Cryptography Reference
In-Depth Information
Table 10.3
The Inverse Initial Permutation
IP
−
1
of the DES
08 8 6 6 4 4 2
97 7 5 5 3 3 1
86 6 4 4 2 2 0
75 5 3 3 1 1 9
64 4 2 2 0 0 8
53 3 1 1 9 9 7
42 2 0 0 8 8 6
33
1
41
9
49
17
57
25
Table 10.4
The Expansion Function
E
of the DES
212345456789
8
9
10
11
12
13
12
13
14
15
16
17
16
17
18
19
20
21
20
21
22
23
24
25
24
25
26
27
28
29
28
29
30
31
32
1
28
28
), and
PC
2 maps two 28-bit strings to a 48-bit string (i.e.,
{
0
,
1
}
×{
0
,
1
}
28
28
48
).
PC
2:
{
0
,
1
}
×{
0
,
1
}
→{
0
,
1
}
•
The function
PC
1 is illustrated in Table 10.7. The upper half of the table
specifies the bits that are taken from
k
to construct
C
, and the lower half
of the table specifies the bits that are taken from
k
to construct
D
.If
k
=
k
1
k
2
...k
64
,then
C
=
k
57
k
49
...k
36
and
D
=
k
63
k
55
...k
4
. Note that the
8 parity bits
k
8
,k
16
,...,k
64
are not considered and occur neither in
C
nor in
D
.
•
The function
PC
2 is illustrated in Table 10.8. The two 28-bit strings that are
input to the function are concatenated to form a 56-bit string. If this string is
b
1
b
2
...b
56
, then the function
PC
2 turns this string into
b
14
b
17
...b
32
.Note
Table 10.5
The Permutation
P
of the DES
6 7 0 1 9 2 8 7
1
15
23
26
5
18
31
20
2
8
24
14
32
27
3
9
19
13
30
6
22
11
4
25
