# Wireless-Channel Key Distribution Based on Laser Synchronization
## 1 Introduction  
With the increase in wireless communication rates, high-speed key distribution has become more important [1]. Existing key distribution is divided into two types: computational security-based and information-theoretic security-based key distribution. The former presupposes that the eavesdropper's computational power is constrained, thus an inherent risk of being decoded by using high-performance computers. The latter has attracted increasing attention because of its ability to resist unlimited computational power. It has been proved that two users with access to common random sources can generate a shared secret key by exchanging messages over a public channel [2, 3]. Many key distribution schemes based on common random sources have been proposed and investigated [4, 5, 6, 7, 8, 9, 10].  
Information-theoretic security key distribution has been successfully demonstrated in the wireless domain [11, 12, 13], where the channel reciprocity properties of the wireless fading channel provide the common random sources for key establishment. However, limited by the bandwidth of channel randomness, the scheme has limited key rates (bit/s-kbit/s). Although various approaches have been investigated to improve the key rate [14, 15, 16], the improvement effect is quite limited. Additionally, the key generated in a static or free space environment lacks randomness, rendering it susceptible to prediction.  
It has been demonstrated that optical chaos in semiconductor lasers is a promising physical entropy source for generating high-speed random bits at Gbit/s or even Tbit/s [17, 18]. The synchronization of optical chaos can be used as a source of common randomness and has been intensively investigated for applications in high-speed securekey distribution [19; 20; 21; 22; 23; 24]. [PERSON] et al. firstly experimentally demonstrated a 182-kbit/s key distribution using the chaos synchronization of two optical-feedback lasers driven by a common random light [20]. The security of the scheme is based on information theory and the practical difficulties of completely observing the fast and complex optical process [8; 25]. The key rate of the scheme is limited by the chaos synchronization recovery time in the magnitude of tens of nanoseconds. Recently, [PERSON] et al. experimentally demonstrated a 0.75-Gbit/s key distribution by using the open-loop configuration of commonly driven lasers [26]. Nevertheless, the utilization of these schemes in wireless secure communication is restricted due to the presence of optical fiber links among users.  
In this paper, we propose and demonstrate a high-speed wireless key distribution scheme based on laser synchronization induced by a common wireless random signal. It enhances the key distribution scheme based on common-signal-induced synchronization to accommodate wireless environments. We successfully achieve synchronization of commonly driven lasers and demonstrate a secure key generation rate of up to 150 Mbit/s while maintaining a bit error rate (BER) below the threshold of 3.8 \(\times\) 10\({}^{-3}\). In addition, the distribution distance of the proposed scheme is studied by numerical simulation.