<s>
A	O
device	B-Protocol
fingerprint	I-Protocol
or	O
machine	B-Protocol
fingerprint	I-Protocol
is	O
information	O
collected	O
about	O
the	O
software	O
and	O
hardware	B-Architecture
of	O
a	O
remote	O
computing	O
device	O
for	O
the	O
purpose	O
of	O
identification	O
.	O
</s>
<s>
The	O
information	O
is	O
usually	O
assimilated	O
into	O
a	O
brief	O
identifier	O
using	O
a	O
fingerprinting	B-Algorithm
algorithm	I-Algorithm
.	O
</s>
<s>
A	O
browser	B-Protocol
fingerprint	I-Protocol
is	O
information	O
collected	O
specifically	O
by	O
interaction	O
with	O
the	O
web	B-Application
browser	I-Application
of	O
the	O
device	O
.	O
</s>
<s>
Device	B-Protocol
fingerprints	I-Protocol
can	O
be	O
used	O
to	O
fully	O
or	O
partially	O
identify	O
individual	O
devices	O
even	O
when	O
persistent	O
cookies	O
(	O
and	O
zombie	O
cookies	O
)	O
cannot	O
be	O
read	O
or	O
stored	O
in	O
the	O
browser	B-Application
,	O
the	O
client	O
IP	O
address	O
is	O
hidden	O
,	O
or	O
one	O
switches	O
to	O
another	O
browser	B-Application
on	O
the	O
same	O
device	O
.	O
</s>
<s>
Basic	O
web	B-Application
browser	I-Application
configuration	O
information	O
has	O
long	O
been	O
collected	O
by	O
web	O
analytics	O
services	O
in	O
an	O
effort	O
to	O
measure	O
real	O
human	O
web	O
traffic	O
and	O
discount	O
various	O
forms	O
of	O
click	O
fraud	O
.	O
</s>
<s>
Since	O
its	O
introduction	O
in	O
the	O
late	O
1990s	O
,	O
client-side	B-Language
scripting	I-Language
has	O
gradually	O
enabled	O
the	O
collection	O
of	O
an	O
increasing	O
amount	O
of	O
diverse	O
information	O
,	O
with	O
some	O
computer	O
security	O
experts	O
starting	O
to	O
complain	O
about	O
the	O
ease	O
of	O
bulk	O
parameter	O
extraction	O
offered	O
by	O
web	B-Application
browsers	I-Application
as	O
early	O
as	O
2003	O
.	O
</s>
<s>
In	O
2005	O
,	O
researchers	O
at	O
University	O
of	O
California	O
,	O
San	O
Diego	O
showed	O
how	O
TCP	B-Protocol
timestamps	O
could	O
be	O
used	O
to	O
estimate	O
the	O
clock	O
skew	O
of	O
a	O
device	O
,	O
and	O
consequently	O
to	O
remotely	O
obtain	O
a	O
hardware	B-Protocol
fingerprint	I-Protocol
of	O
the	O
device	O
.	O
</s>
<s>
In	O
2010	O
,	O
Electronic	O
Frontier	O
Foundation	O
launched	O
a	O
website	O
where	O
visitors	O
can	O
test	O
their	O
browser	B-Protocol
fingerprint	I-Protocol
.	O
</s>
<s>
After	O
collecting	O
a	O
sample	O
of	O
470161	O
fingerprints	B-Algorithm
,	O
they	O
measured	O
at	O
least	O
18.1	O
bits	O
of	O
entropy	O
possible	O
from	O
browser	B-Protocol
fingerprinting	I-Protocol
,	O
but	O
that	O
was	O
before	O
the	O
advancements	O
of	O
canvas	B-Protocol
fingerprinting	I-Protocol
,	O
which	O
claims	O
to	O
add	O
another	O
5.7	O
bits	O
.	O
</s>
<s>
In	O
2012	O
,	O
Keaton	O
Mowery	O
and	O
Hovav	O
Shacham	O
,	O
researchers	O
at	O
University	O
of	O
