1) What is the meaning of one-way function?

a. It can be used by the sender but not by the receiver.
b. It can be used by the receiver but not by the sender.
c. It implements a many-to-one mapping.
d. It implements a one-to-many mapping.

Answer: c

Solution: Hashing is a type of one-way function, which refers to a function that implements a many-to-one mapping. Several different messages may map to the same hash value, but the converse is not true. The correct option is (c).

2) Which of the following are examples of hash functions?

a. MD5
b. Triple-DES
c. SHA-1
d. All of these.

Answer: a, c

Solution: MD5 and SHA-1 are examples of hash function, while Triple-DES is used in encryption. Thus the correct options are (a) and (c).

3) In terms of speed (slowest to fastest), which of the following orders are correct?

a. Hash computation, Public-key encryption, Symmetric-key encryption
b. Public-key encryption, Symmetric-key encryption, Hash computation
c. Symmetric-key encryption, Public-key encryption, Hash computation
d. None of these.

Answer: b

Solution: Computation of hash function is the fastest, which computation of public-key encryption is the slowest. Symmetric-key encryption lies in between the two. Hence, the correct option is (b).

4) The hash digest length of SHA-256 is __ bits.

Answer: 256

Solution: The size of the hash digest or the number of bits in the hash for SHA-256 is 256 bits. This follows from the definition of SHA-256.

5) What is birthday attack?

a. It is an attack on public-key cryptography.
b. It is an attack on symmetric-key cryptography.
c. It is an attack on hash functions.
d. None of these.

Answer: c

Solution: Birthday attack utilizes some statistical properties to mount attacks on hash functions. The correct option is (c).