(NCS). The OTAT feature permits a key to be extracted from an OTAT-capable cryptographic system using a fill device, such as the KYK-13 or KYX-15/KYX-15A and then loaded ("squirted") into another cryptographic system as needed. Alternatively, encryption systems may also be configured to automatically receive and update code keys with virtually no manual intervention, as is the case for GPS (Global Positioning System) navigation satellite signals. Present and future Now that OTAR applications have been adapted for civilian emergency service providers and other users requiring enhanced communications security, extensive parallel technology conversion and development have produced commercially viable systems that include end-to-end key generation, distribution, management, and control. Network controllers can remotely, dependably, and securely change encryption keys for an entire network at their discretion. This simplifies and streamlines operations while virtually eliminating risk of compromise. In practical terms, this means users need not bring or return their units for manual updates, nor must technicians visit each user, station, or node to service their units in the field. Further, in the unlikely event that a unit, station, or node is stolen, mimicked, or otherwise compromised, a network controller may: Remotely inhibit access of additional users, stations, or nodes to the network. Remotely and securely enable network access to additional users, stations, or nodes. Remotely "zeroize" or remove a user's, station's, or node's cryptographic key material. Remotely and securely change or update a user’s, station's, or node's cryptographic keys. Significance Because introduction of this technology obviated previous requirements for risky, expensive, wide-spread, distribution of paper code keys, it thereby extinguished vulnerability to physical theft and loss as exploited by the infamous "Johnny Walker" spy ring. Elimination of this vulnerability, although little appreciated at the time, was an innovation of inestimable impact. Placing this technology in perspective, OTAR comprised a transformation at the most basic foundations of communications security such that through the decades since introduction of OTAR, not a single new breach of US code systems has occurred. Introduction of OTAR technology into practical application precipitated NSA creation of the Electronic Key Management System (EKMS) which permanently altered the power balance in communications security and espionage. Recent declassification of the details relating to its introduction may be expected to now become the subject of more scholarly work. Vulnerabilities Vulnerabilities due to accidental, unencrypted “In the clear” transmissions have been demonstrated with systems incorporating OTAR as implemented in Project 25 Digital Mobile