Abstract: An encryption/decryption device, system and method for providing secure communication over a communication channel. The encryption device includes a radio interface unit connected to a conventional radio, wherein the interface unit selectively couples a codec, signal processor and modem to the transmit and receive path during secure operation. The codec digitally encodes non-secure analog signals and places them in pulse code modulated format. The signal processor then compresses the pulse code modulated signals into voice coded and then digitally encrypted NRZ signals which are then input into the conventional radio for modulating a carrier frequency on an occupied bandwidth approved for 15 KHz to 25 KHz, or as little as 11.4 KHz, spaced channels. The modem can input the digitally encrypted signals using modified frequency modulation to place the modified digitally encrypted signals substantially within the voice passband of 300 Hz to 3200 Hz.