EP1076902A2 - Authentification de supports optiques numeriques et protection contre les copies - Google Patents

Authentification de supports optiques numeriques et protection contre les copies

Info

Publication number
EP1076902A2
EP1076902A2 EP97933829A EP97933829A EP1076902A2 EP 1076902 A2 EP1076902 A2 EP 1076902A2 EP 97933829 A EP97933829 A EP 97933829A EP 97933829 A EP97933829 A EP 97933829A EP 1076902 A2 EP1076902 A2 EP 1076902A2
Authority
EP
European Patent Office
Prior art keywords
optical media
symbol
digital optical
data
symbols
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP97933829A
Other languages
German (de)
English (en)
Other versions
EP1076902A4 (fr
Inventor
Bruce David Sollish
Dennis Howe
Henry Marshall Israel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ttr Technologies Ltd
Original Assignee
Ttr Technologies Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ttr Technologies Ltd filed Critical Ttr Technologies Ltd
Publication of EP1076902A2 publication Critical patent/EP1076902A2/fr
Publication of EP1076902A4 publication Critical patent/EP1076902A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • G11B20/00572—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which change the format of the recording medium
    • G11B20/00579—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which change the format of the recording medium said format change concerning the data encoding, e.g., modulation schemes violating run-length constraints, causing excessive DC content, or involving uncommon codewords or sync patterns
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/06009—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code with optically detectable marking
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/14—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation using light without selection of wavelength, e.g. sensing reflected white light
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/14—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation using light without selection of wavelength, e.g. sensing reflected white light
    • G06K7/1404—Methods for optical code recognition
    • G06K7/146—Methods for optical code recognition the method including quality enhancement steps
    • G06K7/1465—Methods for optical code recognition the method including quality enhancement steps using several successive scans of the optical code
    • 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
    • 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
    • G11B20/00094—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which result in a restriction to authorised record carriers
    • G11B20/00123—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which result in a restriction to authorised record carriers the record carrier being identified by recognising some of its unique characteristics, e.g. a unique defect pattern serving as a physical signature of the record carrier
    • 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
    • G11B20/0021—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving encryption or decryption of contents recorded on or reproduced from a record carrier
    • 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
    • G11B20/00572—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which change the format of the recording medium
    • G11B20/00586—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which change the format of the recording medium said format change concerning the physical format of the recording medium
    • 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
    • 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
    • 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
    • G11B20/18—Error detection or correction; Testing, e.g. of drop-outs
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
    • H03M13/35—Unequal or adaptive error protection, e.g. by providing a different level of protection according to significance of source information or by adapting the coding according to the change of transmission channel characteristics
    • 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
    • G11B20/18—Error detection or correction; Testing, e.g. of drop-outs
    • G11B20/1833—Error detection or correction; Testing, e.g. of drop-outs by adding special lists or symbols to the coded information

Definitions

  • the present invention relates to data protection in general and to protection of data on optical media, such as Compact Disc Digital Audio (CDDA), Compact Disc Read-Only Memory (CD-ROM), and Digital Video Disc (DVD)
  • CDDA Compact Disc Digital Audio
  • CD-ROM Compact Disc Read-Only Memory
  • DVD Digital Video Disc
  • the present application utilizes the term "digital optical media” to denote any media which stores data in digital form which can be read by optical means, including but not limited to laser
  • data to refer to any information stored on media, including, but not limited to text, images, program instructions and parameters (collectively known as "software"), audio, and video, including interactive graphics and motion pictures
  • Digital optical media is well-known in the art and is utilized to store large amounts of data in digital form, such as audio data, video data, software data, or document data
  • Software, document, and audio-visual data (“multi-media” data) may be read and utilized by a computer from digital optical media, such as Compact Disc Read-Only Memory (CD-ROM)
  • CD-ROM Compact Disc Read-Only Memory
  • players include, but are not limited to, CD players, CD-ROM multi-media players, game-playing systems, and DVD-players, which can reproduce sound, images, text, and motion pictures from data stored on digital optical media
  • Some computers are also configured to duplicate the functionality of CD players, CD-ROM multi-media players, game-playing systems and DVD-players In order to protect the proprietary rights of the creators or owners of the data recorded on media, it is desirable to be able to determine if a particular instance of media is authentic or if it is an unauthorized copy It is furthermore desirable to be able to effect such
  • optical media recorder such as a CD-ROM recorder
  • Low-cost optical media recorders are generally available to the public, and it is both easy and inexpensive for an ordinary consumer who has access to such a device to duplicate the data on a piece of optical media, in violation of the copyrights or other proprietary rights which may exist for the data on such media
  • Large-quantity duplication requires a mastering machine, a technology which is expensive and not generally available
  • Certain commercial enterprises however, duplicate optical media on a mass scale in violation of the copyrights or other proprietary rights which may exist for data on such media
  • duplication requires special equipment, it results in a large quantity of unauthorized copies
  • Both small- and large-scale unauthorized copying deprive the creators and owners of data stored on media of control of the distribution and use of their property There is therefore a widely-recognized need for, and it would be advantageous to have, an automatic method of verifying the authenticity of a particular instance of optical media, and a method of preventing the
  • Fig 1 is a cross-sectional schematic of a portion of the data surface of a digital optical medium
  • Fig 1 illustrates digital optical media having at least one layer of transparent refractive material 10 which has data recorded on one surface which is coated with a reflective material 12, and covered with an optional protective layer 14
  • Reflective material 12 in combination with transparent refractive material 10 produces transparent reflective layer 24 whose optical properties depend on the properties both of reflective material 12 and transparent refractive material 10
  • Transparent reflective layer 24 comprises the data surface (/ e the surface on which optically detectable features that correspond to digital data reside) of the digital optimal medium
  • Layer 24 usually resides on one surface of a thick transparent disc-shaped substrate (substrate thickness is 1 2 mm for CD and 0 6 mm for DVD)
  • Layer 24 is embossed directly onto a surface of such disc-shaped substrate when mass-producing digital optical media
  • Different embodiments of digital optical media have different numbers of transparent reflective layers 24 CD's for example, have a single such layer, while DVD's have up to four such layers
  • Reading Data from Digital Optical Media In order to read the data written onto digital optical media, such as CD and DVD, the media is rotated at a precisely-controlled speed, and light from a laser is focused through the disc-shaped substrate into transparent reflective layer 24 from which it is reflected back to a detector which measures the intensity of the reflected light.
