data encoded in accordance with Standard 908 of the International Electrotechnical Commission;
incorporating the digital audio data in a audio session of a multi-session recording, which further comprises a data session;
introducing an error in a sub-code Q channel of the data session, so as to prevent a computer from reproducing the recording, without preventing playback of the audio data by an audio player; and recording the audio and data sessions, including the error in the sub-code Q
channel, on the original storage medium.
2. A method according to claim 1, wherein the medium comprises a compact disk.
3. A method according to claim 1, and comprising altering a portion of the encoded audio data to introduce a further error in the audio session, such that the sub-code Q channel of the audio session is inconsistent with Standard 908, but does not prevent playback of the audio data by the audio player following recording thereof.
4. A method according to claim 3, wherein altering the data comprises specifying an erroneous absolute time in the data to be recorded on the medium.
5. A method according to claim 4, and comprising storing a correct absolute time in reserved sub-code bits on the medium.
6. A method according to claim 4, wherein specifying the erroneous absolute time comprises shifting absolute times recorded in three consecutive blocks of a selected track.
7. A method according to claim 3, wherein altering the data comprises duplicating one or more blocks of the data to a new location on the storage medium, without changing an absolute time recorded in the sub-code Q channel of the one or more blocks.
8. A method according to claim 3, wherein altering the data comprises specifying an erroneous point index number in a track of the data to be recorded on the medium.
9. A method according to claim 8, and comprising storing a correct index number in reserved sub-code bits on the medium.
10. A method according to claim 1, wherein introducing the error comprises creating a lead-in to the data session that points to one or more tracks located in the audio session.
11. A method according to claim 1, wherein introducing the error comprises creating a lead-in to the data session that includes a larger number of tracks than is permitted by the standard.
12. A method according to claim 1, wherein introducing the error comprises inserting a modified absolute time at a start of the data session.
13. A method according to claim 1, wherein incorporating the digital audio data comprises creating multiple sessions at least two of which are identified as audio sessions.
14. A method according to claim 1, wherein recording the audio and data sessions comprises compressing and encrypting the audio data on the medium, for use by an authorized computer in playback of the medium.
15. Apparatus for protecting data recorded on an original data storage medium against unauthorized use, comprising:
an encoder, adapted to receive a stream of digital audio data for recording on the medium and to encode the digital audio data in accordance with Standard 908 of the International Electrotechnical Commission;
a data session generator, which is adapted to incorporate the digital audio data in an audio session of a multi-session recording, which further comprises a data session;
a sub-code generator, operative to introduce an error in a sub-code Q channel of the data session, so as to prevent a computer from reproducing the recording, without preventing playback of the audio data by an audio player; and an eight-to-fourteen bit (EFM) modulator, coupled to modulate the audio and data sessions, including the error in the sub-code Q channel, for recording on the original storage medium.
an encoder, adapted to receive a stream of digital audio data for recording on the medium and to encode the digital audio data in accordance with Standard 908 of the International Electrotechnical Commission;
a data session generator, which is adapted to incorporate the digital audio data in an audio session of a multi-session recording, which further comprises a data session;
a sub-code generator, operative to introduce an error in a sub-code Q channel of the data session, so as to prevent a computer from reproducing the recording, without preventing playback of the audio data by an audio player; and an eight-to-fourteen bit (EFM) modulator, coupled to modulate the audio and data sessions, including the error in the sub-code Q channel, for recording on the original storage medium.
16. Apparatus according to claim 15, wherein the medium comprises a compact disk.
17. Apparatus according to claim 15, wherein the sub-code generator is adapted to introduce a further error in the sub-code Q channel of the audio session, such that the sub-code Q channel of the audio session is inconsistent with Standard 908, but does not prevent playback of the audio data by the audio player following recording thereof.
18. Apparatus according to claim 17, wherein the further error in the sub-code Q
channel comprises an erroneous value of the absolute time of a track of the data to be recorded on the medium.
channel comprises an erroneous value of the absolute time of a track of the data to be recorded on the medium.
19. Apparatus according to claim 17, wherein the further error in the sub-code Q
channel is engendered by duplicating one or more blocks of the data to a new location on the storage medium, without changing an absolute time recorded in the Q
channel of the one or more blocks.
channel is engendered by duplicating one or more blocks of the data to a new location on the storage medium, without changing an absolute time recorded in the Q
channel of the one or more blocks.
20. Apparatus according to claim 17, wherein the further error in the sub-code Q
channel comprises an erroneous value of a point index number of a track of the data to be recorded on the medium.
channel comprises an erroneous value of a point index number of a track of the data to be recorded on the medium.
21. Apparatus according to claim 15, wherein the error comprises a lead-in to the data session that points to one or more tracks located in the audio session.
22. Apparatus according to claim 15, wherein the error comprises a lead-in to the data session that includes a larger number of tracks than is permitted by the standard.
23. Apparatus according to claim 15, wherein the error comprises a modified absolute time at a start of the data session.
24. Apparatus according to claim 15, wherein the multi-session recording comprises at least two audio sessions.
25. Apparatus according to claim 15, and comprising an audio compressor, which is adapted to compress and encrypt the audio data on the medium, for use by an authorized computer in playback of the medium.
