The document describes a teaching tool developed in 1996 at Santa Clara University by Professor Edward Schaefer, which involves an 8-bit block plaintext and a 10-bit key to encrypt and decrypt data. It details the processes of initial and inverse permutations, as well as complex and simple permutations used within the encryption algorithm. The document outlines the steps and functions involved in transforming data to ensure secure communication.

1.  Developed 1996 as a teaching tool
 Santa Clara University
 Prof. Edward Schaefer
 Takes an 8-bit block plaintext, a 10 –bit key and
produces an 8-bit block of ciphertext
 Decryption takes the 8-bit block of ciphertext, the
same 10-bit key and produces the original 8-bit
block of plaintext

2. IP
fk
SW
fk
IP - 1
P10
P8
IP
fk
SW
fk
IP - 1
SHIFT
SHIFT
P8
Encryption
Decryption
8-bit plaintext 8-bit plaintext
8-bit ciphertext 8-bit ciphertext
K1 K1
K2 K2

3.  IP – an initial permutation
 fk - a complex, 2-input function
 SW – a simple permutation that swaps the two
nybles
 fk - a complex, 2-input function; again
 IP-1 – inverse permutation of the initial permutation

4. I P
E/P
S0 S1
P4
E/P
S0 S1
P4
SW
I P -1
K 1
K 2
4
4
8
4 4
2 2
4

5. Move the bits of the original character around a little…
k1 k2 k3 k4 k5 k6 k7 k8
k2 k6 k3 k1 k4 k8 k5 k7

6. k4 k1 k2 k3 k2 k3 k4 k1
k1 k2 k3 k4
Expand 4 bits into 8 and permutate them…

7. P10
P8
P8
LS-1 LS-1
LS-2 LS-2
8
8
5 5
5 5
5 5
K1
K2
10

8. k1 k2 k3 k4 k5 k6 k7 k8 k9 k10
k3 k5 k2 k7 k4 k10 k1 k9 k8 k6

9. k1 k2 k3 k4 k5 k6 k7 k8 k9 k10
k6 k3 k7 k4 k8 k5 k10 k9
Permutate 10 into 8

10. k3 k 5 k 2 k 7 k 4
k5 k 2 k 7 k 4 k 3
k10 k1 k9 k8 k6
k1 k9 k8 k6 k10
Left circular shift 1 each 5 bit group

11. k3 k 5 k 2 k 7 k 4
k2 k7 k4 k3 k5
k10 k1 k9 k8 k6
k9 k8 k6 k10 k1
Left circular shift 2 each 5 bit group

12. 1 0 3 2
3 2 1 0
0 2 1 3
3 1 3 2
0 1 2 3
2 0 1 3
3 0 1 0
2 1 0 3
S0 S1