Redeemable Reputation Based Secure Routing Protocol for Wireless Sensor Networks by Younghun Chae a Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science in Computer Science University of Rhode Island

Wireless Sensor Networks (WSNs) can be used for various applications, such as military, environmental, health, home, and other commercial applications. Since thousands of sensor nodes are densely deployed, and they are based on mobile ad-hoc networks, a secure routing scheme become a critical and challenging issue to WSNs. Recent advances in WSNs have led to many new protocols designed for securing against external attacks and internal attacks. The defense against external attacks can be achieved by employing strong cryptography, but it requires a huge amount of hardware resource, such as memory for storing neighboring nodes’ keys or battery power for calculating the complex encryption and decryption processes. Moreover, cryptography is not enough to defend against internal attacks when the key information is exposed. Thus, secure routing protocols against internal attacks need to be employed simultaneously. When these two secure schemes are employed by WSNs, the length of the transaction path affects to the network lifetime and the transaction time of a network because every transaction requires the calculation energy and time for cryptography. Therefore, secure routing protocols should try to shorten the transaction path. On one hand, some proposals protocols have blocked the badly evaluated nodes without a second chance, although the bad behaviors can be temporary. On the other hand, even if the protocol provides a second opportunity to a node, they were easily disturbed by On-off attacks. Since there is an opportunity that a transaction can achieve the shortest path to destination through the badly reputed node, the secure routing protocol should give more number of opportunities to the node. This paper presents three contributions. First, we propose a new concept of trust value and management scheme that can efficiently defend against On-off attacks. Second, we show the benefits of our protocol with experiment results. Last, we present flexible design of our trust management scheme with analytical results.