Protecting Against Eavesdroppers with Symmetric Cryptography - Implementing SSL/TLS Using Cryptography and PKI - page 37

This fi ve step procedure is referred to as the Feistel function after its originator.
Graphically, the rounds look like Figure 2-5.

L0 R0

K1

Feistel Function

L1=R0 R1=L0 xor f(R0, K1)

K2

Feistel Function

L2=R1 R2=L1 xor f(R1, K2)

K3

Feistel Function

L3=R2 R3=L2 xor f(R2, K3)

...

L15=R14 R15=L14 xor f(R14, K15)

K16

Feistel Function

L16=R15 R16=L15 xor f(R15, K16)

Figure 2-5: DES overview