July 01, 2019

Network Security Assignment - SEM 7


Question
Identify the security principle: When data must arrive at receiver exactly as it was sent
Nonrepudiation
Integrity
Confidentiality
Authentication

Question
Identify the security principle: When a sender cannot deny sending a sent message
Nonrepudiation
Integrity
Confidentiality
Authentication

Question
When an attacker performs a capture of a data unit and its subsequent retransmission, which attack he is performing?
Denial of service
Disruption
Spoofing
Replay

Question
What is the block cipher structure in DES?
RSA
Feistel
Shannon
Diffie-Hellman

Question
What does it mean that a hash function H is “collision resistant”?
It is easy to compute h = H(M) for any message M
Given h, it is infeasible to find x such that H(x) = h
Given x, it is infeasible to find y such that H(x) = H(y)
It is infeasible to find any x, y such that H(y) = H(x)

Question
Company XYZ wants to elect their new president by electronic voting. Which security principle will be applicable if only employees are allowed to vote.
Authentication
Integrity
Non-repudiation
Confidentiality

Question
Company XYZ wants to elect their new president by electronic voting. Which security principle will be applicable if No one should be able to see who the other voted for.
Authentication
Integrity
Non-repudiation
Confidentiality

Question
Company XYZ wants to elect their new president by electronic voting. Which security principle will be applicable if An employee should be able to verify that his vote was not changed.
Authentication
Integrity
Non-repudiation
Confidentiality

Question
Company XYZ wants to elect their new president by electronic voting. Which security principle will be applicable if The employee cannot deny having voted
Authentication
Integrity
Non-repudiation
Confidentiality

Question
Alice and Bob share a common secret password, P. Using this, they want to authenticate each other. Which of the following is the correct way to do so?
Alice sends P to Bob. Bob verifies P to authenticate Alice.
Alice sends the message encrypted with P. If Bob is able to decrypt it successfully, Alice is authenticated.
Alice sends a random number encrypted with P. Bob decrypts the number and authenticates Alice.
Bob sends Alice a random challenge. Alice returns the challenge encrypted with P.
Bob sends Alice a random challenge encrypted with P. Alice returns the challenge+1 encrypted with P.

Question
In which algorithmic mode does the corresponding cipher text block repeat if a plain text block repeats in the original message? Select all correct options
ECB
CBC
CFB
OFB

Question
In which algorithmic mode can the ciphering operation be performed in parallel? Select all correct options
ECB
CBC
CFB
OFB

Question
Consider the following scenario.A and B both share a secret key with a Key Distribution Center (KDC). We call these keys Ka-kdc and Kb-kdc respectively. A wants to establish a shared symmetric key with B using the following steps:A sends a message to the KDC encrypted by Ka-kdc. Encrypt Ka-kdc(B)KDC responds by sending Encrypt Ka-kdc(Kb-kdc)A now corresponds with B using Kb-kdc. Is this solution correct or incorrect. Justify.
The solution is correct. The KDC first verifies A since Ka-kdc is known only to A. Only the KDC and B know Kb-kdc.
The solution is incorrect. The KDC first verifies A since Ka-kdc is known only to A. Only the KDC and B know Kb-kdc.

Question
Consider the following scenario.Alice wants to send assignment grades from her home computer to Bob at work. She wants to prevent anyone from modifying the grades. So Alice sends a message M to Bob along with H = Hash(M). Bob receives M and H, and calculates H’ = Hash(M). Only if H = H', Bob accepts the message. Is this solution foolproof?
Yes because if the message is changed, the hash will also change and Bob will be able to detect the modified
No because the intruder may replace M with M' and H with Hash(M').

Question
A class has n students. How many symmetric secret keys are needed if each students wants to send secret messages to another?
1
n
n*n
n(n-1)/2

Question
A class has n students. If they all trust the classteacher, how many symmetric secret keys are needed?
1
n
n*n
n(n-1)/2

Question
If the class teacher distributes a temporary one-time session key for a communicating pair, how many keys are needed? The temporary key is encrypted and sent to both members.
1
n
n*n
n(n-1)/2

Question
If public key cryptography is used, how many keys are needed in all?
1
2
n
2n

Question
An attack on a cipher text message where the attacker attempts to use all possible permutations and combinations is called:
Brute force attack
Man-in-the-middle
Chosen plaintext
Chosen ciphertext

Question
Which of the following is most efficient to achieve confidentiality and digital signature for message M
Use public key cryptography to hide message M by applying Encrypt-with-Kreceiverpublic(M) and sign message M applying Encrypt-with-Ksenderprivate(M)
Use public key cryptography to hide message M by applying Encrypt-with-Kreceiverpublic(M) and sign message by applying Encrypt-with-Ksenderprivate(Hash(M))
Use public key cryptography to share key by applying Encrypt-with-Kreceiverpublic(Kshared), hide message by applying Encrypt-with-Kshared(M) and sign message by applying Encrypt-with-Ksenderprivate(Hash(M))
Use private key cryptography to hide message M by applying Encrypt-with-Kshared(M) and sign message by applying Encrypt-with-Kshared(Hash(M))

Question
Key distribution often involves the use of _________ which are generated and distributed for temporary use between two parties.
Session keys
Public keys
private keys
Certificates

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