18 International Journal of Wireless Networks and Broadband Technologies, 3(1), 18-33, January-March 2014 Copyright © 2014, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. ABSTRACT Secure node localization in wireless sensor networks (WSN) has become an important research topic. Although, Global Positioning System (GPS) based node localization has got signifcant attention from researchers, GPS-free node localization trend is evolving in recent times. GPS-free node localization in mobile sensor networks can be constructed in two ways: Beacon based (BB) and Without Beacon based (WBB). The BB approach has been studied extensively under adversarial model and many algorithms based on BB approach have been proposed in literature in order to localize nodes in a secure manner. In contrast, WBB approach for node localization under adversarial model has not received substantial attention from researchers. In this paper, the authors discuss WBB approach for node localization under adversarial model. The authors discuss static and dynamic key settings for node localization using WBB approach. The authors present an improved protocol for node localization in mobile sensor networks, aiming at minimizing the impact of node capture threats. The authors consider the LEAP (Localized Encryption and Authentication Protocol) (Zhu, Setia, & Jajodia, 2003) and the LOCK (Localized Combinatorial Keying) (Eltoweissy, Moharrum, & Mukkamala, 2006) as the building blocks of their proposed scheme. The authors show that the improved protocol provides effective node localization in a secure manner with minimal node capture threats. Secure Node Localization in Mobile Sensor Networks Rachit Mittal, Dhirubhai Ambani Institute of Information and Communication Technology, Gandhinagar, Gujarat, India Manik Lal Das, Dhirubhai Ambani Institute of Information and Communication Technology, Gandhinagar, Gujarat, India Keywords: Beacon Node, Distance Bounding, Key Management, Localization, Sensor Networks INTRODUCTION Localization is a process by which sensor nodes in Wireless Sensor Networks (WSN) determine spatial relationships between themselves (Srini- vasan, & Wu, 2007; Rasmussen, Capkun, & Cagalj, 2007; Mi, Stankovic, & Stoleru, 2012). The determination of spatial relationship signi- fies that the networks are able to assign location coordinates to each other either with reference to a coordinate system localized to a particular network or with reference to a global coordi- DOI: 10.4018/ijwnbt.2014010102