With each embodiment of the present invention, a content providing system comprises a content encrypting section which encrypts content by use of a session key and a header generating section which encrypts the session key by use of an encryption key in such a manner that the session key can be obtained by use of a decryption key assigned to a user system and generates header information including the encrypted session key and one or more values based on user identification information of each of the user systems that are permitted to obtain the session key. The content providing system transmits the encrypted content and the header information to each user system. Since the header information does not explicitly include user identification information of the user systems, information about whose decryption keys have been revoked is not leaked out in the block box tracing.