Location-Dependent Key Management Protocol for a WSN with a Random Selected Cell Reporter Harith Fakhrey*, Said Boussakta, R. Tiwari, Yasir Al-Mathehaji and Alex Bystrov School of Electrical and Electronic Engineering, Newcastle University, Newcastle Upon Tyne, NE1 7RU, UK Email: {h.al-shwaily, said.boussakta, rajesh.tiwari, y.a.a.al-mathehaji}@ncl.ac.uk Abstract—A wireless sensor network (WSN) employed to serve smart city applications is usually located in a vast and vulnerable territory. In order to secure vital and critical information, the security requirements of data confidentiality, authenticity and availability should be guaranteed. One of the leading key man- agement schemes is based on using location information to gen- erate security credentials. However, existing location-dependent schemes have disadvantages related to cell capture caused by a threshold number of nodes (e) being compromised. This paper presents a location-dependent key management protocol with a random selected cell reporter, LKMP-RSCR, where a set of cell reporters are selected randomly by the base station (BS) to provide a third level of report endorsement. In the LKMP- RSCR, an adversary would need to compromise all cell reporters in addition to endorsement (e) nodes to capture a particular cell. The LKMP-RSCR is presented and evaluated using an extensive analysis that shows a significant enhancement achieved in comparison with LEDS and MKMP schemes in terms of data confidentiality (85%), authenticity (35%) and availability (85%). Index Terms—Wireless Sensor Network (WSN), Smart Cities, Location-Dependent Key Management System, End-to-End Se- curity. I. I NTRODUCTION Wireless sensor networks have become prominent in the past decade inspired by the commonplace scenario, consisting of small size sensors with limited resources deployed in a large area [1]. It is indispensable to secure data flow processes inside the WSN. Thus, cryptography primitives are used to guarantee security services such as authentication, confidentiality and availability [2], [3]. A key management system (KMS) is crucially required to handle both the generation and distribution of security credentials. However, several types of KMS used in traditional wireless networks [4]–[6] are infeasible to be used in WSN due to its limited resources. All solutions proposed to solve this problem are based on the assumption of the pairwise establishment of keys between each node and others in its vicinity after the completion of the deployment process. Hop-by-hop security schemes are adequate for use in a WSN that has a convergent pattern of communication between each node to other nodes/BS. *Harith Fakhrey is also a staff member with the University of Baghdad in Iraq and sponsored by the MoHE in Iraq to study his Ph.D. However, WSN used in smart cities applications do not experience such uniformity in communication patterns between the WSN elements, while the dominant communication pattern is between each particular node in the region of event and the BS. In such cases, hop-by-hop security designs might be vulnerable to communication- pattern-oriented node capture attacks [7]. Consequently, the confidentiality, availability and authenticity of data might be seriously affected by the absence of end-to-end security in links between the event nodes and the BS. In this paper, a novel location-dependent key management protocol assisted by a random selected cell reporter (LKMP-RSCR) is presented to provide enhanced data protection in WSN used to serve the smart city. The main contributions of the LKMP-RSCR are the novel participation of the cell reporter in the reports generated as an important condition to legitimate it. In addition, the novel criterion of a hybrid communication category assumed to decrease communication overhead in the network. Moreover, it guarantees end-to-end security rather than hop-by-hop security. The rest of this paper is organised as follows; section II discuss a brief overview of the relevant work. The proposed scheme is discussed in section III, and the security analysis of our system is discussed in section IV. The conclusion is shown in section V. II. RELATED WORK In order to secure data authenticity in a WSN, an event report is generated by the group of (n) nodes located within an event spot. A valid report is that signed by e (1 <e<n) nodes expressed by an endorsement collaboratively created by them. Both the intermediate cells and the BS drop any report that does not contain a valid endorsement, under the assumption of event detection by all nodes in each cell simultaneously. Based on this approach, a few schemes have been proposed in last decade. One of the robust schemes is the location- dependent end-to-end data security (LEDS) in [7]. The terrain of a WSN in this scheme is divided into a virtual grid with several cells. Inside each cell, a node key alongside a cell key are derived by each node individually based on their location and the location of cell centre respectively. All generated event report are endorsed by threshold number of nodes and bogus reports are filtered according to this endorsement. It is clear that LEDS has considerable advantages like the limited impact