<s>
In	O
cryptography	O
,	O
CIKS-1	B-Algorithm
is	O
a	O
block	O
cipher	O
designed	O
in	O
2002	O
by	O
A.A.	O
Moldovyan	O
and	O
N.A.	O
</s>
<s>
Like	O
its	O
predecessor	O
,	O
Spectr-H64	B-Algorithm
,	O
it	O
relies	O
heavily	O
on	O
permutations	B-Algorithm
of	O
bits	O
,	O
so	O
is	O
better	O
suited	O
to	O
implementation	O
in	O
hardware	O
than	O
in	O
software	O
.	O
</s>
<s>
It	O
uses	O
an	O
8	O
round	O
structure	O
in	O
which	O
half	O
of	O
the	O
block	O
determines	O
the	O
transformation	O
of	O
the	O
other	O
half	O
in	O
each	O
round	O
,	O
similar	O
to	O
a	O
Feistel	B-Algorithm
cipher	I-Algorithm
or	O
RC5	B-Algorithm
.	O
</s>
<s>
CIKS-1	B-Algorithm
uses	O
four	O
types	O
of	O
operations	O
:	O
data-dependent	O
permutations	B-Algorithm
,	O
fixed	O
permutations	B-Algorithm
,	O
XORs	B-Application
,	O
and	O
addition	O
mod	O
4	O
.	O
</s>
<s>
The	O
designers	O
of	O
CIKS-1	B-Algorithm
did	O
n't	O
specify	O
any	O
key	B-Algorithm
schedule	I-Algorithm
for	O
the	O
cipher	O
,	O
but	O
it	O
uses	O
a	O
total	O
key	O
size	O
of	O
256	O
bits	O
.	O
</s>
<s>
Kidney	O
,	O
Heys	O
,	O
and	O
Norvell	O
showed	O
that	O
round	B-Algorithm
keys	I-Algorithm
of	O
low	O
Hamming	O
weight	O
are	O
relatively	O
weak	O
,	O
so	O
keys	O
should	O
be	O
chosen	O
carefully	O
.	O
</s>
<s>
The	O
same	O
researchers	O
have	O
also	O
proposed	O
a	O
differential	O
cryptanalysis	O
of	O
CIKS-1	B-Algorithm
which	O
uses	O
256	O
chosen	O
plaintexts	O
.	O
</s>
