## 2 Related Works  
In emerging sensor networks, as long as the tiny sensors are arrayed, the position of the sensor remains unchanged. This type of wireless sensor networks is called a static WSN. A commonly used detection principle of node clone attacks in static WSNs is that the same identity with different locations for a sensor node is impossible. This kind of scheme, called claimer-reporter-witness framework is widely adopted to detect static replicated nodes. Two kinds of basic detection methods are often used. One is centralized techniques [14; 15; 16], the other is decentralized techniques [17; 18; 19; 20; 21]. [PERSON] et al. [15] presented an approach utilizing the technology of compressive sensing to distinguish replicas from normal nodes in networks. [PERSON] et al. [18] described a decentralized method applying Localized Multicast to complete the inspection task. In the study by [PERSON] et al. [21] for clone detection, two kinds of frameworks called Random Walk and Improved Random Walk based on Table were presented. Those schemes are not suitable for mobile scenarios due to the continuous movement. When the sensor nodes are mobile, the mobile sensor nodes are not fixed at any specific location. Moreover, it is even harder to forward location claim packets to some witness nodes in a mobile WSN. In the study by [PERSON] et al. [22] a mechanism based on a three-tier hierarchical network structure was used. The principle of the scheme is based on the use of a Bloom filter. The process of detection can be split into three steps: first of all, cryptographic keying materials and some relative parameters are pre-distributed; and secondly, the cluster-head is determined by a relative algorithm; thirdly, the Bloom filter is utilized for the cluster-heads to exchange the ID information, and a node whose ID belongs to more than two clusters is detected as a cloned node. The storage cost of this protocol is significantly reduced. For the additional overhead of Bloom filter and clustering, the communication cost is relatively high. Based on the theory of similarity, the scheme presented in [23] was proposed by utilizing the token-based authentication technology. In the scheme, the broadcast of a timestamp indicates the start of the detection process. Once the detection process starts, a mobile sensor node randomly selects a protected value \(S_{i}\in\left\{0,1\right\}^{l}\). When a mobile sensor node first encounters another node in the detection period, the two nodes will swap a token with each other, and then save it in their memories. When they meet again in the same detection period, each will request the token exchanged in advance. If the right token is provided, the provider is a genuine node, otherwise the provider is a cloned node. As long as the access between replicas and comprised node is set up by the smart attacker, the token is exposed to replicas, and the scheme fails. In order to prevent conspiracy attack which is launched by communicating with each other, [PERSON] et al. used a statistics method to detect mobile clones. This principle asserts that a moving node which encounters another node too regularly has probably been captured. Specific counters and lists for recording acquainted nodes are utilized to calculate the total amount of meeting times. The base station is used for centralized analysis. In the study by [PERSON] et al. [24] the sequential probability ratio test (SPRT) is applied to detect cloned nodes. In the scheme, those mobile sensor nodes whose speed exceeds a predefined speed threshold are detected as replicas. A deadly vulnerability of the scheme introduces an invalid signal peer which is the inherent drawback of centralized techniques. [PERSON] et al. [25] proposed a distributed scheme based on the optimized SPRT. In the scheme, nodes' speed is optimized to implement a sequential probability ratio test. At the same time, the message transmission paths are explored to position the intersection. The advantage of the scheme is that higher the node speed, the easier the detection is.