Princess Nora Bint Abdul Rahman University
College of Computer and Information Systems
Network and Data Communication Department
Network Security ( NET 536)
Sheet#1 ( Cryptography)
Student Name:
Student ID
Section No
Question 1:
A. Encrypt the following message using transposition cipher based
on the key shown below:
The message is “ SWEET HEART ”.
The ciphertext will be:____________________________
B. Is the encryption algorithm classified as monoalphabetic cipher or
polyalphabetic cipher? And why?
Princess Nora Bint Abdul Rahman University
College of Computer and Information Systems
Network and Data Communication Department
Network Security ( NET 536)
Sheet#1 ( Cryptography)
Question 2:
A. Alice wants to encrypt a message to Bob by using the
shift cipher algorithm “Caesar cipher” and the key= 20.
The plaintext = “QUIZ”.
A 00
B 01
C 02
D 03
E 04
F 05
G 06
H 07
I 08
J 09
K 10
L 11
M 12
N 13
O 14
P 15
Q 16
R 17
S 18
T 19
U 20
V 21
W 22
X 23
B. In A, the encryption algorithm classified as monoalphabetic cipher
or polyalphabetic cipher? And why?
Y 24
Z 25
Princess Nora Bint Abdul Rahman University
College of Computer and Information Systems
Network and Data Communication Department
Network Security ( NET 536)
Sheet#1 ( Cryptography)
Question 3:
a. In DES, if the M = 0000 2000 8000 0000 ( Hex), Find the IP(M).
IP(M)
Original M
IP(M)=………………………………………………………………………………….. ( Hex)
b. In DEA, the S-Box3 given below, if b3= 110010, the output would be:
S-Box 3
10 0 9
13 7 0
13 6 4
1 10 13
14
9
9
0
6
3
8
6
3
4
15
9
15
6
3
8
5
10
0
7
1
2
11
4
13
8
1
15
12
5
2
14
7
14
12
3
11
12
5
11
4
11
10
5
2
15
14
2
8
1
7
12
Princess Nora Bint Abdul Rahman University
College of Computer and Information Systems
Network and Data Communication Department
Network Security ( NET 536)
Sheet#1 ( Cryptography)
Question 4:
A. Perform encryption using the RSA algorithm
for the following word :
Plaintext: “IF”. Where p=3; q=11; e=7;
Suppose Alice sends this word to Bob by
representing each alphabetic as an integer
between 0 and 25 (A 0 …… Z25).
Hint: Encrypt each number separately.
A 00
B 01
C 02
D 03
E 04
F 05
G 06
H 07
I 08
J 09
K 10
L 11
M 12
N 13
O 14
P 15
Q 16
R 17
S 18
T 19
U 20
V 21
W 22
X 23
Y 24
Z 25
B. Using RSA algorithm, find the d, Where p=5; q=11; e=3.
Decrypt the following word: “PRLJ” using RSA algorithm.
Decrypt each character separately; then, write the plaintext that
the receiver can read.
GOOD LUCK