<s>
In	O
cryptography	O
,	O
SC2000	B-Algorithm
is	O
a	O
block	O
cipher	O
invented	O
by	O
a	O
research	O
group	O
at	O
Fujitsu	O
Labs	O
.	O
</s>
<s>
Each	O
round	O
consists	O
of	O
S-box	B-Algorithm
lookups	O
,	O
key	O
additions	O
,	O
and	O
an	O
unkeyed	O
two-round	O
Feistel	B-Algorithm
network	I-Algorithm
.	O
</s>
<s>
There	O
are	O
3	O
S-boxes	B-Algorithm
:	O
a	O
4×	O
4-bit	O
one	O
used	O
at	O
the	O
beginning	O
of	O
each	O
round	O
,	O
and	O
a	O
5×	O
5-bit	O
one	O
and	O
6×	O
6-bit	O
one	O
used	O
in	O
the	O
Feistel	B-Algorithm
network	I-Algorithm
.	O
</s>
<s>
No	O
analysis	O
of	O
the	O
full	O
SC2000	B-Algorithm
has	O
been	O
announced	O
,	O
but	O
a	O
reduced	O
version	O
of	O
4.5	O
rounds	O
is	O
susceptible	O
to	O
linear	O
cryptanalysis	O
,	O
and	O
a	O
reduced	O
version	O
of	O
5	O
rounds	O
is	O
susceptible	O
to	O
differential	O
cryptanalysis	O
.	O
</s>
<s>
In	O
2014	O
,	O
Alex	O
Biryukov	O
and	O
Ivica	O
Nikolić	O
found	O
a	O
weakness	O
in	O
the	O
key	B-Algorithm
schedule	I-Algorithm
of	O
SC2000	B-Algorithm
which	O
allows	O
an	O
attacker	O
to	O
find	O
colliding	O
keys	O
which	O
result	O
in	O
identical	O
encryptions	O
in	O
just	O
239	O
time	O
for	O
256	O
bit	O
keys	O
.	O
</s>
