Platform for Multi-User Channel-Based Encryption of Speech Communication with AES on 2.45 GHz

This paper outlines a hardware platform for half-duplex, real-time encrypted digital speech communication on 2.45 GHz. The platform is based on a STM32F415 MCU with a low power ADF7242 transceiver for wireless communication. The Advanced Encryption Standard (AES) Electronic Code Book encryption scheme is performed on the transmitted packets with symmetrically generated channel-based keys. Encryption keys of 128-bit are obtained, based on the unique reciprocal channel characteristics of the employed link. Key reconciliation is applied by means of a Hamming code and a cyclic redundancy check (CRC) to correct key mismatch. A multi-user system is introduced by splitting voice key distribution and speech communication into different abstraction layers. Measurements reveal a maximum communication range of 400 m without significant packet loss. A high key entropy of 0.94 bit is established with a packet rate of 167 packets/s and a key bit generation delay of four received signal strength (RSS) measurements.