Patent ID: 8646061

Claim:
A method of transmitting rights object information between a device and a portable storage, which is performed by the portable storage, the method comprising: receiving a request from the device; generating a current permission status format including information of a rights object designated by the request; and transmitting the current permission status format to the device, wherein the portable storage is at least one of a smart medium, memory stick, compact flash card, xD card, and multimedia card, wherein the request is one of a request for permission information of the rights object, a request for playback of a particular content, and a request for update of the rights object, wherein the current permission status format comprises a content ID field for a content ID identifying an encrypted content that can be played back using the rights object, a content encryption key (CEK) field for a CEK used to decrypt the encrypted content, a message digest field for a message digest value for integrity of transmitted data, and a permission information field for the permission information of the rights object, and wherein if the request received from the device is the request for the permission information of the rights object or the request for update of the rights object, the CEK field is set to a null value.