1 Cryptography Issues in Wireless Sensor Networks Ace Dimitrievski 1 , Biljana Stojkoska 2 , Danco Davcev 3 Faculty of Electrical Engineering – Skopje {ace 1 , biles 2 , etfdav 3 }@etf.ukim.edu.mk Biljana Stojkoska Faculty of Electrical Engineering – Skopje biles@etf.ukim.edu.mk Abstract: In the near future wireless sensor networks are expected to become increasingly popular due to their low cost and ease use. As a distributed systems, they are usually deployed in unattended and hostile environment which makes them vulnerability to “man in the middle attack” since the medium they are using could not be restricted. The only way to protect the content from being exposed to the adversary is by using cryptography. Most often the public key and the symmetric key encryption are used. However the cryptographic algorithms are processor and memory demanding. When using wireless sensor networks (WSN) we need to consider the aspects of protecting communication among the nodes. We are investigating the possible attacks and suggest our adaptive holistic approach to secure the network while minimizing the cost. Index Terms – Wireless Sensor Networks, Cryptography, Security, Attacks. 1. INTRODUCTION In the recent years, there is a huge advancement in computing technology. This has led to the production of wireless sensors that are not only capable of observing and reporting physical phenomena, but also, this new generation of tiny sensor nodes can accomplish other operations, like data processing and communication. The sensors are organized in a network and communicate and exchange information using radio modules. Wireless Sensor Networks (WSN) are widely used in industry, habitat monitoring, battlefield surveillance, enemy tracking, etc. The fundamental fashion of operation in WSN is meaningfully different from traditional networks, due to their constraints. These unique characteristics make the development of applications not trivial. WSN are more vulnerable to attacks than conventional computing devices. Because of the way the data is transmitted, WSN inherited the most common attacks of wireless networks including the man-in-the-middle attack. The imposed limitations in energy and processing power, the routing protocols, as well as the exposure of the nodes make WSN more sustainable to new threats like energy drain, black hole and hello flood attack. The majority of these attacks are possible because the adversary can falsify or damage the data exchanged among the nodes of WSN. Because of this it is necessary to identify the main cryptographic goals: confidentiality, data integrity and authentication in order to protect the integrity of the network and prevent information leakage of sensor data. These threats present great danger in cases of industrial or military espionage. In this paper we present the various attacks and we propose cryptographic solutions for some of the threats. In Section 2 we discuss the issues of concern about security of WSN. Section 3 presents the application of cryptography in WSN and gives possible solutions for the attacks In section 4 we present our adaptive holistic approach. Finally section 5 concludes the paper and gives directions for future research. 2. SECURITY THREATS IN WSN 2.1. Sniffing attacks These attacks are committed when an adversary node, placed in the proximity of sensor network, is capturing data that is transmitted by its neighbors. This is so-called passive attack because there is no interaction with the network and therefore it is hard to detect. It’s goal is to gather valuable sensor information that later can be analyzed at remote location. Sink Node Adversary Intruder’s data processing center