California	O
,	O
San	O
Diego	O
,	O
showed	O
how	O
the	O
HTML5	B-Language
canvas	I-Language
element	O
could	O
be	O
used	O
to	O
create	O
digital	O
fingerprints	B-Algorithm
of	O
web	B-Application
browsers	I-Application
.	O
</s>
<s>
In	O
2014	O
,	O
5.5	O
%	O
of	O
Alexa	O
top	O
10,000	O
sites	O
were	O
found	O
to	O
use	O
canvas	B-Protocol
fingerprinting	I-Protocol
scripts	O
served	O
by	O
a	O
total	O
of	O
20	O
domains	O
.	O
</s>
<s>
The	O
overwhelming	O
majority	O
(	O
95%	O
)	O
of	O
the	O
scripts	O
were	O
served	O
by	O
AddThis	O
,	O
which	O
started	O
using	O
canvas	B-Protocol
fingerprinting	I-Protocol
in	O
January	O
that	O
year	O
,	O
without	O
the	O
knowledge	O
of	O
some	O
of	O
its	O
clients	O
.	O
</s>
<s>
In	O
2015	O
,	O
a	O
feature	O
to	O
protect	O
against	O
browser	B-Protocol
fingerprinting	I-Protocol
was	O
introduced	O
in	O
Firefox	B-Application
version	O
41	O
,	O
but	O
it	O
has	O
been	O
since	O
left	O
in	O
an	O
experimental	O
stage	O
,	O
not	O
initiated	O
by	O
default	O
.	O
</s>
<s>
The	O
same	O
year	O
a	O
feature	O
named	O
Enhanced	O
Tracking	O
Protection	O
was	O
introduced	O
in	O
Firefox	B-Application
version	O
42	O
to	O
protect	O
against	O
tracking	O
during	O
private	B-Protocol
browsing	I-Protocol
by	O
blocking	O
scripts	O
from	O
third	O
party	O
domains	O
found	O
in	O
the	O
lists	O
published	O
by	O
Disconnect	B-Operating_System
Mobile	I-Operating_System
.	O
</s>
<s>
At	O
WWDC	O
2018	O
Apple	O
announced	O
that	O
Safari	B-Application
on	O
macOS	B-Device
Mojave	I-Device
"	O
presents	O
simplified	O
system	O
information	O
when	O
users	O
browse	O
the	O
web	O
,	O
preventing	O
them	O
from	O
being	O
tracked	O
based	O
on	O
their	O
system	O
configuration.	O
"	O
</s>
<s>
In	O
2019	O
,	O
starting	O
from	O
Firefox	B-Application
version	O
69	O
,	O
Enhanced	O
Tracking	O
Protection	O
has	O
been	O
turned	O
on	O
by	O
default	O
for	O
all	O
users	O
also	O
during	O
non-private	O
browsing	O
.	O
</s>
<s>
The	O
feature	O
was	O
first	O
introduced	O
to	O
protect	O
private	B-Protocol
browsing	I-Protocol
in	O
2015	O
and	O
was	O
then	O
extended	O
to	O
standard	O
browsing	O
as	O
an	O
opt-in	O
feature	O
in	O
2018	O
.	O
</s>
<s>
Motivation	O
for	O
the	O
device	B-Protocol
fingerprint	I-Protocol
concept	O
stems	O
from	O
the	O
forensic	O
value	O
of	O
human	B-Algorithm
fingerprints	I-Algorithm
.	O
</s>
<s>
In	O
order	O
to	O
uniquely	O
distinguish	O
over	O
time	O
some	O
devices	O
through	O
their	O
fingerprints	B-Algorithm
,	O
the	O
fingerprints	B-Algorithm
must	O
be	O
both	O
sufficiently	O
diverse	O
and	O
sufficiently	O
stable	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
assimilation	O
of	O
an	O
additional	O
browser	B-Application
setting	O
into	O
the	O
browser	B-Protocol
fingerprint	I-Protocol
would	O
usually	O
increase	O
