To effectively protect the copyright of music data.
Additional music data Dwav' synthesizing second compressed music data provided by compressing music data Dwav and enciphered additional data Dadd' are recorded on a new CD 21. This new CD 21 is sold through a sales shop 22 to a user. On the other hand, a decipher key KEY is sold by a second selling route through the Internet 23. The user, who acquires the decipher key KEY, deciphers the enciphered additional data Dadd', generates additional data Dadd and can utilize these data.
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