A novel user authentication and key agreement scheme for heterogeneous ad hoc wireless sensor networks, based on the Internet of Things notion

Abstract

The idea of the Internet of Things (IOT) notion is that everything within the global network is accessible and interconnected. As such Wireless Sensor Networks (WSN) play a vital role in such an environment, since they cover a wide application field. Such interconnection can be seen from the aspect of a remote user who can access a single desired sensor node from the WSN without the necessity of firstly connecting with a gateway node (GWN). This paper focuses on such an environment and proposes a novel user authentication and key agreement scheme for heterogeneous ad hoc wireless sensor networks. The proposed scheme enables a remote user to securely negotiate a session key with a general sensor node, using a lightweight key agreement protocol. The proposed scheme ensures mutual authentication between the user, sensor node, and the gateway node (GWN), although the GWN is never contacted by the user. The proposed scheme has been adapted to the resource-constrained architecture of the WSN, thus it uses only simple hash and XOR computations. Our proposed scheme tackles these risks and the challenges posed by the IOT, by ensuring high security and performance features.

Introduction

We are evermore surrounded by ubiquitous, intelligent interconnected objects (i.e. smart objects) which engage us with new applicative perspectives on our everyday lives, like RFID, smartphones, semantic web, wireless sensors, etc. This can be seen as the Internet of Things (IOT) notion, which was announced a decade ago [1]. The idea was that in the future everything (i.e. including live objects) would be accessible, sensed, and interconnected inside the global, dynamic, living structure of the Internet. Wireless sensor networks (WSN) play an important role regarding this notion, since they cover a wide application field by collecting various environmental information.

In the early years WSNs started as simple and ambivalent research projects mainly motivated and funded by the military, e.g. DARPA (Defense Advanced Research Projects Agency) [2]. These early military-funded WSN research projects, according to their type of applications, presented a definition of the WSN as a large-scale, wireless, ad hoc, multi-hop, un-partitioned network of homogeneous, tiny, mostly immobile sensor nodes which are randomly deployed within a particular area of interest [2]. Such a definition does not apply to all of today’s WSN applications, since WSN applications can also be heterogeneous, single-hop, infrastructure-based (i.e. non ad hoc), have mobile sensor nodes, etc. At that time the WSN research papers focused only on the theoretical and broad applicative uses of WSNs (e.g. military, environment, healthcare), but the research and applicative use of WSN has significantly increased over the last few years. Today we talk about the use of WSN for traffic monitoring [3], pipeline monitoring [4], landslide detection [5], methane leak detection [6], border patrol [7], precision agriculture [8], rehabilitation applications [9], laboratory tutoring [10], asset tracking [11], real-time soccer playing monitoring [12] and many more [13], [14], [15], [16]. A list of real-life applicative WSN projects was summed up by Romer and Mattern [2].

In the beginning it was thought that WSN would only be homogeneous, consisting only of equal sensor nodes. Today we also talk of heterogeneous WSNs since sensor networks can be built with different types of nodes, some more computationally-powerful than others (e.g. gate-way nodes). In view of the IOT notion, the heterogeneity of a WSN is not the only thing rapidly adapting, hence the infrastructure has moved from mainly infrastructure-based networks, where nodes can only communicate directly with the base station, to ad hoc networks whereby nodes can also communicate directly with each other and with rest of the world.

WSNs are becoming evermore numerous and interconnected with the IOT, thereby presenting new opportunities but also challenges which need to be addressed. An example of such would be a remote user who wants to access a particular sensor node of the WSN. Such a user needs to be authorized and, if done positively, allowed to gather data from or send commands to the sensor node. Since the most important and distinct characteristic of WSNs is their resource-constrained architecture (i.e., limited computational and communicational capabilities), a lightweight security solution is required, thus urging the security design to be more prudent.

A key challenge is how to enable the establishment of a shared cryptographic key in a secure and lightweight manner, between the sensor node and the user outside the network. Mutual authentication is also needed for such a scenario, and is highly important since all parties need to be sure of the legitimacies of all the entities involved. Numerous cryptographic schemes for the security of the WSN have been proposed but very few have addressed the aforementioned scenarios, challenges, and requirements [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27]. This was the motivation for us to develop and propose a challenge-specific cryptographic scheme, which uses a rare four-step authentication model that we believe is the most appropriate for the mentioned scenario, when a remote user wants to connect to a sensor node inside a WSN. Since our scheme uses smart cards for users to authenticate, the security architecture is also smart-card oriented. The proposed scheme is also lightweight and resource-friendly, hence it is based only on symmetric cryptography, whereby using only hash and XOR computation.

The remainder of the paper is organized as follows. Section 2 for better understanding of the topic below, provides some brief preliminaries. We present an overview of the existing work in Section 3. Our proposed mutual authentication and key agreement scheme for heterogeneous wireless sensor ad hoc networks is presented in Section 4, followed by the security and performance evaluations in Sections 5 Security evaluation of the proposed scheme, 6 Performance evaluation of the proposed scheme. Finally, Section 7 concludes the paper.