Secret Key Generation Protocol for Optical OFDM Systems in Indoor VLC Networks

Although the visible light communication (VLC) channel has superior security than radio frequency channels, its broadcast character makes VLC links vulnerable to eavesdropping. Therefore, VLC networks need to support security to protect the user's data against its eavesdroppers. Keyless security approaches have been proposed to provide security for VLC in the literature. Although these approaches support good security against eavesdroppers, they require complicated implementation. Algorithms of keys generation are essential to secure wireless links. Nevertheless, the common keys generation algorithms can be very complex and costly in many setups. They use up limited resources such as bandwidth. In this paper, we enhance the confidentiality of VLC networks by suggesting a new key extraction protocol for optical orthogonal frequency division multiplexing (OFDM) schemes in an indoor environment. We introduce to extract keys from the bipolar OFDM samples produced from optical OFDM schemes. We propose to allocate a portion of cyclic prefix samples placed in the area of low channel impact for keys extraction throughout session duration. The introduced protocol extracts keys for the medium access control (MAC) level and the physical level. It supports high physical-layer security as every OFDM signal frame is encrypted by a various key. Thus, the encryption at the MAC level can be switched off beyond any danger in security. This setup can improve the throughput of the system because it decreases the processing delay in the upper layer process. Also, the presented protocol supports zero bit mismatch rates with key extraction on the fly.