A server device (100a) includes a first generation unit (102a) generating binding information binding a user with content, a second acquisition unit (103a) acquiring a usage rule, a second generation unit (104a) generating a converted title key from a title key by using the binding information and the usage rule, and an output unit (105a) outputting content encrypted using the title key, the converted title key and the usage rule to the storage medium (600a). A playback device (700a) includes a generation unit (704a) performing the reverse of the conversion on the converted title key of the storage medium (600a) to generate a decrypted title key, by using the binding information received from the server device (100a) and the usage rule of the storage medium (600a), and a decryption unit (705a) decrypting the encrypted content of the storage medium (600a) by using the title key.