Path Construction Under MAC Address Randomization

MPhil Thesis Defence


Title: "Path Construction Under MAC Address Randomization"

By

Mr. Lichao HAN


Abstract

In order to discover the available access points in its proximity, a 
WiFi-enabled device periodically broadcasts probe requests. Traditionally, the 
probes encapsulate their globally unique physical addresses. By chronologically 
ordering the probes according to their addresses, the behavior of the user 
carrying the device can be analyzed. To better protect user privacy, recent 
operating systems have been using randomized (virtual) MAC addresses in 
probing, with addresses altered at unpredictably short intervals. This 
fragments the path of a user and makes analytics on the user over the long term 
challenging.

In this thesis, we study how to concatenate and sequence the probes of devices 
emitting virtual addresses as paths, each for a device. For generality, we do 
not consider the location information of the probes, and there may be an 
unknown number of devices emitting randomized addresses. Though our work does 
not discover the physical addresses of the devices, it enables aggregated or 
individual analytics over the long term, for example, dwell time, heatmap, 
people counting and so on.

We propose FIESEQ, which is based on the keen observations of the Information 
Elements (IE) and sequence number (SEQ) in probe requests. We first use the IE 
fields which may identify devices as fingerprints to group the probes likely 
belonging to a device. Since a group may contain multiple devices, we use the 
gap and growth rate of the sequence numbers in probes to identify the path of 
each device. Besides F-measure, we propose a novel metric called Degree of 
Concatenation (DOC), which evaluates how the probes belonging to the same 
device are scattered into multiple constructed paths. Using several realworld 
datasets, we demonstrate that FIESEQ is able to path devices with randomized 
MAC addresses with high accuracy and outperforms the state-of-the-art 
techniques.


Date:			Friday, 20 July 2018

Time:			2:30pm - 4:30pm

Venue:			Room 3494
 			Lifts 25/26

Committee Members:	Prof. Gary Chan (Supervisor)
 			Prof. Cunsheng Ding (Chairperson)
 			Dr. Kai Chen


**** ALL are Welcome ****