A system and method operate on a first electronic device and a second electronic device. The first device has a control system and a cryptographic communications module. The second device has a key generator, a user interface, and a cryptographic communications module. The second device generates a single-mission cryptographic key that is securely programmed into the first device, and the first device is deployed to a remote location. The user interface receives a command for controlling the first device. The second device encrypts the command according to the cryptographic key, and transmits the encrypted command to the first device. The first device authenticates the command, decrypts it, and passes the decrypted command to the control system. The first device may be actively guided ordnance, and the second device may be a control element for controlling the actively guided ordnance. The key may be automatically obfuscated upon mission completion or termination.