Abstract:
A storage medium carrying data content has an electronically readable modification-resistant identifier for distinguishing that medium from other storage media. The medium stores a digital signature associated with a data content portion carried by the storage medium. The identifier read from the storage medium generates the digital signature. The identifier and digital signature enable verification of storage of the data content on an authorized storage medium in an authorized manner.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates primarily, but not exclusively, to a method of, and data storage medium adapted for, providing authentication of a data copy. It also relates, but not exclusively, to an electronic control device, for example a PC, adapted to sample a storage medium in order to authenticate the data thereupon and/or software to adapt the electronic control device to sample the storage medium.  
           [0002]    Currently it is very simple to obtain a perfect copy of data recorded on digital media due to the proliferation of technologies such as, for example, CD rewriters. This has led to the massive growth of counterfeiting of computer software, DVD&#39;s and music CD&#39;s. Indeed in certain areas of the world there is virtually no genuine software, it is almost exclusively counterfeit.  
           [0003]    Manufacturers of software and entertainment products currently have no convenient way of authenticating the data stored on a medium (e.g. a CD) in such a way that the authentication cannot be copied along with the data. This restricts the tracking of and quality control of products.  
           [0004]    The ability of computers to copy data to floppy disks, the growth of MP3 players/recorders and the use of CD-rewriters to copy CD&#39;s, with no means of tracing the source data medium from which the data was copied and the machine used to copy the data, has resulted in the proliferation of untraceable copies of data.  
           [0005]    U.S. Pat. No. 5,706,047 discloses an optical storage disc having a bar code in a mirror region of the disc. The code does not uniquely identify the disc.  
           [0006]    U.S. Pat. No. 5,805,551 discloses a system for preventing illegal duplication from a CD or CD-ROM . On an optical mark section, there is recorded an ID number which is different at every disk. However, there is still a possibility of illegal printing. In order to improve prevention, a magnetic section is provided to record a magnetic ID number in the factory. A cipher to be recorded on the magnetic recording track is based on a mixture signal of the ID number, created by a unique ID number generator, and a disk physical arrangement (e.g. address, angular arrangement, tracking, pit depth, error rate) table, thus being different for every disk. First physical feature information and the different ID number are enciphered together. Accordingly, even if a disk whose password is known is obtained to replace the first cipher of this disk with the first cipher of another disk, operation is stopped because the physical information i.e. the original record is not the same. U.S. Pat. No. 5,805,551 does not disclose incorporating in the disk an electronically readable modification-resistant identifier for distinguishing the disk from other disks, which can be read from the disk in use.  
           [0007]    WO 98/33176 A2 discloses a system for copy protection of recorded information. An information carrier comprises a medium mark representing a first bit pattern which cannot be copied on standard recording devices. The recorded information comprises a watermark representing a second bit pattern which has a predefined relationship to the first bit pattern. The medium mark indicates the status of the medium e.g. a code indicating a professional disk manufactured by pressing and is unique to a publisher or a title. Also, the recorded data is altered by the watermarking process.  
         SUMMARY OF THE INVENTION  
         [0008]    According to a first aspect of the present invention there is provided a storage medium for carrying data content, comprising an electronically readable modification-resistant identifier for distinguishing said medium from other storage media, and having stored thereon a digital signature associated with a data content portion carried by the storage medium, the digital signature having been generated using said identifier, read from said storage medium, whereby the identifier and the digital signature can be used for verifying that the data content is stored on an authorised storage medium in an authorised manner.  
           [0009]    The digital signature may be certified. The digital signature stored on the medium may be time-stamped. The timestamp may be provided by a trusted third party.  
           [0010]    The identifier (i.d.) may be a media i.d. The identifier may be readable by a storage device, or a PC or a processor. The storage device, PC or processors may require modification from their ‘as sold’ state to be able to read the identifier. Such a modification may take the form of a plug-in card, firmware or software. The modification may be contained/concealed within the operating systems of the storage device, PC or processor. This limits the opportunities for pirates to access and decompile the modifications in order to circumvent them.  
           [0011]    The identifier may be non-copyable, at least by consumer read/write devices. The identifier may be a serial number. The identifier may be written to a non-copyable section of the medium. The non-copyable section of the medium may be made of a different material to the remainder of the medium. The identifier may be integrally formed with the medium. The identifier may be written to the medium at the time of manufacture of the medium. The identifier may be stamped into a subsequently non-modifiable section of the medium. The non-modifiable section of the medium may be aluminium.  
           [0012]    The storage device, PC or processor may not allow access to data stored on the medium if the identifier is not present or has been altered, on the medium. This allows only original, first generation, copies of software to be accessed.  
