Randomness evaluation of key generation based on optical OFDM system in visible light communication networks

Recently, the authors proposed a physical‐layer key generation scheme for optical orthogonal frequency division multiplexing (OFDM) techniques in an indoor scenario. The key generation protocol exploits bipolar and real‐valued optical OFDM samples to create confidential keys. It determines a chunk of cyclic prefix samples positioned in the space of small channel impact to generate the confidential keys during the session duration. This key‐generation approach offers strong computational security to counter passive eavesdroppers and key creation on the fly, with zero bit‐mismatch rates. In this Letter, the authors evaluate the randomness of the confidential keys produced from the recently proposed key‐generation protocol to validate if the keys are truly random. The authors apply a statistical test suite of the National Institute of Standards and Technology to test randomness. The results demonstrate that the keys generated from the proposed key generation system pass all the tests. The results also demonstrate that the proposed key generation system provides uncorrelated keys with an approximately equal probability of bits (discrete uniform distribution) on an average, which yields a high security system against statistical attacks.