26. A data storage medium that is resistant to unauthorized copying, on which medium data encoded in accordance with Standard 908 of the International Electrotechnical Commission are stored in an audio session of a multi-session recording, which further comprises a data session, wherein an error is introduced in a sub-code Q channel of the data session, so as to prevent a computer from reproducing the recording, without preventing playback of the audio data on the medium by an audio player.
27. A medium according to claim 26, wherein the medium comprises a compact disk.
28. A medium according to claim 26, wherein the a further error is introduced in the sub-code Q channel of the audio session, such that the sub-code Q channel of the audio session is inconsistent with Standard 908, but does not prevent playback of the audio data by the audio player following recording thereof.
29. A medium according to claim 26, wherein the error comprises a lead-in to the data session that points to one or more tracks located in the audio session.
30. A medium according to claim 26, wherein the error comprises a lead-in to the data session that includes a larger number of tracks than is permitted by the standard.
31. A medium according to claim 26, wherein the error comprise a modified absolute time at a start of the data session.
32. A medium according to claim 26, wherein the multi-session recording comprises at least two audio session.
33. A medium according to claim 26, wherein the audio data are further stored on the medium in a compressed and encrypted form, for use by an authorized computer in playback of the medium.
34. A method according to claim 1, further comprising altering a portion of the data so that a digital output of the altered data will be inconsistent with Standard 958 of the International Electrotechnical Commission.
35. Apparatus according to claim 15, wherein the encoder is further adapted to alter the data so that a digital output of the altered data will be inconsistent with Standard 958 of the International Electrotechnical Commission.
36. A data storage medium according to claim 26, wherein the audio session further comprises altered data, such that a digital output of the altered data will be inconsistent with Standard 958 of the International Electrotechnical Commission.
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|---|---|---|---|
| US09/549,820 | 2000-04-14 | ||
| US09/549,820 US6988206B1 (en) | 1998-10-20 | 2000-04-14 | Prevention of CD-audio piracy using sub-code channels |
| PCT/IL2001/000295 WO2001080546A2 (en) | 1999-08-09 | 2001-03-29 | Prevention of cd-audio piracy using sub-code channels |
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| CA2422515A1 CA2422515A1 (en) | 2001-10-25 |
| CA2422515C true CA2422515C (en) | 2011-05-03 |
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| CA2422515A Expired - Fee Related CA2422515C (en) | 2000-04-14 | 2001-03-29 | Prevention of cd-audio piracy using sub-code channels |
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| JP (1) | JP2004501477A (en) |
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| KR200452225Y1 (en) * | 2008-06-05 | 2011-02-14 | (주)시공사 | Wallboard Panel For Interior With Discarded Wood |
| US20100214893A1 (en) * | 2009-02-25 | 2010-08-26 | Aylward Adrian R | Copy protection using complexity and uncomputability |
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| JPH08153331A (en) * | 1994-09-29 | 1996-06-11 | Applics:Kk | Method and device for discriminating copied cd-rom |
| CN1294588C (en) * | 1996-07-24 | 2007-01-10 | 皇家菲利浦电子有限公司 | Improvement on optically readable discs and disc recording apparatus |
| AU3706197A (en) * | 1996-08-05 | 1998-03-06 | T.T.R. Technologies Ltd. | Digital optical media authentication and copy protection method |
| AU7362198A (en) * | 1997-05-16 | 1998-12-08 | Imation Corp. | Arrangement for preventing use of unauthorized duplicates of a data storage medium using subcode and method therefor |
| ES2155230T3 (en) * | 1997-08-28 | 2001-05-01 | Sony Dadc Austria Ag | SYSTEM FOR MANAGING COPYING OF AN OPTICAL DISK. |
| US6104679A (en) | 1998-10-01 | 2000-08-15 | T.T.R. Technologies Ltd. | Method for determining an unauthorized copy of an optical disc |
| AU6082799A (en) * | 1998-10-05 | 2000-04-26 | Koninklijke Philips Electronics N.V. | System for copy protection of recorded information |
| WO2000068945A1 (en) * | 1999-05-11 | 2000-11-16 | Macrovision Corporation | Secure compact disk and player |
| GB9912312D0 (en) * | 1999-05-26 | 1999-07-28 | Dilla Limited C | The copy protection of digital audio compact discs |
| GB0003530D0 (en) * | 2000-02-15 | 2000-04-05 | Dilla Limited C | The copy protection of digital audio compact discs |
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- 2001-03-29 CA CA2422515A patent/CA2422515C/en not_active Expired - Fee Related
- 2001-03-29 EP EP01919729A patent/EP1297651A4/en not_active Withdrawn
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| AU4678701A (en) | 2001-10-30 |
| JP2004501477A (en) | 2004-01-15 |
| KR20030064618A (en) | 2003-08-02 |
| CA2422515A1 (en) | 2001-10-25 |
| CN100336336C (en) | 2007-09-05 |
| BR0110039A (en) | 2003-12-30 |
| KR100712429B1 (en) | 2007-04-27 |
| MXPA02010186A (en) | 2004-08-19 |
| AU781208B2 (en) | 2005-05-12 |
| EP1297651A4 (en) | 2006-04-12 |
| IL152251A0 (en) | 2003-05-29 |
| EP1297651A2 (en) | 2003-04-02 |
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