           [0013]    There may be a second identifier associated with a storage device. The second identifier may used to generate the digital signature written to the medium, or may be written direct to the medium. The storage device may, in use, write data to the medium. The second identifier may be encrypted. The second identifier may be symmetrically or asymmetrically encrypted.  
           [0014]    The second identifier may be a unique i.d, for example a serial number, of the storage device which, in use, wrote data to the medium. The second identifier may be written to a section of the medium which is modifiable only once, i.e. it is a ‘write once-read many’ section of the medium. The ‘write once-read many’ section of the medium may be made of a different material to the majority of the medium.  
           [0015]    The second identifier may form part of a signature which identifies the storage device which wrote the data. The signature may also include a first identifier which identifies the medium from which the data originated The signature may be appended to the data, in use. There may be a timestamp associated with the second identifier. The timestamp may be issued by a trusted third party. This allows manufacturers to track and find when and where a copy of a medium was made and from which original medium the copy was taken.  
           [0016]    The second identifier may be readable by a storage device, or a PC or a processor. The storage device, PC or processors may require modification from their ‘as sold’ state to be able to read the second identifier. Such a modification may take the form of a plug in card, firmware or software. The modification may be contained/concealed within the code of an operating systems of the storage device, PC or processor.  
           [0017]    The storage device, PC or processor may read the second identifier prior to allowing access to data stored on the medium, in use. The storage device, PC or processor may not allow access to data stored on the medium if the second identifier is not present or has been altered, on the medium, or it may allow only restricted access to the data.  
           [0018]    The storage medium may be any one of the following, non-exhaustive list; CD, CD-ROM, DVD), tape, magneto-optical disk, or magnetic disk RAM or any form of ROM.  
           [0019]    According to a second aspect of the present invention there is provided a method for verifying that data content is stored on an authorised storage medium in an authorised manner, comprising providing a storage medium bearing an electronically readable modification-resistant identifier for distinguishing said medium from other storage media, generating a digital signature associated with a data content portion by reading the identifier from the storage medium and encrypting a digest of a combination of the identifier and the data content portion, and storing the resulting digital signature and the data content portion on the storage medium.  
           [0020]    According to a third aspect of the present invention there is provided a method of authenticating data stored on a medium comprising the steps of:  
           [0021]    i) searching a data storage medium for an identifier data element; and  
           [0022]    ii) executing an action in relation to the data stored on the medium if the data element is not found or does not correspond to a media i.d. assigned to the medium.  
           [0023]    The action may be denying access to the data stored on the medium. The action may be restricting access to certain portions of the data, for example, a virus scanning routine. The action may be creating a message for display to a user of the media. The action may be informing a third party of an attempt to load illicit data. The action may be to allow further copying of the data.  
           [0024]    According to a fourth aspect of the present invention there is provided a method of data authentication comprising the second and third aspects of the present invention.  
           [0025]    According to a fifth aspect of the present invention there is provided a data writer having a write head, the write head being adapted to write data and either, or both, of media identifiers or/and device identifiers to a storage medium according to the first aspect of the present invention.  
           [0026]    According to a sixth aspect of the present invention there is provided a data reader having a read head, the read head being adapted to read data and either, or both, of media identifiers or/and device identifiers from a storage medium according to the first aspect of the present invention.  
           [0027]    According to a seventh aspect of the present invention there is provided a data storage device according to the fifth and sixth aspects of the present invention.  
           [0028]    According to an eighth aspect of the present invention there is provided a method for detecting the use of illicitly copied data storage media comprising the steps of:  
           [0029]    i) assigning a unique identifier to a medium;  
           [0030]    ii) recording the identifier upon a non-copyable portion of the medium;  
           [0031]    iii) appending a data segment corresponding to the identifier to data stored upon the medium;  
           [0032]    iv) inserting the medium into a reader and processor;  
           [0033]    v) searching the medium for the data segment and unique identifier; and  
           [0034]    vi a) notifying a third party if either or both of the data segment or the unique identifier are not found on the medium; or  
           [0035]    vi b) notifying a third party if upon comparison, the data segment does not correspond to the identifier.  
           [0036]    The method may include the step of restricting access to the data stored on the medium if either of steps vi a) or vi b) are enacted, for example by preventing virus checking. The method may further include preventing access to the data stored on the medium.  
           [0037]    The method may further include allowing copying of the data if either of steps vi a) or vi b) are enacted.  
           [0038]    The reader and processor may be networked. The third party may be a network manager. The third party may be an author of the data.  
           [0039]    Steps vi a) and vi b) may involve e-mailing the notification to the third party. The e-mail may include an identifier of the reader and/or processor, for example an IP number/address.  
           [0040]    This has the advantage of allowing network managers to know when, and possibly on which machines, illicit copies of data are being used on the networks for which they have responsibility. It may also allow authors to know if their data is being illicitly used.  
