CIS 3362 Test #2: Symmetric Block Ciphers Solution
Date: 10/13/2010
1) (10 pts) In order to teach DES, Arup has come up with a new symmetric block cipher, similar
to DES, with 16 bit blocks and a 16 bit key, called mini-DES. It follows a similar structure to
DES and has an IP matrix as follows:
13
9
5
1
16
12
8
4
15
11
7
3
14
10
6
2
What is the corresponding matrix, IP
-1
that matches this matrix?
4
16
1
2
8
3
15
1
1
7
2
14
1
0
6
1
13
9
5
Grading: ½ point for each entry, 2 pts bonus if all are correct.
2) (4 pts) If the input to S-box
6 was 110100, what is the output?
Row = 10 = 2, Col = 1010 = 10, the entry in row 2, col 10 of S-box 6 is 4.
4, grading: full credit for 4, 2 pts for 0, 10, 1, 13, 1 pt for 1, 7 14.
3) (5 pts) Why are the numbers 8, 16, 24, 32, 40, 48, 56 and 64 missing from the matrix PC-1?