Design of secure near-field communication for smartphones using sound and vibration

In this paper, a secure acoustic communication system using a loudspeaker, vibration motor and microphone is proposed. The transmitter (smartphone) transmits an encrypted message and the encryption key from the loudspeaker and the vibration motor, respectively. While the sound emitted from the loudspeaker propagates long distances, the vibration emitted from the vibration motor propagates short distances. Hence, only receivers touching to the transmitter can receive both the encrypted message and key, resulting in secure communication. We designed the communication system and evaluated its performance in experiments. From experiments, it was found that the proposed system could transmit information with a bit error rate of 0 at a bit rate of 0.98 kbps.