diversity	O
,	O
but	O
it	O
would	O
also	O
reduce	O
stability	O
,	O
because	O
if	O
a	O
user	O
changes	O
that	O
setting	O
,	O
then	O
the	O
browser	B-Protocol
fingerprint	I-Protocol
would	O
change	O
as	O
well	O
.	O
</s>
<s>
A	O
certain	O
degree	O
of	O
instability	O
can	O
be	O
compensated	O
by	O
linking	O
together	O
fingerprints	B-Algorithm
that	O
,	O
although	O
partially	O
different	O
,	O
might	O
probably	O
belong	O
to	O
the	O
same	O
device	O
.	O
</s>
<s>
This	O
can	O
be	O
accomplished	O
by	O
a	O
simple	O
rule-based	O
linking	O
algorithm	O
(	O
which	O
,	O
for	O
example	O
,	O
links	O
together	O
fingerprints	B-Algorithm
that	O
differ	O
only	O
for	O
the	O
browser	B-Application
version	O
,	O
if	O
that	O
increases	O
with	O
time	O
)	O
or	O
machine	O
learning	O
algorithms	O
.	O
</s>
<s>
Applications	O
that	O
are	O
locally	O
installed	O
on	O
a	O
device	O
are	O
allowed	O
to	O
gather	O
a	O
great	O
amount	O
of	O
information	O
about	O
the	O
software	O
and	O
the	O
hardware	B-Architecture
of	O
the	O
device	O
,	O
often	O
including	O
unique	O
identifiers	O
such	O
as	O
the	O
MAC	O
address	O
and	O
serial	O
numbers	O
assigned	O
to	O
the	O
machine	O
hardware	B-Architecture
.	O
</s>
<s>
The	O
most	O
prominent	O
example	O
is	O
that	O
of	O
web	B-Application
browsers	I-Application
,	O
which	O
have	O
been	O
proved	O
to	O
expose	O
diverse	O
and	O
stable	O
information	O
in	O
such	O
an	O
amount	O
to	O
allow	O
remote	O
identification	O
,	O
see	O
.	O
</s>
<s>
The	O
collection	O
of	O
a	O
large	O
amount	O
of	O
diverse	O
and	O
stable	O
information	O
from	O
web	B-Application
browsers	I-Application
is	O
possible	O
for	O
most	O
part	O
due	O
to	O
client-side	B-Language
scripting	I-Language
languages	O
,	O
which	O
were	O
introduced	O
in	O
the	O
late	O
'	O
90s	O
.	O
</s>
<s>
Today	O
there	O
are	O
several	O
open-source	O
browser	B-Protocol
fingerprinting	I-Protocol
libraries	O
,	O
such	O
as	O
FingerprintJS	O
,	O
ImprintJS	O
,	O
and	O
ClientJS	O
,	O
where	O
FingerprintJS	O
is	O
updated	O
the	O
most	O
often	O
and	O
supersedes	O
ImprintJS	O
and	O
ClientJS	O
to	O
a	O
large	O
extent	O
.	O
</s>
<s>
Browsers	B-Application
provide	O
their	O
name	O
and	O
version	O
,	O
together	O
with	O
some	O
compatibility	O
information	O
,	O
in	O
the	O
User-Agent	B-Protocol
request	O
header	O
.	O
</s>
<s>
Instead	O
,	O
the	O
type	O
and	O
version	O
of	O
the	O
browser	B-Application
can	O
be	O
inferred	O
from	O
the	O
observation	O
of	O
quirks	O
in	O
its	O
behavior	O
:	O
for	O
example	O
,	O
the	O
order	O
and	O
number	O
of	O
HTTP	B-Protocol
header	I-Protocol
fields	I-Protocol
is	O
unique	O
to	O
each	O
browser	B-Application
family	O
and	O
,	O
most	O
importantly	O
,	O
each	O
browser	B-Application
family	O
and	O
version	O
differs	O
in	O
its	O
implementation	O