  • the optical properties of the layer 24 are physically modified according to the data to be recorded so that the reflected light will vary significantly in intensity depending on where the laser light strikes.
  • pits and lands may be physically implemented in different ways, but they always have the property of reflecting discernibly different light intensities Moreover, pits and lands are specified by the standards to have sharp, well-defined boundaries 22, so that according to the standards it is normally possible to precisely identify the location where a pit ends and a land begins and where a land ends and a pit begins.
  • edge refers to a precise, well-defined boundary between one region and another, as for example, boundary 22.
  • Data is recorded onto digital optical media in a spiral track along which these patterns of pits and lands are laid out in a linear fashion.
  • the laser light sweeps along the track and its reflected intensity depends on whether the light falls on land (high reflectivity) or pit (low reflectivity)
  • a change in the reflected intensity is referred to as a "transition " , and whenever the intensity of the reflected light changes from one value to another, (that is, when the incident light passes either from land to pit or from pit to land), the detector circuitry signals that a transition has occurred It is not the intensity of the reflected iight, however, but rather the precise timing of these transitions from one intensity to the other (relative to a data clock maintained within the digital data detector of the medium reader) which represents the digital data recorded on the media.
  • the standards imply that a detected transition will indicate the position of an edge.
  • Digital data is represented within a computer or digital optical media player as a series of "bits" (binary digits, i.e., 1 's and O's), where 8 bits are typically grouped into a data unit referred to as a "byte".
  • bits binary digits, i.e., 1 's and O's
  • the sequence of bits in unconstrained in the sense that any specific bit can be succeeded by a 1 or a 0. It is not desirable, however, to record unconstrained data on digital optical media using the recording technique previously described (e.g., if pits represent 1 's and lands represent O ' s or if a transition occurs only when a 1 is recorded), because transitions may then occur too frequently or not frequently enough, depending on the data.
  • mapping between bytes of the data stream and representations thereof, known as "symbols", recorded on the media.
  • symbols the mapping is bi-directional since any given data byte can be mapped into a unique symbol, which in turn can be mapped uniquely back into the original data byte.
  • these two directional mappings of the bi-directional mapping are inverses of one another
  • the specific mappings of digital optical media according to the present standards are such that prior to recording, every byte of data is encoded to convert it to a constrained binary sequence that exhibits at least a desired minimum number of O's but not more than a desired maximum number of O's, between any two 1 ' s
  • the inverse directional mapping converts these bit sequences back into the original data bytes when the digital optical media is read
  • the constraints which specify the minimum and maximum number of consecutive O's are known as "run length-limited rules", or "RLL rules"
  • the channel bits are represented in the digital optical media as regions of pits alternating with regions of lands, such that the regions have well-defined sizes in the m-track direction which are integer multiples of a size corresponding to the length unit, a channel bit
  • this size is about 0 3 ⁇ m and the minimum size of a region is three times this size (for a total length of about 0.9 ⁇ m), while the maximum size of a region is eleven times this size (for a total length of about 3.3 ⁇ m).
  • FIG 4 illustrates a frame for a CD.
  • the CD frame begins with a synchronization header 40, which is a special sequence of transitions used by the player to detect the beginning of the frame, to calibrate its timing, and to adjust the rotational speed of the media.
  • a special control symbol 41 which is followed by 12 data symbols 42, four error correction symbols 44, 12 more data symbols 46, and another four error correction symbols 48, for a total of 33 symbols.
  • Each EFM encoded symbol 43 comprises 14 channel bits, and adjacent symbols are separated by a pattern of 3 merge bits 45. A group of a specified number of successive frames is referred to as a "sector ".
  • 98 contiguously recorded frames constitute a sector
  • Sectors recorded on CD digital optical media track are assigned unique numbers, and because each frame is uniquely identified by its number within a sector, and each symbol is uniquely identified by its number within a frame, it is thus possible to uniquely specify any individual symbol on the disk
  • the present application utilizes the term "address" to refer to the unique position of a specific symbol on an instance of digital optical media.
