ITEC 810 – Project Unit

Trustworthy Sensor NetworksDaniel Aegerter, 41542053

Supervisor: Rajan Shankaran

Agenda

Problem Statement

Wireless Sensor Networks

Notion of Trust in Wireless Sensor Networks

Comparative Analysis

Recommendations

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Problem

Security is critical in many applications of Wireless Sensor Networks (WSNs)

— Battlefield surveillance— Patient monitoring— Environment monitoring

Security mechanisms assume trustworthiness of participating nodes

What happens if nodes get compromised?— Access key material— Change content of messages— Drop messages

Lives and livelihoods might depend on the correctness of the data

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Wireless Sensor Networks (WSNs)

Sensor nodes sense data from the environment and detect specific events

Sensor nodes are equipped with sensors to monitor a wide range of physical conditions:

— Temperature, Humidity, Light, Pressure, Object motion, Noise, etc.

Sensor nodes are constrained by limited resources

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Memory

Processor UnitCommunicationdevice

Power Unit

Sensor Unit

Network Architecture

Components of Wireless Sensor Networks — Common Sensor Nodes— Base Station

Multihop communication

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Notion of Trust

“Trust is the subjective probability by which an individual, A, expects that another individual, B, performs a given action on which its welfare depends” (Gambetta, 1988)

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In the context of WSNs

Trustworthy sensor nodes don’t:— Manipulate gathered information— Alter information received from neighbouring nodes— Flood the network with bogus routing information— Drop messages received from other nodes

Challenges in Evaluating Trust for WSNs

Limited processing, storage, and energy resources— Existing protocols and mechanisms are not applicable— Minimise communication overhead

Trusted authority not present in WSNs— Public key mechanisms and certificates not suitable

Adoption of architectural network changes— Dynamic nature of WSNs— Nodes may become faulty or compromised

Trust re-evaluation is essential

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Concept of Reputation-Based Trust Systems

Trust is based on a node’s behaviour— Does the node behave in a correct manner?— Network events and correctness of gathered information

Trust evaluation through first and second-hand information— Direct observations— Recommendations from peers

Building blocks— Watchdog mechanism collects evidence— Reputation system evaluates and maintains trust

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Comparative Analysis

Compares five reviewed reputation-based frameworks1. Reputation-based framework for high integrity sensor network

(RFSN) 2. Gaussian trust model and reputation system (GRSSN) 3. Lightweight group based trust management scheme (GTMS)4. Trust-based cluster head election5. Certificate and behaviour-based approach

Determines characteristics and constraints of each framework

Proposes categories to conduct the comparative analysis— Trust management— Node and network requirement— Trust evaluation

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Comparative Analysis – Some Criteria

Evidence— Network events vs. correctness of sensed data

Pre-established trust relationships— Do sensor nodes trust each other at time of deployment?

Storage complexity— Tables, keys, certificates

Revocation— What happens with non-cooperative sensor nodes?

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Comparative Analysis – Outcomes

All frameworks have some design problems— Difficult to take all characteristics and constraints of WSNs into

account

Frameworks are application specific— Different assumptions— Different requirements (e.g. supernodes, keys, certificates)

Sophisticated frameworks are more complex— Economical issues— Management issues

Evidence analysis— Network events or also correctness of sensed data?

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Recommendations

Collaborative reputation-based approach for establishing trust

Behaviour of nodes is observed by a subset of sensor nodes— Other nodes do not have to monitor network events— Guardian nodes

Guardian nodes evaluate collaborative trustworthiness of nodes

— All sensor nodes are directly observable by guardian nodes— Guardian node evaluate whether a node is cooperative— Opinions are shared among guardian nodes

Blacklist entry has to be confirmed by other guardians— Sensor node keep list with non-cooperative nodes

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Recommendations - Example

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Future Research Directions

Analyse correctness of sensed data not only network events

Trust evaluation for different roles that sensor node can perform

— Forward messages— Aggregate data— Sense information

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Thank you

Questions

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