security protocols & platform for wsn based medical applications

Security protocols & platformFOR WSN BASED MEDICAL APPLICATIONS

-AVIJ IT MATHUR

SUPERVISOR: DR. THOMAS NEWE

OFSRC

OverviewWSN: Nodes collected and organized in some fashion in order to make a cooperative network.

Usage: Monitoring of patients wirelessly. (Routine/emergency/mass causality) thereby providing healthcare services.

As the population increases there is a need for continuous medical monitoring.

Patients monitored wirelessly has several advantages.

Traditional wired methods do not allow mobility with the added difficulty of time constraints.

Provide a secure, reliable and energy-efficient Wireless Sensor Network for medical devices.

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Advantages: Mobility, real time monitoring, easy for doctor/nurse, free up hospital wards

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Body sensor network systems can help people by providing healthcare services such as medical monitoring, memory enhancement, medical data access, and communication with the healthcare provider in emergency situations

In Home/hospital architectureTo M

ain

Server

Base StationRepeater

Access point 1

Access point 2

Access point 3

GSM/3g/4gWiFiWiMAXZIGBEEBLE

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Avijit11/18/2013ADVANTAGES of WSNs:•Portability and unobtrusiveness•Ease of deployment and scalability•Real time and always on•Reconfiguration & self-organization

TopologiesStar

Mesh:

Hierarchical tree

Clustered Hierarchical

Star Topology

Partial Mesh Topology

Hierarchical Tree

Clustered HierarchicalCluster Head Central Hub/Switch

Gateway Nodes Sensor Nodes

Source: A Performance Comparison of Different Topologies for Wireless Sensor Networks by Akhilesh Shrestha and Liudong Xing

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Scalability, reliability, self-forming and self-healingSelf-induced black-hole effectAddress is non-hierarchical

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Maximum 1 or 2 Hops, least latencyNot scalableLocal-node failure only

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less reliability,

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more energr conumption with less latency & travel time

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reliability lies between Hierarchical tree and mesh

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lesser latency than mesh since only CH performs data aggreagation

ZIGBEE Bluetooth Low energy Wi-Fi 4G

Range 10-100 m >60m(10m for Classic BT)

Depends on specification In Kilometers

Power Low Very Low (High for classic BT and medium for others)

High (variable for WiFi Direct)

High

Entries 254 (>64000 per network)

2 Billion (Classic: 7)

Depends on no. of IP addresses

-

Latency Low 3 ms (compared to 100ms in classic BT)

Variable -

Self healing Yes - Yes Yes

Topologies Mesh, Star and Cluster-tree Star Star, Point-to-Point Ring

Data transmission rate Up to 250Kbps 1Mbps (BT v4.0: 25Mbps) 11Mbps & 54Mbps (250 Mbps: WiFi Direct)

100Mbps & 1Gbps(fixed access)

Bandwidth 2.4GHz, 915MHz & 868 MHz

2.4 GHz only(BT + HS: 6-9 GHz)

2.4, 3.6 & 5 GHz Similar to WiFi

Transmission technique DSSS DS/FA? Adaptive FHSS(Classic BT: FHSS)

DSSS, CCK & OFDM OFDMA

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IEEE 802.11b & 802.11g

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FHSS: less transmission failures due to low sensibility to radio pertubations

IEEE 802.15.6New standard specified for Wireless Body Area Networks (WBANs)

Extremely low power, good data rate and safety compliant.

Flexible frequencies => selecting the right physical layer very important

MICS and WMTS do not support high data rate while ISM band supports high data rate at the cost of interference.

PHY layers

Security levels

Source :An Overview of IEEE 802.15.6 Standard (Invited Paper)Kyung Sup Kwak, Sana Ullah, and Niamat Ullah; UWB-ITRC Center, Inha University; 253 Yonghyun-dong, Nam-gu, Incheon (402-751), South Korea

Table Source:Body Area NetworksArif Onder ISIKMAN, Loris Cazalony, Feiquan Chenz, Peng LixChalmers University of Technology, SE-412 96, Gothenburg, Sweden

IEEE 802.15.4 / ZigBee IEEE 802.15.6

Range 10-100m 2-5m

Data rate 20,40 & 250 Kbps Few Kbps – 10 Mbps

Power 25-35mW 0.01 mW (stand by), 40mW (active)

Entries 65535 devices 256 devices per network

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medical implant communications service &Wireless medical telemetry services

Security & ReliabilitySecurity services: Authentication, access control, data confidentiality, integrity and Non-repudiation. Reliability depends on two main factors: network connectivity and sensing coverage.Security is very important as the technology may be vulnerable to attacks Traditional security mechanisms (PKI) cannot be used.Semantic security Secure routing & storage are most important

