1. SeRLoc: Secure Range-Independent Localization for Wireless Sensor Networks
Presenter: Yawen Wei
Author: Loukas Lazos and Radha Poovendran
Network Security Lab, Dept. of EE,
University of Washington, Seattle, WA

2. Problem:
Enabling nodes of a wireless sensor network to determine their location even in the presence of malicious adversaries.
Design Goal:
Decentralized implementation
Resource efficiency
Robustness against security threats

3. Outline
Overview
SeRloc Algorithm
Comparison & Simulation
Conclusion

4. Overview What is Localization System?
How to determine position? (Schemes)
1.range-dependent
GPS, Active Badge, Active Bat, Cricket
2.range-independent
DV-hop, amorphous localization, APIT, Centroid
Why security?

5. Range-dependent Location System
Time of arrival (TOA)
Angle of arrival
Signal strength
RF, acoustic, infrared and ultrasound
Disadvantages
(x1,y1); (x2,y2);(x3,y3)

6. SeRloc Algorithm Network Model Location Determination Security Scheme
Threat Analysis

7. Network Model N: unknown locations
L: known locations and orientations, “locators”
spatial homogeneous Poisson point process

8. SeRloc: Location Determination
Secure Range-Independent Localization
a. the locator’s coordinates
b. the angles of the antenna boundary lines
c. R: the locator-sensor-communication range
d. Overlapping region
e. CoG (Center of Gravity)

9. Step 1: Locators heard
Step 2: Search area

10. Determination of the search area
A rectangular area of size less than
A rectangular area of size greater than

11. Step 3: Overlapping region-Majority vote
Step 4: Location estimation

12. SeRloc: Security Scheme
Encryption:
Global symmetric key
Sensor s & locator shares pairwise key
Locator ID authentication
Collision-resistant hash function (e.g. MD5)
Beacon of locator Li

13. SeRloc: Threat Analysis
Types: Wormhole / Sybil / Compromised nodes
Wormhole attack
Packet leshes: geographical / temporal
Time measuring in challenge-reply scheme

14. Wormholes 1. Sector uniqueness property
: area of locators heard by origin point
: area of locators heard by s

15. Wormholes 2. Communication range violation property
A sensor cannot hear two locators that are more than 2R apart

17. the first message: q = k − 1
the last message: q = 0
All locators wait for a q ∗ Ts time

18. SeRloc: Threat Analysis
Sybil Attack and Compromised nodes
Multiple network entities
Assume sensor identities
Assume locators (Not directly heard)

19. Outline
Overview
SeRloc Algorithm
Comparison & Simulation
Conclusion

20. Comparison
Dv-hop and Amorphous localization

21. Comparison
APIT localization 5

22. Simulation Localization Error vs. Locators heard
Localization Error vs. Antenna Sectors
Localization Error vs. Sector Error
Localization Error vs. GPS Error
Communication Cost vs. Locators Heard

23. Conclusion Secure localization in WSN Range independent Decentralized
Security mechanisms
Threats
Higher accuracy and fewer locators