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The use of Wireless Sensors Networks (WSNs) is rapidly growing in the areas of research, application, operation, and commerce. These kind of networks are used for monitoring a desired region of an environment. So, many abilities of these networks, by considering their lower cost, have caused them to be applicable in various areas. WSNs are designed in scale of hundreds to thousands nodes, wherein this great scale is technologically the most challenging issue. One of the most basic and challenging problem is the coverage issue. Security is another important issue. Coverage is the most paramount goal of creating and implementing of WSNs, because coverage is directly related to the degree of quality, method, and durability of the WSNs for recognizing the parameters and defined aims of the regions, and the implementation cost. In this paper, the methods of improving the security of public places (by increasing the coverage of the regions based on the sensors networks) have been investigated.  The results indicate that by choosing an appropriate and optimum coverage, it is possible not only to cover the entire region by utilizing the minimum number of sensors, but also it is possible to increase the security of the monitored places of the network by lesser nodes.

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Wireless sensor networks have many applications in the real world and have been developed in various environments. But the limitations of these networks, including the limitations on the energy and processing power of the sensors, have posed many challenges to researchers. One of the major challenges is the security of these networks, and in particular the issue of authentication in the wireless sensor network. An authentication scheme in a wireless sensor network must have the following security features: anonymity, Unlink sessions, session key agreement, session key security, and perfect forward secrecy and prevent attacker’s attacks. An important feature of the authentication scheme is that by capturing the sensor, the attacker will not be able to obtain the private values of the protocol parties. Chen et al propose an authentication scheme with key agreement using wireless sensor network for an agricultural monitoring system, which claims to have security features. This articcle proves that Chen et al’s scheme is vulnerable to sensor capture attacks that Obtain session key, sensor impersonation, User anonymity violation, forward and backward secrecy violation, and sessions link. In the rest of the article, the proposed solution to improve the design of Chen et al. will be presented and the improved design will be evaluated.