A method using a Non-Volatile Memory circuit which operates as an interface between a key loader and an encryption device in a missile's telemetry system. The method includes a step for storing a crypto key and an associated check word and a backup crypto key and check word in the EEPROM of a microcontroller, and a step for indicating the status of a load of the crypto key in the microcontroller as well as a step for indicating the status of an erase of the crypto key from the microcontroller. The method also includes a step for turning off the missile's transmitter when a key load occurs to prevents transmission of the crypto key and its corresponding check word. The method further includes a step for erasing the crypto key and its associated check word from an EEPROM within the microcontroller upon a missile launch.