C21. Analytical analysis of a Cluster Controlled Mobility scheme for data security and reliability in UWSNs

Unattended wireless sensor networks (UWSNs) are operated in hostile environments without constant supervision by a trusted sink; so it faces the risk of compromising by adversaries (ADVs). In this study, proposed is a cooperative hybrid self-healing randomised distributed (CHSHRD) scheme, a new mechanism to enhance the confidentiality of the data collected by UWSNs. The proposed scheme employs both proactive and reactive peers to ensure both backward secrecy and data reliability. It helps the unattended sensors to self-heal and restore their backward secrecy by asking for help from the best qualified neighbours to generate a new secret key to regain their secrecy. The sick sensors also use the best qualified neighbours to distribute the data parts among them to protect the data from eavesdropping and this will enhance the data reliability. In this study, they also present a powerful, realistic and agile ADV model and show how CHSHRD scheme can result in sensor regaining secrecy and achieving high data reliability, despite the adversary efforts to the contrary. The evaluation of the proposed scheme relies on both theoretical probabilistic results and simulation results that compare the proposed scheme to other protection schemes. The results show that this hybrid scheme provides better protection than other schemes that use either proactive or reactive peers.

Unattended Wireless Sensor Networks (UWSNs) operated in hostile environments face a risk on data security due to the absence of real-time communication between sensors and sinks, which imposes sensors to accumulate data till the next visit of a mobile sink to off-load the data. Thus, how to ensure forward secrecy, backward secrecy and reliability of the accumulated data is a great challenge. For example, if a sensor is compromised, pre-compromise data accumulated in the sensor is exposed to access. In addition, by holding key secrecy of the compromised sensor, attackers also can learn post-compromise data in the sensor. Furthermore, in practical UWSNs, once sensors stop working for accidents due to node crash or battery depletion, all the data accumulated will be lost. To address the challenges, we propose a secure and reliable data distribution scheme in this paper. Detailed analysis shows that our scheme can provide forward secrecy, probabilistic backward secrecy and data reliability. To further improve probabilistic backward secrecy and data reliability, a constrained optimization data distribution scheme is proposed. Detailed analysis and simulation results show the superiority of the proposed scheme in comparison with several previous approaches developed for UWSNs.

For distributed data storage in Unattended Wireless Sensor Networks (UWSNs), security issues have been focused on by extensive researches in recent years. In this paper, an enhanced, reliable, and secure data distribution scheme based on erasure codes for UWSNs is proposed, which adapt the MOVE-ONCE survival strategy. In the proposed scheme, two-hop neighbor set has been utilized as data shareholders of data distribution. Through the analysis, we can find that there is more number of candidate secure data holders in two-hop neighbor set than one-hop neighbor set. Thus our new scheme could further enhance both probabilistic Backward Secrecy (BSe) and the reliability on data retrieval. Theoretical analysis and dense simulations show advantages of our new scheme which is compared with several previous related schemes proposed for UWSNs.

This study investigates the performance analysis of mobile unattended wireless sensor networks (UWSNs) during the self-healing process under informed movement inside a cluster of healed and sick sensors. Introducing mobility within a cluster can increase the chance that a sick sensor has healthy neighbours and this will aid the sick sensor to be healed faster and better. However, sensor mobility is considered as one of the most energy consuming factors in UWSNs. This study proposes a new self-healing scheme based on a single flow controlled mobility within a cluster to make a trade-off between self-healing and energy consumption in mobile UWSNs. The obtained results show that using the proposed scheme, UWSNs can exploit controlled sensor mobility to enhance network capability in terms of self-healing and reduce the communication-related energy consumption. In addition, the proposed scheme with single flow controlled mobility does not disturb the number of neighbours per sensor and the network coverage.

Most approaches to human action recognition is limited due to the use of simple action datasets under controlled environments or focus on excessively localized features without sufficiently exploring the spatio-temporal information.This paper proposed a framework for recognizing realistic human actions.Specifically, a new action representation is proposed based on computing a rich set of descriptors from keypoint trajectories.To obtain efficient and compact representations for actions, we develop a feature fusion method to combine spatial-temporal local motion descriptors by the movement of the camera which is detected by the distribution of spatio-temporal interest points in the clips.A new topic model called Markov Semantic Model is proposed for semantic feature selection which relies on the different kinds of dependencies between words produced by "syntactic " and "semantic" constraints.The informative features are selected collaboratively based on the different types of dependencies between words produced by short range and long range constraints.Building on the nonlinear SVMs, we validate this proposed hierarchical framework on several realistic action datasets.

