Patent ID: 7434266

Claim:
A reproducing apparatus for reproducing a recording medium on which main data has been divided into blocks on a unit basis of a predetermined length, address data has been allocated to each of said divided main data blocks, and both of said main data and said address data have been encrypted by predetermined key information and recorded, comprising: reproducing means for reproducing said main data and said address data from said recording medium; decrypting means for decrypting, by using predetermined key information, the encryption of the main data and the address data reproduced by said reproducing means; detecting means for detecting validity of the address data decrypted by said decrypting means, wherein said detecting means detects the validity of the address data decrypted by said decrypting means on the basis of whether the address data is continuous, and wherein verification of whether a disc key used for the decryption is a same key as the disc key used for the encryption of the data is made on the basis of the validity of encrypted address data rather than the disc key itself, wherein the validity of the address data is performed on the basis of whether the address data is continuous and whether the address data is equal to a value in a valid range, and wherein the validity of the data is performed on the basis of whether the address data at a predetermined position is the address data that was inherently recorded at the predetermined position by an optical disk; and suppressing means for inhibiting an output of the main data decrypted by said decrypting means if it is determined by said detecting means that the address data decrypted by said decrypting means is invalid.