## 1 Introduction  
The technology implementation of multifunctional micro-sensor benefits from the rapid development of Micro-Electro-Mechanism System (MEMS) technology, wireless communications, and System on Chip [1; 2; 3]. Emerging wireless sensor networks are distributed sensing network architectures constituted by many small, cheap micro-sensors deployed in a monitoring region. These emerging sensor networks have become more and more popular due to their ease of deployment, especially, mobile sensor networks, which include mobile nodes with sensing, communication capacity, and movement ability, are appealing for many applications, for instance, monitoring of animals living in the wild, tracking patients' heart condition, etc. At the same time, the introduction of the mobile node can also broaden the sampling capacity in the network space [4; 5; 6; 7; 8; 9], for example, mobile nodes are utilized as information collecting nodes to collect other static nodes' data in applications [10]. Today mobile wireless sensor networks have been extensively applied in all kinds of applicable fields. For example, mobile information systems with the two functions of mobile communication and mobile computing, are especially suitable for the military operational environment. The solution of the security requirements for mobile wireless sensor networks is highly desired. All kinds of different attacks could be launched by an adversary, which include capture attack, wormhole attack, sinkhole attack, eavesdropping, node clone attacks, etc. Node clone attacks have always been the key issue that affects the security of wireless sensor networks. Because the tiny sensor nodes are arbitrarily deployed and unprotected, generally speaking, these tiny sensor nodes are deployed in locations readily accessible to attackers. The adversary can capture sensor nodes which lack hardware support for tamper-resistance, and can analyze the captured node for assorted information such as ID, code, key pairs, and then use the credentials of the compromised node to deploy cloned nodes in different strategic locations. The destructiveness would be indefinitely spread throughout the network. Clones with legitimate identities would be able to paralyze the network completely by the way of inside attack, for example, the replicas could not only capture correct data, but also inject false data. They could spy on network traffic, and capture data from the sensor networks. A more serious threat is that the clone could distribute false routing information or silence some nodes to control the network structure [11]. A problem-solving method to avoid cloned nodes is to make nodes tamper-resistant, but the cost implications are prohibitive. Accordingly, detection of cloned nodes is one kind of way to solve the problem effectively. As far as the location of witness nodes is concerned, there are two kinds of frameworks: centralized detection and decentralized detection. In centralized detection, the data packets including location information are usually forwarded to the base station for detection. To assure the accuracy of detection, the base station must be trusted and powerful. According to the principle of the centralized method, the system has some fatal drawbacks. Firstly, the base station undertaking the arduous task of detecting replicas must be a trusted third party. Once the trusted third party is compromised, a signal peer invalid will appear, and the centralized detection scheme fails. Secondly, nodes surrounding the base station possess undue data communication flaws. Once an adversary damages the communications networks around the witness node, the detection would fail. There is another dimension, which is the power supply of sensor node can easily run out, so the network lifetime is dramatically cut down. Finally the high cost of expensive trusted third parties makes it hard for the centralized detection to be widely used in many wireless sensor networks, so researchers have proposed a new method called distributed detection [12].