Ayan Banerjee & Karthik Thangavel

Project Goals Study of present state of security in Body Area Networks(BAN) Cyber-Physical security Resource Footprint Energy efficiency Sustainability Effect of security on present day BANs Vision of security in future wearable sensor platforms Intel Atom based wearable platforms

Body Area Networks (BAN) A network of low capability sensors (physiological, environmental and activity monitoring) Sensors communicate with each other through wireless media Base Station is a gateway for the sensors to the internet SpO2 EKG EEG BP Base Station Motion Sensor Base Station Sensors Environmental sensors Physiological sensors Activity sensors

Why ? BANs deal with sensitive information Wireless media open to security breaches Requirements Integrity Confidentiality Authentication Plug-n-Play Security in BAN  Non intrusive and low deployment overhead  Traditional Schemes not applicable  Can a cyber–physical approach provide the solution?

Cyber-Physical Security Interaction through sensing Feedback Use this to provide security Signal Processing Cryptographic primitives Cyber-Physical Security The term Cyber-physical implies interaction of computing world with the physical environment

PKA Index Peak Values PV FFT Values Peak Values Index PV FFT Values SENSOR 1 SENSOR 2 Time FFT Peak Detection Index Peak Detection Index Quantize Polynomial Generation and evaluation Polynomial Generation and evaluation F s = [f s 1 f s 2 …….. f s n ] F r = [f r 1 f r 2 …….. f r n ] fs1fs1 p(f s 1 ) fsnfsn p(f s n ) p(f s 2 ) fs2fs2 cf i,d i Adding Chaff Transmit Vault R Receive Vault p(x) Lagrangian Interpolation Lagrangian Interpolation Transmit Acknowledgement Transmit Acknowledgement Receive Acknowledgement Receive Acknowledgement Sensing Extensive experiments with Plethysmogram data Data obtained from 10 volunteers  Data collected using Smith Medical pulse oximeter boards Processing done in MATLAB environment

Related Work PKI based security [1] The idea of using signals from environment to provide security was first proposed in [2] and [3] [3] proposed an algorithm to generate security keys from localized measurements of Inter Pulse Interval signals. [4] proposes a secure key agreement protocol PKA (Physiological value based Key Agreement) Resource Usage ?Energy Efficiency ?Sustainability ? 1.D. J. Malan, M. Welsh, and M. D. Smith. A Public-Key Infrastructure for Key Distribution in TinyOS Based on Elliptic Curve Cryptography. pages 71–80, Oct In Proc. of IEEE 2nd Intl. Conf. on Sensor & Ad Hoc Comm. & Networks. 2.S. Cherukuri, K. Venkatasubramanian, and S. K. S. Gupta. BioSec: A Biometric Based Approach for Securing Communication in Wireless Networks of Biosensors Implanted in the Human Body. pages 432–439, Oct In Proc. of Wireless Security & Privacy Workshop K. Venkatasubramanian and S. K. S. Gupta. Security for Pervasive Health Monitoring Sensor Applications. pages 197–202, Dec In Proc. of the 4th Intl. Conf. on Intelligent Sensing & Information Processing. 4.C. C. Y. Poon, Y.-T. Zhang, and S.-D. Bao. A Novel Biometrics Method To Secure Wireless Body Area Sensor Networks for Telemedicine And M-Health. IEEE Communications Magazine, 44(4):73–81, K. K. Venkatasubramanian, A. Banerjee, and S. K. S. Gupta. Plethysmogram-based secure inter-sensor communication in body area networks. Military Communications Conference, MILCOM IEEE, pages 1-7, Nov

Resource Footprint Security protocol RAM requirements RAM Limit in motes Code SizeROM LimitTime (sec) PVS~ 7KB10KB~ 16 KB16 KB~ 20 PKI~ 4KB10KB~ 10 KB16 KB~ 34 70% of RAM utilization Near 100% ROM usage 20 seconds to perform a single iteration TelosB sensors 8 MHz clock 10 KB RAM TinyOS operating system that supports NesC

Experimental Setup for power measurement Bread board circuit for power measurement

Energy Efficiency & sustainability 59 mW of power required for 20 seconds to perform one iteration Offhand analysis of scavenging techniques Body Heat – 200 mW Respiration – 420 mW Ambulation – 1500 mW Solar Power – 100 mW/cm 2 PKA can be sustained using scavenged energy

Effect of security in present day BAN Pros Secure Energy efficient Sustainable Cons High memory usage Applications getting complex Security will be obtrusive Require more and more computing in sensor nodes

Vision of a future BAN Intel Atom based sensors as nodes ? High computing capability 1.6 GHz processor 512 KB L1 cache Present Future

Open research questions Can we guarantee energy efficient operation of Atom based platforms? Can we sustain Atom operation through scavenging of energy? What effect does the power dissipation in Atom has on human body? Do we need changes in the security protocols in order to sustain operation of Atom based platforms?

Off hand analysis Atom requires 2W of power at normal operation and 0.5 W in deep sleep states. Source Power Gain (mW) Hrs of scavenging operation in a day Energy stored (J) Energy leaked (J) Available energy (J) Hrs of operating ATOM in deep sleep Hrs of operating Atom in normal mode F sleep Body Heat200 – – – – – – Respiration Ambulation 1500 – – – – – 4.74 Sun Light100 – 200 (on a 1cm 2 – 2cm 2 photovoltai c cell) 30.3 – 0.6 ~ – – – 0.3

Conclusions Security has huge resource overhead on present day wireless sensor platforms Sensor node capability have to be increased in order to provide security along with complex applications Atom based platforms are promising

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