<s>
In	O
cryptography	O
,	O
CIPHERUNICORN-A	B-Algorithm
is	O
a	O
block	O
cipher	O
created	O
by	O
NEC	O
in	O
2000	O
.	O
</s>
<s>
The	O
algorithm	O
uses	O
a	O
16-round	O
Feistel	B-Algorithm
network	I-Algorithm
structure	O
similar	O
to	O
its	O
predecessor	O
,	O
CIPHERUNICORN-E	B-Algorithm
,	O
but	O
with	O
significant	O
changes	O
.	O
</s>
<s>
The	O
round	O
function	O
is	O
even	O
more	O
complicated	O
than	O
that	O
of	O
CIPHERUNICORN-E	B-Algorithm
,	O
but	O
the	O
extra	O
mixing	O
function	O
between	O
rounds	O
has	O
been	O
removed	O
.	O
</s>
<s>
The	O
round	O
function	O
is	O
still	O
split	O
into	O
two	O
nearly	O
parallel	O
computations	O
;	O
both	O
of	O
these	O
are	O
Feistel	B-Algorithm
networks	I-Algorithm
themselves	O
.	O
</s>
<s>
The	O
first	O
part	O
(	O
the	O
main	O
stream	O
)	O
is	O
a	O
10-round	O
Feistel	B-Algorithm
network	I-Algorithm
,	O
using	O
four	O
8×	O
8-bit	O
S-boxes	B-Algorithm
much	O
like	O
the	O
ones	O
from	O
CIPHERUNICORN-E	B-Algorithm
.	O
</s>
<s>
This	O
second	O
,	O
6-round	O
Feistel	B-Algorithm
network	I-Algorithm
uses	O
modular	O
multiplication	O
,	O
as	O
well	O
as	O
two	O
of	O
the	O
S-boxes	B-Algorithm
.	O
</s>
<s>
In	O
contrast	O
to	O
CIPHERUNICORN-E	B-Algorithm
,	O
subkeys	O
are	O
included	O
only	O
at	O
the	O
beginning	O
of	O
each	O
main	O
round	O
.	O
</s>
<s>
The	O
key	B-Algorithm
schedule	I-Algorithm
of	O
CIPHERUNICORN-A	B-Algorithm
makes	O
repeated	O
use	O
of	O
a	O
function	O
called	O
MT	O
,	O
using	O
modular	O
multiplication	O
and	O
all	O
of	O
the	O
S-boxes	B-Algorithm
.	O
</s>
<s>
A	O
flaw	O
was	O
discovered	O
in	O
the	O
key	B-Algorithm
schedule	I-Algorithm
,	O
such	O
that	O
certain	O
keys	O
are	O
equivalent	O
,	O
but	O
it	O
is	O
unknown	O
just	O
how	O
much	O
of	O
a	O
weakness	O
this	O
is	O
.	O
</s>
<s>
The	O
great	O
complexity	O
of	O
CIPHERUNICORN-A	B-Algorithm
'	O
s	O
round	O
function	O
has	O
made	O
it	O
difficult	O
to	O
analyze	O
.	O
</s>