  • the present application utilizes the term "erroneous symbol” to refer to any symbol which will cause the error-correcting system of a digital optical media player to detect that a symbol in a particular codeword does not have the proper value
  • the present application utilizes the term "invalid symbol” to refer to any channel bit sequence which can be written to digital optical media but which does not correspond to a possible symbol value as specified by the bi-directional mapping cited in the applicable standards for the digital optical media
  • an invalid symbol will always be detected by the media player as an erroneous symbol Moreover, it will be detected as an erroneous symbol immediately by the player's decoder, even before the application of any error-detecting and correcting system
  • the optical media player reads the channel bit sequences corresponding to each symbol from the digital optical media, it checks them to make sure that they are valid For example, if a CD player encounters a channel sequence with two transitions less than 3 or more than 1 time units apart, it flags that symbol as invalid, since the channel bit sequences used in CD are the
  • an invalid symbol causes an RLL error, or is simply an undefined symbol
  • the invalid symbol is flagged by the decoder
  • a flagged symbol represents an error in a known position and is referred to as an "erasure'
  • an invalid symbol implies that the media has been damaged in such a way that the transition timing cannot be read properly In certain conditions, such errors may be corrected by the ECC decoder
  • the ECC decoder checks every recovered ECC codeword to determine if any of its constituent symbols have been read erroneously In certain conditions, such errors may also be corrected by the ECC decoder but the number of such errors which are correctable is only half as large as the number of correctable erasures (since the position of an erasure is known when it is detected, but the position of a non-erasure error must be separately determined)
  • interleaving The purpose of interleaving is to spread out the physical locations of the sequential input data over the media so that localized damage to the media surface will not grossly impact any one segment of the data Instead, the effect of the damage will be distributed over a large area
  • the interleaving is chosen to sufficiently insure that reasonable levels of digital storage medium imperfection damage will corrupt only a few constituent symbols of an ECC codeword This will insure that the position of the erroneous symbols in the codeword can be located and that then correct values can be calculated when the ECC codeword is decoded in such a way that only small number of erroneously recovered data symbols (/ e , errors) will occur in any one contiguous segment of the data
  • the input bytes of data to be recorded on a CD are considered to be in groups of 24
  • the size of this group corresponds to the number of input data symbols within a frame on the media data track
  • Fig 6 illustrates precisely how sequential bytes of data in 24-byte group n (column 74) are mapped to non-sequential frames (column 76) and symbol locations (column 78) within those frames on a CD data track It may be noted from Fig 6 that no data is mapped to frame symbol number 0 since this location is where the control symbol is placed Furthermore, no data is mapped to frame symbol numbers 13, 14, 15, and 16, nor to frame symbol numbers 29, 30, 31 , and 32, since these locations are used for the error-correcting redundancy symbols
  • the player re-orders the data symbols contained in the sequentially recovered frames recorded on the media into their correct sequence
  • CD digital optical media there are two separate phases of the data reordering, and at each phase a different set of error correcting code words are formed and checked (by the ECC decoder) for errors
  • Other embodiments may employ additional phases This is schematically illustrated for CD's in Fig 7, reference to which is now briefly made
  • the decoded channel bit symbols 80 corresponding to the last 32 symbols of each recovered frame pass through a partial de-interleaving step 82, comprising a number of delays 81 for selected symbol positions
  • C1 the first level of error correction 84 is applied to the resulting 32-symbol C1 ECC codeword
  • C2 the second level of error correction 88 is applied to the resulting 28-symbol C2 codeword
  • the final de-interleaving step 90 results in the data bytes 92 being reassembled
  • the C1 decoder may be able to correct errors not only in the 24 data symbols, but also errors in the four C2 redundancy symbols that comprise the C1 codeword
  • Each of the 24 data symbols in a particular C1 codeword was originally contained in one of 24 different input data frames
  • Each of the four C2 redundancy symbols belong to one of four different C2 codewords, all four C1 redundancy symbols below to the particular C1 codeword
  • the C2 codeword obtained in the second level error correction comprises 24 input data symbols taken from only two input data frames and the four C2 parity symbols all belong to the particular C2 codeword
  • Each phase of the CIRC error-correcting decoding is able to detect the existence of erroneous symbols in a specific codeword, and within any such codeword may correct up to two erroneous symbols whose locations within the codeword are unknown Error locations are normally unknown when the erroneous symbols were obtained from valid EFM code sequences, for such errors are not immediately recognizable by the EFM decoding process as such If, on the other hand, the locations of the erroneous symbols are known, the CIRC method may correct up to four erroneous symbols Error locations are normally known when the errors correspond to invalid EFM code sequences which were previously marked by the EFM decoder as erasures Thus, each phase of error correction may correct up to t p valid symbols which are erroneous, and up to t, erasures, such that t e and t comprise jointly satisfy the inequality 2t e + t x ⁇ 5 Each phase of error correction may thus also correct one valid symbol which is erroneous and
  • the decoder fails to detect that a non-correctable number of errors has corrupted a specific codeword, it will deliver (at its option) a valid codeword that is different from the original (corrupted) codeword
  • This output codeword will, in general, have symbol values in several codeword locations that are different from those in either the original uncorrupted codeword or the corrupted original codeword
  • the player reorders the data from the symbols recorded on the digital optical media track and while so doing, it attempts to detect errors and to correct them in two related, but distinct, phases In this manner, under normal conditions a player will be able to recover virtually error-free all the data from digital optical media which has been subjected to ordinary care in handling
  • digital optical media comprising at least one non-copyable symbol stored thereon
