CUSTOMER_CODE
SMUDE
DIVISION_CODE
SMUDE
EVENT_CODE
SMUAPR15
ASSESSMENT_CODE MIT4022_SMUAPR15
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
12785
QUESTION_TEXT Discuss overview of Rijndael Algorithm.
SCHEME OF
EVALUATION
Rijndael is a fast algorithm with strong mathematical foundation but
require simple processors for implementation. It primarily uses
substitution, transposition, and the shift, exclusive OR, and addition
operations. Algorithm also uses repeated cycles. There are 9, 11, or
13 cycles for keys of 128, 192, and 256 bits, respectively.
(2 marks)
Each cycle consists of four steps:
*Byte substitution: This step uses a substitution box structure similar
to the DES, substituting each byte of a 128-bit block according to a
substitution table. This is straight confusion operation.
*Shift row: A transposition step for 128- and 192-bit block sizes, row
n is shifted left circular (n-1) bytes; for 256-bit blocks, row 2 is
shifted I byte and rows 3 and 4 are shifted 3 and 4 bytes, respectively.
This is straight confusion operation.
*Mix Column: This step involves shifting left and exclusive-ORing
bits with themselves. These operations provide both confusion and
diffusion.
*Add subkey: here, a portion of the key unique to this cycle is
exclusive-ORed with the cycle result. This operation provides
confusion and incorporates the key. (2 marks each)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
72791
QUESTION_TEXT
Explain how cryptanalyst uses different information to break the
cipher?
SCHEME OF
EVALUATION
a. Ciphertext only: The cryptanalyst decrypt messages based on
probabilities, distributions, and characteristics of the available
ciphertext, plus publicly available knowledge.
b. Full or partial plaintext: the analyst may be fortunate to have a
sample message and its decipherment. In these cases, the analyst
can use what is called a probable plaintext analysis. After doing part
of the decryption, the analyst may find places where the known
message fits with the deciphered parts, thereby giving more clues
about the total translation.
c. Ciphertext of any plaintext: the analyst might have infiltrated
the sender’s transmission process so as to be able to cause
messages to be encrypted and sent at will. This attack is called a
chosen plaintext attack. For instance, the analyst may be able to
insert records into a database and observe the change in statistics
after the insertions. Linear programming some times enables such
an analyst to infer data that should be kept confidential in the
database. This attack is very favorable to the analyst.
d. Algorithm and Ciphertext: the analyst may have both the
encryption algorithm and the ciphertext. In a chosen plaintext
attack, the analyst can run the algorithm on massive amounts of
plaintext to find one plaintext message that encrypt as the
ciphertext. This approach fails if two or more distinct keys can
produce the same ciphertext as the result of encrypting meaningful
plaintext.
e. Ciphertext and Plaintext: the cryptanalyst may lucky enough to
have some pairs of plaintext and matching ciphertext. Then, the
game is to deduce the key by which those pairs were encrypted so
that the same key can be used in cases in which the analyst has only
the ciphertext. (2 marks each)
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
72792
QUESTION_TEXT
List and briefly explain five types of Firewalls
Explanation about the following five types of firewalls:
i. Packet filtering gateways or screening routers
ii. Stateful inspection firewalls
SCHEME OF EVALUATION
iii. Application Proxies
iv. Guards
v. Personal Firewalls
2 x 5 = 10 marks
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
72794
QUESTION_TEXT
List different Session state parameter and Connection state
parameter
SCHEME OF
EVALUATION
Different Session state parameters are :
i. Session ID
ii. Peer Certificate
iii. Compression method
iv. Cipher Suite
v. Master Secret
vi. Is Resumable
5 marks
Different Connection state parameters are:
i. Server and client random number
ii. Server write MAC secret
iii. Client write MAC secret
iv. Server write secret
v. Client write secret
vi. Initialization
vii. Sequence number
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
118697
QUESTION_TEXT Write a short note on IPSec architecture.
Ans:
It provides a set of security services which includes access control,
connectionless integrity, data origin authentication, rejection of
replayed packets, confidentiality. These services are provided at the
IP layer. They can be used by any higher layer protocols.
These security services are met through the use of two traffic security
protocols; the AH and the ESP, and through the use of cryptographic
key management procedures and protocols. The set of IPSec
protocols employed in any context, and the ways in which they are
employed, will be determined by the security and the system
requirements of users, applications, and/or organizations. 4M
SCHEME OF
EVALUATION
When these mechanisms are correctly implemented and deployed,
they will not affect the other parts of the implementation such as
hosts, and other internet components that do not employ these
security mechanisms for protection of their traffic. These mechanisms
are also providing modularity which permits selection of different set
of algorithms without affecting the other parts of the implementation.
So we can say these mechanisms are algorithm–independent. For
example, different user communities may select different set of
algorithms. 4M
A standard set of default algorithms in conjunction with IPSec traffic
protection and key management protocols, is intended to permit
system and application developers to deploy high quality, internet
layer, cryptographic security technology. 2M
QUESTION_TYPE
DESCRIPTIVE_QUESTION
QUESTION_ID
118699
QUESTION_TEXT
Explain the various types of threats in a computing
environment
SCHEME OF
EVALUATION
(Each threat carries 2 ½ marks)
a. Interception
b. Interruption
c. Passive attacks
d. Active attacks