Cryptography Reference
In-Depth Information
Example 3.2.
The S-box input
b
=(100101)
2
indicates the row 11
2
= 3 (i.e., fourth
row, numbering starts with 00
2
) and the column 0010
2
= 2 (i.e., the third column).
If the input
b
is fed into S-box 1, the output is
S
1
(37 = 100101
2
)=8 = 1000
2
.
1
1
fourth row
100101
third column
0010
Fig. 3.12
Example of the decoding of the input 100101
2
by S-box 1
Table 3.2
S-box
S
1
S
1
0123456789101112131415
0
14 04 13 01 02 15 11 08 03 10 06 12 05 09 00 07
1
00 15 07 04 14 02 13 01 10 06 12 11 09 05 03 08
2
04 01 14 08 13 06 02 11 15 12 09 07 03 10 05 00
3
15 12 08 02 04 09 01 07 05 11 03 14 10 00 06 13
Table 3.3
S-box
S
2
S
2
0123456789101112131415
0
15 01 08 14 06 11 03 04 09 07 02 13 12 00 05 10
1
03 13 04 07 15 02 08 14 12 00 01 10 06 09 11 05
2
00 14 07 11 10 04 13 01 05 08 12 06 09 03 02 15
3
13 08 10 01 03 15 04 02 11 06 07 12 00 05 14 09
Table 3.4
S-box
S
3
S
3
0123456789101112131415
0
10 00 09 14 06 03 15 05 01 13 12 07 11 04 02 08
1
13 07 00 09 03 04 06 10 02 08 05 14 12 11 15 01
2
13 06 04 09 08 15 03 00 11 01 02 12 05 10 14 07
3
01 10 13 00 06 09 08 07 04 15 14 03 11 05 02 12
The S-boxes are the core of DES in terms of cryptographic strength. They are
the only nonlinear element in the algorithm and provide confusion. Even though the
entire specification of DES was released by NBS/NIST in 1977, the motivation for
the choice of the S-box tables was never completely revealed. This often gave rise
