CSC/ECE 774 Advanced Network Security - Peng Ning @ NC State

• 11/21/10

• 1

Computer Science

CSC/ECE 774 Advanced Network Security

Topic 7.1 Wireless Physical Layer Security

CSC/ECE 774 Dr. Peng Ning 1

Computer Science

Agenda

•  A few example problems •  Two of our recent efforts

–  Anti-jamming wireless communication – RD-DSSS •  Provide security for wireless physical layer

–  Authentication of primary users in cognitive radio networks •  Exploit wireless physical layer properties for other security goals

•  Conclusion


Computer Science

Why Wireless Physical Layer Security?

•  Wireless communication is ubiquitous today –  WiFi, sensor networks, Bluetooth, cellular networks,

cognitive radio, …

•  Wireless physical layer offers new opportunities –  Device physical

properties –  Channel characteristics –  Proximity verification –  Others?

CSC/ECE 774 Dr. Peng Ning

•  Unique security needs in wireless physical layer –  Anti-jamming –  Authentication of signal –  Device identification –  Privacy –  Others?

3

• 11/21/10

• 2

Computer Science

A Few Example Problems

•  RF fingerprinting –  Device identification/authentication

•  E.g., [Gerdes et al., NDSS 2006], [Hall, thesis 2006], [Brik et al., Mobicom 2008]

–  Fingerprinting device drivers (not exactly RF fingerprinting)

•  E.g., [Franklin et al., USENIX Security 2006]

–  RF fingerprinting can be faked •  [Danev et al., WiSec 2010]

–  More research is needed…


Computer Science

A Few Example Problems (Cont’d)

•  Anti-jamming wireless communication –  Traditional approaches

•  Frequency Hopping (FH), Direct Sequence Spread Spectrum (DSSS) •  Vulnerable to insider attacks

–  Examples of recent efforts •  Uncoordinated FH (UFH)

–  [Strasser et al., S&P 2008], [Strasser et al., Mobihoc 2009] •  Uncoordinated DSSS (UDSSS)

–  [Popper et al., USENIX Security 2009], [Popper et al., JSAC 2010]

•  Randomized Differential DSSS (RD-DSSS) –  [Liu et al., INFOCOM 2010]

•  Delayed Seed Disclosure DSSS (DSD-DSSS) –  [Liu et al., ACSAC 2010]


Computer Science

A Few Example Problems (Cont’d)

•  Distance bounding (or secure ranging) protocols –  Verify the distance from a device is within a certain range –  Based on timing the delay between a challenge and a response message –  E.g., [Capkun & Hubaux, INFOCOM 2005], [Tippenhauer & Capkun,

ESORICS 2010], [Avoine et al., USENIX Security 2010]

•  Proximity-based access control –  An application of distance bounding –  E.g., [Rasmussen et al., CCS 2009]


• 11/21/10

• 3

Computer Science

Two of Our Recent Efforts

•  RD-DSSS: Jamming-resistant wireless communication –  Provide security (availability) for wireless physical layer

•  Authenticating primary user’s signals in cognitive radio networks –  Use wireless physical layer property for authentication


Computer Science

RD-DSSS: Jamming-Resistant Wireless Broadcast Communication �


Computer Science

The Problem

•  Broadcast Communication –  Essential to wireless networks –  Packets are transmitted to multiple

receivers

•  Some receivers may be malicious or compromised –  They have access to whatever secrets

normal receivers have –  They can help jammers to effectively

defeat traditional anti-jamming techniques


• 11/21/10

• 4

Computer Science

Related Work

•  Traditional anti-jamming techniques –  FH, DSSS –  Require shared secrets

•  Some recent research –  Common theme: Remove the need of shared secret –  BBC [Baird et al., IA Workshop ’07]

•  Expensive when applied to FH and DSSS

–  UFH [Strasser et al., S&P08], [Strasser et al., MobiHoc09], and [Slater et al., WiSec09]

•  Vulnerable to intelligent reactive jammers

–  UDSSS [Pöpper et al., USENIX Security09, JSAC 2010] •  Vulnerable to intelligent reactive jammers


Computer Science

Randomized Differential (RD)-DSSS

•  Key observation –  A receiver can wait to decode received signal until end of

the transmission –  A jammer must jam the transmission before it is finished –  Acknowledgment: Pöpper et al. independently had the same

observation in their JSAC ’10 paper.

