Secure communication protocol for a low-bandwidth audio channel

Data transmission over an inaudible audio channel describes a low-bandwidth alternative to exchange data between devices without any additional infrastructure. However, the established communication channel can be eavesdropped and manipulated by an attacker. To prevent this, we introduce a tailored protocol with smallest possible overhead to secure the communication. The proposed protocol produces an overhead of 256 bits for the handshake message for setting up the first conversation with each partner. Further, the protocol produces dmsg len/64e ∗ 3 + 67 bits overhead for each message. The overhead of 67 bits at the beginning of each message corresponds to one second transmission time with the used FSK modulation in the frequency range of 16kHz-20kHz. The additional overhead of 3-bit per 64-bit sequence poses a relation of 95% message to 5% overhead. For the implementation of the protocol, algorithms implemented in the Crypto++ library such as SHA-256, CCM and PBKDF2 have been used.