1.
The process of converting from plaintext to ciphertext is known as deciphering
or decryption. (T)
2.
When using symmetric encryption it is very important to keep the algorithm
secret. (F)
3.
DES uses a 56-bit block and a 64-bit key. (F)
4.
A prime concern with DES has been its vulnerability to brute-force attack
because of its relatively short key length (T)
5.
There are no practical cryptanalytic attacks on 3DES. (T)
6.
The Nonce must be a data block that is unique to each execution of the
encryption operation and may be a counter, a timestamp, or a message number. (T)
7.
Asymmetric encryption can be used for confidentiality but not for
authentication. (F)
8.
If the authenticator is encrypted with the sender's private key, it serves as a
signature that verifies origin, content, and sequencing. (T)
9.
is 950 a multiplicative inverse of 14 in mod 1023 (T)
10.
The MD5 takes 512 bits as an input and produces 512 as an output (F)
b-
Select the correct answer and put the result in the table below:
1.
A __________ attack involves trying every possible key until an intelligible
translation of the ciphertext is obtained.
A)
brute-force
B)
Caesar attack
C)
ciphertext only
D)
chosen plaintext
E)
None of these
2.
If both sender and receiver use the same key, the system is referred to as:
A)
public-key encryption
B)
two-key
C)
asymmetric
D)
Symmetric encryption
E)
None of these
3.
A sequence of plaintext elements is replaced by a __________ of that sequence
which means that no elements are added, deleted or replaced in the sequence,
but rather the order in which the elements appear in the sequence is changed.
A)
permutation
B)
diffusion
C)
stream
D)
substitution
E)
None of these
4.
The greater the number of rounds, the __________ it is to perform
cryptanalysis.
A)
easier
B)
less difficult
C)
equally difficult
D)
harder
E)
None of these
5.
A change in one bit of the plaintext or one bit of the key should produce a
change in many bits of the
ciphertext.
This is referred to as the __________ effect.
A)
avalanche B)
Confusion C) diffusion D) none of these
6.
Triple DES makes use of __________ stages of the DES algorithm, using a total
of two or three distinct
keys.
A)
nine B) six C) twelve D) three E) None of these
7.
The ___________ perform encryption as ( ) 1 1 C Enc IV P key = Å and the following sequence of
(
) i key i 1 i C = Enc
C ÅP - , where i = 1,n and IV is an initial
vector
A)
Cipher Block
Chaining
mode
CBC
B)
Electronic
Codebook
mode
ECB
C)
Cipher
Feedback
mode
CFB
D)
Counter mode
CTR
E)
None of these
8.
In ___________ there is an opportunities for parallel execution in encryption
A.
CBC B. CTR C. ECB D. CFB E) None of these
9.
Asymmetric encryption can be used for __________ .
A.
both confidentiality and authentication B. neither confidentiality nor authentication
C.
confidentiality D. authentication E) None of these
10.
A _____________ accepts a variable length block
of data as input and produces a fixed size hash value
h = H(M).
A.
hash resistance B. hash value C. hash function D. hash code E) None of
these
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