           [0041]    According to a ninth aspect of the present invention there is provided a method of logging the number of users of a piece of software comprising:  
           [0042]    i) providing a data storage medium according to the first aspect of the present invention;  
           [0043]    ii) mounting the storage medium upon a reader;  
           [0044]    iii) recording an indication that the data has been accessed; and  
           [0045]    iv) accusing data stored upon the storage medium.  
           [0046]    The method may further include incrementing a counter each time the data has been accessed. The method may include networking the reader. The method may include providing the reader as a network server. The method may further include charging a user accessing the data.  
           [0047]    his allows the use of data and/or software and/or music to be monitored and possibly charged for. In a factory environment it is possible for employees to use machinery unauthorised during scheduled downtime to produce counterfeit goods. This method allows the unauthorised use of software to be detected. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0048]    The invention will be described by way of example, with reference to the accompanying drawings in which:  
         [0049]    [0049]FIG. 1 is a schematic representation of a storage medium according to one aspect of the present invention;  
         [0050]    [0050]FIG. 2 is a schematic representation of a data block to be stored on the medium of FIG. 1;  
         [0051]    [0051]FIG. 3 is a schematic representation of a storage system incorporating the present invention;  
         [0052]    [0052]FIG. 4 is a flow chart showing a method of recording data according to the present invention;  
         [0053]    [0053]FIG. 5 is a flow chart showing a method of reading data according to the present invention; and  
         [0054]    [0054]FIG. 6 is a schematic representation of a copying arrangement of a medium according to the present invention; and  
         [0055]    [0055]FIG. 7 is a schematic representation of a counter arrangement according to one aspect of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0056]    A data storage medium  10 , has a major portion  12 , a minor portion  14  and a write once-read many portion  15 . The major portion  12  is typically read-write; thereby allowing reuse of the data storage medium  10 .  
         [0057]    The minor portion  14  is typically read-only thereby preventing the alteration of any data which is recorded thereupon. A media identifier (i.d.)  17  distinguishes the medium  10 , preferably uniquely, from other storage media, and is encoded and stored as an identification block  16  within the minor portion  14 . The identifier  17  is electronically readable and modification-resistant, preferably substantially non-modifiable, by commonly available consumer devices adapted for use with such media.  
         [0058]    A data block  18  intended to be written to the medium  10  comprises body data  20 , optionally a data segment  22  which corresponds to the unique media i.d.  17  and optionally a digest  24 . The digest  24  is a digest of the body data  20  and the data segment  22  and may be encrypted to form a signature  25 .  
         [0059]    Digital signatures reduce the opportunities for data tampering and falsification. In the embodiment, the digital signature  25  is generated by passing the data  20  and the identifier data  22  through a hashing algorithm to obtain the digest  24  of the message. The digest  24  is then encrypted using an asymmetric encryption private key to provide a signature  25 . The signature  25  is appended to the data  20  or otherwise stored on the medium  10  for transmission with the data  20 .  
         [0060]    A third party who has the public key which is complementary to the private key used in the encryption process can decrypt the signature  25  to obtain the digest. The third party can also rehash a combination of the received data  20  and the identifier  17  read from the medium  10  and calculate the digest of this. The digest from the decrypted signature  25  and the digest from the rehash are compared, if they do not match then the data has been tampered with.  
         [0061]    The data block  18  optionally includes a certificate  26  issued to the author of the data  20  and an optional timestamp  28 . The certificate  26  can include the public key necessary to decrypt the signature  25 . It will be understood that the certificate could conveniently be obtained from other channels when required, and thus need not be stored on the disk.  
         [0062]    Certificates are electronic documents which attest to the identity of the person from whom the document came. They are issued by trusted identity certification authorities and have an expiry date to reduce the time available for them to be hacked or cracked.  
         [0063]    The timestamp  28  serves to verify that the data block  18  was signed prior to the expiry of the certificate  26  and can be provided by a trusted third party.  
         [0064]    Writing Data to the Data Carrier  
         [0065]    The body data  20  is received from a data source by an interface  29  of a storage device  30 , (step  50 ). The unique media i.d.  17  is read from the medium (step  51 ) and added to or associated with the body data  18  (step  52 ) as an i.d. data segment  22 , typically either a header or a footer. This “body data and media ID” information is temporarily held in the device  30 .  
         [0066]    The digest  24  of the combined data  20  and i.d. data segment  22  is calculated (step  53 ) by the device  30 , for example by using a hash function. The digest  24  is encrypted (step  54 ) using a private key owned by the author of the data to form the signature  25  (step  56 ). The digest  24  and/or i.d. data segment  22  are optionally appended to the body data  20 . In the preferred embodiment, the digest  24  and i.d. data segment  22  are not included in the data block  18 .  
