Patent ID: 7437770

Claim:
A data transfer system including a data transfer apparatus and a data-recording apparatus wherein: the data transfer apparatus comprises: means for storing content data in an encrypted state, a first content ID unique to the content data, and table data onto the primary recording medium of the data transfer apparatus; means for transferring content data to the data-recording apparatus as a result of a check-out operation of the content data; means for receiving a second content ID generated by the data-recording apparatus based on the transferred content data of the check-out operation, wherein the second content ID is stored as an element of the table data: means for transmitting a command requesting, from the data-recording apparatus, information including a third content ID which corresponds to the content data stored on a secondary recording medium of the data-recording apparatus, as a result of a check-in operation of the content data; means for receiving a third content ID generated by the data-recording apparatus; means for comparing the third content ID to the second content ID previously received from the data-recording apparatus, for ensuring that the content data checked-in corresponds to the content data checked-out; and means for checking-in the content data corresponding to the first content ID if the second content ID and the third content ID match; and the data-recording apparatus comprises: means for exchanging content data with the data transfer apparatus; means for recording and reproducing data onto and from the secondary recording medium; means for decrypting encrypted content data received from the data transfer apparatus; means for recording the decrypted content data onto the secondary recording medium; means for generating the second content ID and the third content ID based on data extracted from two sampling locations in the content data, wherein the locations are determined in accordance with the data length of the content data; and means for transmitting the second content ID or the third content ID to the data transfer apparatus.