•  Basic ideas –  Only rely on publicly known information –  Disclose de-spreading information at the end of message –  Reshuffle spread message to defeat reactive jamming


Computer Science

Preliminary: Correlation of Spreading Codes �

•  A spreading code is a sequence of chips (short bits) –  E.g., +1, −1, +1, −1, +1, −1, +1, −1

•  Correlation between two spreading codes –  P1= +1, −1 and P2 = −1, −1 –  Cor (P1,P2) = ( (+1) × (−1)+ (−1) × (−1) )/2=0

•  Correlation between two identical codes is high, and that between two different codes is low –  P1 = +1, −1, +1, −1, +1, −1, +1, −1 –  P2 = +1, −1, +1, −1, +1, −1, +1, −1 –  Cor(P1, P1) = 1, Cor(P2, P2) = 1, and Cor(P1, P2) =0

•  Example spreading codes –  Gold codes, Walsh codes, and m sequences


• 11/21/10

• 5

Computer Science

Basic Scheme: An Example �


• Index code

Computer Science

Basic Scheme: Properties

•  No need to have a secret –  A sender randomly chooses a code sequence to spread each

message –  The index code is placed at the end of each message

•  Still vulnerable to reactive jamming –  The correlation between the spread message and the chosen

code sequence is high –  A computationally powerful reactive jammer can gradually

narrow down the possible code sequences


Computer Science

Enhanced Scheme �

•  Enhancing basic scheme by two mechanisms – Spread each message using multiple code

sequences •  A reactive jammer must know all code sequences

– Permute all codes of the spread message •  The correlation is reduced


• 11/21/10

• 6

Computer Science

Enhanced Scheme: An Example �


Computer Science

Ability to Handle Reactive Jamming �

•  A reactive jammer must do an exhaustive search over all possible combinations – The number of correlations is

•  where k is the number of chosen code sequences, and q is the number of index codes

– The computation must finish before the transmission ends


Computer Science

Selected Evaluation Results �

•  Random jamming –  Jammer randomly picks codes to jam transmission –  Message size: 1024 bits �

• Tolerate 60 bit error using ECC • 120 codes in the public code set


• 11/21/10

• 7

Computer Science

Selected Evaluation Results (Cont’d) �

•  Reactive jamming – Correlation between observed codes (by jammer)

and unselected/selected code sequences

More detailed evaluation results are in the paper. CSC/ECE 774 Dr. Peng Ning 19

Computer Science

Authenticating Primary Users’ Signals in Cognitive Radio Networks �


Computer Science

Background

•  Increasing demand for wireless bandwidth


Unlicensed channels become over-crowed �

21

• 11/21/10

• 8

Computer Science

Background (Cont’d)


• U.S. Spectrum allocation chart

We are running out of wireless channels!!! 22

Computer Science

Background (Cont’d) �

•  Cognitive radio networks – Unlicensed users use licensed channels on a non-

interference basis


Computer Science

Background (Cont’d)

•  Primary user detection – A secondary user monitors for the presence of a

primary user’s signal on target channels •  Existing methods for primary user detection

– Energy detection •  E.g., [Shellhammer et al. 06 ]

– Feature detection •  E.g., [Goh et al. 07], [Sahai et al. 05] �


• 11/21/10

• 9

Computer Science

Attacks against Primary User Detection �

•  Primary user emulation (PUE) attacks –  [Chen et al. 08] �


Computer Science

PUE Attacks �

•  Root cause of PUE attacks –  Lack of authentication

•  Unique constraint –  Cryptographic signatures cannot be used directly –  Federal Communications Commission (FCC) states that