         [0067]    In some embodiments a certificate containing a public key corresponding to the private key is appended (step  58 ) to the data block  18 . This identifies the author of the data and has an expiry date. The temporal limit on the validity of a certificate  26  resists the opportunities for the cracking/hacking of the private key associated with the certificate. A trusted third party may timestamp the data (step  60 ) in order to verify that the data was recorded prior to the expiry of the certificate  26 .  
         [0068]    Reading Data from the Data Carrier  
         [0069]    Upon receiving a request to access the body data  20  (step  61 ) a processor  31  associated with a storage device  30  accesses the medium  10  (step  62 ) and decrypts (step  64 ) the signature  25  to obtain a digest. This digest is compared to a digest calculated using the public key (step  66 ) from a combination including the body data  20  and the unique i.d.  17  read from the medium  10 .  
         [0070]    If the decrypted signature and the rehash of the body data and unique i.d. do not match, or the unique i.d. is not found, the processor  31  can refuse to access (step  72 ) the data.  
         [0071]    Either or both of the processor  31  or storage device  30  may require adaptation in order to allow it to access the media i.d.  17  stored in the minor portion  14  of the medium  10  and carry out the matching process described above. This can be achieved in a number of ways for example, software alterations to the operating system, firmware or hardware additions to the systems of either or both of the processor  31  or storage device  30 .  
         [0072]    It is envisaged that each data storage device  30  could have its own unique i.d. which is written to the write once-read many portion  15  of the medium  10 , for example, at the same time as the writing of the data block  18  to the medium  10 . The storage device  30  i.d. can be incorporated into the signature  25 . Thus, it is possible to track the reproduction of the data with reference to the storage device  30  upon which the copy was made.  
         [0073]    In use, a first CD  76  being a unique media i.d.  17  is inserted in a CD rewriter  78  a copy of data stored on the first CD  76  is made to a second CD  80 . The copy of the data includes the digital signature  25  generated using the unique media i.d.  17 . However, as the hard-written unique media i.d.  17  is recorded upon a non-copyable portion  14  of the first CD  76  it is not possible for a commonly available consumer rewriter device to transfer this to the second CD  80 .  
         [0074]    When the second CD  80  is inserted in a commonly available consumer reader  82 , for example on a PC, DVD player, music system or network server, which is in accordance with an aspect of the present invention, the reader  82  may be able to decrypt the data segment  22  containing the copy of the unique media i.d. 17 , if optionally included, but will not be able to locate the hard-written copy of unique media i.d.  17  on the second CD  80 .  
         [0075]    Upon failing to read the hard-written media i.d.  17  the reader  82  can deny access to the data contained upon the second CD  80 . Alternatively the reader  82  may restrict access to certain portions of the data, for example a virus scanning routine as if a copy has been made the author of the data makes no guarantees and accepts no liability for any viruses present upon the media  10 . As a second alternative the reader  82 , in conjunction with a processor  84  may produce a message, either audio or visual, which informs a potential user of the illicit copy that for example, they are using an illegal copy and should desist. As a third alternative, if the reader  82  and a processor  84  are connected to a network  86 , for example the Internet, it is possible to send a message over the network  86  informing either, for example, a network manager  88  or the author  90  of the software that an illicit counterfeit copy is attempted to be loaded on the network  86 . This may reduce office liability for counterfeit software use, as it would allow the network manager to act swiftly to eradicate such abuses.  
         [0076]    It will be appreciated that references to date in the preceding paragraphs relate to any form of data e.g. text, video, audio (for example sound, music, recordings), computer programs, databases or the machine readable codes.  
         [0077]    It will further be appreciated that although reference has been made to first and second CD&#39;s either of the first and second media could be any one of tape, magnetic-optical disks, DVD, magnetic disk, or ROM.  
         [0078]    The reader  82  can act as a network server and data on a medium  10  mounted thereupon can be accessed via the network  86  by a plurality of devices  92   a ,  92   b,  shown in FIG. 7, as PC&#39;s. The devices could be any one of a PC, storage device, DVD, music player or server. Each time the medium  10  is accessed an identifier of the devices, for example  92   a , accessing the medium  10  is recorded and a counter  94  is incremented. The counter  94  can be internal of the reader  82  or can be a separate external device such as a PC or server. A counter can be arranged for each device  92   a ,  92   b  or a single counter can count the total number of times the medium is accessed.  
         [0079]    This arrangement allows users accessing the data on the medium  10  to be charged for the number of times they access the data. Each user may have an identifier such as a PIN which increments their individual counter whichever device  92   a ,  92   b  they access the data from.