  • recording the digital optical media to include such special (non-standard) symbols which can be read by ordinary media readers, but which require special recorders or mastering equipment to write, it will be possible to identify the digital optical media as authentic and distinguish it from an unauthorized copy by detecting such non-copyable symbols
  • non-copyable symbol to refer to a symbol on optical media which is readable as a valid symbol by ordinary players of the optical media and which is distinguishable from a regular symbol by ordinary players of the optical media, but which does not conform to the applicable specifications for the optical media in such a way that it is not reproducible by ordinary recorders and mastering equipment for the optical media
  • Such special recorders and maste ⁇ ng equipment would not be generally available to either the public or to commercial optical media replicators When optical media is recorded or manufactured with these non-copyable symbols, an ordinary player will be able to detect them on the original authentic media Unauthorized copies, however, will not have them,
  • the media is scanned by the reader to detect these non-copyable symbols If they are present, the optical media is determined to be authentic Otherwise, it is determined to be an unauthorized copy This determination can be done automatically as the optical media is read (such as by computer) without the need for a separate physical inspection of the optical media Copy Protection by Using Patterns of Non-Copyable Symbols
  • non-copyable symbols can be used not only for optical media verification, but also for copy protection.
  • a simple way is for the software on the optical media to check for the presence of the non-copyable symbols If they are present, the software will have determined that the optical media is authentic and will execute the application. Otherwise, the software will have determined that the optical media is an unauthorized copy and will refuse to run.
  • Another method of copy protection which provides a higher degree of security is to encrypt the data on the optical media using an acceptable encryption method, such as the DES algorithm, and to encode the decryption key in a special pattern of non-copyable symbols.
  • an acceptable encryption method such as the DES algorithm
  • the present application will utilize the term "signature" to refer to such a special pattern of non-copyable symbols on optical media, such that information, such as a decryption key, may be encoded within the special pattern.
  • non-copyable symbols for digital optical media by carefully departing from the standards for writing data so that the decoded value of the symbol is no longer well-defined, but such that the reader will interpret the symbol as a valid symbol having one of two different predetermined data values which will be randomly interpreted for the symbol during each separate reading operation.
  • the present application will utilize the term "ambiguous symbol" to refer to such a non-copyable symbol whose data value is not well-defined according to the standards for digital optical media
  • error detection and correction is desirable, as it reduces the probability that the data read from digital optical media and delivered to the user will become corrupted by minor physical damage to the media Error-correcting, however, interferes with the reading of the (non-copyable) ambiguous symbols which serve to identify optical media as authentic, since the ambiguous values will be adjusted by the error correcting circuitry to stable values It is therefore necessary to override the error correction in specific locations, so that the ambiguous symbols can be detected
  • a simple way of bypassing error correction in the writing of ambiguous symbols is to write them in the final sector of the lead-out area of a CD-ROM disk, for example This is not completely satisfactory, however, as it restricts the location of the ambiguous symbols
  • the present invention overcomes this disadvantage by providing a method for overriding the error correction in arbitrary locations on digital optical media, thus allowing ambiguous symbols to be written in many locations
  • the overriding of error correction makes use of the fact that the mathematical principles of the Reed-Solomon error-correcting algorithm do not distinguish between an error in the data symbols and an error in the error correcting redundancy symbols themselves
  • the overriding of the ECC is accomplished by causing a non-correctable pattern of erroneous symbols to occur in the ECC portion of the codeword
  • the non-correctable error pattern is immediately recognized by the ECC decoder as being non-correctable
  • the ECC decoder will not attempt to change the values of any symbols of an ECC codeword that is corrupted by the detected non-correctable error pattern
  • the overriding of the ECC is applicable to a wide variety of digital optical media, including CD, CD-ROM, and DVD, and it is usable for digital optical media recordings which are both mass-produced by plastic molding apparatus as well as those which are produced in small quantities by individual recorders controlled by desktop computers, workstations, and the like
  • the method of the present invention by which correction of erroneous and/or erased symbols recovered from digital optical media by the media reader's ECC decoder is overridden involves several innovations in writing and formatting data to digital optical media
  • the present method further discloses a class of special patterns to be recorded onto digital optical media, consisting of invalid channel bit sequences written on the digital optical media
  • fourteen bit codes which are invalid are marked onto CDDA such as compact disks
  • CDDA such as compact disks
  • a standard CD reader will read these invalid fourteen bit codes ambiguously (i e sometimes the CD reader will produce one eight bit code and sometimes it will produce a different eight bit code for the same invalid fourteen bit code)
  • the present invention utilizes the invalid codes for at least two different purposes
  • the present invention utilizes the invalid codes to mark compact disks with identifying data
  • specific invalid fourteen bit codes are written to specific locations on the compact disk
  • the present invention may incorporate an identifying unit which checks the compact disk and identifies which, if any of the fourteen bit codes thereon are invalid
  • the checking operation utilizes the fact that the invalid data will provide ambiguous data when read Thus, the checking operation repeatedly reads the locations where markings are expected If the data in the specified locations is not identical for each reading (i e sometimes it has one value and sometimes it has another value), then the compact disk is marked with invalid codes
  • the identifying unit can also determine if the invalid fourteen bit codes correspond, in location and code values, to codes which identify the compact disk as being marked in a further embodiment, the present invention utilizes the marked compact disk as a key for protecting software.
