Assignment 5
Submission
Answer Sheet
2025.12.02 2
8 questions
1. How many integers between 1 and 80 are relatively prime to 80?
1
2
3
6
7
8
4
5
Multiple-Choice (12.5 Points)
12.5Points
A. 32
B. 79
Correct
Wrong
C. 60
D. 40
Right Answer: A
2. Which of the following algorithms cannot compute the modular
multiplicative inverses of a in
?
Wrong
Multiple-Choice (12.5 Points)
0Points
A. Fermat’s Little Theorem
B. Sieve of Eratosthenes algorithm
C. Euler’s Theorem
D. The extended Euclidean algorithm
Right Answer: B
3. Which of the following statements is incorrect?
Multiple-Choice (12.5 Points)
12.5Points
A. There is an infinite number of primes
B. The smallest prime is 2
C. 63 and 65 are coprime
D. 203 is a prime number
Right Answer: D
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4. Which of the following algorithms can efficiently compute the greatest
common divisor (GCD)?
Multiple-Choice (12.5 Points)
12.5Points
A. Chinese remainder theorem
B. Sieve of Eratosthenes algorithm
C. Euclidean algorithm
D. Fermat algorithm
Right Answer: C
5. What is the result of (–53) mod 7?
Multiple-Choice (12.5 Points)
12.5Points
A. 4
B. - 4
C. 3
D. - 3
Right Answer: C
6. What is the result of
Multiple-Choice (12.5 Points)
?
12.5Points
A. 4
B. 8
C. 7
D. 11
Right Answer: B
7. What is the multiplicative inverse of 21 in
Multiple-Choice (12.5 Points)
?
12.5Points
A. 23
B. 43
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C. 21
D. It has no inverse in
Right Answer: D
8. What is the result of
Multiple-Choice (12.5 Points)
?
12.5Points
A. 17
B. 28
C. 8
D. 23
Right Answer: C
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Assignment 5
Submission
Answer Sheet
2025.12.02 2
8 questions
1. How many integers between 1 and 80 are relatively prime to 80?
1
2
3
6
7
8
4
5
Multiple-Choice (12.5 Points)
12.5Points
A. 32
B. 79
Correct
Wrong
C. 60
D. 40
Right Answer: A
2. Which of the following algorithms cannot compute the modular
multiplicative inverses of a in
?
Wrong
Multiple-Choice (12.5 Points)
0Points
A. Fermat’s Little Theorem
B. Sieve of Eratosthenes algorithm
C. Euler’s Theorem
D. The extended Euclidean algorithm
Right Answer: B
3. Which of the following statements is incorrect?
Multiple-Choice (12.5 Points)
12.5Points
A. There is an infinite number of primes
B. The smallest prime is 2
C. 63 and 65 are coprime
D. 203 is a prime number
Right Answer: D
https://iclass.tku.edu.tw/exam/168813/subjects#/submission/10955092
12/17/25, 10:32 AM
Page 1 of 3
4. Which of the following algorithms can efficiently compute the greatest
common divisor (GCD)?
Multiple-Choice (12.5 Points)
12.5Points
A. Chinese remainder theorem
B. Sieve of Eratosthenes algorithm
C. Euclidean algorithm
D. Fermat algorithm
Right Answer: C
5. What is the result of (–53) mod 7?
Multiple-Choice (12.5 Points)
12.5Points
A. 4
B. - 4
C. 3
D. - 3
Right Answer: C
6. What is the result of
Multiple-Choice (12.5 Points)
?
12.5Points
A. 4
B. 8
C. 7
D. 11
Right Answer: B
7. What is the multiplicative inverse of 21 in
Multiple-Choice (12.5 Points)
?
12.5Points
A. 23
B. 43
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C. 21
D. It has no inverse in
Right Answer: D
8. What is the result of
Multiple-Choice (12.5 Points)
?
12.5Points
A. 17
B. 28
C. 8
D. 23
Right Answer: C
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Assignment 7
Submission
Answer Sheet
8 questions
2025.12.09 2
1. Which of the following ensures the integrity of a message by detecting any
modifications during transmission?
1
2
3
6
7
8
4
5
Multiple-Choice (12.5 Points)
12.5Points
A. Asymmetric-key algorithms
Correct
Wrong
B. Hash functions
C. One-way function
D. Symmetric-key algorithms
Right Answer: B
2. What is the primary purpose of a Modification Detection Code (MDC)?
Multiple-Choice (12.5 Points)
12.5Points
A. To verify the integrity of the message
B. To encrypt the message
C. To ensure the confidentiality of the message
D. To sign the message for authentication
Right Answer: A
3. How does a Modification Detection Code (MDC) function?
Multiple-Choice (12.5 Points)
12.5Points
A. It provides encryption and decryption of the message.
B. It generates a checksum based on the message content to detect any
alterations.
C. It uses public and private keys to secure the message.
D. It converts the message into a fixed-length output.
Right Answer: B
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4. Which of the following algorithms is primarily used for generating a hash to
check message integrity?
Multiple-Choice (12.5 Points)
12.5Points
A. SHA
B. RSA
C. AES
D. Diffie-Hellman algorithm
Right Answer: A
5. Which property of a cryptographic hash function ensures that it is
computationally infeasible to find two different inputs that produce the
same output?
