0 — Test 324

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.

Correct Answer: D. D. Collision resistant
Explanation: Hash function is referred as weak, when it only satisfies the Efficiency, preimage resistant, second image resistant, fixed length output, variable length input. It is referred as strong if it satisfies the collision resistant along with all of the above.

Correct Answer: B. B. False
Explanation: The attacks that are on hash functions are brute force attack and crypt-analysis. Brute force attack mainly concentrates on the bit length of the hash function, whereas crypt-analysis concentrates on cryptographic algorithms.

Correct Answer: B. B. Total break
Explanation: Total break is finding private key and Universal forgery is finding signing algorithm. Selective forgery is doing forgery of signature for particular message. Atleast one message can have forgery signature.