A sensing device for authenticating an object. The device includes a sensor for sensing coded data provided on or in a surface associated with the object. The coded data encodes an identity and, at least one part of a signature, the signature being a digital signature of at least part of the identity. The sensed coded data is then used by a processor, to determine a sensed identity and at least one sensed signature part, which are then in turn used to authenticate the object. The processor may form part of the sensing device, or be connected to the sensing device via a communications system.