Information Technology Reference
In-Depth Information
a,c)
e
b,d)
V
1
V
2
V
3
V
4
V
5
V
6
(
V
,
e
)
S
n
;
m
e
X
V'
n
1
1
(
e
)
P
2
x
k
;1
(
e
)
P
2
x
k
;1
(
e
)
P
2
x
k
;1
m
(
e
)
P
m
;1
S
n
;
m
V
m
k
n
b)
:
n
=32;
m
= 96
d)
:
n
=64;
m
= 192
(
e
)
P
6
k
;1
V'
1
V'
2
V'
3
V'
4
V'
5
V'
6
Y
a)
:
k
= 16
c)
:
k
= 32
Fig. 4.
Structure of the boxes
P
(
e
)
96;1
(a),
S
(
V
,
e
)
32;96
(b),
P
(
e
)
192;1
(c), and
S
(
V
,
e
)
64;192
(d)
attack [1]. The switchable operation in the ciphers SCO-1, SCO-2, and SCO-3 are used
in a way preventing possibility to define homogeneity of the encryption procedure by
choosing certain types of keys.
Figure 5 presents round encryption function of SCO-1. The 32-bit round subkeys
are denoted as
K
r
,
G
r
,and
T
r
. Two input data subblocks
A
and
B
are of the 32-bit length.
The operational boxes
S
(
e
)
32;96
,
S
(
e
)
32;96
and
P
(
e
)
32;1
have been specified in Section 2.2. The
extension box
E
forming the controlling vectors is described as follows
V
1
=(
2
×
l
7
,
l
8
,
l
1
,
l
2
,
l
16
,
l
15
,
l
10
,
l
9
,
l
5
,
l
6
,
l
3
,
l
4
,
l
11
,
l
12
,
l
13
,
l
14
)
,
V
2
=(
l
9
,
l
10
,
l
11
,
l
12
,
l
1
,
l
2
,
l
7
,
l
8
,
l
13
,
l
14
,
l
15
,
l
16
,
l
5
,
l
6
,
l
3
,
l
4
)
,
V
3
=(
l
13
,
l
14
,
l
15
,
l
16
,
l
5
,
l
6
,
l
3
,
l
4
,
l
1
,
l
2
,
l
7
,
l
8
,
l
9
,
l
10
,
l
11
,
l
12
)
,
V
4
=(
l
21
,
l
22
,
l
29
,
l
30
,
l
25
,
l
26
,
l
23
,
l
24
,
l
31
,
l
32
,
l
27
,
l
28
,
l
17
,
l
18
,
l
19
,
l
20
)
,
V
5
=(
l
31
,
l
32
,
l
27
,
l
28
,
l
17
,
l
18
,
l
19
,
l
20
,
l
29
,
l
30
,
l
25
,
l
26
,
l
21
,
l
22
,
l
23
,
l
24
)
,
V
6
=(
l
19
,
l
20
,
l
23
,
l
24
,
l
27
,
l
28
,
l
29
,
l
30
,
l
21
,
l
22
,
l
17
,
l
18
,
l
32
,
l
31
,
l
25
,
l
26
)
,
where bits
l
i
corresponds to vector
L
=(
l
1
,
l
2
,...,
l
32
)
that is input of the
E
-box and the
. The second-type extension box
E
used in SCO-1
output vector is
V
=(
V
1
,
V
2
,...,
V
6
)
is specified as follows:
E
(
L
>>>
16
,where
L
>>>
k
L
)=
E
(
)
denotes rotation of the word
L
by
k
bits:
∀
i
∈{
1
,...,
n
−
k
}
we have
y
i
=
x
i
+
k
and
∀
i
∈{
n
−
k
+
1
,...,
n
}
we have
y
i
=
x
i
+
k
−
n
. The extension boxes has been constructed in accordance with the following
criteria:
1.
Let X be the input n-bit vector of the box
S
(
e
)
32;96
. Then for all L and i the bit x
i
should be permuted depending on six different bits of L.
2.
For all i the bit l
i
should define exactly three bits of V .
The generalized encryption procedure is described as follows.
1. Perform the initial transformation (IT):
A
:
=
A
⊕
G
0
B
:
=
B
⊕
T
0
,where
A
and
B
are input 32-bit data subblocks.
2. For rounds
r
Using the round subkeys
K
r
,
G
r
,and
T
r
perform the
round transformation and then swap data subblocks
=
1to8do
{
.
3. Swap data subblocks and perform the final transformation (FT):
A
:
}
=
A
⊕
G
9
,
B
:
=
B
⊕
T
9
.