Patent ID: 6975730

Claim:
A method of transmitting contents information, comprising the steps of: generating a first-key signal representative of a first key from first-key base information being a base of the first key; encrypting contents information into encryption-resultant contents information in response to the first-key signal; generating a second-key signal representative of a second key on the basis of initial-value information of a given initial value according to one selected from a plurality of predetermined key generation algorithms; encrypting at least a part of the first-key base information into encryption-resultant first-key base information in response to the second-key signal; and transmitting the encryption-resultant contents information, the encryption-resultant first-key base information, the initial-value information, and algorithm identification information for identifying the one selected from the plurality of predetermined key generation algorithms; wherein it is previously decided that the plurality of predetermined key generation algorithms are usable by a decrypting device in decryption of the encryption-resultant contents information, and the algorithm identification information is for identifying the one among the plurality of predetermined key generation algorithms which should be used by the decrypting device in response to a reference table holding the plurality of predetermined key generation algorithms.