1. Green and Sustainable Cyber-Physical Security Solutions for Body Area Networks 1. Introduction 2. Security in Body Area Networks: Need and Approach Krishna K. Venkatasubramanian, Ayan Banerjee, Sandeep K. S. Gupta Department of Computer Science and Engineering, Arizona State University Definition: BAN - A network of health & environmental monitoring sensors deployed on a person managing their health. Principal Features: Continuous real time monitoring Remove time & space restrictions on care Improved deployability Ideal for life-saving scenarios: Enables caregivers on field to make informed decisions about treatment of soldiers in time-constrained scenarios. Base Station Sensors Environmental sensors Physiological sensors Activity sensors SpO2 EKG EEG BP Base Station Motion Sensor 3. PKA: Physiological signal based Key Agreement 4. Problem Statement 5. Energy Measurement 6. Energy Model 7. Power Profile 9. Energy Scavenging Need: BANs collect sensitive medical data Legal Requirement (HIPAA) Potential for exploitation - Loss of privacy, Physical harm Possible Attacks: Fake warnings & resource wastage Prevent legitimate warnings. Unnecessary Actuations. Security Requirements: Integrity Confidentiality Authentication Plug-n-Play Solution: Cyber-physical Solution Tightly coupled with their environment- the human body Require many signal processing and mathematical routines Example - Physiological signal based Key Agreement (PKA). PRIMARY ISSUE Secure Inter- Sensor Communication in BAN Peak Values Index SENDERRECEIVER FFT FFT Values IndexFFT Values FFT Peak Detection + Quantization Index Peak Detection + Quantization Peak Values Index Feature Gen 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 fsnfsn fs2fs2 p(f s 1 ) p(f s n ) p(f s 2 ) cf i,d i Adding Chaff Transmit Vault Receive Vault p(x) Lagrangian Interpolation Transmit Acknowledgement Receive Acknowledgement Sensing Security adds overhead. Energy analysis for security primitives important Analyze PKA’s energy-footprint to: Evaluate its total energy cost Cost of its individual components Evaluate if it can be powered in a plug-n-play manner using energy scavenging techniques PKA executed on a pair of TelosB motes. Across the two power leads of the mote, 2.7 ohm resistance was connected in series with an Ammeter. An oscilloscope was connected across the resistance to measure duty cycle. Each stage of PKA is executed in 2 modes– Radio Off/On 2.7 ohms Mote Multi-meter Oscilloscope (Executing PKA) (Ammeter) (Measures current pulses and duty cycle) Energy Measurement Setup supply voltage current draw from processor exec. time current drawn from processor exec. current draw from processor idle. time current drawn from processor idle time current drawn by other components current drawn by other components supply voltage current draw for each Tx. time current drawn for each Tx. current draw for each Rx time current drawn for each Rx time current drawn when transceiver off current drawn with transceiver off Computational Model Communication Model MoteStageCurrent (Radio –off)Current (Radio-On)Time (msec) Sender/ReceiverSensing6.6mA 12800 FFT1mA19.56mA2138 Peak detect + Quantization0.14mA18.72mA12.4 Feature Generation0.11mA18.72mA13.6 SenderPolynomial Generation + Evaluation0.08mA18.68mA8 Chaff Point Generation0.01mA18.61mA14 Vault Tx (1K-5K)--19.33mA1350(1K), 2700(2K), 4000(3K), 5360(4K), 6750(5K) Acknowledgement Rx--19.11mA20 ReceiverVault Rx (1K-5K)--19.41mA1400(1K), 2750(2K), 4100(3K), 5370(4K), 6760(5K) Lagrangian Interpolation0.43mA19.04mA50 Acknowledgement Tx--19.20mA17 Max Power 58mW Radio-On Es ~ Er Radio-Off Es << Er 100015002000250030003500400045005000 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 PKA Computation Energy Consumption for Different Vault Sizes Vault Size (Chaff Points) Energy (Joules) Sender(Radio ON) Sender(Radio OFF) Receiver(Radio ON) Receiver(Radio OFF) Sensing E sense >> Es 100015002000250030003500400045005000 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 PKA Communication Energy Consumption for Different Vault Sizes Vault Size (Chaff Points) Energy (Joules) Sender Receiver Sensing Radio-On E sense << Es < Er 100015002000250030003500400045005000 0 0.5 1 1.5 2 2.5 3 PKA Computation/Communication Energy Ratio for Different Vault Sizes Vault Size (Chaff Points) Ratio Sender(Radio ON) Sender(Radio OFF) Receiver(Radio ON) Receiver(Radio OFF) Radio-On Sender & Rec. (Ratio= ~2.5 – 1.5) Radio-Off Rec. (Ratio ~ 1) Radio-Off Sender (Ratio ~ 0.1) E comp, E comm comparable 100015002000250030003500400045005000 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 PKA Total Energy Consumption for Different Vault Sizes Vault Size (Chaff Points) Energy (Joules) Sender(Radio ON) Sender(Radio OFF) Receiver(Radio ON) Receiver(Radio OFF) Radio-On Es ~ Er Radio-Off Es << Er 8. Energy Results Scavenging model: “On-the-fly” consumption No storage Minimal User Involvement Scavenging Techniques: Scavenging TechniqueSourcePower GainIdeal Deployment Body HeatLatent heat of vaporization of perspiration 200mW – 320mWMost cases, ideal when subject moving RespirationChest Expansion while breathing ~420mWStrenuous physical activity AmbulationArm & Leg Movement1.W-1.6WPhysical movement Photovoltaic Cells 100mW/cm 2 Direct Sunlight Vibrational GeneratorsShaking of source4uW/cm 3 N/A Ambient AirflowMicro-electromechanical Turbine 1mW/cm 2 N/A Ambient RadioPower induced in antenna by RF < 1uW/cm 2 N/A MAX Power Needed = 58mW 10. Conclusions Security adds overhead. Energy analysis for security primitives important. Here we analyzed its energy-footprint: To evaluate its energy cost To show if it can be powered in a plug-n-play manner Communication power is comparable with computation power The max power required by PKA low enough to be sustained by prominent energy scavenging techniques http://impact.asu.eduhttp://impact.asu.edusandeep.gupta@asu.edu