Through-body capacitive touch communication. Hoang Truong, Phuc Nguyen, Viet Nguyen, Mohamed Ibrahim, Richard Howard, Marco Gruteser, Tam Vu

Transcription

1 Through-body capacitive touch communication Hoang Truong, Phuc Nguyen, Viet Nguyen, Mohamed Ibrahim, Richard Howard, Marco Gruteser, Tam Vu

2 Do you have smart devices? *Total number (billions) *Device type distribution *Statista and TheVerge statistic

3 Do you have smart devices? Total number (billions) Device type distribution Most common component: Touchscreen Same core technique: Capacitive touch *Statista and TheVerge statistic

4 How do you unlock them securely? *More than 80 times per day Pin code Touch ID Face ID Cumbersome Need at least 2 touches Not there yet *Apple report

5 Shared devices / Collaborative works

6 Shared devices What can be the most simple and intuitive unlocking? How to save our time for this authentication process?

7 Idea: Per-touch authentication Integrate authentication data into touches Target billions of touch interfaces Capacitve touch communication

8 Capacitive touch communication Concept was introduced in 2012 Transmitter Complex channel Receiver Wearable devices Capacitance 0 Touch manipulation Time

9 Touchscreen spoofing Create artificial touches Measure capacitance changes Control capacitance change

10 Cap.Touch evolution Hard surface in contact with screen - Through-body cap.touch - Per-touch authentication - Introduce concept of CTC - Electrical pulse injection - Object interaction - Capacitance variation - Object authentication - User identification New approach Artifact Touch-enabled device Token MOBICOM 12 SENSYS 16

11 Through-body System Bit message Tx Modulator Signal generator Ring-form device

12 Through-body System Bit message Touch event detection Tx Modulator Demodulator Rx Signal generator Application Ring-form device

13 Through-body System Tx Channel Rx Bit message Modulator Signal generator User body Capacitive sensor Touch controller Touch event detection Demodulator Application

14 Challenge: Constrain with off-the-shelf devices Diversity touch ICs & mechanisms *Diversity touch scanning rates *MIDAS, SENSYS 16

15 Challenge: Constrain with off-the-shelf devices Generalization for touch mechanism Diversity touch ICs & mechanisms Diversity touch scanning rates

16 Source Approach: General model for touch mechanism S 1 1 st plate S 2 Output to processing MCU Csensor Cintegrated Rbleed Comparator 2 nd plate Signal characteristic Generator decision More detail in paper

17 Challenge: Unpredictable intrabody channel Tx Rx Traditional intrabody channel Smaller portion of body part Significant role of touch device

18 Challenge: Unpredictable intrabody channel Tx Rx Analysis for system model in detail Traditional intrabody channel Smaller portion of body part Significant presence of touch device

19 Approach: Detail capacitive coupling circuit model Positive electrode Negative electrode Body Screen Real ground p n b s g Predict signal flow Predict signal output More detail in paper

20 Prelim Evaluation: Encoding Generation requirement at least 50V Minimum voltage to trigger communication V V fingertip < V generated 100

21 Prelim Evaluation: Encoding Generation requirement at least 50V Generate high input voltage V SAFE due to low current <1mA Minimum voltage to trigger communication V V fingertip < V generated 100 Encode data by switching signal generator

22 Touch presence Prelim Evaluation: Decoding Touches appear along horizontal grid Recover original bit stream based on touch event manipulation Valid feasibility of through-body scheme 600ms 600ms 600ms Timeline More detail in paper

23 Average event numbers vs. Signal duration (ms) Smallest touch interval = 17ms Limitation due to off-the-shelf devices

24 Future work Data rate incensement Per-touch authentication deployment Hardware/software optimization

25 Conclusion Propose new approach for CTC Tackle challenges Valid feasibility of through-body CTC

26 Through-body capacitive touch communication Hoang Truong, Phuc Nguyen, Viet Nguyen, Mohamed Ibrahim, Richard Howard, Marco Gruteser, Tam Vu

27 One more thing Potential security advantage