A method for restricting access to media data generated by a camera, comprising: setting a non-public initial user key (K ICU) in the camera, providing a user client with the initial user key (K ICU), establishing an authenticated relation between the user client and the camera by sending an authentication message including information based on the initial user key (K ICU) from the user client to the camera, checking if an operational user key (K OCU) is already set in the camera, if the operational user key (K OCU) is not yet set, performing the acts a) - e) of a) acquiring an operational user key (K OCU), b) setting the operational user key (K OCU) in the camera, c) distributing the operational user key (K OCU) to the user client under protection by the initial user key (K ICU), d) setting the operational user key (K OCU) in the user client, and e) indicating in the camera that the operational user key (Kocu) is set, and if the operational user key (K OCU) is already set, indicating to the user client that the operational user key (K OCU) is set, thereby indicating that someone already has acquired the operational user key (K OCU) and that steps a)-e) thereby are not performed, setting, in the camera, a media data encryption/decryption key associated with the operational user key (K OCU), encrypting media data registered by the camera using the media data encryption key, and sending the encrypted media data to a service provider management server. setting a non-public initial user key (K ICU) in the camera, providing a user client with the initial user key (K ICU), establishing an authenticated relation between the user client and the camera by sending an authentication message including information based on the initial user key (K ICU) from the user client to the camera, checking if an operational user key (K OCU) is already set in the camera, if the operational user key (K OCU) is not yet set, performing the acts a) - e) of a) acquiring an operational user key (K OCU), b) setting the operational user key (K OCU) in the camera, c) distributing the operational user key (K OCU) to the user client under protection by the initial user key (K ICU), d) setting the operational user key (K OCU) in the user client, and e) indicating in the camera that the operational user key (Kocu) is set, and a) acquiring an operational user key (K OCU), b) setting the operational user key (K OCU) in the camera, c) distributing the operational user key (K OCU) to the user client under protection by the initial user key (K ICU), d) setting the operational user key (K OCU) in the user client, and e) indicating in the camera that the operational user key (Kocu) is set, and if the operational user key (K OCU) is already set, indicating to the user client that the operational user key (K OCU) is set, thereby indicating that someone already has acquired the operational user key (K OCU) and that steps a)-e) thereby are not performed, setting, in the camera, a media data encryption/decryption key associated with the operational user key (K OCU), encrypting media data registered by the camera using the media data encryption key, and sending the encrypted media data to a service provider management server.