Abstract: Reconfigurable security systems, devices, and methods are provided. These can include systems having a configuration device, a reconfigurable lock system, and a reconfigurable key system, where transferable tumbler code carriers, having transferable tumbler codes, may be exchanged in order to provide controlled access to the devices or structures secured by the security system. By way of metaphor, the particular teeth configuration of a manual key may be understood as reflecting a single or fixed tumbler code. In embodiments, such a tumbler code may be exchanged, compared, and stored to allow for selective configuration of keys, mating of keys and locks, and selective access to security systems by a key system configured with a proper tumbler code.