Hash Functions — Test 1

Correct Answer: C. C. N = h(m)
Explanation: M is a block of data that is accepted by the hash function. Hash function(H) accepts the input and hash function will be performed. N is the fixed length of hash value of the block of input.

Correct Answer: C. C. Apparently random and evenly distributed values
Explanation: When a huge set of input blocks are given to a hash function, a good hash function will result in unique random values with no relation between them. At the same all the hash values will be equal that is fixed length.

Correct Answer: A. A. Integrity
Explanation: Integrity means retrieving the lost data as soon as possible. Hash functions accomplish integrity, because, even one bit is changed in the data, it will result in a change of hash value with high probability.

Correct Answer: B. B. Cryptographic hash function
Explanation: The cryptographic hash function is an algorithm, which is used in security applications. It is computationally infeasible to attack the algorithm. Because it doesn’t allow the attacker to crack either of its properties, that are collision free property and one-way property.

Correct Answer: A. A. Message authentication
Explanation: The application “message authentication” is used to obtain the integrity of the message. Sender sends hash value of the message along with message, then receiver performs the same hash function on the message. If both the message digests are same, means, integrity is achieved.

Correct Answer: B. B. Message authentication code
Explanation: Message authentication code that is key hash function is mostly used in message authentication. This MAC function results a MAC value, by taking the input block of data and secret key. This MAC value is used to check whether data has changed or not.

Correct Answer: B. B. Ith bit of the hash code
Explanation: “m” is the number of n-bit blocks in the input, bij is the ith bit in the jth block, ci is the ith bit of the hash code. Operation between the bits is exclusive OR and this operation is performed on every input block.

Correct Answer: D. D. When x != y
Explanation: Hash function’s primary objective is to provide integrity. No two inputs should have the same hash value, which causes the collision. Collisions are undesirable in hash functions.

Correct Answer: A. A. 2b-n
Explanation: In the hash value h = H(x), x is the preimage of the hash value. 2b-n formula finds the total number of possible collisions for a hash value. Here b > n and 2b is the total number of possible messages, 2n is the total number of possible hash values.

Correct Answer: D. D. Preimage resistant
Explanation: Hash function will produce fixed lengths of outputs and accepts any size of blocks as input. It is efficient to calculate. If these three requirements need to be met to implement hash function in practical applications.