# Ethical Hacking | Week 7

Course Name: Ethical Hacking

#### Q1. Consider a hash function H that generates hash values h1 and h2, when fed with messages m1and m2 respectively. Which of the following options can never be true?a. hland h2 are equal, but m1 and m2 are unequal.b. m1 and m2 are equal, but hl and h2 are unequal.c. None of these.

Answer: b. m1 and m2 are equal, but hl and h2 are unequal.

Q2. What is meant by collision in the context of hashing?
a. More than one different message can generate the same hash value.
b. After encryption, the ciphertexts corresponding to two or more plaintexts are the same.
c. The hash function generates the all zero string as the hash value.
d. None of these.

Answer: a. More than one different message can generate the same hash value.

These are NPTEL Ethical Hacking Week 7 Assignment 7 Answers

Q3. A message M is fed to a hash function HASH to generate the hash value H:
H = HASH (M)
Which of the following statements is true?

a. The number of bits in H is much larger than the number of bits in M.
b. The number of bits in H and M are almost equal.
c. The number of bits in M is much larger than the number of bits in H.
d. None of these.

Answer: c. The number of bits in M is much larger than the number of bits in H.

Q4. What of the following does not correspond to the first preimage resistance in the context of hash functions?
a. Itis difficult to find a message M such that HASH(M) = H, except for a few hash values H.
b. Given a message M1, it is difficult to find another message M2 such that HASH(M1) = HASH(M2).
c. Itis difficult to find two messages M1 and M2 such that HASH(M1) and HASH(M2) and unequal.
d. None of these.

These are NPTEL Ethical Hacking Week 7 Assignment 7 Answers

Q5. Which of the following statement(s) is/are true?
a. Hashing realizes a one-to-one mapping.
b. Encryption realizes a one-to-one mapping.
c. Hashing realizes a many-to-one mapping.
d. Encryption realizes a many-to-one mapping.

Q6. Which of the following are hash functions?
a. MDS
b. Triple-DES
c. SHA-1
d. AES

These are NPTEL Ethical Hacking Week 7 Assignment 7 Answers

Q7. Which of the following statement(s) is/are true?
a. Computing a hash function is faster than computing symmetric-key encryption.
b. Computing public-key encryption is slower than computing symmetric-key encryption.
c. Computing public-key encryption is slower than computing hash function.
d. Both public-key and symmetric-key encryption take approximately the same time.

Q8. What are the block size and key size of the DES algorithm?
a. 64 bits, 56 bits
b. 56 bits, 64 bits
c. 64 bits, 64 bits
d. 64 bits, 128 bits

Answer: a. 64 bits, 56 bits

These are NPTEL Ethical Hacking Week 7 Assignment 7 Answers

Q9. What kinds of algorithms are typically used in the computation of digital signature?
a. Cryptographic hash function.
b. Symmetric-key encryption.
c. Biometric authentication.
d. All of these

Q10. The SSL record protocol is responsible for
a. High-speed data transmission
b. Data authentication
c. Non repudiation
d. None of these

These are NPTEL Ethical Hacking Week 7 Assignment 7 Answers

These are NPTEL Ethical Hacking Week 7 Assignment 7 Answers