<s>
In	O
cryptography	O
,	O
decorrelation	B-General_Concept
theory	I-General_Concept
is	O
a	O
system	O
developed	O
by	O
Serge	O
Vaudenay	O
in	O
1998	O
for	O
designing	O
block	O
ciphers	O
to	O
be	O
provably	O
secure	O
against	O
differential	O
cryptanalysis	O
,	O
linear	O
cryptanalysis	O
,	O
and	O
even	O
undiscovered	O
cryptanalytic	O
attacks	O
meeting	O
certain	O
broad	O
criteria	O
.	O
</s>
<s>
Ciphers	O
designed	O
using	O
these	O
principles	O
include	O
COCONUT98	B-Algorithm
and	O
the	O
AES	O
candidate	O
DFC	B-Algorithm
,	O
both	O
of	O
which	O
have	O
been	O
shown	O
to	O
be	O
vulnerable	O
to	O
some	O
forms	O
of	O
cryptanalysis	O
not	O
covered	O
by	O
the	O
theory	O
.	O
</s>
<s>
According	O
to	O
Vaudenay	O
,	O
the	O
decorrelation	B-General_Concept
theory	I-General_Concept
has	O
four	O
tasks	O
:	O
1	O
)	O
the	O
definition	O
of	O
a	O
measurement	O
for	O
the	O
decorrelation	O
,	O
which	O
usually	O
relies	O
on	O
a	O
matrix	O
norm	O
;	O
2	O
)	O
the	O
construction	O
of	O
simple	O
primitive	O
or	O
"	O
decorrelation	O
module	O
"	O
with	O
a	O
quite	O
good	O
decorrelation	O
;	O
3	O
)	O
the	O
construction	O
of	O
cryptographic	O
algorithms	O
with	O
decorrelation	O
modules	O
so	O
that	O
the	O
primitive	O
can	O
be	O
inherited	O
by	O
the	O
algorithm	O
;	O
and	O
,	O
4	O
)	O
proving	O
that	O
the	O
decorrelation	O
provides	O
security	O
against	O
attacks	O
.	O
</s>
