A device for authenticating a user is described. This device comprises transceiver circuitry configured to receive motion information from a plurality of wearable devices located on a user's body indicative of the motion of the user's body at the location of the respective wearable device at a particular time; and 5 controller circuitry configured to: compare the received motion information and the location of the respective wearable device and authenticate the user in the event of a positive comparison between the received motion information and the location of the respective wearable device with stored motion information and the location of the respective wearable device.