Copyright protection system, recording device, and reproduction device

Abstract

A copyright protection system includes a recording device and a reproduction device. The recording device writes encrypted content, an encrypted content key for decrypting the encrypted content, and license information on a recording medium on which a unique media number has been recorded in an unrewritable state. The license information is generated using both the media number and the encrypted content key, and therefore reflects both values. The reproduction device reads the media number, the encrypted content key, and the license information from the recording medium, and judges whether the license information reflects both the media number and the encrypted content key. The reproduction device decrypts the encrypted content key, and decrypts the encrypted content using the content key only if the license information reflects both values. Thus, the copyright protection system allows only original recording media to be reproduced, and prohibits reproduction of copy recording media.

1 . A copyright protection system comprising a recording device for recording encrypted content on a recording medium and a reproduction device for decrypting the encrypted content recorded on the recording medium, the recording medium having an unrewritable area in which a media number unique to the recording medium is recorded, 
 the recording device including: 
 a generating unit operable to acquire the media number from the recording medium, and generate license information by performing a specific operation using the media number and decryption key so that the license information reflects both the media number and the decryption key, the decryption key being necessary to decrypt the encrypted content;  
 a recording unit operable to record the license information, a decryption information generated by using the decryption key, and the encrypted content on the recording medium, and  
   the reproduction device including: 
 a judging unit operable to read the media number, the decryption information, and the license information from the recording medium, and judge whether the read license information can be obtained if the specific operation is performed using the read media number and the decryption key which can be obtained from the read decryption information;  
 a decrypting unit operable to read the encrypted content from the recording medium and decrypt the encrypted content using the decryption key obtained from the decryption information;  
 a reproduction unit operable to reproduce the decrypted content; and  
 a suppressing unit operable to control the unit of the reproduction device not to reproduce the content, if the judgment by the judging unit is in the negative.  
   
     
     
         2 . The copyright protection system of  claim 1 , wherein 
 the decrypting unit includes a decryption key computing unit operable to perform a predetermined computation on the decryption information, to obtain decryption key, and    the decrypting unit decrypts the encrypted content using the decryption key.    
     
     
         3 . The copyright protection system of  claim 2 , wherein 
 the recording device further includes: 
 a recording device possessing unit operable to possess a secret key, by either acquiring the secret key from outside or storing the secret key in advance; and  
 a decryption key encrypting unit operable to encrypt the decryption key using the secret key according to a secret key cipher, to generate the decryption information,  
   the reproduction device further includes a reproduction device possessing unit operable to possess the same secret key as the recording device possessing unit, by either acquiring the secret key from outside or storing the secret key in advance, and    the decryption key computing unit decrypts the decryption information using the secret key according to the secret key cipher, to obtain the decryption key.    
     
     
         4 . The copyright protection system of  claim 3 , wherein 
 the generating unit performs the specific operation using the secret key in addition to the media number and the decryption key, and    the judging unit makes the judgment using the secret key in addition to the read media number and the decryption key.    
     
     
         5 . The copyright protection system of  claim 3 , wherein 
 secret key information has been recorded in the unrewritable area of the recording medium, the secret key information being an encrypted secret key which can be correctly decrypted when a specific device key is used,    each of the recording device possessing unit and the reproduction device possessing unit includes:    a device key storing unit operable to store a device key unique to a device to which the device key storing unit belongs, in advance;    a secret key decrypting unit operable to decrypt the secret key information recorded on the recording medium using the device key in the device key storing unit; and    a secret key storing unit operable to store, if the secret key decrypting unit has succeeded in correctly decrypting the secret key information to acquire the secret key, the acquired secret key, and each of the recording device, and    the suppressing unit is operable to stop subsequent processing if the secret key decrypting unit has failed to correctly decrypt the secret key information.    
     
