In one embodiment, a content data management system that handles control information on management of content data decryption includes a first device (a recorder/player) for recording/reproducing the content data, a second device (a magnetic disk drive) for storing the content data, and a host processor for controlling data transfer between the first and second devices. The host processor exercises control for the system to inquire of both devices as to a transfer function for internal data of the devices, then depending on particular inquiry results, set up, prior to the data transfer between the two devices, either a first transfer mode for transferring the control information unidirectionally from the first device to the second device, or a second transfer mode for transferring the control information bidirectionally between both devices, authenticate mutual validity between the first and second devices, share key data (symmetric key data) between the first and second devices if authentication results indicate validity, encrypt the control information with the first or second device by using the key data, and transfer the control information that has been encrypted with either device to the other device in the first or second transfer mode that has been set up.