Quiz 7

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1 CSI270 Quiz on Quiz 7, created by Joshua Villy on 08/05/2013.
Joshua Villy
Quiz by Joshua Villy, updated more than 1 year ago
Joshua Villy
Created by Joshua Villy over 11 years ago
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Resource summary

Question 1

Question
The process of transforming ciphertext to plaintext is known as:
Answer
  • Decryption
  • Encryption
  • Key recovery
  • Hashing

Question 2

Question
Which of the following statements is true about the Vernam cipher:
Answer
  • It is a polyalphabetic cipher
  • It is a running-key cipher
  • The encryption key is used for only one message
  • Another name for it is a one-time hash

Question 3

Question
What is the minimum key length for a one-time pad?
Answer
  • 128 bits
  • 64 bits
  • 56 bits
  • The length of the plaintext message

Question 4

Question
All of the following statements about the polyalphabetic cipher are true EXCEPT:
Answer
  • It is a form of one-time pad
  • It is resistant to frequency analysis attacks
  • It uses multiple substitution alphabets
  • It is a type of substitution cipher

Question 5

Question
A running-key cipher can be used when:
Answer
  • The plaintext is longer than the encryption key
  • The plaintext is shorter than the encryption key
  • The plaintext is streaming media
  • The plaintext is changing rapidly

Question 6

Question
In modulo arithmetic, when A – B
Answer
  • 26 is subtracted from the result
  • 100 is added to the result
  • 26 is added to the result
  • 32 is added to the result

Question 7

Question
A computer user is listening to an audio broadcast on the Internet through an SSL VPN. The type of encryption cipher used in this case is:
Answer
  • Block cipher
  • Stream cipher
  • Running key cipher
  • Vernam Cipher

Question 8

Question
In an electronic codebook (ECB) cipher, each block of ciphertext:
Answer
  • Is used to encrypt the next block
  • Is used to encrypt the previous block
  • Is used to decrypt the next block
  • Is not used to encrypt the next block

Question 9

Question
The encryption mode where ciphertext output from each encrypted plaintext block in the encryption used for the next block is known as:
Answer
  • Cipher feedback
  • Output feedback
  • Cipher block chaining
  • Electronic codebook

Question 10

Question
Public key cryptography is another name for:
Answer
  • Secure Sockets Layer
  • Asymmetric cryptography
  • Symmetric key cryptography
  • Kerberos

Question 11

Question
Public key cryptography is so-named because:
Answer
  • It is the world standard for HTTPS
  • It works on all popular computer operating systems
  • It uses an encryption key that can be released to the public
  • The encryption algorithms reside in the public domain

Question 12

Question
A security manager is searching for an encryption algorithm to be used to encrypt data files containing sensitive information. Which of the following algorithms should NOT be considered:
Answer
  • FISH
  • Twofish
  • Blowfish
  • CAST

Question 13

Question
A particular encryption algorithm transforms plaintext to ciphertext by XORing the plaintext with the encryption key. This is known as:
Answer
  • Electronic codebook
  • Cipher block chaining
  • Block cipher
  • Stream cipher

Question 14

Question
Two parties that have never communicated before wish to send messages using symmetric encryption key cryptography. How should the parties begin?
Answer
  • The receiving party should send its public encryption key to the transmitting party
  • Each party should exchange public encryption keys
  • Each party should send the encryption key via the communications channel to the other party
  • One party should transmit the encryption key via an out of band communications channel to the other party

Question 15

Question
Two parties that have never communicated before wish to send messages using asymmetric key cryptography. How should the parties begin?
Answer
  • The receiving party should send its private encryption key to the transmitting party.
  • The transmitting party should send its private encryption key to the receiving party.
  • The receiving party should send its public encryption key to the transmitting party.
  • The transmitting party should send its public encryption key to the receiving party.

Question 16

Question
Two parties, Party A and Party B, regularly exchange messages using public key cryptography. One party, Party A, believes that its private encryption key has been compromised. What action should Party B take?
Answer
  • Request a new public key from Party A
  • Request a new private key from Party A
  • Send a new public key to Party A
  • Send a new private key to Party A

Question 17

Question
The Advanced Encryption Standard is another name for which cipher:
Answer
  • Digital Encryption Algorithm (DEA)
  • 3DES
  • Rijndael
  • International Data Encryption Algorithm (IDEA)

Question 18

Question
The Data Encryption Standard:
Answer
  • Is used by Secure Sockets Layer (SSL) encryption
  • Has been replaced by the International Data Encryption Algorithm (IDEA)
  • Uses a 64-bit encryption key
  • Uses a 56-bit encryption key

Question 19

Question
Two parties are exchanging messages using public key cryptography. Which of the following statements describes the proper procedure for transmitting an encrypted message?
Answer
  • The sender encrypts the message using the recipient’s public key, and the recipient decrypts the message using the recipient’s private key
  • The sender encrypts the message using the sender’s public key, and the recipient decrypts the message using the recipient’s public key
  • The sender encrypts the message using the sender’s private key, and the recipient decrypts the message using the recipient’s private key
  • The sender encrypts the message using the sender’s public key, and the recipient decrypts the message using the sender’s public key

Question 20

Question
A stream cipher encrypts data by XORing plaintext with the encryption key. How is the ciphertext converted back into plaintext?
Answer
  • XORing it with the encryption key
  • XORing it with the inverse of the encryption key
  • ANDing it with the encryption key
  • NANDing it with the encryption key

Question 21

Question
The purpose of digitally signing a message is to ensure:
Answer
  • Integrity of the sender
  • Confidentiality of the message
  • Authenticity of the sender
  • Confidentiality of the sender

Question 22

Question
The purpose of digitally signing a message is to ensure:
Answer
  • Integrity of the message
  • Confidentiality of the message
  • Integrity of the sender
  • Confidentiality of the sender

Question 23

Question
The purpose of the Diffie-Hellman key exchange protocol is:
Answer
  • To decrypt a symmetric encryption key
  • To encrypt a symmetric encryption key
  • To permit two parties who have never communicated to establish public encryption keys
  • To permit two parties who have never communicated to establish a secret encryption key

Question 24

Question
An attacker is attempting to learn the encryption key that is used to protect messages being sent between two parties. The attacker is able to create his own messages, get them encrypted by one of the parties, and can then examine the ciphertext for his message. This type of attack is known as:
Answer
  • Ciphertext only attack
  • Chosen ciphertext attack
  • Chosen plaintext attack
  • Man in the middle attack

Question 25

Question
Which is the best approach for two parties who wish to establish a means for confirming the confidentiality and integrity of messages that they exchange:
Answer
  • Digital signatures
  • Encryption and digital signatures
  • Key exchange
  • Encryption
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