  Browser fingerprinting consists in collecting attributes from a web browser
to build a browser fingerprint. In this work, we assess the adequacy of browser
fingerprints as an authentication factor, on a dataset of 4,145,408
fingerprints composed of 216 attributes. It was collected throughout 6 months
from a population of general browsers. We identify, formalize, and assess the
properties for browser fingerprints to be usable and practical as an
authentication factor. We notably evaluate their distinctiveness, their
stability through time, their collection time, and their size in memory. We
show that considering a large surface of 216 fingerprinting attributes leads to
an unicity rate of 81% on a population of 1,989,365 browsers. Moreover, browser
fingerprints are known to evolve, but we observe that between consecutive
fingerprints, more than 90% of the attributes remain unchanged after nearly 6
months. Fingerprints are also affordable. On average, they weigh a dozen of
kilobytes, and are collected in a few seconds. We conclude that browser
fingerprints are a promising additional web authentication factor.
