Haodong Wang

Elliptic curve cryptography-based access control in sensor networks

Access control in sensor networks is used to authorise and grant users the right to access the network and data collected by sensors. Different users have different access right due to the access restriction implicated by the data security and confidentiality. Even though symmetric-key scheme, which has been investigated extensively for sensor networks, can fulfil the requirement, public-key cryptography is more flexible and simple rendering a clean interface for the security component. Against the popular belief that a public key scheme is not practical for sensor networks, this paper describes a public-key implementation of access control in a sensor network. We detail the implementation of Elliptic Curve Cryptography (ECC) over primary field, a public-key cryptography scheme, on TelosB, which is the latest sensor network platform. We evaluate the performance of our implementation and compare with other implementations we have ported to TelosB.

Body sensor network security: an identity-based cryptography approach

A body sensor network (BSN), is a network of sensors deployed on a persons body, usually for health care monitoring. Since the sensors collect personal medical data, security and privacy are important components in a body sensor network. At the same time, the collected data has to readily available in the event of an emergency. In this paper, we present IBE-Lite, a lightweight identity-based encryption suitable for sensors, and developed protocols based on IBE-Lite for a BSN.

IBE-Lite: A Lightweight Identity-Based Cryptography for Body Sensor Networks

A body sensor network (BSN) is a network of sensors deployed on a persons body for health care monitoring. Since the sensors collect personal medical data, security and privacy are important components in a BSN. In this paper, we developed IBE-Lite, a lightweight identity-based encryption suitable for sensors in a BSN. We present protocols based on IBE-Lite that balance security and privacy with accessibility and perform evaluation using experiments conducted on commercially available sensors.

Comparing Symmetric-key and Public-key Based Security Schemes in Sensor Networks: A Case Study of User Access Control

While symmetric-key schemes are efficient in processing time for sensor networks, they generally require complicated key management, which may introduce large memory and communication overhead. On the contrary, public-key based schemes have simple and clean key management, but cost more computational time. The recent progress of elliptic curve cryptography (ECC) implementation on sensors motivates us to design a public-key scheme and compare its performance with the symmetric-key counterparts. This paper builds the user access control on commercial off-the-shelf sensor devices as a case study to show that the public-key scheme can be more advantageous in terms of the memory usage, message complexity, and security resilience. Meanwhile, our work also provides insights in integrating and designing public-key based security protocols for sensor networks.

Privacy-aware routing in sensor networks

A typical sensor network application is to monitor objects, including wildlife, vehicles and events, in which information about an object is periodically sent back to the sink. Many times, the object needs to be protected for security reasons. However, an adversary can detect message flows and trace the message back to its source by moving in the reverse direction of the flows. This paper aims to maximize source location privacy, which is evaluated by the adversarys traceback time, by designing routing protocols that distribute message flows to different routes. First, we give the performance bound for any routing scheme. Then, we present our routing schemes, which maximize the adversarys average traceback time and achieve max-min traceback time given certain energy constraints. We then propose WRS, a suboptimal but practical privacy-aware routing scheme, and provide simulation results. Finally, we extend the discussion to an extreme adversary model, which allows the adversary to deploy an adversary sensor network to monitor the message routing activities. Accordingly, we propose a random schedule scheme to confuse the adversary. To reduce the message delivery time, we give an approximation algorithm for message routing.

LightFlood: Minimizing Redundant Messages and Maximizing Scope of Peer-to-Peer Search

Flooding is a fundamental file search operation in unstructured peer-to-peer (P2P) file sharing systems, in which a peer starts the file search procedure by broadcasting a query to its neighbors, who continue to propagate it to their neighbors. This procedure repeats until a time-to-live (TTL) counter is decremented to 0. Flooding can seriously limit system scalability, because the number of redundant query messages grows exponentially during the message propagation. Our study shows that more than 70 percent of the generated messages are redundant in a flooding with a TTL of 7 in a moderately connected Gnutella network. Existing efforts to address this issue have been focused on limiting the use of the flooding operation. We propose a new flooding scheme, called LightFlood, with the objective of minimizing the number of redundant messages and retaining a similar message-propagating scope as that of the standard flooding. In the scheme, each peer keeps track of the connectivities of every immediate and next indirect neighbor peers, which can be acquired locally. LightFlood identifies the neighbor with the highest connectivity and uses the link to that neighbor to form a suboverlay within the existing P2P overlay. In LightFlood, flooding is divided into two stages. The first stage is a standard flooding with a limited number of TTL hops, where a message can spread to a sufficiently large scope with a small number of redundant messages. In the second stage, message propagating is only conducted along the suboverlay, significantly reducing the number of redundant messages. Our analysis and simulation experiments show that the LightFlood scheme provides a low-overhead broadcast facility that can be effectively used in P2P search. For example, compared with standard flooding with seven TTL hops, we show that LightFlood with an additional two to three hops can reduce up to 69 percent of the flooding messages and retain the same flooding scope. We believe that LightFlood can be widely used as a core mechanism for efficient message broadcasting in P2P systems due to its near-optimal performance.

Snoogle: A Search Engine for Pervasive Environments

Embedding small devices into everyday objects like toasters and coffee mugs creates a wireless network of objects. These embedded devices can contain a description of the underlying objects, or other user defined information. In this paper, we present Snoogle, a search engine for such a network. A user can query Snoogle to find a particular mobile object, or a list of objects that fit the description. Snoogle uses information retrieval techniques to index information and process user queries, and Bloom filters to reduce communication overhead. Security and privacy protections are also engineered into Snoogle to protect sensitive information. We have implemented a prototype of Snoogle using off-the-shelf sensor motes, and conducted extensive experiments to evaluate the system performance.

Snoogle: A Search Engine for the Physical World

Hardware advances will allow us to embed small devices into everyday objects such as toasters and coffee mugs, thus naturally form a wireless object network that connects the object with each other. This paper presents Snoogle, a search engine for such a network. Snoogle uses information retrieval techniques to index information and process user queries, and compression schemes such as Bloom filters to reduce communication overhead. Snoogle also considers security and privacy protections for sensitive data. We have implemented the system prototype on off-the-shelf sensor motes, and conducted extensive experiments to evaluate the system performance.

Microsearch: A search engine for embedded devices used in pervasive computing

In this article, we present Microsearch, a search system suitable for embedded devices used in ubiquitous computing environments. Akin to a desktop search engine, Microsearch indexes the information inside a small device, and accurately resolves a users queries. Given the limited hardware, conventional search engine design and algorithms cannot be used. We adopt Information Retrieval (IR) techniques for query resolution, and proposed a new space-efficient top-k query resolution algorithm. A theoretical model of Microsearch is given to better understand the trade-offs in design parameters. Evaluation is done via actual implementation on off-the-shelf hardware.

Microsearch: When Search Engines Meet Small Devices

In this paper, we present Microsearch, a search system suitable for small devices used in ubiquitous computing environments. Akin to a desktop search engine, Microsearch indexes the information inside a small device, and accurately resolves user queries. Given the very limited hardware resources, conventional search engine designs and algorithms cannot be used. We adopt information retrieval techniques for query resolution, and propose a space efficient algorithm to perform top-k query on limited hardware resources. Finally, we present a theoretical model of Microsearch to better understand the tradeoffs in system design parameters. By implementing Microsearch on actual hardware for evaluation, we demonstrate the feasibility of scaling down information retrieval systems onto very small devices.