# Secure D2D Group Authentication Employing Smartphone Sensor Behavior Analysis
## 2 Related Works  
As the underlay to the upcoming 5G networks, the development of D2D communication has attracted a lot of attention from both academia and industry. Major research regarding radio resource allocation [5], mode selection [1] and interference management [2] have been widely studied, while only a few works have been done emphasizing on the security and privacy protection for D2D communication in both the academic and standardization communities. In 2014, a detailed survey emphasizing on the D2D infrastructure, the major threads and security requirements [3] is presented by [PERSON] et al. After that, [PERSON] et al. initially illustrated the D2D communication into information-theoretic secrecy problem of cellular communication, where the secrecy outage probability is utilized to depict the uncertainty of the eavesdropper [18]. Subsequently, a secure data sharing scheme SeDS is designed for D2D communication in LTE-A network, where the public-key-based digital signature is applied for mutual authentication. Note that the proposed SeDS is capable of detecting free-riding attack and achieving reception nonrepudiation by key hint transmission so as to improve system availability [19]. Similarly, due to the potential threats caused by the open access feature of wireless channel, [PERSON] et al. designed a short authentication-string-based key management scheme for secure D2D communication over WiFi direct [4]. In Reference [20], the spatiotemporal matching is formulated, which is considered to be the crucial primitive for D2D communications. Note that the Bloom filter is adopted during the estimation process as well. The combination between D2D communication and 5G network enables a new research direction. The structure intended for the LTE-D2D system and its corresponding security threats are discussed in Reference [6] by [PERSON] et al., where the frameworks for cross-layer D2D security are designed. In 2017, a robust D2D-assisted secure transmission scheme for mobile healthcare system is introduced, where certificateless generalized signcryption (CLGSC) is deployed. Meanwhile, [PERSON] et al. investigated the physical layer security for secure key generation rate (SKGR) among D2D communication. In order to prevent attack from both the eavesdropper and non-trusted relays, the related privacy protection scheme is conducted [21]. Subsequently, [PERSON] et al. designed a secure link establishing protocol for LoRaWAN D2D communication, where the D2D nodes share cryptographic keys with each other. The proposed scheme is able to guarantee fundamental security requirements with sufficient feasibility [22]. Next, in order for device recognition in D2D communication, the advantage of RF fingerprint of wireless D2D device is taken into consideration in Reference [7]. Note that the support vector machine (SVM) is deployed with the purpose of classifying all the activated devices. Recently, [PERSON] et al. presented the privacy-preserving authentication and keying schemes PPAKA-HAMC and PPAKA-IBS so as to offer reliable anonymous D2D communications [9]. According to their assumption, the D2D user group members mutually authenticate with each other using the anonymous identity. The group session key for secure D2D communications is built accordingly. For the same purpose, [PERSON] et al. presented network-absent and network-covered authenticated key exchange schemes, where the authentication process is evaluated under the analytic model, proving that the proposed schemes satisfy proper performance requirements [12]. Moreover, another reliable D2D key distribution protocol is proposed in Reference [10], where the information exchange is conducted through the RF channel and the audio channel. Furthermore, advancements in human activity recognition regarding smartphone sensors have been presented, which provide a new paradigm for daily health monitoring compared to the initial recognition mechanism with wearable sensors. In 2010, [PERSON] et al.