Medium, apparatus, and method related to encryption resultant information

Abstract

A disk-shaped recording medium includes a transparent substrate, and an optical recording layer formed on the transparent substrate. A light source emits light. An optical head is operative for applying the light to the optical recording layer from the light source via the transparent substrate, for focusing the light on the optical recording layer, and for reproducing information from the optical recording layer. A position detecting device is operative for detecting at least one of a pit depth and a physical position of information which has a first given relation with a specified address and which is recorded on the recording medium, and for generating first positional information representing at least one of the pit depth and the physical position. A previously-recorded secret code is reproduced from the recording medium. The secret code represents second positional information. The secret code is decoded into the second positional information. The second positional information represents at least one of a predetermined reference pit depth and a predetermined reference physical position. The first positional information and the second positional information are collated, and a check is made as to whether or not the first positional information and the second positional information are in a second given relation. When the first positional information and the second positional information are not in the second given relation, one of outputting of a reproduced signal of the recording medium, operation of a program stored in the recording medium, and decoding of the secret code is stopped.

1. A reproducing apparatus for reproducing signals from a recording medium in which first physical features information indicative of a physical feature unique to said recording medium was recorded as ciphered information, said apparatus comprising:
 deciphering means for deciphering said ciphered information to obtain said first physical feature information;    detecting means for detecting and obtaining second physical feature information from said first physical feature information;    checking means for checking whether or not said first and second physical feature information have a specific relationship; and    means for stopping a specific operation when said checking means indicates that said first and second physical feature information do not have said specific relationship.    
     
     
       2. The reproducing apparatus as claimed in  claim 1 , wherein said specific operation comprises outputting information reproduced from said recording medium. 
     
     
       3. The reproducing apparatus as claimed in  claim 1 , wherein said specific operation comprises an operation under control of a program reproduced from said recording medium. 
     
     
       4. The reproducing apparatus as claimed in  claim 1 , wherein a public key cipher key is used, in said deciphering means, as a key for deciphering said ciphered information. 
     
     
       5. The reproducing apparatus as claimed in  claim 4 , wherein RSA cipher is used as said public key cipher key. 
     
     
       6. A reproducing method for reproducing signals from a recording medium in which first physical feature information indicative of a physical feature unique to said recording medium was recorded as ciphered information, said method comprising the steps of:
 deciphering said ciphered information to obtain said first physical feature information;    detecting and obtaining second physical feature information from said first physical feature information;    checking whether or not said first and second physical feature information have a specific relationship; and    stopping a specific operation when said checking means indicates that said first and second physical feature information do not have said specific relationship.    
     
     
       7. The reproducing method as claimed in  claim 6 , wherein said specific operation comprises outputting information reproduced from said recording medium. 
     
     
       8. The reproducing method as claimed in  claim 6 , wherein said specific operation comprises an operation under control of a program reproduced from said recording medium. 
     
     
       9. The reproducing method as claimed in  claim 6 , further comprising a step of performing a specific display when said checking step indicates that said first and second physical feature information do not have said specific relationship. 
     
     
       10. The reproducing method as claimed in  claim 6 , wherein a public key cipher key is used, in said deciphering means, as a key for deciphering said ciphered information. 
     
     
       11. The reproducing apparatus as claimed in  claim 10 , wherein RSA cipher is used as said public key cipher key. 
     
     
       12. A reproducing method for reproducing video signals recorded in a recording layer of an optical disk in such a manner that tracking variations are formed at an address position in a circular or spiral track comprising:
   disk driving step of rotating an optical disk;        an optical head operating step for emitting a light beam and receiving light from said optical disk to read information recorded in said disk in the form of pits;        tracking controlling step of effecting tracking control so that a light spot on said recording layer of said optical disk resulted from said light beam follows a series of pits on a track of said optical disk;        a tracking amount detection step of detecting from a tracking amount sensor an amount of the tracking variation in the address position;        a disk checking step of properly judging whether the current disk is legal or illegal according to the distribution of tracking variations, comparing the amount of the tracking variation with a tolerance value, wherein said tolerance value is set so that the current disk is judged to be legal if the amount of the tracking variation is within the tolerance and to be illegal if the amount of the tracking variation is outside the tolerance;        reproducing step responsive to an output signal at said optical head operating step for reproducing a video signal; and        an output/operation stopping step of stopping outputting of video information reproduced at said reproducing step to be externally outputted or stopping said reproducing step in accordance with said disk checking step.