A method of recording data from a recorder to a recording medium, where it is judged whether a terminal unit having user identification information recorded in memory therein is connected to the recorder. When the terminal unit is found connected, an encryption key is exchanged between the recorder and terminal unit, user identification information read from the memory of the terminal unit is encrypted with the exchanged encryption key, sent from the terminal unit to the recorder, and the encrypted user identification information is recorded to the recording medium.