of	O
HTML5	B-Application
,	O
CSS	B-Language
and	O
JavaScript	B-Language
.	O
</s>
<s>
Such	O
differences	O
can	O
be	O
remotely	O
tested	O
by	O
using	O
JavaScript	B-Language
.	O
</s>
<s>
A	O
Hamming	O
distance	O
comparison	O
of	O
parser	O
behaviors	O
has	O
been	O
shown	O
to	O
effectively	O
fingerprint	B-Algorithm
and	O
differentiate	O
a	O
majority	O
of	O
browser	B-Application
versions	O
.	O
</s>
<s>
A	O
combination	O
of	O
extensions	B-Protocol
or	O
plugins	B-Application
unique	O
to	O
a	O
browser	B-Application
can	O
be	O
added	O
to	O
a	O
fingerprint	B-Algorithm
directly	O
.	O
</s>
<s>
Extensions	B-Protocol
may	O
also	O
modify	O
how	O
any	O
other	O
browser	B-Application
attributes	O
behave	O
,	O
adding	O
additional	O
complexity	O
to	O
the	O
user	O
's	O
fingerprint	B-Algorithm
.	O
</s>
<s>
Adobe	B-Operating_System
Flash	I-Operating_System
and	O
Java	B-Device
plugins	B-Application
were	O
widely	O
used	O
to	O
access	O
user	O
information	O
before	O
their	O
deprecation	O
.	O
</s>
<s>
User	B-Protocol
agents	I-Protocol
may	O
provide	O
system	B-Architecture
hardware	I-Architecture
information	O
,	O
such	O
as	O
phone	O
model	O
,	O
in	O
the	O
HTTP	B-Protocol
header	I-Protocol
.	O
</s>
<s>
Properties	O
about	O
the	O
user	O
's	O
operating	B-General_Concept
system	I-General_Concept
,	O
screen	B-General_Concept
size	I-General_Concept
,	O
screen	O
orientation	O
,	O
and	O
display	B-General_Concept
aspect	I-General_Concept
ratio	I-General_Concept
can	O
be	O
also	O
retrieved	O
by	O
using	O
JavaScript	B-Language
to	O
observe	O
the	O
result	O
of	O
CSS	B-Language
media	O
queries	O
.	O
</s>
<s>
The	O
fingerprinter	O
could	O
determine	O
which	O
sites	O
the	O
browser	B-Application
had	O
previously	O
visited	O
within	O
a	O
list	O
it	O
provided	O
,	O
by	O
querying	O
the	O
list	O
using	O
JavaScript	B-Language
with	O
the	O
CSS	B-Language
selector	O
.	O
</s>
<s>
However	O
,	O
browsers	B-Application
have	O
since	O
then	O
mitigated	O
this	O
risk	O
.	O
</s>
<s>
The	O
letter	O
bounding	O
boxes	O
differ	O
between	O
browsers	B-Application
based	O
on	O
anti-aliasing	B-Algorithm
and	O
font	O
hinting	O
configuration	O
and	O
can	O
be	O
measured	O
by	O
JavaScript	B-Language
.	O
</s>
<s>
Canvas	B-Protocol
fingerprinting	I-Protocol
uses	O
the	O
HTML5	B-Language
canvas	I-Language
element	O
,	O
which	O
is	O
used	O
by	O
WebGL	B-Library
to	O
render	O
2D	O
and	O
3D	O
graphics	O
in	O
a	O
browser	B-Application
,	O
to	O
gain	O
identifying	O
information	O
about	O
the	O
installed	O
graphics	B-Application
driver	I-Application
,	O
graphics	B-Device
card	I-Device
,	O
or	O
graphics	B-Architecture
processing	I-Architecture
unit	I-Architecture
(	O
GPU	B-Architecture
)	O
.	O
</s>
<s>
Canvas-based	O
techniques	O
may	O
also	O
be	O
used	O
to	O
identify	O