ABSTRACTUnattended wireless sensor networks operating in hostile environments face the risk of compromise. Given the unattended nature, sensors must safeguard their sensed data of high value temporarily. However, saving data inside a network creates security problems due to the lack of tamper‐resistance of sensors and the unattended nature of the network. In some occasions, a network controller may periodically dispatch mobile sinks to collect data. If a mobile sink is given too many privileges, it will become very attractive for attack. Thus, the privilege of mobile sinks should be restricted. Additionally, secret keys should be used to achieve data confidentiality, integrity, and authentication between communicating parties. To address these security issues, we present mAKPS, an asymmetric key predistribution scheme with mobile sinks, to facilitate the key distribution and privilege restriction of mobile sinks, and schemes for sensors to protect their collected data in unattended wireless sensor networks. Copyright © 2011 John Wiley & Sons, Ltd.

Optimized secure and reliable distributed data storage scheme and performance evaluation in unattended WSNs

In unattended wireless sensor networks, data are stored locally and retrieved on demand. To efficiently transmit the collector’s retrieval results, data are aggregated along being forwarded. The data confidentiality and integrity should be protected at the intermediate nodes. End-to-end encryption or hop-by-hop encryption based schemes are not efficient. Straightforward homomorphic encryption based scheme is not compromise resilient. To achieve all the desires, we propose a scheme - H2S by making use of both homomorphic secret sharing and homomorphic encryption. The security and efficiency of our scheme are justified by extensive analysis.

Data Security in Unattended Wireless Sensor Networks through Aggregate Signcryption

In the past decades, wireless Sensor Networks (WSNs) attracted many researchers. A lot of them considered important issues such as: routing, security, power awareness and data abstraction, But security is prior common assumption in the most of works. On the other hand, WSNs should collect small size and especially secure data in real-time manner. This problem is considered because sensor nodes are small, low power with low storage. Therefore, classical algorithms maybe inapplicable, i.e. considering constrained sensor, these algorithms cannot guarantee the security of data. The aforementioned problem is very critical in the new generation of WSNs referred to as Unattended or disconnected wireless sensor networks.

In traditional Wireless Sensor network’s (WSN’s), the sink is the only unconditionally trusted authority. If the sink is not connected to the nodes for a period of time then the network is considered as unattended. In Unattended Wireless Sensor Network (UWSN), a trusted mobile sink visits each node periodically to collect data. This network differs from the traditional multi hop wireless sensor networks where the nodes close to the sink deplete their power earlier than the other nodes. An UWSN can prolong the life time of the network by saving the battery of the nodes and also it can be deployed in environments where it is not practical for the sink to be online all the time. Saving data in the memory of the nodes for a long time causes security problems due to the lack of tamper-resistant hardware. Data collected by the nodes has to be secured until the next visit of the sink. Securing the data from an adversary in UWSN is a challenging task. We present two non-cryptographic algorithms (DS-PADV and DS-RADV) to ensure data survivability in mobile UWSN. The DS-PADV protects against proactive adversary which compromises nodes before identifying its target. DS-RADV makes the network secure against reactive adversary which compromises nodes after identifying the target. We also propose a data authentication scheme against a mobile adversary trying to modify the data. The proposed data authentication scheme uses inexpensive cryptographic primitives and few message exchanges. The proposed solutions are analyzed both mathematically and using simulations proving that the proposed solutions are better than the previous ones in terms of security and communication overhead.

Providing forward and backward secrecy is still a big challenge in Unattended Wireless Sensor Networks (UWSNs), though some storage schemes have been proposed. Additionally, high storage requirement needs efficient storage techniques. In this paper, we propose a novel homomorphic encryption and key-evolution based scheme for efficient and secure data storage, which supports both forward and backward secrecy in UWSNs. We show that the stored data based on our scheme can be used to efficiently compute statistic values, e.g., expected value and variance of the sensed data, and at the same time the storage cost is significantly reduced using our scheme. Detailed analysis has been conducted to evaluate the scheme in terms of efficiency and security.

