A device includes a substrate, an array of metal pads on a first surface of the substrate, a carbon polymer composite covering the array of metal pads, the composite having variations that result in random resistance values between the metal pads usable as a random code. A method of manufacturing a secure device, including forming an array of metal pads on a dielet substrate, the dielet substrate containing at least one memory in which is stored an encryption key, and an RF communication section, covering the array of metal pads with a carbon polymer composite such that variations in the carbon concentration in the polymer forms a unique pattern of resistance, attaching the dielet substrate to a host component, receiving a request from a security server for a unique code determined by the unique pattern of resistance, and using the encryption key, encrypting and providing the unique code to the security server.