Method and apparatus of enciphering and deciphering data using multiple keys

Abstract

On a recording medium, first information obtained by enciphering data with the first key and second information obtained by enciphering the first key with each of the predetermined second keys are recorded. A deciphering method is characterized by comprising the steps of inputting the first and second information, deciphering the first key using at least one of the second keys, determining by a specific method that the obtained first key is correct, and then deciphering the data using the first key to obtain the data.

1 - 22 . (canceled) 
   
   
       23 . A key control method, comprising:
 keeping a plurality of second keys;   obtaining first information composed of enciphered data by enciphering data with a first key;   obtaining second information composed of a p number of enciphered first keys, where p is an integer greater than or equal to two, obtained by enciphering the first key with a p number of second keys of the kept plurality of second keys, respectively;   recording the first and second information on a first recording medium in manufacturing of the first recording medium; and   in a case where part of the plurality of second keys has been broken, using remaining second keys except for the broken part of the plurality of second keys in manufacturing of a second recording medium other than the first recording medium.   
   
   
       24 . The key control method according to  claim 23 , wherein using the remaining second keys comprises:
 obtaining third information composed of a q number of enciphered first keys, where q is an integer smaller than p, obtained by enciphering the first key with a q number of remaining second keys except for the broken part of the plurality of second keys, respectively;   recording the first and third information on the second recording medium in manufacturing of the second recording medium.   
   
   
       25 . The key control method according to  claim 23 , further comprising:
 in a case where part of the plurality of second keys has been broken, using the remaining second keys except for the broken part of the plurality of second keys in manufacturing of a player.