  • a protected software product Before a protected software product performs certain operations, it ascertains that a marked compact disk is present in its compact disk drive.
  • the marked compact disk has to have the markings specific to the protected software. If the invalid codes are in the places specific to the protected software, the software can operate. If the invalid codes are in the wrong places or if there are no invalid codes, the software cannot operate.
  • the key can also function as the encryption and/or decryption key if the data, or a software program, has been encrypted. Upon reading the key, decryption software can decrypt the data.
  • Fig. 1 is a schematic illustration of a data-storage layer of prior art digital optical media
  • Fig. 2 is a partial listing of prior art EFM codes used to map 8-bit byte values to constrained 14-b ⁇ t channel sequences;
  • Fig. 3 is a schematic illustration of digital signals detected from p ⁇ or art digital optical media
  • Fig. 4 is a schematic illustration of a frame of data on prior art digital optical media
  • Fig. 5 is a conceptual illustration of data interleaving on prior art digital optical media
  • Fig. 6 is a table showing the prior art mapping of input (user) data bytes to frame and symbol locations on a digital optical media track
  • Fig. 7 is a schematic illustration of the symbol reading, error checking, and reordering operations of a prior art digital optical media player
  • Fig. 8 is a table showing unused EFM channel bit sequences that are usable for invalid symbol representation
  • Fig. 9 illustrates some invalid EFM channel bit code sequences with run-length-limited (RLL) errors
  • Fig. 10A is a table showing the mapping of data bytes to their corresponding frame locations and certain C1 redundancy symbols on an audio CD
  • Fig. 10B is a table showing the mapping of data bytes to their corresponding frame locations and certain C1 redundancy symbols on a CD-ROM
  • Fig 1 1 is a table showing the mapping of data bytes to their corresponding C2 redundancy symbols and related C1 redundancy symbols
  • Fig 12 is a schematic block diagram illustration of a mechanism for recording non-copyable symbols onto digital optical media
  • Fig 13 is a schematic illustration of an ambiguous symbol recorded onto an original CD, in accordance with a preferred embodiment of the invention and the alternative interpretations of the symbol by a digital optical media player
  • Fig 14 is a schematic illustrations of an ambiguous symbol recorded onto an original CD, in accordance with a further preferred embodiment of the invention and the alternative interpretations of the symbol by a digital optical media player
  • Fig 15 is a schematic illustration of a marked compact disk, constructed in accordance with a preferred embodiment of the present invention and two compact disks copied therefrom
  • Fig 16 is a block diagram illustration of a unit for creating the marked compact disk of Fig 15,
  • Fig 17 is a flow chart illustration of a method of identifying the marked compact disk of Fig 15
  • Fig 18 is a block diagram of a system for encrypting software utilizing the marked compact disk of Fig 15, and
  • Fig 19 is a block diagram of a system for decrypting software utilizing the marked compact disk of Fig 15,
  • the present invention describes a method for identifying original digital optical media and distinguishing o ⁇ ginal optical media from unauthorized copies by recording non-copyable ambiguous symbols on the media and protecting them by overriding the error correction which is normally in effect
  • the present invention furthermore describes a method for copy protection of digital optical media
  • the present invention moreover describes a method of overriding the error correction normally in effect by replacing the error correction codes (ECC) or symbols with invalid symbols, thereby protecting the ambiguous symbols from being corrected during the media player s attempt to correct what it assumes is an "error"
  • ECC error correction codes
  • one of the transitions is shifted so that it will no longer be synchronized with the channel data detection clock signal.
  • the result is that the decoding of the channel bit code sequence (the symbol) into an 8-b ⁇ t data value (a byte) is no longer well-defined
  • Symbol 100 which is recorded onto the authentic original CD, in accordance with a preferred embodiment of the invention
  • Symbol 100 comprises an ambiguous transition 102 which has been shifted relative to the clock position 103
  • the result is that the detected transitions of the EFM code sequence, generally referenced
  • the media player digitizes transition 102 to be at clock position 106, it will interpret the code sequence as symbol 105, which decodes to a data byte with a hexadecimal value of E4. If, on the other hand, the media player digitizes transition 102 to be at clock position 108, it will interpret the code sequence as symbol 107, which decodes to a data byte with a hexadecimal value of F8. Subsequent readings of the symbol will result in a random distribution of interpreted data values. Some will be interpreted as E4, while others will be interpreted as F8.
