Patent ID: 8095469

Claim:
A non-transitory machine-readable recording medium, storing a content management program, causing a computer to execute: a content storing in a content storage unit step of storing encrypted content and an encryption key which is under a copy right use condition to prohibit a copy by a client machine having received the encrypted content; a decoding step of decoding encrypted content by the encryption key; a content copy step of copy-transferring the encrypted content, which encrypted content cannot be accessed without the proper encryption key, to the client machine through the network; and an encryption key transfer step of transferring the encryption key to the client machine through the network; wherein the encryption key transfer step transfers the encryption key of the content storage unit through the network, and after that, deletes a stored encryption key; the encryption key transfer step registers the client machine storing the encryption key for each content in an encryption key management table, the decoding step, when decoding the encrypted content, obtains the encryption key by a transfer request to the client machine storing the encryption key recognized from the management table and decodes the encrypted content, the encryption key transfer step, when having transferred the encryption key to another client machine, renews a transferred machine information in own encryption key management table, and at the same time, informs the transferred machine information to the client machine and allows it to renew its encryption key management table, the client machine connected through the network is a client machine owned by the same user registered in a client machine management table; and the encrypted content is any one of the music, screen image, and document under a copy right or a combined thereof.