A fin resistor and method of fabrication are disclosed. The device also comprises a cooling structure comprising at least one bundle of first nanotubes for cooling the hot spot area and at least one bundle of additional nanotubes for cooling the intermediate temperature area, and having heat conductivity lower than the bundle of first nanotubes. A first network device may encrypt a key using a password-based key derived from a password, and authenticate a second device based on the second network device’s ability to decrypt the encrypted key using a key derived from the same password.