  • the media player reads the symbol a plurality of times. If the interpreted value shows any variation from one reading to the next, owing to the two possible values for the symbol, then it has detected the presence of an ambiguous symbol.
  • the copy will not contain ambiguous symbols, because standard optical media equipment (described hereinabove with respect to Fig. 1 ) cannot copy the ambiguous symbols Specialized equipment is needed to write ambiguous symbols.
  • a copy made according to digital optical media technology standards will only contain regular symbols whose values are not ambiguous and which will be read and decoded consistently as having the same value.
  • ambiguous symbols are non-copyable symbols, they can be used for authentication and for copy protection of digital optical media. Because the detection of ambiguous symbols involves a random process, it is preferable to include a number of ambiguous symbols in order to ensure that at least one of the ambiguous symbols is detected. If enough ambiguous symbols are recorded on an instance of digital optical media, and the media is read a sufficient number of times, the probability of detecting at least one of the ambiguous symbols which was written to the original media approaches unity. Consequently, if an ambiguous symbol is not detected, it is nearly certain that the optical media is an unauthorized copy.
  • Fig. 14 illustrates an alternative embodiment of the invention in which the ambiguous symbol 10 comprises a smooth transition, referenced 1 12, between the pits and lands, in contrast to the sharp transition required by the standards.
  • the media player can digitize transition 112 to be at clock position 115, and thus will interpret the code sequence as symbol 124, which decodes to a data byte with a hexadecimal value of E4.
  • the media player can digitize transition 112 to be at clock position 117, which decodes to a data byte with a hexadecimal value of F8. Subsequent readings of the symbol will result in a random distribution of interpreted data values, either E4 or F8.
  • error correction for an ambiguous symbol may be overridden by intentionally introducing certain errors in the codeword where the ambiguous symbol is located. By so doing, the error-correcting capabilities of the player will be used up on these deliberate errors and there will be no alteration of the ambiguous symbol
  • erroneous symbols are substituted within certain ECC codewords at particular locations to create a non-correctable error pattern
  • the digital optical reader of the ECC decoder reading the digital optical media will be able to detect the non-correctable error pattern, it will not attempt to carry out any error correction of the corrupted ECC codeword containing the erroneous and erased symbols.
  • the values of the erroneous and erased symbols will remain unaltered.
  • the detected non-correctable error pattern comprises errors or erasures principally located in the redundancy bytes of the targeted ECC codewords and further comprises errors or erasures in the input data symbols contained in the targeted codewords.
  • Fig. 8 illustrates a table of unused 14-b ⁇ t EFM channel bit sequences (i.e., those sequences are not used to represent any of the possible 256 byte values in the CD system specification)
  • Each code represented by a row, referenced r1 , r2 r9, does not correspond to a valid channel bit sequence
  • the channel bit sequence 01001000000000 (row r7) is invalid since it does not correspond to any byte value or other assigned value
  • Fig 9 illustrates two examples of 14-b ⁇ t channel data sequences, referenced
  • Sequence 140 is invalid because it causes two transitions 142 which are less than three (3) clock periods apart
  • Sequence 144 is invalid because it causes adjacent transitions 146 which are more than eleven (1 1 ) clock periods apart
  • Fig 10A is a table showing the mapping of 24 sequentially input audio
  • Fig 11 is a table showing the mapping of data bytes to their corresponding C2 redundancy symbols and the related C 1 redundancy symbols on both an audio CD and a CD-ROM
  • the table of Fig 10A comprises five columns, referenced 120, 122, 124,
  • Fig 1 1 shows the mapping of data bytes to their corresponding C2 redundancy symbols and the related C1 error correcting symbols (i e , the C1 redundancy symbols used to correct errors in the C2 redundancy symbols)
  • Fig 1 1 comprises four columns, referenced 132, 134, 136 and 138
  • Column 132 lists the C2 byte and symbol number
  • column 134 lists the C2 symbol and frame numbers
  • Fig 10A illustrates the mapping of data bytes to their corresponding frame locations and certain C1 redundancy symbols on an audio CD
  • Fig 10B is similar to Fig 10A and illustrates the mapping of data bytes to their corresponding frame locations and certain C1 redundancy symbols on a CD-ROM
  • the method for overriding the error-correction in an audio CD comprises the following steps
  • CD-ROM players utilize a third level of correction, known as the
  • RSPC error correction Reed-Solomon Product Code (RSPC) error correction.
  • the RSPC error correction process is initially de-activated, (by means of software, for example) while the player is carrying out its ECC functions and only activated later.
  • the method has applications in evaluating the efficiency of digital optical media decoder mechanisms, quality control of digital optical media production, and the writing of signatures on digital optical media for copy protection purposes.
  • non-decodable codewords may be effected by the process of causing erroneous target bytes and by causing certain parity bytes to be erroneous when read by CD readers employing different CIRC block decoders. This is especially suitable for players which have marginal playback channel bit clocks and would be incapable of reading a CD having too many invalid EFM sequences.
  • the embodiment utilized may be varied according to the type of decoder and the maximum number of error/erasures it will attempt to correct. For example, three errors per targeted codeword may be created to override the error correction. These errors may use legal (but incorrect) EFM sequences. Alternatively, targeted codewords may affected with five invalid sequences. It will be further appreciated, by persons skilled in the art, that the location of the target bytes in a sector is not restricted to a particular sector.
