A survey of security issues in wireless sensor networks <s> OPEN RESEARCH ISSUES <s> This paper describes an INtrusion-tolerant routing protocol for wireless SEnsor NetworkS (INSENS). INSENS securely and efficiently constructs tree-structured routing for wireless sensor networks (WSNs). The key objective of an INSENS network is to tolerate damage caused by an intruder who has compromised deployed sensor nodes and is intent on injecting, modifying, or blocking packets. To limit or localize the damage caused by such an intruder, INSENS incorporates distributed lightweight security mechanisms, including efficient one-way hash chains and nested keyed message authentication codes that defend against wormhole attacks, as well as multipath routing. Adapting to WSN characteristics, the design of INSENS also pushes complexity away from resource-poor sensor nodes towards resource-rich base stations. An enhanced single-phase version of INSENS scales to large networks, integrates bidirectional verification to defend against rushing attacks, accommodates multipath routing to multiple base stations, enables secure joining/leaving, and incorporates a novel pairwise key setup scheme based on transitory global keys that is more resilient than LEAP. Simulation results are presented to demonstrate and assess the tolerance of INSENS to various attacks launched by an adversary. A prototype implementation of INSENS over a network of MICA2 motes is presented to evaluate the cost incurred. <s> BIB001 </s> A survey of security issues in wireless sensor networks <s> OPEN RESEARCH ISSUES <s> Sensor networks are often deployed in unattended environments, thus leaving these networks vulnerable to false data injection attacks in which an adversary injects false data into the network with the goal of deceiving the base station or depleting the resources of the relaying nodes. Standard authentication mechanisms cannot prevent this attack if the adversary has compromised one or a small number of sensor nodes. In this paper, we present an interleaved hop-by-hop authentication scheme that guarantees that the base station will detect any injected false data packets when no more than a certain number t nodes are compromised. Further, our scheme provides an upper bound B for the number of hops that a false data packet could be forwarded before it is detected and dropped, given that there are up to t colluding compromised nodes. We show that in the worst case B is O(t/sup 2/). Through performance analysis, we show that our scheme is efficient with respect to the security it provides, and it also allows a tradeoff between security and performance. <s> BIB002
Selecting the appropriate cryptography method for sensor nodes is fundamental to providing security services in WSNs. However, the decision depends on the computation and communication capability of the sensor nodes. Open research issues range from cryptography algorithms to hardware design as described below: • Recent studies on public key cryptography have demonstrated that public key operations may be practical in sensor networks. However, private key operations are still too expensive in terms of computation and energy cost to accomplish in a sensor node. The application of private key operations to sensor nodes needs to be studied further. • Symmetric key cryptography is superior to public key cryptography in terms of speed and low energy cost. However, the key distribution schemes based on symmetric key cryptography are not perfect. Efficient and flexible key distribution schemes need to be designed. • It is also likely that more powerful motes will need to be designed in order to support the increasing requirements for computation and communication in sensor nodes. Although some key management protocols have been proposed for sensor networks, the design of key management protocols is still largely open to research. Open research issues include the following: • The proposed key management protocols discussed in this section employ different strategies on the trade-off between memory, processing and communication overhead. These protocols could be improved and new key management protocols need to be designed. • All key management protocols discussed in literature so far are based on symmetric key cryptography. Recent progress in public key cryptography has shown that public key cryptography may be suitable for sensor networks. Key management schemes based on public key cryptography need to be designed. • Current proposed key management schemes assume that the base station is trustworthy. However, there may be situations (e.g., in the battlefield) where the security of a base station needs to be considered. New schemes need to be designed considering the security of base stations. The development of secure routing protocols is challenging because sensor nodes are prone to failures and the topology of a sensor network changes frequently due to node failures and possible mobility. Key open research issues include the following: • The proposed secure routing protocols for WSNs focus on static sensor networks only, ignoring mobility. Secure routing protocols for mobile sensor networks need to be investigated. • Current broadcast authentication schemes such as µTES-LA and its extensions require the sensor network to be loosely time-synchronized. This requirement is often hard to meet and new techniques that do not require  desirable to learn the performance of these protocols. The performance matrices might include security, processing overhead, communication overhead, energy consumption, and data compression rate. • New data aggregation protocols need to be developed to address higher scalability and higher reliability against aggregator and sensor node cheating. Intrusion detection in WSNs is still largely open to research. Key research issues include the following: • Due to the constraints in WSNs, intrusion detection has many aspects that are not of concern in other network types. The problem of intrusion detection needs to be well defined in WSNs. • The proposed IDS protocols in literature focus on filtering injected false information only BIB002  BIB001 . These protocols need to be improved so as to address scalability issues.