     
         6 . The copyright protection system of  claim 1 , wherein 
 the judging unit includes:    a reference license information generating unit operable to perform the specific operation using the read media number and the decryption key, to generate reference license information; and    a comparing unit operable to (a) compare the reference license information with the read license information, (b) judge in the affirmative if the reference license information matches the read license information, and (c) judge in the negative if the reference license information does not match the read license information.    
     
     
         7 . The copyright protection system of  claim 1 , wherein 
 the generating unit generates a set of license information for each of a plurality of sets of encrypted content, by performing the specific operation on the media number and a set of decryption key which corresponds to the set of encrypted content,    the recording unit records the plurality of sets of encrypted content, a plurality of sets of decryption information which are in a one-to-one correspondence with the plurality of sets of encrypted content, and a plurality of sets of license information which are generated by the generating unit and are in a one-to-one correspondence with the plurality of sets of encrypted content, on the recording medium in combination, and    the judging unit and the decrypting unit respectively perform the judgment and the decryption on each combination recorded on the recording medium.    
     
     
         8 . The copyright protection system of  claim 1 , wherein 
 the generating unit generates a set of license information for a plurality of sets of encrypted content, by performing the specific operation on the media number and a plurality of sets of decryption key which are in a one-to-one correspondence with the plurality of sets of encrypted content.    
     
     
         9 . The recording device for recording encrypted content on a recording medium, the recording medium having an unrewritable area in which a media number unique to the recording medium is recorded, comprising: 
 a generating unit operable to acquire the media number from the recording medium, and generate license information by performing a specific operation using the media number and decryption key so that the license information reflects both the media number and the decryption key, the decryption key being necessary to decrypt the encrypted content; and    a recording unit operable to record the license information, a decryption information generated by using the decryption key, and the encrypted content on the recording medium.    
     
     
         10 . A reproduction device for decrypting encrypted content recorded on a recording medium, wherein the encrypted content, decryption information necessary to decrypt the encrypted content, and license information used for judging whether the encrypted content is permitted to be decrypted are recorded on the recording medium, and the recording medium has an unrewritable area in which a media number unique to the recording medium is recorded, comprising: 
 a judging unit operable to read the media number, the decryption information, and the license information from the recording medium, and judge whether the read license information can be obtained if a specific operation is performed using the read media number and the decryption key which can be obtained from the read decryption information;    a decrypting unit operable to read the encrypted content from the recording medium and decrypt the encrypted content using the decryption information;    a reproduction unit operable to reproduces the decrypted content; and    a suppressing unit operable to control the unit of the reproduction device not to reproduce the content, if the judgement by the judging unit is in the negative.    
     
     
         11 . A copyright protection method for use in a copyright protection system including a recording device for recording encrypted content on a recording medium and a reproduction device for decrypting the encrypted content recorded on the recording medium, the recording medium having an unrewritable area in which a media number unique to the recording medium is recorded, comprising: 
 acquiring, by the recording device, the media number from the recording medium; generating license information by performing a specific operation using the media number and decryption key so that the license information reflects both the media number and the decryption key, the decryption key being necessary to decrypt the encrypted content;    recording, by the recording device; the license information, a decryption information generated by using the decryption key, and the encrypted content on the recording medium;    reading, by the reproduction device, the media number, the decryption information, and the license information from the recording medium;    judging, by the reproduction device, whether the read license information can be obtained if the specific operation is performed using the read media number and the decryption key;    reading, by the reproduction device, the encrypted content from the recording medium;    decrypting, by the reproduction device, the encrypted content using the decryption information;    reproducing the decrypted content; and    suppressing the processing by the reproduction device not to reproduce the content, if the judgment in the judging is in the negative.    
     
     
         12 . A recording method for recording encrypted content on a recording medium, the recording medium having an unrewritable area in which a media number unique to the recording medium is recorded, comprising: 
 acquiring the media number from the recording medium;    generating license information by performing a specific operation using the media number and decryption key so that the license information reflects both the media number and the decryption key, the decryption key being necessary to decrypt the encrypted content; and    recording the license information, a decryption information generated by using the decryption key, and the encrypted content on the recording medium.    
     