  • suitable target sector bytes are the parity bytes of the RSPC code used in the CD-ROM. In this case, the changed target bytes will only be visible during a raw read and it will not be possible to determine the location of the errors without decoding the RSPC codewords.
  • a signature which encodes a value, such as a decryption key.
  • a signature is to assign a non-copyable symbol to each binary digit, or bit, of the information which is to be encoded in the signature.
  • the address of its corresponding symbol would be predetermined differently, in such a manner that the occurrence of a non-copyable symbol in a particular address would uniquely determine the value of a specific bit in the signature.
  • FIG. 12 is schematic block diagram illustration of a system, generally designated 150, for writing ambiguous and invalid symbols, on digital optical media mastering and recording apparatus, in accordance with an embodiment of the invention.
  • the system 150 comprises an encoder 162, laser writing control 164, and laser 166, standard components known in the art of digital optical media mastering and recording.
  • Serial data 160 is fed into encoder 162, which creates a serial data stream of channel bit sequences corresponding to data symbols and the error-correcting symbols, and performs the data interleaving as needed before sending the information in the form of channel bits to laser writing control 164.
  • laser 166 writes the channel bits onto the digital optical media or the master for creating the digital optical media.
  • the system 150 further comprises additional apparatus, generally designated 152, which comprises a multiplexer 170, a control unit 172, an encoder 162, and ambiguous/invalid symbol generator 174.
  • the ambiguous/invalid symbol generator creates a serial data stream of channel bit sequences corresponding to ambiguous and invalid symbols.
  • Multiplexer 170 is driven by timing and control unit 172, which selects its input from encoder 162 and ambiguous/invalid symbol generator 174.
  • the additional apparatus 152 is inserted between encoder 162 and laser writing control 164.
  • the direct connection between encoder 162 and laser writing control 164 is broken as shown by symbol X (168).
  • timing and control unit 172 keeps track of the current frame and symbol that is currently being written, and is programmable to intercept certain symbols selected according to the methods of the present invention.
  • timing and control unit 172 detects a symbol position that is to be made ambiguous or invalid, it switches the output of multiplexer 170 from the normal channel bit stream from encoder 162, and substitutes an ambiguous or invalid symbol created by ambiguous/invalid symbol generator 174, whose timing it also controls.
  • the apparatus 150 creates augmented and invalid symbols in predetermined locations on the digital optical media.
  • the present invention includes a marked compact disk which has invalid fourteen bit codes thereon and the various methods for utilizing such a marked compact disk.
  • Fig. 15 illustrates a compact disk, labeled 250, and one, very enlarged, fourteen bit code 252.
  • Fig. 15 illustrates two possible copies 252 and 253 of compact disk 250 with their fourteen bit codes 255 and 257.
  • the bits storing a zero are marked with a dot and the bits storing a one are marked with an X.
  • the fourteen bit code 252 has the bit sequence: 0101000001000.
  • this code has two ones, labeled 254 and 256 in Fig. 15, which have less than two zeros therebetween (in fact, there is only one zero, labeled 258, between them), fourteen bit code 252 is invalid.
  • a standard compact disk player will read the fourteen bit code 252 as one of a few possible codes. For example, it might read code 252 as its true bit sequence 0101000001000 or it might have read it as bit sequence 0100000001000 or as bit sequence 0010000001000. The compact disk player will then convert the fourteen bit code it has read to the closest fourteen bit code for which there is an associated eight bit code For code 252 the two possible close fourteen bit codes are
  • code 255 differs from code 252 in the fourth and fifth bits and code 257 differs from code 252 in the second bit only
  • a standard CD player will select one of codes 255 and 257 randomly
  • 251 and 253 are not perfect copies of marked compact disk 250 since a) they have incorrect codes for code 252 and b) since the CD player will always read the same value when reading either of codes 251 and 253 and when reading code
  • 252 will read either code 251 or 253
  • invalid code 252 provides an ambiguous output when read by a standard compact disk player and therefore, can be utilized as a marking signature on compact disk 250 Since there are 2 possible fourteen bit codes of which only 267 are valid, there are plenty of invalid codes available for use as identifiers
  • a pit might represent less than three or more than eleven bits Fig 16, to which reference is now made, illustrates one add-on system 278 to be added to a bitstream generator 280 of a standard compact disk writer, such as writer 46, for creating the non-standard surface 60 of Fig 15
  • the bit stream generator 280 receives the actual data to be stored and format data (indicating the location at which a bit is to be written) and creates therefrom a bitstream to be written onto the compact disk
  • add-on system 270 modifies the bitstream
  • the add-on system 278 includes a synchronization generator 282, an error generator 284, a summer 286 and an AND gate 288 Synchro
  • the control signal activates the error generator 284 to provide a one bit to the summer 286 Summer 286 combines the one bit with the bitstream thereby changing the bit of interest to a one
  • the summer 286 provides the resultant, modified bitstream to a laser modulator forming part of the CD writer
  • Fig 17 illustrates one method for identifying marked disks with modified data using a standard CD reader