installed	O
fonts	O
.	O
</s>
<s>
Furthermore	O
,	O
if	O
the	O
user	O
does	O
not	O
have	O
a	O
GPU	B-Architecture
,	O
CPU	B-Device
information	O
can	O
be	O
provided	O
to	O
the	O
fingerprinter	O
instead	O
.	O
</s>
<s>
A	O
canvas	B-Protocol
fingerprinting	I-Protocol
script	O
first	O
draws	O
text	O
of	O
specified	O
font	O
,	O
size	O
,	O
and	O
background	O
color	O
.	O
</s>
<s>
The	O
image	O
of	O
the	O
text	O
as	O
rendered	O
by	O
the	O
user	O
's	O
browser	B-Application
is	O
then	O
recovered	O
by	O
the	O
ToDataURL	O
Canvas	B-Language
API	B-Application
method	O
.	O
</s>
<s>
The	O
hashed	O
text-encoded	O
data	O
becomes	O
the	O
user	O
's	O
fingerprint	B-Algorithm
.	O
</s>
<s>
Canvas	B-Protocol
fingerprinting	I-Protocol
methods	O
have	O
been	O
shown	O
to	O
produce	O
5.7	O
bits	O
of	O
entropy	O
.	O
</s>
<s>
Because	O
the	O
technique	O
obtains	O
information	O
about	O
the	O
user	O
's	O
GPU	B-Architecture
,	O
the	O
information	O
entropy	O
gained	O
is	O
"	O
orthogonal	O
"	O
to	O
the	O
entropy	O
of	O
previous	O
browser	B-Protocol
fingerprint	I-Protocol
techniques	O
such	O
as	O
screen	O
resolution	O
and	O
JavaScript	B-Language
capabilities	O
.	O
</s>
<s>
Benchmark	O
tests	O
can	O
be	O
used	O
to	O
determine	O
whether	O
a	O
user	O
's	O
CPU	B-Device
utilizes	O
AES-NI	B-Algorithm
or	O
Intel	B-Device
Turbo	I-Device
Boost	I-Device
by	O
comparing	O
the	O
CPU	B-Device
time	O
used	O
to	O
execute	O
various	O
simple	O
or	O
cryptographic	O
algorithms	O
.	O
</s>
<s>
Specialized	O
APIs	B-Application
can	O
also	O
be	O
used	O
,	O
such	O
as	O
the	O
Battery	O
API	B-Application
,	O
which	O
constructs	O
a	O
short-term	O
fingerprint	B-Algorithm
based	O
on	O
the	O
actual	O
battery	O
state	O
of	O
the	O
device	O
,	O
or	O
OscillatorNode	O
,	O
which	O
can	O
be	O
invoked	O
to	O
produce	O
a	O
waveform	O
based	O
on	O
user	O
entropy	O
.	O
</s>
<s>
A	O
device	O
's	O
hardware	B-Architecture
ID	O
,	O
which	O
is	O
a	O
cryptographic	B-Algorithm
hash	I-Algorithm
function	I-Algorithm
specified	O
by	O
the	O
device	O
's	O
vendor	O
,	O
can	O
also	O
be	O
queried	O
to	O
construct	O
a	O
fingerprint	B-Algorithm
.	O
</s>
<s>
Different	O
approaches	O
exist	O
to	O
mitigate	O
the	O
effects	O
of	O
browser	B-Protocol
fingerprinting	I-Protocol
and	O
improve	O
users	O
 '	O
privacy	O
by	O
preventing	O
unwanted	O
tracking	O
,	O
but	O
there	O
is	O
no	O
ultimate	O
approach	O
that	O
can	O
prevent	O
fingerprinting	O
while	O
keeping	O
the	O
richness	O
of	O
a	O
modern	O
web	B-Application
browser	I-Application
.	O
</s>
<s>
Users	O
may	O
attempt	O
to	O
reduce	O
their	O
fingerprintability	O
by	O
selecting	O
a	O
web	B-Application
browser	I-Application
which	O
minimizes	O
the	O
availability	O
of	O
identifying	O
information	O
,	O
such	O
as	O
browser	B-Application
fonts	O