In recent years, wireless sensor networks (WSNs) have been a very popular research topic, offering a treasure trove of systems, networking, hardware, security, and application-related problems. Much of prior research assumes that the WSN is supervised by a constantly present sink and sensors can quickly offload collected data. In this paper, we focus on unattended WSNs (UWSNs) characterized by intermittent sink presence and operation in hostile settings. Potentially lengthy intervals of sink absence offer greatly increased opportunities for attacks resulting in erasure, modification, or disclosure of sensor-collected data. This paper presents an in-depth investigation of security problems unique to UWSNs (including a new adversarial model) and proposes some simple and effective countermeasures for a certain class of attacks.

In recent years, sensors and sensor networks have been extremely popular in the research community. One of the most exciting aspects of sensor networks research is the confluence of diverse areas, such as databases, networking, distributed systems and security. In particular, security issues in have received a lot of attention. Due to low cost of individual sensors and commensurately meager resources, security in sensor networks poses some unique and formidable challenges. A large body of research has been accumulated in recent years, dealing with various aspects of sensor security, such as: key management, data authentication, privacy, secure aggregation, secure routing as well as attack detection and mitigation.One common assumption in prior WSN security research has been that data collection is performed in (or near) real time: a trusted entity --- usually called a sink --- is assumed to be always (or mostly) present. Data sensing can be event-driven (triggered by some changes in the sensing environment), on-demand (initiated by a query from the sink) or scheduled (prompted by a timer). No matter how sensing is activated, the presence of an on-line sink allows nodes to submit measurements soon after sensing. In this model, an adversary capable of compromising nodes and corrupting data has relatively little time to pursue its goals.While many operate in this general setting, there are emerging WSN scenarios and applications that fall outside the real-time data collection model. We refer to such networks as WSNs or UWSNs. For example, deployed in military or law enforcement environments might not have the luxury of an ever-present sink: sensed data can be off-loaded only when the sink visits the network. Another example might be a WSN monitoring compliance with a nuclear non-proliferation treaty operating in a rogue country.We further narrow our scope to UWSNs operating in hostile environments. Unattended sensors deployed in such environment represent an attractive and easy target for an adversary. The sensors' inability to off-load data in real time exposes them and their data to increased risk. Without external connectivity, sensors can be compromised with impunity and collected data can be read, altered or simply erased. Sensor compromise is a realistic threat, since a typical sensor is a mass-produced commodity device with no specialized secure hardware or tamper-resistant components. Prior security research typically assumed that some number of sensors can be compromised during the entire operation of the network and the main challenge is to detect such compromise. This is a reasonable assumption, since --- with a constantly present sink --- attacks can be detected and isolated. The sink can then immediately take appropriate actions to prevent compromise of any more sensors.In contrast, in the UWSN setting, the adversary can compromise up to a certain number of sensors within a particular time interval. This interval can be much shorter than the time between successive sink visits. Given enough intervals, the adversary can subvert the entire network as it moves between sets of compromised nodes, gradually undermining security. The adversary's goals might include: reading, erasing or modifying data collected by unattended sensors.In this talk, we discuss in detail a number of security challenges in unattended WSNS. In doing so, our main goal is to bring the problem to light and engender interest from the research community to investigate it further.

This paper proposes a new Self-Healing scheme based on Cluster Controlled Mobility (SH-CCM) for UWSNs. The proposed SH-CCM scheme uses the idea of mobility within a cluster of sick sensors beside the idea of the hybrid cooperation between both reactive and proactive peers and these sick sensors. This increases the chance of finding health neighbours and as a result it enhances both data security and reliability. The proposed SH-CCM scheme will help the sick sensor to self-heal and restore its backward secrecy faster and better than the schemes without mobility. A set of simulation results are carried out to demonstrate the effectiveness of the proposed SH-CCM scheme in the presence of a powerful, realistic adversary (ADV). The performance is measured in terms of compromising probability, probability of Bse (Backward Secrecy) to be compromised, and the data reliability. The obtained results ensure that the proposed scheme has a better performance over the conventional schemes without controlled mobility.