At least one method, apparatus and system disclosed involves providing a restricted access protocol for accessing a memory device. A first memory portion of a memory device is selected for providing an access confirmation. At least one of setting or resetting of memory cells of the first memory portion is performed. A first voltage is provided for switching the memory cells. The first voltage is associated with a predetermined switching probability. A first input signal comprising at least one address associated with the memory cells is provided. A first responsive signal is received in response to the input signal. The first responsive signal comprises data relating to the state of the memory cells. An access key is provided for the access confirmation based upon a relationship between the first input signal and the first responsive signals for providing an access key.