Security enhancement for OFDM-UWOC system using three-layer chaotic encryption and chaotic DFT precoding

Security is one of the key issues in communications, but it has not attracted much attention field underwater wireless optical communication (UWOC). This Letter proposes a UWOC encryption scheme with orthogonal frequency division multiplexing (OFDM) modulation, based on three-layer chaotic and discrete Fourier transform (DFT) precoding. The processes are bit stream diffusion, in-phase/quadrature encryption, time-frequency scrambling. With multi-fold data can create keyspace 9.7×10179, effectively resisting brute force attacks chosen-plaintext attacks. A 3 Gbit/s encrypted OFDM signal successfully transmitted over 7 m water channel.