1
C839 Introduction to Cryptography Questions
with Correct Answers for a Specific Exam Mail
Cryptography
Ans: the science that studies encryption, which is the hiding of messages so
that only the sender and receiver can read them. Cybersecurity, computer
science, programming, and other IT career fields require a conceptual
understanding of cryptography and familiarity with its basic vocabulary.
Caesar Cypher
Ans: letter-by-letter method to make a cipher. For each letter, substitute
another letter 4 letters ahead. For "a", write "d".
Employee B sends Employee A an encrypted message. What does
employee A use to decrypt the message from employee B
Ans: Employee As private key
Advanced encryption system (AES)
Ans: is an example of a symmetric algorithm. RSA, SHA, and MD5 are not
symmetric algorithms.
Employee A created a secret key and wants to send it to Employee B
without any coworkers being able to decrypt the message. Which key needs
to encrypt the message?
Ans: Employee B's public key
Pretest - Stuvia US
,2
Which type of cipher is ChaCha?
Ans: stream
What is the key size for RC4 with WEP?
Ans: 40 bits
What is the length (in bits) of an MD5 hash output?
Ans: 128 bits
Which mode encrypts each group with the same key, leaving each group
independent of the others?
Ans: ECB Electronic Code Book (ECB) is a simple mode of operation with a
block cipher that's mostly used with symmetric key encryption. It is a
straightforward way of processing a series of sequentially listed message
blocks. The input plaintext is broken into numerous blocks.
ECB
Ans: Electronic Code Book
Which mode of block encryption results in the same outcome for matching
blocks of a plaintext message?
Ans: Electronic Code Book (ECB)
Which encryption mode always produces the same result for the same
plaintext?
Pretest - Stuvia US
,3
Ans: Electronic Code Book (ECB)
Skipjack
Ans: Promoted by the NSA. Skipjack uses an 80-bit key, supports the same
four modes of operation as DES, and operates on 64-bit blocks of text.
Skipjack provides cryptographic routines in support of Clipper and Capstone.
Skipjack faced public opposition because it was developed so that the
government could maintain information enabling legal authorities (with a
search warrant or approval of the court) to reconstruct a Skipjack access key
and decrypt private communications between affected parties.
How many transformation rounds does AES use with a 192-bit key?
Ans: 12
How many transformation rounds does AES use with a 128-bit key?
Ans: 10
Why is symmetric stream used to encrypt video when speed is a major
concern?
Ans: It uses the same key to encrypt and decrypt large amounts of media.
So, it is faster.
Why should an asymmetric public key be used to encrypt a symmetric key
that is being sent to one person?
Ans: It encrypts a small amount of information, which is decrypted with the
corresponding private key.
Pretest - Stuvia US
, 4
Which mechanism mitigates a copy-and-paste attack when using AES?
Ans: Output feedback (OFB) loop
Which mechanism can be used to ensure perfect forward secrecy during
key exchange when using symmetric encryption?
Ans: Elliptical curve Diffie-Hellman (ECDH)
Which encryption component ensures that the compromise of a long-term
key prevents the compromise of any previous session keys?
Ans: Forward secrecy
How does cipher block chaining (CBC) create randomness in a second
block after encrypting the first block with an initialization vector (IV)?
Ans: Uses the results of the Initialization Vector (IV) to encrypt the next block
How is information about Bitcoin transactions stored?
Ans: Distributed peer-to-peer network
What is one of the primary characteristics of a blockchain in the context of
Bitcoin?
Ans: Adding blocks to a blockchain is computationally expensive.
What is the length (in bits) of the private key used to sign transactions and
associated with an individual wallet in the context of Bitcoin?
Ans: 256 bits
Pretest - Stuvia US
C839 Introduction to Cryptography Questions
with Correct Answers for a Specific Exam Mail
Cryptography
Ans: the science that studies encryption, which is the hiding of messages so
that only the sender and receiver can read them. Cybersecurity, computer
science, programming, and other IT career fields require a conceptual
understanding of cryptography and familiarity with its basic vocabulary.
Caesar Cypher
Ans: letter-by-letter method to make a cipher. For each letter, substitute
another letter 4 letters ahead. For "a", write "d".
Employee B sends Employee A an encrypted message. What does
employee A use to decrypt the message from employee B
Ans: Employee As private key
Advanced encryption system (AES)
Ans: is an example of a symmetric algorithm. RSA, SHA, and MD5 are not
symmetric algorithms.
Employee A created a secret key and wants to send it to Employee B
without any coworkers being able to decrypt the message. Which key needs
to encrypt the message?
Ans: Employee B's public key
Pretest - Stuvia US
,2
Which type of cipher is ChaCha?
Ans: stream
What is the key size for RC4 with WEP?
Ans: 40 bits
What is the length (in bits) of an MD5 hash output?
Ans: 128 bits
Which mode encrypts each group with the same key, leaving each group
independent of the others?
Ans: ECB Electronic Code Book (ECB) is a simple mode of operation with a
block cipher that's mostly used with symmetric key encryption. It is a
straightforward way of processing a series of sequentially listed message
blocks. The input plaintext is broken into numerous blocks.
ECB
Ans: Electronic Code Book
Which mode of block encryption results in the same outcome for matching
blocks of a plaintext message?
Ans: Electronic Code Book (ECB)
Which encryption mode always produces the same result for the same
plaintext?
Pretest - Stuvia US
,3
Ans: Electronic Code Book (ECB)
Skipjack
Ans: Promoted by the NSA. Skipjack uses an 80-bit key, supports the same
four modes of operation as DES, and operates on 64-bit blocks of text.
Skipjack provides cryptographic routines in support of Clipper and Capstone.
Skipjack faced public opposition because it was developed so that the
government could maintain information enabling legal authorities (with a
search warrant or approval of the court) to reconstruct a Skipjack access key
and decrypt private communications between affected parties.
How many transformation rounds does AES use with a 192-bit key?
Ans: 12
How many transformation rounds does AES use with a 128-bit key?
Ans: 10
Why is symmetric stream used to encrypt video when speed is a major
concern?
Ans: It uses the same key to encrypt and decrypt large amounts of media.
So, it is faster.
Why should an asymmetric public key be used to encrypt a symmetric key
that is being sent to one person?
Ans: It encrypts a small amount of information, which is decrypted with the
corresponding private key.
Pretest - Stuvia US
, 4
Which mechanism mitigates a copy-and-paste attack when using AES?
Ans: Output feedback (OFB) loop
Which mechanism can be used to ensure perfect forward secrecy during
key exchange when using symmetric encryption?
Ans: Elliptical curve Diffie-Hellman (ECDH)
Which encryption component ensures that the compromise of a long-term
key prevents the compromise of any previous session keys?
Ans: Forward secrecy
How does cipher block chaining (CBC) create randomness in a second
block after encrypting the first block with an initialization vector (IV)?
Ans: Uses the results of the Initialization Vector (IV) to encrypt the next block
How is information about Bitcoin transactions stored?
Ans: Distributed peer-to-peer network
What is one of the primary characteristics of a blockchain in the context of
Bitcoin?
Ans: Adding blocks to a blockchain is computationally expensive.
What is the length (in bits) of the private key used to sign transactions and
associated with an individual wallet in the context of Bitcoin?
Ans: 256 bits
Pretest - Stuvia US
