<s>
MARS	B-Algorithm
is	O
a	O
block	O
cipher	O
that	O
was	O
IBM	O
's	O
submission	O
to	O
the	O
Advanced	O
Encryption	O
Standard	O
process	O
.	O
</s>
<s>
MARS	B-Algorithm
was	O
selected	O
as	O
an	O
AES	O
finalist	O
in	O
August	O
1999	O
,	O
after	O
the	O
AES2	O
conference	O
in	O
March	O
1999	O
,	O
where	O
it	O
was	O
voted	O
as	O
the	O
fifth	O
and	O
last	O
finalist	O
algorithm	O
.	O
</s>
<s>
The	O
MARS	B-Algorithm
design	O
team	O
included	O
Don	O
Coppersmith	O
,	O
who	O
had	O
been	O
involved	O
in	O
the	O
creation	O
of	O
the	O
previous	O
Data	B-Algorithm
Encryption	I-Algorithm
Standard	I-Algorithm
(	O
DES	B-Algorithm
)	O
twenty	O
years	O
earlier	O
.	O
</s>
<s>
IBM	O
's	O
official	O
report	O
stated	O
that	O
MARS	B-Algorithm
and	O
Serpent	B-Algorithm
were	O
the	O
only	O
two	O
finalists	O
to	O
implement	O
any	O
form	O
of	O
safety	O
net	O
with	O
regard	O
to	O
would-be	O
advances	O
in	O
cryptographic	O
mathematics	O
.	O
</s>
<s>
The	O
Twofish	B-Algorithm
team	O
made	O
a	O
similar	O
statement	O
about	O
its	O
cipher	O
.	O
</s>
<s>
MARS	B-Algorithm
has	O
a	O
128-bit	O
block	O
size	O
and	O
a	O
variable	O
key	O
size	O
of	O
between	O
128	O
and	O
448	O
bits	O
(	O
in	O
32-bit	O
increments	O
)	O
.	O
</s>
<s>
Unlike	O
most	O
block	O
ciphers	O
,	O
MARS	B-Algorithm
has	O
a	O
heterogeneous	O
structure	O
:	O
several	O
rounds	O
of	O
a	O
cryptographic	O
core	O
are	O
"	O
jacketed	O
"	O
by	O
unkeyed	O
mixing	O
rounds	O
,	O
together	O
with	O
key	B-Algorithm
whitening	I-Algorithm
.	O
</s>
<s>
Subkeys	O
with	O
long	O
runs	O
of	O
ones	O
or	O
zeroes	O
may	O
lead	O
to	O
efficient	O
attacks	O
on	O
MARS	B-Algorithm
.	O
</s>
<s>
A	O
meet-in-the-middle	O
attack	O
published	O
in	O
2004	O
by	O
John	O
Kelsey	O
and	O
Bruce	O
Schneier	O
can	O
break	O
21	O
out	O
of	O
32	O
rounds	O
of	O
MARS	B-Algorithm
.	O
</s>
