MAC Address Anonymization for Crowd Counting

TL;DR

This paper presents a crowd counting system using WiFi probe requests, employing a hash-based MAC address anonymization method that maintains counting accuracy while protecting user privacy.

Contribution

It introduces a MAC address anonymization procedure for WiFi-based crowd counting that minimizes collision rates and synchronization issues, ensuring accurate estimations.

Findings

Low collision rates in anonymization process

Time-synchronization inaccuracies are negligible

Analytical bounds for collision rate approximation

Abstract

Research has shown that counting WiFi packets called probe requests (PRs) implicitly provides a proxy for the number of people in an area. In this paper, we discuss a crowd counting system involving WiFi sensors detecting PRs over the air, then extracting and anonymizing their media access control (MAC) addresses using a hash-based approach. This paper discusses an anonymization procedure and shows time-synchronization inaccuracies among sensors and hashing collision rates to be low enough to prevent anonymization from interfering with counting algorithms. In particular, we derive an approximation of the collision rate of uniformly distributed identifiers, with analytical error bounds.