Cryptography Reference
In-Depth Information
schedule where the subkeys have to be generated in reversed order, as we will see
in Sect. 3.4.
k
64
PC − 1
56
C
D
0
0
28
28
Transform 1
LS
LS
1
1
28
28
C
D
k
PC − 2
1
1
1
48
56
28
28
LS
LS
2
2
LS
LS
16
16
C
D
k
PC − 2
16
16
16
48
56
Fig. 3.14
Key schedule for DES encryption
To derive the 48-bit round keys
k
i
, the two halves are permuted bitwise again
with
PC
2 permutes the 56 input
bits coming from
C
i
and
D
i
and ignores 8 of them. The exact bit-connections of
PC
−
2, which stands for “permuted choice 2”.
PC
−
−
2 are given in Table 3.12.
Table 3.12
Round key permutation
PC
−
2
PC
−
2
14 17 11 24 1 5 3 28
15 6 2110231912 4
2681672720132
41 52 31 37 47 55 30 40
51 45 33 48 44 49 39 56
34 53 46 42 50 36 29 32
