UGC NET CSE | October 2020 | Part 2 | Question: 54

Question

Which among the following statement(s) is(are) true?

1. A hash function takes a message of arbitrary length and generates a fixed length code
2. A hash function takes a message of fixed length and generates a code of variable length
3. A hash function may give same hash value for distinct messages

Choose the correct answer from the options given below:

• A. $(i)$ only
• B. $(ii)$ and $(iii)$ only
• C. $(i)$ and $(iii)$ only
• D. $(ii)$ only

Answer 1

Answer is (C).

1. A hash function takes a message of arbitrary length and generates a fixed length code. This is correct, this is directly from definition of hash function.  Ref: https://en.wikipedia.org/wiki/Hash_function

2. As I is correct II is wrong.

3. This is true. eg: Hash function N%8, this will generate same values for 1 as well as 9.

(Even in cryptographic hash functions collision happens, just that it is not easy to find colliding instances).

Answer 2

A hash function is any function that can be used to map data of arbitrary size to fixed-size values. The values returned by a hash function are called hash values, hash codes, digests, or simply hashes. The values are usually used to index a fixed-size table called a hash table. Use of a hash function to index a hash table is called hashing or scatter storage addressing.

option c