Determine which of the following message hashvalue pairs sho

Determine which of the following message hash-value pairs shows that there has been a manipulation or corruption of the message or hash.

a) x= MAKEH AYWHI LETHE SUNSH INESX hash: QYAJD

b) x= MAKEH AYWHI LETHE MOONS HINES hash: QYAJD

c) x= TODAY IS THE FIRST DAYOF THERE STOFY OURLI FEXXX hash: NMRRH

d) x= THERE STOFY OURLI FEXXX hash: NMRRH

the answer is (a) is likely uncorrupted; (b) is corrupted; (c) is likely uncorrupted; (d) is corrupted.

but how to get to that answer. This is a cryptology question.

Solution

Answer would be : d) x= THERE STOFY OURLI FEXXX hash: NMRRH

Reason Explaination :   

Hash function is used in hash value pair technique in cryptography and an example of hash function is like take message string of any length for message encryption.

\"THERE STOFY OURLI FEXXX\" is the part of message TODAY IS THE FIRST DAYOF THERE STOFY OURLI FEXXX which becomes the reason of Length extension attack.

Length extension attack is the attempt done by attacker to use Hash(message1) or length of message1 to calculate hash(message1 || message2) for an attacker-controlled mesage2. here || denotes concatenation.

To know the message2, length of message1 itself provide help to the attacker to manipualte or courrpte the whole string or message.

Rest of the option are not matching with hash value pair encryption technique beacuse option A abd option b has minor changes and according to hash value pair technique a small change in the input string drastically changes the output.

Thanks,

Thanks,

Deepak

Length extension attack is the attack where an attacker can use Hash(message₁) and the length of message₁ to calculate Hash(message₁ message₂) for an attacker-controlled message₂