A system and method for device security is described, the system and method including at least one integrated circuit including a CPU, a key register storing a hardware enabling key, the key including a large number of bits, such that each bit of the large number of bits has a correct value, and if any one bit of the large number of bits is set to an incorrect value the key will not function correctly a combination circuit for performing a function, f, the function f being essential for correct functionality of the CPU, such that the combination circuit is activated by the key, the combination circuit only performing function f if each of the large number of bits of the key is set to the correct value, and there exists no set of intermediate or output bits derived from the large number of bits of the key, which determine if the combination circuit performs function f, the set intermediate or output bits including fewer bits than are included in the key. Related apparatus, methods, and systems are also described.