A first-key signal representative of a first key is generated from first-key base information being a base of the first key. Contents information is encrypted into encryption-resultant contents information in response to the first-key signal. A second-key signal representative of a second key is generated on the basis of initial-value information of a given initial value according to a predetermined key generation algorithm. The first-key base information is encrypted into encryption-resultant first-key base information in response to the second-key signal. The encryption-resultant contents information, the encryption-resultant first-key base information, the initial-value information, and algorithm identification information for identifying the predetermined key generation algorithm are transmitted or recorded.