Sending Location-Based KeysUsing Visible Light Communication

In this thesis we present a Security Application based on Visible Light Communication(VLC). As VLC continues to develop, the need to protect valuable informationtransmitted using this type of communication is also growing. We aim to protect thisvaluable information by proposing a security application in which the data is encryptedin a multiple-light system and only recoverable in specific locations of a movingpattern within specific time. We use the Shamir Secret Sharing algorithm as basis forthe encryption combined with additional algorithms to provide a more securetransmission. The application is formed by the Physical Layer which is in charge ofproviding the optimal configuration for transmission and the Application Layer inwhich we implement the encryption and decryption algorithms for the application.The Physical Layer is formed by a group of LED bulbs controlled by an FPGA usingPWM to represent the information. We propose a scheduling algorithm in which thelights are scheduled in a bit-by-bit manner. The reception part is formed by theOPT101 optical receiver connected to the ultra-low power TS881 comparator. Asecond FPGA is in charge of demodulating the signals from the comparator bymeasuring the period of each signal to detect the corresponding bit. To evaluate theSecurity Application and to find best configurations for the Physical Layer we performa series of experiments in which we modify the responsivity of the receiver underdifferent scenarios including variations of transmission angles, data rates, and heights.The results show that adjusting the sensitivity of the receiver plays a major role in theapplication as we shows different types of configurations to adjust the areas in whichthe information can be received