A data processing system, recording device, data processing method and program providing medium are provided to execute authentication processing and content storing processing between apparatuses. Program localization is employed to restrict access to program content. A plurality of key blocks store key data for authentication processing. Key block designation information is set in a recorder/reproducer, which is configured for executing authentication processing with the recording device by designating a key block. The recorder/reproducer can set a key block for each product, model or the like. In addition, data stored according to a selected key block cannot be utilized in a recorder/reproducer in which a different key block is set. Furthermore, an encryption processing controlling section of a recording device executes control in accordance with a pre-defined setting sequence. Furthermore, an illegal instrument that has not completed the authentication processing can be prevented from utilizing program content.