<s>
A	O
mimic	B-General_Concept
function	I-General_Concept
changes	O
a	O
file	O
so	O
it	O
assumes	O
the	O
statistical	O
properties	O
of	O
another	O
file	O
.	O
</s>
<s>
That	O
is	O
,	O
if	O
is	O
the	O
probability	O
of	O
some	O
substring	O
occurring	O
in	O
,	O
then	O
a	O
mimic	B-General_Concept
function	I-General_Concept
,	O
recodes	O
so	O
that	O
approximates	O
for	O
all	O
strings	O
of	O
length	O
less	O
than	O
some	O
.	O
</s>
<s>
It	O
is	O
commonly	O
considered	O
to	O
be	O
one	O
of	O
the	O
basic	O
techniques	O
for	O
hiding	B-Application
information	I-Application
,	O
often	O
called	O
steganography	O
.	O
</s>
<s>
The	O
simplest	O
mimic	B-General_Concept
functions	I-General_Concept
use	O
simple	O
statistical	O
models	O
to	O
pick	O
the	O
symbols	O
in	O
the	O
output	O
.	O
</s>
<s>
Even	O
more	O
sophisticated	O
models	O
use	O
reversible	O
Turing	B-Architecture
machines	I-Architecture
.	O
</s>