  • the method begins by determining, in loop 290, the locations of the invalid data words on the disk This is found by indicating (step 292) to the compact disk reader to read the compact disk If the compact disk reader finds a bad word in a sector, it will consider the sector to be bad For each bad sector which the compact disk reader finds, the method performs the loop 294, finding the invalid word (step 296) and entering the invalid word into a table (step 298) The table typically lists the bad sector and the location of the invalid word within the bad sector
  • loop 290 is repeated a number N of times
  • the resultant table is sorted (step 300) according to the bad sectors
  • the sorted table is reviewed to determine if the invalid words always fall in similar locations (e g in the same locations or in their neighboring locations) If this is true for none of the words, then the compact disk is a fraud and step 303 labels it as such Otherwise, in step 304, the invalid words at the similar locations are checked to see if they have two different values If so, then the compact disk has ambiguous data The disk is then a marked disk, as noted in step 305
  • the locations and values of the invalid words at the similar locations can be compared against a signature of marked words to identify the compact disk
  • Step 306 determines whether or not the signature formed from the invalid words of interest match a desired signature If so, the compact disk being read is identified as the correct disk Otherwise, it is a disk marked by the method of the present invention but with the wrong signature
  • each software program includes a section which continually or occasionally checks a) that the marked compact disk is present and b) that the pattern of marks thereon matches the signature for the software program The latter operation is performed by the method of Fig 17 If conditions a) and b) are met, the software program continues to operate Otherwise, the software program will stop operating Furthermore, as described in U.S. Patent Application 08/653,205, the key can be utilized as a decryption key, for decrypting some or all of the software to be executed
  • FIGs. 18 and 19 are block diagram illustrations of the system for encrypting and decrypting software, respectively.
  • the software encryptor 310 comprises the unencrypted software 312, an encryption key 316 and a data encryption standard (DES) encryptor 314, such as are known in the art
  • the software manufacturer uses software encryptor 310, together with the encryption key 316 supplied by the compact disk manufacturer, in order to encrypt the unencrypted software 312.
  • the resulting encrypted software 318 is supplied to the customer.
  • the software decryptor 320 comprises DES decryptor 333, a marked compact disk 322, such as any of those described hereinabove, the encrypted software 318 and a key extractor 326.
  • the key extractor 326 which utilize the method of Fig 17, is used to generate the decryption key 330 from the pattern of marks on the marked compact disk 322.
  • the extracted decrpytion key 330 is then used to decrypt the encrypted software 318 to generate the decrypted software 332.
  • a customer wishing to install an application receives a marked compact disk 322, the encrypted software 318 and installation software 318.
  • Key extractor 316 is a component of the installation software 328.
  • the customer inserts marked compact disk 322 into a drive of his computer system (not shown).
  • the installation software 328 reads the marked compact disk 322 and extracts a decrpytion key 330 therefrom The installation software 328 then uses the extracted decrpytion key 330 to decrypt the encrypted software 318 and install the software application
  • the extracted encryption key 330 matches encryption key 316, the decrypted software 332 will match the unencrypted software 312, and the original software program is successfully reconstructed If an unmarked or incorrectly marked compact disk is used, the key generated therefrom will not match the original encryption key 316, and consequently, the decrypted software will not be the same as the original software

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Abstract

Nouveaux supports optiques numériques sur lesquels sont enregistrés certains symboles appartenant à deux classes de codes spéciaux se trouvant dans des emplacements spécifiques déterminés. L'une des classes fournit des symboles dont le décodage, après plusieurs lectures par un lecteur classique de supports optiques, indique que les symboles en question sont valables mais qu'ils ont des valeurs variables. La seconde classe est composée de codes dont le décodeur du lecteur reconnaît immédiatement l'invalidité. Les codes de la première classe de codes spéciaux peuvent être lus par un lecteur classique de supports optiques, mais ils ne peuvent pas être écrits ou copiés par les enregistreurs classiques de supports optiques, ni par les appareils de matriçage. Par conséquent, leur présence sur les supports optiques sert à indiquer l'authenticité des supports optiques et à les distinguer d'une copie non autorisée qui serait dépourvue de ces symboles spéciaux. Les symboles de la seconde classe de codes spéciaux servent à protéger la lecture des symboles de la première classe contre toute modification ou stabilisation par le système de correction d'erreurs du lecteur. Des groupes de symboles issus des deux dites classes et disposés selon une configuration particulière constituent un marquage impossible à copier permettant la vérification automatique de l'authenticité des supports optiques, et la protection des données enregistrées sur ces supports, de sorte qu'elles ne puissent être exploitées que lorsqu'elles sont présentes sur des supports authentiques.
EP97933829A 1996-08-05 1997-08-05 Authentification de supports optiques numeriques et protection contre les copies Withdrawn EP1076902A4 (fr)

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US689209 1985-01-07
US68920996A 1996-08-05 1996-08-05
US3808097P 1997-03-06 1997-03-06
US38080P 1997-03-06
PCT/IL1997/000266 WO1998008180A2 (fr) 1996-08-05 1997-08-05 Authentification de supports optiques numeriques et protection contre les copies

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WO1998008180A2 (fr) 1998-02-26

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