     
         13 . A reproduction method for decrypting encrypted content recorded on a recording medium, wherein the encrypted content, decryption information necessary to decrypt the encrypted content, and license information used for judging whether the encrypted content is permitted to be decrypted are recorded on the recording medium, and the recording medium has an unrewritable area in which a media number unique to the recording medium is recorded, comprising: 
 reading the media number, the decryption information, and the license information from the recording medium;    judging whether the read license information can be obtained if a specific operation is performed using the read media number and the decryption key which can be obtained from the read decryption information; and    reading the encrypted content from the recording medium;    decrypting the encrypted content using the decryption key obtained from the decryption information;    reproducing the decrypted content; and    suppressing the processing of the reproduction method not to reproduce the content, if the judgment in the judging is in the negative.    
     
     
         14 . A recording program for use in a recording device for recording encrypted content on a recording medium, the recording medium having an unrewritable area in which a media number unique to the recording medium is recorded, the recording program having the recording device execute: 
 acquiring the media number from the recording medium;    generating license information by performing a specific operation using the media number and decryption key so that the license information reflects both the media number and the decryption key, the decryption key being necessary to decrypt the encrypted content; and    recording the license information, a decryption information generated by using the decryption key, and the encrypted content on the recording medium.    
     
     
         15 . A reproduction program for use in a reproduction device for decrypting encrypted content recorded on a recording medium, wherein the encrypted content, decryption information necessary to decrypt the encrypted content, and license information used for judging whether the encrypted content is permitted to be decrypted are recorded on the recording medium, and the recording medium has an unrewritable area in which a media number unique to the recording medium is recorded, the decryption program having the reproduction device execute: 
 reading the media number, the decryption information, and the license information from the recording medium;    judging whether the read license information can be obtained if a specific operation is performed using the read media number and the decryption key which can be obtained from the read decryption information;    reading the encrypted content from the recording medium;    decrypting the encrypted content using the decryption key obtained from the decryption information;    reproducing the decrypted content; and    suppressing the processing of the reproduction program not to reproduce the content, if the judgment by the judging is in the negative.    
     
     
         16 . A computer-readable storage medium storing a recording program for use in a recording device for recording encrypted content on a recording medium, the recording medium having an unrewritable area in which a media number unique to the recording medium is recorded, the recording program having the recording device execute: 
 acquiring the media number from the recording medium;    generating license information by performing a specific operation using the media number and decryption key so that the license information reflects both the media number and the decryption key, the decryption key being necessary to decrypt the encrypted content; and    recording the license information, a decryption information generated by using the decryption key, and the encrypted content on the recording medium.    
     
     
         17 . A computer-readable storage medium storing a reproduction program for use in a reproduction device for decrypting encrypted content recorded on a recording medium, wherein the encrypted content, decryption information necessary to decrypt the encrypted content, and license information used for judging whether the encrypted content is permitted to be decrypted are recorded on the recording medium, and the recording medium has an unrewritable area in which a media number unique to the recording medium is recorded, the decryption program having the reproduction device execute: 
 reading the media number, the decryption information, and the license information from the recording medium;    judging whether the read license information can be obtained if a specific operation is performed using the read media number and the decryption key which can be obtained from the read decryption information;    reading the encrypted content from the recording medium;    decrypting the encrypted content using the decryption key obtained from the decryption information;    reproducing the decrypted content; and    suppressing the processing of the reproduction program not to reproduce the content, if the judgment by the judging is in the negative.    
     
     
         18 . A recording medium comprising: 
 an unrewritable area in which a media number unique to the recording medium is recorded; and    a rewritable area in which (a) encrypted content, (b) decryption information necessary to decrypt the encrypted content, and (c) license information that is obtained by a specific operation using the media number and the decryption key and that reflects both the media number and the decryption key are recorded.