Body-Guided Communications: A Low-Power, Highly Confined Primitive - - PowerPoint PPT Presentation

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Body-Guided Communications: A Low-Power, Highly Confined Primitive - - PowerPoint PPT Presentation

MobiCom 18 New Delhi, India Body-Guided Communications: A Low-Power, Highly Confined Primitive to Track and Secure Every Touch Viet Nguyen 1 , Mohamed Ibrahim 1 , Hoang Truong 2 , Phuc Nguyen 2 , Marco Gruteser 1 , Richard Howard 1 , Tam Vu 2 1


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SLIDE 1

Body-Guided Communications: A Low-Power, Highly Confined Primitive to Track and Secure Every Touch

Viet Nguyen1, Mohamed Ibrahim1, Hoang Truong2, Phuc Nguyen2, Marco Gruteser1, Richard Howard1, Tam Vu2

1 WINLAB/Rutgers University 2 University of Colorado at Boulder

MobiCom 18 New Delhi, India

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SLIDE 2

Motivation: User identification/authentication

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Increasing number of devices Decreasing interaction time Multiple users working on the same device

A convenient yet secure user identification/authentication is desirable

Overhead for authentication

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SLIDE 3

Existing user identification/authentication techniques

  • Vulnerable to man-in-the-middle attack
  • Radio tokens
  • NFC
  • Low data rate
  • SignetRing [1]
  • Hessar et al. [2]
  • High power consumption
  • Vibratory communication [3]

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[1] Vu et al. “Distinguishing Users with Capacitive Touch Communication” [2] Hessar et al. “Enabling On-body Transmissions with Commodity Devices” [3] Roy et al. “Ripple II: Faster Communication through Physical Vibration”

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Key idea

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A body-guided communication system that ▪ Confines signal to a few cm around the hand ▪ Achieves high data rate to transmit a complete authentication code on every touch ▪ Achieves low power consumption

Most interactions are through touch Increasing use of wearable devices

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On On-body communication

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Resistive Coupling Capacitive Coupling

  • The received signal decreases with Tx-Rx distance
  • The received signal is higher when interelectrode

spacing is longer

  • Path loss is much more dependent on the

surrounding environments

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SLIDE 6

Challenges

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Resistive Coupling

  • The received signal decreases with Tx-Rx distance
  • The received signal is higher when interelectrode

spacing is longer RX: inter-electrode distance too small RX: electrodes hidden behind non-conductive layers

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Body-guided Communication

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Cff: the limiting factor when the finger moves away from the touch surface → Touch association for per- touch authentication Major path Minor path Conductive Tissue Epidermis Electrode

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SLIDE 8

Wearable prototype design

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H = 2.4cm d = 0.6cm H = 2cm d = 0.3cm

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Design of f electrode on touched devices

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Electrode size: 1cm2 Under the front-facing case (1mm thick) Electrode size: 13x6cm2 On the back of the phone (phone thickness = 1cm)

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Receiver design

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❖ Dual-buffered memory ❖ Ping-pong DMA → real-time decoding

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Received signal

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Zoomed-in from red area on the left Transmitter modulates a 128-bit ID using OOK Carrier frequency = 150KHz Signal after mixing at the receiver = 5KHz

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Protection against remote monitoring

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Wearable token Intended receiver Adversary receiver Highly-confined signal Per-touch authentication Low-power @ Intended Receiver @ Adversary Receiver

signal advantage

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Protection against contacts

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RX TX Adversary User TX RX User Adversary Conductive Surface Shared screen User TX RX Table Metal Base

Highly-confined signal Per-touch authentication Low-power

Signal advantage is always greater than 10dB

No positive signal advantage possible for RF, NFC, etc.

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Per-touch authentication/identification

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  • 2170 touches over 5 days
  • Touch duration: 50.7ms - 1.78s
  • 32, 64, 128, and 256-bit code
  • Data rate: 1kbps

Highly-confined signal Per-touch authentication Low-power

For 128-bit code: 89.5% accuracy for 200-300ms touch duration 100% for above 300ms touch duration

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SLIDE 15

Power consumption

11/5/2018 Body-Guided Communications 15 1 10 100 1000 10000 100000 Body-guided Communication Vibratory communication RF NFC

Energy per bit

3.9mW@1kbps (3.9uJ/bit) 200mW@2kbps (100uJ/bit) Highly-confined signal Per-touch authentication Low-power nJ/bit nJ/bit nj/bit Susceptible to eavesdropping No touch association Current MSP430-based prototype Theoretical limit 90nJ/bit

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Conclusion

  • Proposed a body-guided communication method for securing every

touch interaction from users with a variety of devices

  • More secure against eavesdropping than other wireless methods
  • The signal received at the intended receiver is at least 20dB higher than that

at an adversary’s receiver in proximity

  • Low power consumption
  • Token consumes 3.9uJ/bit, much lower than vibratory communication (per-

touch communication)

  • Robust per-touch authentication
  • Reliably deliver a 128-bit ID code on every touch longer than 300ms

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Thank you!