Source: Integrated Modeling for Wireless Sensor Networks by Liudong Xing, Ph. D., University of Massachusetts, Dartmouth & Howard E. Michel, Ph.D., University of Massachusetts, Dartmouth

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An eavesdropper is not able to gain any information about plaintext even after observing many encryptions of the same

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can be achieved by counter + IV

Security protocolsTinySec

MiniSec

SPINS: SNEP & uTesla

LiSP

MAC

SIA

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SNEP: 2 party protocol& semantic security, replay protection & data auth, low comms overhead

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can provide strong freshness if nounce added

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authenticated broadcastapplications: authenticated routing

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Sender setup, broadcast authenticated pckts, bootstrap new receiver, authenticate broadcast packets

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TinySec-auth only & TinySec-AE

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must provide against eavesdropping and potential threat. variants: S-MAC, T-MAC, PMACS, etc.weakness: Idle listening periods, collision, BW wastage

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1.reliable key distribution2.solves key reuse prob by periodic rekeying3.Robust to DoS and replay

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Low energy consumption + high sec and publicly availableweakness: large packtes send by RF => higher energy consumption

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Data integrity maintainedseveral ways to aggregateweakness:DoS, stealth attacks, resource consuming

Security Mechanism

Steganography: Channel is hidden under the Physical layer to provide covert data transmission

Cryptography: Encryption & authentication mechanisms

Key management: Global, pair-wise node, pair-wise group & individual

Localization: Geographically detect a malicious node

Trust management: Select route based on trustworthy nodes

Data Partitioning

6 6

6

6

7

7

7

6

Periodic key generation

Data: D

D1D2

D3

D1

D1D2

D3 D3

Source: Wireless Sensor Network Attacks and Security Mechanisms : A Short Survey David Martins and Hervé GuyennetComputer Science Department, University of Franche-Comté, France

Energy managementEnergy consuming layers

Use VCO based radio architecture since it is:Robust to interference Allows communication at different carrier frequenciesBetter sleep synchronizationUses Flash over SRAM memory

Efficient programming techniques

Collision avoidance

Idle listening periods must be reduced

Routing: with the usage of real-time protocols, reduce the size of routing tables

Clustering: Hierarchical clustering

Data gathering

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flash may be slower but requires no energy to maintain data

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through energy aware intra-cluster routing

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acquire data from closer set of nodes.

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Phy: Radio parameters DLL: MAC -> CA, Idle listening periods etc.Network Layer: Routing, clustering

Issues & ChallengesPrivacy & security

Trust

Coverage

Communication delay

Need for reliable, fault tolerant, self-healing and organising cluster-scheme for key distribution

Choosing the right blend of encryption and authentication schemes

Movement of patient is challenging with regards to architecture, coverage and routing.

Decentralized security mechanism.

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accuracy of sensors may be marred due to harsh environments, interference from other devices (WiFi, Bluetooth, cordless). This is exacerbated as WSNs use low power radiosQoS is therefore a major challenge

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RBAC, who sees how mucheach system may have their own privacy policy. sometimes it might be required to be more flexible to achieve some functionalities

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Limited resources (memory, storage, processer speed, battery etc)

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sensors fail / weak signal

FindingsResearch into network topologies and clustering algorithms.

Securing both the nodes and the communication network.

Group key distribution techniques.

WSNs require node scalability and mobile agent.

Sensors may capture confidential data.

Motes must authenticate the stored public key of Base station.

In the future it may be possible for patients to interpret their results on a PDA/desktop.

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if every node has a unique key, then management is difficult and the process is energy consuming

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Securing the communication layer is not enough, must secure end nodes as they are more easy to access and if compromised may lead to privacy violations and danger to the patients

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give user access to data?but this may affect the credibility of data!

FindingsKey management schemes to be further researched.

Nodes should automatically decide on a routing strategy.

Medical environment may call for high reporting times from the nodes (emergency).

Reporting of failed nodes and healing of the network is important.

Connectivity: USB, Ethernet, RS232 + WiFi, ZigBee,

Bluetooth & cellular.

Machine learning algorithm can act as a mediator.

Image source: Medical Applications based on Wireless Sensor Networks by Stanković, Stanislava

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One possible solution for using PKI is to only compute the public key at the nodes, the private key operations will be handled by a common entity (trusted server). since private key operations are resource consuming

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because of the dynamic nature of mobile WSNs

Motes

Tmote Sky

Tmote sky: http://insense.cs.st-andrews.ac.uk/examples/Micaz: http://www.cse.chalmers.se/~larandr/master.htmlShimmer: http://www.eecs.Harvard.edu/~mdw/proj/codeblue

Shimmer

Micaz

The EndTHANK YOU

security protocols & platform for wsn based medical applications

Engineering

high data rate

hierarchical clustering

data confidentiality

confidential data

network topologies

good data rate

communication network

security protocols platform