The Snapcell’s software can be programmed and upgraded factory based, remotely or via a USB connection to PC. Whenever a subscriber wishes to place a secure call from his cellular handset, the Snapcell will first establish a data session with another Snapcell device by creating a GSM modem session and after successfully synchronized, will establish an agreement key session using Diffie-Hellman algorithm in order to generate a mutual secret AES key that will secure the channel.