,	O
device	O
ID	O
,	O
canvas	B-Language
element	I-Language
rendering	O
,	O
WebGL	B-Library
information	O
,	O
and	O
local	B-Protocol
IP	I-Protocol
address	I-Protocol
.	O
</s>
<s>
As	O
of	O
2017	O
Microsoft	B-Application
Edge	I-Application
is	O
considered	O
to	O
be	O
the	O
most	O
fingerprintable	O
browser	B-Application
,	O
followed	O
by	O
Firefox	B-Application
and	O
Google	B-Application
Chrome	I-Application
,	O
Internet	B-Application
Explorer	I-Application
,	O
and	O
Safari	B-Application
.	O
</s>
<s>
Among	O
mobile	B-Application
browsers	I-Application
,	O
Google	B-Application
Chrome	I-Application
and	O
Opera	B-Protocol
Mini	I-Protocol
are	O
most	O
fingerprintable	O
,	O
followed	O
by	O
mobile	O
Firefox	B-Application
,	O
mobile	O
Edge	O
,	O
and	O
mobile	O
Safari	B-Application
.	O
</s>
<s>
Tor	O
Browser	B-Application
disables	O
fingerprintable	O
features	O
such	O
as	O
the	O
canvas	B-Language
and	O
WebGL	B-Library
API	B-Application
and	O
notifies	O
users	O
of	O
fingerprint	B-Algorithm
attempts	O
.	O
</s>
<s>
the	O
user	B-Protocol
agent	I-Protocol
)	O
may	O
create	O
a	O
reduction	O
in	O
diversity	O
,	O
but	O
the	O
contrary	O
could	O
be	O
also	O
achieved	O
if	O
the	O
spoofed	O
information	O
differentiates	O
the	O
user	O
from	O
all	O
the	O
others	O
who	O
do	O
not	O
use	O
such	O
a	O
strategy	O
more	O
than	O
the	O
real	O
browser	B-Application
information	O
.	O
</s>
<s>
Spoofing	O
the	O
information	O
differently	O
at	O
each	O
site	O
visit	O
,	O
for	O
example	O
by	O
perturbating	O
the	O
sound	O
and	O
canvas	B-Language
rendering	O
with	O
a	O
small	O
amount	O
of	O
random	O
noise	O
,	O
allows	O
a	O
reduction	O
of	O
stability	O
.	O
</s>
<s>
This	O
technique	O
has	O
been	O
adopted	O
by	O
the	O
Brave	B-Application
browser	I-Application
in	O
2020	O
.	O
</s>
<s>
by	O
disabling	O
JavaScript	B-Language
or	O
using	O
NoScript	B-Operating_System
)	O
can	O
sometimes	O
render	O
websites	O
unusable	O
.	O
</s>
<s>
The	O
preferred	O
approach	O
is	O
to	O
block	O
only	O
third-party	O
domains	O
that	O
seem	O
to	O
track	O
people	O
,	O
either	O
because	O
they	O
're	O
found	O
on	O
a	O
blacklist	O
of	O
tracking	O
domains	O
(	O
the	O
approach	O
followed	O
by	O
most	O
ad	O
blockers	O
)	O
or	O
because	O
the	O
intention	O
of	O
tracking	O
is	O
inferred	O
by	O
past	O
observations	O
(	O
the	O
approach	O
followed	O
by	O
Privacy	B-Operating_System
Badger	I-Operating_System
)	O
.	O
</s>
<s>
Different	O
browsers	B-Application
on	O
the	O
same	O
machine	O
would	O
usually	O
have	O
different	O
fingerprints	B-Algorithm
,	O
but	O
if	O
both	O
browsers	B-Application
are	O
not	O
protected	O
against	O
fingerprinting	O
,	O
then	O
the	O
two	O
fingerprints	B-Algorithm
could	O
be	O
identified	O
as	O
originating	O
from	O
the	O
same	O
machine	O
.	O
</s>
