In an apparatus not connected to a network can perform the reproduction within a valid viewing period. Also, in order to facilitate the change of the encryption algorithms of a password, a program recorded on the disk comprises the steps of acquiring a first medium identification number recorded on a recording medium, acquiring the current time, acquiring a password, calculating a second medium identification number and the expiry date of the valid viewing period from the password, comparing the first medium identification number with the second medium identification number, and comparing the current time with the expiry date of the valid viewing period. In the case where the first medium identification number coincides with the second medium identification number and the current time has not passed the expiry date of the valid viewing period, then the predetermined information is reproduced from the recording medium.