International Journal of Computer Applications (0975 – 8887) Volume 19– No.6, April 2011 1 A-SMOCK: Authenticated SMOCK for Wireless Sensor Networks Ashly Thomas PG Scholar IT Department Karunya University, India N. Dhinakaran Assistant Professor IT Department Karunya University, India P. Anitha Christy Angelin Assistant Professor IT Department Karunya University, India ABSTRACT The most major requirements of wireless networks in the current network context are security, scalability and memory efficiency. Most of the earlier implementations use cryptographic key exchanges alone for imposing security but mostly proved to be less secure with the presence of many attacks like IP-spoofing and masquerading. This is because, the security is present only during communication i.e., only message integrity is ensured and not the user authenticity. Hence we are trying to include an authentication scheme along with the already existing integrity scheme to provide maximum security all through the lifetime of networks. In this paper, we consider different options for providing authentication, analyze them and find which method can be used for producing better results General Terms Wireless Sensor Networks, Security, Key Management, Authentication. Keywords ASMOCK - Authenticated SMOCK. 1. INTRODUCTION In the current world where the whole world is computerized, with numerous numbers of applications, major of the common people‟s applications are run in Wireless Sensor Networks and security service is demanded to be available “anywhere” and “anytime”. The WSN is built of nodes, from a few to several hundreds or even thousands, where each node is connected to one sensor [1]. Each such sensor network node has typically several parts: a radio transceiver with an internal antenna a microcontroller, an electronic circuit for interfacing with the sensors and an energy source, usually a battery. Designing a key management scheme in current mission-critical networks to fulfill the required attributes of secure communications, such as data integrity, authentication, confidentiality, non-repudiation, and service availability is very challenging. And, to implement security in a communication, the common thing which everyone does is employing cryptographic keys which are effective to an extent. But some attributes of wireless networks like unreliable communication, limited bandwidth, network dynamics with mobile nodes, large number of nodes sharing limited amount of resources etc makes the use of cryptographic keys a challenge. And the main security issues of WSN are small memory, less battery life and less processing capabilities [2]. A certificate based authentication was used [3], [4] but is less used because of the high overhead which also reduces the service availability. Therefore, it is very clear that a self-contained key-management scheme [5] is needed, which allows a mobile node to posses all of the necessary information, the public keys of all other nodes in the network, for authentication locally. One of the very popular concepts of self-contained key management scheme is a trusted centralized server or centralized authenticator with which the nodes can communicate freely before they have been deployed into the network and nodes contact the authenticator for ensuring secure communication between others. The most used security scheme in wireless networks is public key cryptosystem which is found very practical for resource-limited networks[6]. In this paper, we are designing a self-contained public-key- management scheme which in contrast to the traditional schemes, authentication procedure does not require certificate exchanges; instead nodes need to know the ID of the other party in communication to identify the public keys of the other. Also, this scheme uses a smaller set of cryptographic keys and a sender uses multiple keys to encrypt a message and a receiver needs multiple keys to decrypt the message. This will reduce the number of keys used and thus increase memory efficiency, but the security and confidentiality provided is by the verification the node ID alone, which will be received when a node needs to communicate with another. There can be occurrence of many attacks like, in a condition where an attacker masquerades as a valid node, sending its own ID to the node which requests for communication. When the sender node gets an ID as per its request, it is not easy to find whether ID is sent by the actual node. We considering this problem and adding an authentication with the above mentioned public key management system. Thus this paper proposes a self organized public key management system which is more secure with integrity, confidentiality and memory efficiency. 2. OVERVIEW OF SMOCK SMOCK is a self-contained public key management scheme [7] which is able to resist the Sybil attack, achieves zero communication overhead for authentication, and offers high service availability. In this scheme, small number of cryptographic keys is stored off-line at individual nodes before they are deployed in the network. To provide good scalability in terms of number of nodes and storage space, combinatorial design [8] of public-private key pairs is used, which makes sure that a set of keys with one user will not be a subset of keys held by another. According to this, a key chain will be allocated to each node in the network and accordingly uses multiple keys to encrypt and decrypt. The overall scenario of the self-contained key management scheme will be as follows. Before mobile devices are dispatched to an incident area, they are able to communicate securely with the trusted authentication server in their domain center, and get