Name:
FUNDEMENTALS OF INFORMATION SECURITY
EXAM I
ANSWER ALL QUESTIONS
A B C D E F G H I J
0 1 2 3 4 5 6 7 8 9
K
10
L M
11 12
N O
13 14
P Q
15 16
R S
17 18
T U V W
19 20 21 22
X
23
Y Z
24 25
1. Encrypt the string: I GET NO PRIVACY SWIMMING IN A GLASS BOWL using a Row
transposition Cipher with the key:
G
3
I
I
O L
7 6
G E
V A
M M I
G L A
L
D F
1
2
T N
C Y
I S
5
8
O P
S W
H
4
R
I
N
S
I
B
A
W
G
S
N
O
2. Expand the key NETWORK SECURITY into a 5x5 Playfair matrix:
3. Use the key matrix of question 2 to decrypt the string:
BHHWG TDWW WHTKF R5SVWY ISISN GCMGX:
4. Indicate whether the following ciphers/key exchange mechanisms are based on private (symmetric) or
public (asymmetric).
Private
Public
a) Enigma
b) AES
c) Elliptic Curve Cryptography
d) El Gamel
e) Blumb Blumb Shub
5. Different modes of operation for block encryption have different error propagation properties. If a
single bit gets changed during transmission how much of the decrypted data stream is in error if the
following modes are being used?
1 Bit 1 Byte 1 Block 1 Block+1 Byte 2 Blocks
Electronic Code Book
Cipher Block Chaining
8-bit Cipher Feedback
Output Feedback
Counter Mode
Rest of
Transmission
6. Draw a diagram illustrating how Cipher Block Chaining works:
7. AES has the following desirable properties:
TRUE
FALSE
a) Advanced Feistel design
b) It supports block and key sizes of 128, 192, and 256 bits
c) Speed and compactness on a wide range of processors
d) The same functions can be used for encryption and decryption
e) The key schedules are the same for encryption and decryption
8. Why is Cipher Block Chaining a good mode for encryption for generating a Message Authentication
Code?
9. List ways in which secret keys can be distributed to two communicating parties (without using public
key cryptography). (4 minimum)
10. What is a nonce and why is it used?
11. What are the three broad categories of applications of public-key cryptosystems?
12. Using the primes 7 & 11 (p & n) discover an asymmetric key pair:
1) Modulus n = p*n
2) Euler totient = (n) = (p-1)(q-1) =
3) Select public key e such that 1 < e < (n) and gcd((n),e) = 1
4) Find private key d such that d = e-1 mod (n),(d * e)mod (n)=1
13. The RSA algorithm has the following properties:
TRUE
a) Advanced Feistel design
b) It is infeasible to derive the private key from the public key
c) Speed and compactness on a wide range of processors
d) The same functions can be used for encryption and decryption
e) It is relatively easy to factorise the modulus ‘n’
FALSE
14. List four general categories of schemes for the distribution of public keys.
15. Authentication functions:
TRUE
FALSE
a) Hash functions do not use keys to form Message Digests
b) Hash functions can use keys to form MACs
c) MAC functions use a secret key
d) A MAC function needs to be reversible (like encryption)
e) A MADC provides a digital signature
16. Why do message exchanges that provide two way authentication always generate the digital signature
before applying encryption?
17. What are the properties a digital signature should have (in terms of verification and authentication
(list three)?
18. What is the difference between direct and arbitrated digital signature schemes?
19. What information is contained in a X.509 certificate?
20. What is a chain of certificates?
21. Why is R64 conversion useful for an email application?
22. What are the five principal services provided by PGP?
23 What are the three parameters, which uniquely identify a Security Association?
24. Give three reasons for the IPSec ESP to include a padding field.
25. When the tunnel mode ESP is used to encrypt an IP packet show, in a diagram, what f8ields are
encrypted and what new fields are added to the original packet (for IPv4 and IPv6)?