Download presentation

Presentation is loading. Please wait.

Published byShanon Arnold Modified over 2 years ago

1
Physical Layer Security Made Fast and Channel-Independent Shyamnath Gollakota Dina Katabi

2
What is Physical Layer Security? Introduced by Shannon Sender Receiver Channel Time Variations known only to sender and receiver

3
Why is it interesting? No computational hardness assumptions Comes free from wireless channel Combine with cryptography for stronger security

4
Past work Much work 2006 – first empirical demonstration [Trappe’06] Effort to increase secrecy rate [Wyner’75], [Csiszar’78], [Johansson‘01], [Shamai’08] [Trappe’08], [Krishnamurthy’09], [Kasera’10] Theory Practice

5
But, not fast enough Mobile (44 bits/s) For practical key (2048 bits) 0.75 minutes

6
But, not fast enough Static (1 bits/s) Mobile (44 bits/s) For practical key (2048 bits) 0.75 minutes 34 minutes

7
Why is it so slow? Existing practical schemes rely on channel changes Sender Receiver Sender transmits, receiver measures channel Receiver transmits, sender measures channel Exploit Channel Reciprocity Generating new secret bits requires channel to change

8
How can we make physical security fast? Don’t rely on channel changes Instead, introduce changes by jamming

9
Sender repeats its transmission Repetition iJam

10
For every sample, receiver randomly jams either the original sample or the retransmission Repetition iJam

11
Receiver reconstructs signal by picking clean samples Repetition iJam

12
Eavesdropper does not know which samples are clean and hence cannot decode No longer requires channel to change Repetition Generate secret bits faster iJam

13
First practical physical layer security that doesn’t rely on channel changes Implemented and empirically evaluated – 3 orders of magnitude more secret bits – Works with both static and mobile channels Contributions

14
Challenge 1: Making clean and jammed samples indistinguishable BPSK: ‘0’ bit -1 ‘1’ bit +1 Time Samples +1

15
Challenge 1: Making clean and jammed samples indistinguishable BPSK: ‘0’ bit -1 ‘1’ bit +1 Time Samples +1 Jamming should not change structure of transmitted signal

16
Solution 1: Exploit characteristics of OFDM X1X1 X2X2 XNXN +1 +1 IFFT Y1Y1 Y2Y2 YNYN.. Time Samples Modulated bits By central limit theorem, transmitted samples approximate Gaussian distribution Time Samples

17
Solution 1: Exploit characteristics of OFDM X1X1 X2X2 XNXN +1 +1 IFFT Y1Y1 Y2Y2 YNYN.. Time Samples Modulated bits Time Samples Pick jamming samples using a Gaussian Distribution

18
Solution 1: Exploit characteristics of OFDM X1X1 X2X2 XNXN +1 +1 IFFT Y1Y1 Y2Y2 YNYN.. Time Samples Modulated bits Time Samples Jam using a Gaussian Distribution Harder to distinguish between clean and jammed samples

19
Challenge 2: Eavesdropper can still exploit signal statistics Transmitted samples Jammed samples Variance of jammed samples greater than clean samples Using hypothesis testing, eavesdropper can guess Probability Distribution

20
Solution 2: Use xoring to reduce eavesdropper’s guessing advantage Eavesdropper guessing advantage decreases exponentially.... Secret Bit Sequence 1 Bit Sequence 2 Bit Sequence N

21
Challenge 3: Jam effectively independent of eavesdropper’s location Sender Receiver At eavesdropper sender power is larger jamming power Eavesdropper can decode

22
Solution 3: Two-way iJam Sender Receiver maskjam mask Receiver transmits a mask which the sender jams with iJam - Sender receives mask, eavesdropper doesn’t

23
mask secret Solution 3: Two-way iJam Sender Receiver jam Receiver transmits a mask which the sender jams with iJam Sender transmits XOR of the secret with mask which sender jams mask secret mask secret mask - Sender receives mask, eavesdropper doesn’t - Both receiver and eavesdropper receive the XOR

24
Sender Receiver Receiver transmits a mask which the sender jams Sender transmits the XOR of the secret with mask which sender jams mask = secret Receiver can decode secret Eavesdropper can not decode secret Receiver can decode secret Eavesdropper can not decode secret Solution 3: Two-way iJam mask secret mask secret

25
Challenge 4: Stitching samples at the receiver First transmission Repetition

26
Challenge 4: Stitching samples at the receiver First transmission Repetition Channel may change between the two transmissions

27
Challenge 4: Stitching samples at the receiver First transmission Repetition Oscillator phase changes due to lack of synchronization

28
Solution 4: Send back-to-back within the same transmission OFDM SymbolOFDM Symbol Repetition Channel for consecutive symbols is the same

29
OFDM SymbolOFDM Symbol Repetition Solution 4: Send back-to-back within the same transmission Estimate and correct for oscillator phase

30
OFDM SymbolOFDM Symbol Repetition Estimate and correct for oscillator phase Solution 4: Send back-to-back within the same transmission

31
Empirical Results

32
Implementation USRP/USRP2 Carrier Freq: 2.4-2.48GHz OFDM and QAM modulations

33
Testbed 20-node testbed Each run randomly picks two nodes to be Sender and Receiver Every other node acts as eavesdropper Eavesdropper uses optimal hypothesis testing

34
Bit Error Rate at the Eavesdropper Independent of location, Eavesdropper’s BER is close to a random guess

35
Can an iJam receiver decode while jamming? Receiver can decode despite jamming

36
Prior Work: 1 bit/s Secrecy Rate

37
3 orders of magnitude more secret bits than prior schemes Prior Work: 1 bit/s Secrecy Rate

38
Conclusion First practical physical layer security that doesn’t rely on channel changes Implemented and empirically evaluated – 3 orders of magnitude more secret bits – Works with both static and mobile channels

Similar presentations

Presentation is loading. Please wait....

OK

Xiaohua (Edward) Li1 and E. Paul Ratazzi2

Xiaohua (Edward) Li1 and E. Paul Ratazzi2

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Marketing mix ppt on sony picture Ppt on duty roster design Ppt on statistics in maths pie Download ppt on historical monuments of india Ppt on oracle bi publisher View my ppt online maker Ppt on abo blood grouping images Ppt on water pollution and its control Ppt on covering the environmental problems causes effects and solutions Complete ppt on cybercrime