•  Previous solution: received signal strength (RSS) based location distinction [Chen et al. 08] –  Drawbacks: array antennas, overhead, multi-node

collaboration

“no modification to the incumbent system (i.e., primary user) should be required to accommodate opportunistic use of the spectrum by secondary users”


Computer Science

Our Objective�

•  Develop a method for primary user authentication that – Can distinguish primary users’ signals in the

presence of attackers, and – Follows the FCC constraint

•  Our contribution –  Integrated cryptographic and wireless link

signatures


• 11/21/10

• 10

Computer Science

Assumptions and Threat Model

•  Primary users –  Are at fixed locations (e.g., TV towers) –  Under physical protection

•  Attackers –  Objective: getting an unfair share of the bandwidth –  Method: blocking other users’ accesses to target channels –  Capabilities: forge, insert, and high transmit power –  Restriction: cannot get close to the primary user


Computer Science

Preliminaries on Wireless Communications �

•  Multipath effect and channel impulse response


• The received signal is the sum of all signal copies �

• Multipath components

Component response: Characterizes the distortion that each path has on the multipath component

Channel impulse response: The superposition of all component responses

29

Computer Science

Wireless Link Signature [Patwari & Kasera ’07]

•  Observation – The channel impulse response changes as the

receiver or the transmitter changes location

•  A channel impulse response is referred to as a (wireless) link signature


• 11/21/10

• 11

Computer Science

Our Approach

The helper node, deployed close to the primary user, serves as a bridge�

Intuition: PU and attacker are at different locations different link signatures


A chicken first or egg first problem? To authenticate PU SU needs to know link signature To know link signature SU needs to authenticate PU

Computer Science

Two Levels of Authentication �

•  Authentication at a secondary user –  Training: cryptographic signature link signature –  After training: link signature

•  Authentication at a helper node –  The helper node transmits signals only when the primary

user is not transmitting –  How to enable the helper node to authenticate the primary

user’s signal


Computer Science

Authentication at Helper Node: Intuition


If T and R are close to each other, the amplitude of the multipath component that travels on path 1 should be much larger than that travels on path 2�

33

• 11/21/10

• 12

Computer Science

Authentication at A Helper Node �

•  Let d be the amplitude ratio between both multipath components �


How to determine the threshold w? How well does this method work?

34

Computer Science

Two Types of Errors

•  False negative – The attacker’s signal is incorrectly identified as the

primary user’s signal

•  False alarm – The primary user’s signal is incorrectly identified

as the attacker’s signal


Computer Science

How to Determine the Threshold

•  The threshold w is determined – Based on the requirement for false negative and

false alarm rates – For example


• 11/21/10

• 13

Computer Science

Probabilities of False Negative/Alarm �

•  Probabilities of false negative/alarm vs. distance from the attacker to the helper node �

CSC/ECE 774 37 Dr. Peng Ning

For a 0.05 probability of false alarm � For a 0.05 probability of false negative �

Computer Science

Selected Experimental Results

•  CRAWDAD data set [Patwari & Kasera ’07] –  Over 9,300 channel impulse

response measurements (i.e., link signatures)

–  An indoor environment with obstacles (e.g., cubicle offices and furniture) and scatters (e.g., windows and doors).


Computer Science

Selected Experimental Results (Cont’d)

•  False alarm v.s. false negative


€

r =d(primary user, attacker)

d(primary user, helper node)

39

• 11/21/10

• 14

Computer Science

Selected Experimental Results (Cont’d) �

•  Measured link signature by our prototype (GNU Radio; USRP) –  Distance between helper node and primary user is 0.5

meters, and the distance between helper node and attacker is 15 meters


Computer Science

Conclusion

•  Security of wireless physical layer is necessary –  Anti-jamming wireless communication; authentication of

signal; privacy; …

•  Using wireless physical layer properties helps –  Proximity based access control; device authentication; PUE

defense; …

•  More research is needed! •  My prediction

–  Wireless physical layer security will be a fruitful research area in the next 5 – 10 years


CSC/ECE 774 Advanced Network Security - Peng Ning @ NC State

Documents

Transcript of CSC/ECE 774 Advanced Network Security - Peng Ning @ NC State