<s>
In	O
cryptography	O
,	O
CAST-256	B-Algorithm
(	O
or	O
CAST6	B-Algorithm
)	O
is	O
a	O
symmetric-key	B-Algorithm
block	O
cipher	O
published	O
in	O
June	O
1998	O
.	O
</s>
<s>
It	O
was	O
submitted	O
as	O
a	O
candidate	O
for	O
the	O
Advanced	B-Algorithm
Encryption	I-Algorithm
Standard	I-Algorithm
(	O
AES	B-Algorithm
)	O
;	O
however	O
,	O
it	O
was	O
not	O
among	O
the	O
five	O
AES	B-Algorithm
finalists	O
.	O
</s>
<s>
It	O
is	O
an	O
extension	O
of	O
an	O
earlier	O
cipher	O
,	O
CAST-128	B-Algorithm
;	O
both	O
were	O
designed	O
according	O
to	O
the	O
"	O
CAST	O
"	O
design	O
methodology	O
invented	O
by	O
Carlisle	O
Adams	O
and	O
Stafford	O
Tavares	O
.	O
</s>
<s>
CAST-256	B-Algorithm
uses	O
the	O
same	O
elements	O
as	O
CAST-128	B-Algorithm
,	O
including	O
S-boxes	B-Algorithm
,	O
but	O
is	O
adapted	O
for	O
a	O
block	O
size	O
of	O
128	O
bits	O
twice	O
the	O
size	O
of	O
its	O
64-bit	O
predecessor	O
.	O
</s>
<s>
(	O
A	O
similar	O
construction	O
occurred	O
in	O
the	O
evolution	O
of	O
RC5	B-Algorithm
into	O
RC6	B-Algorithm
)	O
.	O
</s>
<s>
CAST-256	B-Algorithm
is	O
composed	O
of	O
48	O
rounds	O
,	O
sometimes	O
described	O
as	O
12	O
"	O
quad-rounds	O
"	O
,	O
arranged	O
in	O
a	O
generalized	O
Feistel	B-Algorithm
network	I-Algorithm
.	O
</s>
<s>
In	O
RFC	O
2612	O
,	O
the	O
authors	O
state	O
that	O
,	O
"	O
The	O
CAST-256	B-Algorithm
cipher	O
described	O
in	O
this	O
document	O
is	O
available	O
worldwide	O
on	O
a	O
royalty-free	O
and	O
licence-free	O
basis	O
for	O
commercial	O
and	O
non-commercial	O
uses.	O
"	O
</s>
<s>
Currently	O
,	O
the	O
best	O
public	O
cryptanalysis	O
of	O
CAST-256	B-Algorithm
in	O
the	O
standard	O
single	O
secret	O
key	O
setting	O
that	O
works	O
for	O
all	O
keys	O
is	O
the	O
zero-correlation	O
cryptanalysis	O
breaking	O
28	O
rounds	O
with	O
2246.9	O
time	O
and	O
298.8	O
data	O
.	O
</s>
