<s>
Keystroke	B-Application
dynamics	I-Application
,	O
keystroke	B-Application
biometrics	I-Application
,	O
typing	B-Application
dynamics	O
and	O
typing	B-Application
biometrics	I-Application
refer	O
to	O
the	O
detailed	O
timing	O
information	O
that	O
describes	O
when	O
each	O
key	O
was	O
pressed	O
and	O
released	O
as	O
a	O
person	O
is	O
typing	B-Application
on	O
a	O
computer	B-Device
keyboard	I-Device
.	O
</s>
<s>
The	O
behavioural	O
biometric	O
of	O
Keystroke	B-Application
Dynamics	I-Application
uses	O
the	O
manner	O
and	O
rhythm	O
in	O
which	O
an	O
individual	O
types	O
characters	O
on	O
a	O
keyboard	B-Device
or	O
keypad	O
.	O
</s>
<s>
The	O
keystroke	O
rhythms	O
of	O
a	O
user	O
are	O
measured	O
to	O
develop	O
a	O
unique	O
biometric	O
template	O
of	O
the	O
user	O
's	O
typing	B-Application
pattern	O
for	O
future	O
authentication	O
.	O
</s>
<s>
Keystrokes	O
are	O
separated	O
into	O
static	O
and	O
dynamic	O
typing	B-Application
,	O
which	O
are	O
used	O
to	O
help	O
distinguish	O
between	O
authorized	O
and	O
unauthorized	O
users	O
.	O
</s>
<s>
Data	O
needed	O
to	O
analyse	O
keystroke	B-Application
dynamics	I-Application
is	O
obtained	O
by	O
keystroke	O
logging	O
.	O
</s>
<s>
Normally	O
,	O
all	O
that	O
is	O
retained	O
when	O
logging	O
a	O
typing	B-Application
session	O
is	O
the	O
sequence	O
of	O
characters	O
corresponding	O
to	O
the	O
order	O
in	O
which	O
keys	O
were	O
pressed	O
.	O
</s>
<s>
it	O
was	O
typed	B-Application
rapidly	O
or	O
slowly	O
,	O
</s>
<s>
the	O
sender	O
used	O
the	O
left	B-Device
shift	I-Device
key	I-Device
,	O
the	O
right	B-Device
shift	I-Device
key	I-Device
,	O
or	O
the	O
caps-lock	B-Device
key	O
to	O
make	O
the	O
"	O
i	O
"	O
turn	O
into	O
a	O
capitalized	O
letter	O
"	O
I	O
,	O
"	O
</s>
<s>
the	O
sender	O
typed	B-Application
any	O
letters	O
wrong	O
initially	O
and	O
then	O
went	O
back	O
and	O
corrected	O
them	O
,	O
or	O
if	O
they	O
got	O
them	O
right	O
the	O
first	O
time	O
.	O
</s>
<s>
During	O
the	O
late	O
nineteenth	O
century	O
,	O
telegram	B-Application
operators	O
began	O
to	O
develop	O
unique	O
"	O
signatures	O
"	O
that	O
could	O
be	O
identified	O
simply	O
by	O
their	O
tapping	O
rhythm	O
.	O
</s>
<s>
The	O
techniques	O
used	O
to	O
do	O
this	O
vary	O
widely	O
in	O
sophistication	O
,	O
and	O
range	O
from	O
statistical	O
techniques	O
to	O
artificial	B-Application
intelligence	I-Application
(	O
AI	B-Application
)	O
approaches	O
like	O
neural	B-Architecture
networks	I-Architecture
.	O
</s>
<s>
The	O
time	O
to	O
seek	O
and	O
depress	O
a	O
key	O
(	O
seek-time	O
)	O
and	O
the	O
time	O
the	O
key	O
is	O
held-down	O
(	O
hold-time	O
)	O
may	O
be	O
very	O
characteristic	O
for	O
a	O
person	O
,	O
regardless	O
of	O
how	O
fast	O
they	O
are	O
typing	B-Application
overall	O
.	O
</s>
<s>
There	O
is	O
an	O
entire	O
taxonomy	O
of	O
errors	O
,	O
such	O
as	O
this	O
person	O
's	O
most	O
common	O
"	O
substitutions	O
"	O
,	O
"	O
reversals	O
"	O
,	O
"	O
drop-outs	O
"	O
,	O
"	O
double-strikes	O
"	O
,	O
"	O
adjacent	O
letter	O
hits	O
"	O
,	O
"	O
homonyms	O
"	O
,	O
hold-length-errors	O
(	O
for	O
a	O
shift	B-Device
key	I-Device
held	O
down	O
too	O
short	O
or	O
too	O
long	O
a	O
time	O
)	O
.	O
</s>
<s>
Keystroke	B-Application
dynamics	I-Application
is	O
part	O
of	O
a	O
larger	O
class	O
of	O
biometrics	O
known	O
as	O
behavioural	O
biometrics	O
,	O
a	O
field	O
in	O
which	O
observed	O
patterns	O
are	O
statistical	O
in	O
nature	O
.	O
</s>
<s>
Because	O
of	O
this	O
inherent	O
uncertainty	O
,	O
a	O
commonly	O
held	O
belief	O
is	O
that	O
behavioural	O
biometrics	O
are	O
not	O
as	O
reliable	O
as	O
biometrics	O
used	O
for	O
authentication	O
based	O
on	O
physically	O
observable	O
characteristics	O
such	O
as	O
fingerprints	B-Algorithm
or	O
retinal	O
scans	O
or	O
DNA	O
.	O
</s>
<s>
The	O
benefit	O
to	O
keystroke	B-Application
dynamics	I-Application
(	O
as	O
well	O
as	O
other	O
behavioural	O
biometrics	O
)	O
is	O
that	O
FRR/FAR	O
can	O
be	O
adjusted	O
by	O
changing	O
the	O
acceptance	O
threshold	O
at	O
the	O
individual	O
level	O
.	O
</s>
<s>
One	O
of	O
the	O
major	O
problems	O
that	O
keystroke	B-Application
dynamics	I-Application
runs	O
into	O
is	O
that	O
a	O
person	O
's	O
typing	B-Application
varies	O
substantially	O
during	O
a	O
day	O
and	O
between	O
different	O
days	O
and	O
may	O
be	O
affected	O
by	O
any	O
number	O
of	O
external	O
factors	O
.	O
</s>