Multiple-Choice (12.5 Points)
12.5Points
A. Collision resistance
B. One-way function
C. Pre-image resistance
D. Fixed-length output
Right Answer: A
6. Which of the following statements is correct?
Multiple-Choice (12.5 Points)
12.5Points
A. Hash outputs have the same length as the input, while encryption ciphers do
not.
B. Hash functions require a key, while encryption ciphers do not.
C. Hash outputs are always unique, while ciphertext may not be.
D. Hash functions are irreversible, while encryption ciphers are reversible.
Right Answer: D
7. A message digest is a unique identifier for a message that ensures its
________.
Multiple-Choice (12.5 Points)
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12.5Points
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Multiple-Choice (12.5 Points)
12.5Points
A. confidentiality
B. availability
C. integrity
D. non-repudiation
Right Answer: C
8. What does it mean if a hashing algorithm produces the same hash for two
different inputs?
Multiple-Choice (12.5 Points)
12.5Points
A. A key exchange has occurred.
B. A collision has occurred.
C. The integrity of the message is confirmed.
D. The message is encrypted.
Right Answer: B
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Assignment 5
Submission
Answer Sheet
2025.12.02 2
8 questions
1. How many integers between 1 and 80 are relatively prime to 80?
1
2
3
6
7
8
4
5
Multiple-Choice (12.5 Points)
12.5Points
A. 32
B. 79
Correct
Wrong
C. 60
D. 40
Right Answer: A
2. Which of the following algorithms cannot compute the modular
multiplicative inverses of a in
?
Wrong
Multiple-Choice (12.5 Points)
0Points
A. Fermat’s Little Theorem
B. Sieve of Eratosthenes algorithm
C. Euler’s Theorem
D. The extended Euclidean algorithm
Right Answer: B
3. Which of the following statements is incorrect?
Multiple-Choice (12.5 Points)
12.5Points
A. There is an infinite number of primes
B. The smallest prime is 2
C. 63 and 65 are coprime
D. 203 is a prime number
Right Answer: D
https://iclass.tku.edu.tw/exam/168813/subjects#/submission/10955092
12/17/25, 10:32 AM
Page 1 of 3
4. Which of the following algorithms can efficiently compute the greatest
common divisor (GCD)?
Multiple-Choice (12.5 Points)
12.5Points
A. Chinese remainder theorem
B. Sieve of Eratosthenes algorithm
C. Euclidean algorithm
D. Fermat algorithm
Right Answer: C
5. What is the result of (–53) mod 7?
Multiple-Choice (12.5 Points)
12.5Points
A. 4
B. - 4
C. 3
D. - 3
Right Answer: C
6. What is the result of
Multiple-Choice (12.5 Points)
?
12.5Points
A. 4
B. 8
C. 7
D. 11
Right Answer: B
7. What is the multiplicative inverse of 21 in
Multiple-Choice (12.5 Points)
?
12.5Points
A. 23
B. 43
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C. 21
D. It has no inverse in
Right Answer: D
8. What is the result of
Multiple-Choice (12.5 Points)
?
12.5Points
A. 17
B. 28
C. 8
D. 23
Right Answer: C
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Assignment 8
Submission
8 / 8 questions,
100 points
Answer Sheet
2025.12.16 2
1. Using the RSA scheme, let p = 7, q = 13, and d = 5. If the message M = 10,
what is the signature S?
1
2
3
6
7
8
4
5
Multiple-Choice (12.5 Points)
A. 40
B. 72
Submitted
Unsubmitted
C. 36
D. 82
2. Which of the following statements is correct regarding a Message
Authentication Code (MAC)?
Multiple-Choice (12.5 Points)
A. It ensures message integrity
B. It uses asymmetric cryptography
C. It provides confidentiality
D. It provides nonrepudiation
3. Which of the following statements is correct regarding a message digest?
Multiple-Choice (12.5 Points)
A. It provides nonrepudiation
B. It provides confidentiality
C. It uses symmetric cryptography
D. It provides message integrity
4. In the RSA digital signature scheme, when Alice wants to sign a message
and send it with the signature to Bob, she would use ______.
Multiple-Choice (12.5 Points)
A. Bob’s public key
B. Bob’s private key
C. Alice's public key
D. Alice’s private key
5. Which of the following can a public key be used for?
Multiple-Choice (12.5 Points)
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A. Encrypting web browser traffic
B. Decrypting wireless messages
C. Digitally signing a message
D. Decrypting the hash of a digital signature
6. Which of the following provides non-repudiation?
Multiple-Choice (12.5 Points)
A. RSA cryptosystem
B. Modification detection code (MDC)
C. Digital signature
D. Message authentication code (MAC)
7. Which of the following statements is incorrect regarding a digital signature?
Multiple-Choice (12.5 Points)
A. It provides nonrepudiation
B. It provides confidentiality
C. It uses asymmetric cryptography
D. It ensures message integrity
8. In the RSA digital signature scheme, when Bob receives a message with its
signature from Alice and wants to verify the message, he would use
______.
Multiple-Choice (12.5 Points)
A. Bob’s private key
B. Alice’s private key
C. Alice's public key
D. Bob’s public key
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