How does MAC address randomization affect BlueZoo analytics?

Different BlueZoo measurements have been impacted differently by the advent of MAC address randomization.

BACKGROUND

Wi-Fi has evolved enormously since it was first introduced in the 1990s. Originally, all MAC addresses were “Global” (i.e. not “Local”) addresses consisting of a 6-hexidecimal-character (3-byte) Organizationally Unique Identifier (OUI) that identified the company making the equipment, and a 6-hexadecimal-character (3-byte) serial number.

Starting in 2014, after revelations by Edward Snowden about the tracking of mobile phones using Wi-Fi, Apple iPhones began probing for access points using “Local” MAC addresses, where bit “b1” of the first byte of the MAC address is set. Google’s Android phones adopted “Local” MAC addresses in 2017. Phones from both companies are able to probe and connect to access points using Local MAC addresses--though not all phones provide these capabilities and others don’t use them by default.

Broadcasting local MAC addresses introduces the possibility of MAC address collisions, but these are still infinitesimally rare because there are 2^46 (70 trillion) different possibilities.

BLUEZOO ANALYTICS

When smartphones probe with local MAC addresses, it has negligible impact on the BlueZoo “visitors” (occupancy) and “visits” (impression) measurements. It has a material impact on “unique visitors / recurrence” measurements where BlueZoo must rely on the share of smartphones that broadcast global MAC addresses (e.g. 10%) because BlueZoo cannot expect to see the same local MAC address one day to the next. Instead, BlueZoo extrapolates unique visitors counts and recurrence based on this sample (e.g. 10%). The share of smartphones that broadcast global MAC addresses varies geographically and we track this number on a per-sensor basis.

When smartphones probe with local MAC addresses, it has some impact on dwell time…though the lifetime of local MAC addresses makes it possible to use local MAC addresses for many dwell time calculations.

The smartphone landscape continues to evolve, bound by the IEEE 802.11 standard: device ID (MAC address) and power level (RSSI) are immutable elements of the Wi-Fi probes emitted by any device. Because both are fundamental features of Wi-Fi technology, they assure the sustainability of BlueZoo’s technology.