Overcoming Adversaries in Sensor Networks: A Survey of Theoretical Models and Algorithmic Approaches for Tolerating Malicious Interference <s> C. Cryptographic Authentication <s> We introduce TinySec, the first fully-implemented link layer security architecture for wireless sensor networks. In our design, we leverage recent lessons learned from design vulnerabilities in security protocols for other wireless networks such as 802.11b and GSM. Conventional security protocols tend to be conservative in their security guarantees, typically adding 16--32 bytes of overhead. With small memories, weak processors, limited energy, and 30 byte packets, sensor networks cannot afford this luxury. TinySec addresses these extreme resource constraints with careful design; we explore the tradeoffs among different cryptographic primitives and use the inherent sensor network limitations to our advantage when choosing parameters to find a sweet spot for security, packet overhead, and resource requirements. TinySec is portable to a variety of hardware and radio platforms. Our experimental results on a 36 node distributed sensor network application clearly demonstrate that software based link layer protocols are feasible and efficient, adding less than 10% energy, latency, and bandwidth overhead. <s> BIB001 </s> Overcoming Adversaries in Sensor Networks: A Survey of Theoretical Models and Algorithmic Approaches for Tolerating Malicious Interference <s> C. Cryptographic Authentication <s> Wireless Sensor Networks (WSNs) are used in many applications in military, ecological, and health-related areas. These applications often include the monitoring of sensitive information such as enemy movement on the battlefield or the location of personnel in a building. Security is therefore important in WSNs. However, WSNs suffer from many constraints, including low computation capability, small memory, limited energy resources, susceptibility to physical capture, and the use of insecure wireless communication channels. These constraints make security in WSNs a challenge. In this article we present a survey of security issues in WSNs. First we outline the constraints, security requirements, and attacks with their corresponding countermeasures in WSNs. We then present a holistic view of security issues. These issues are classified into five categories: cryptography, key management, secure routing, secure data aggregation, and intrusion detection. Along the way we highlight the advantages and disadvantages of various WSN security protocols and further compare and evaluate these protocols based on each of these five categories. We also point out the open research issues in each subarea and conclude with possible future research directions on security in WSNs. <s> BIB002
Another key dimension along which we may compare models is whether the results rely on any cryptographic assumptions. Standard cryptographic tools are often too costly for the sensor network domain. Moreover, the distribution of shared secret keys poses another host of problems. Consequently, several works have explored the pessimistic scenario where neither message nor sender authentication is possible. On the other hand, several recent results show how light-weight cryptographic authentication can be implemented in sensor networks  - BIB001 . These proposed schemes provide high security while being energy efficient. In tandem, the research community has examined how to establish efficient and secure key-distribution schemes; for more on this topic, we refer the reader to the survey by Xiao et al.  . Therefore, in addition to models that do not assume authentication, we will also see models that leverage the benefits of cryptographic authentication to achieve more efficient operations. For an in-depth examination of the role of cryptography in sensor networks, we refer the reader to the work of Walters et al.  and the survey by Wang et al. BIB002 .