Which type of attack is based on the probability of two different messages using the same hash
function producing a common message digest?

A.
Differential cryptanalysis

B.
Differential linear cryptanalysis

C.
Birthday attack

D.
Statistical attack

Explanation:

Attacks Against One-Way Hash Functions: A good hashing algorithm should not produce the same
hash value for two different messages. If the algorithm does produce the same value for two
distinctly different messages, this is referred to as a collision. If an attacker finds an instance of a
collision, he has more information to use when trying to break the cryptographic methods used. A
complex way of attacking a one-way hash function is called the birthday attack. Now hold on to your
had while we go through this — it is a bit tricky. In standard statistics, a birthday paradox exists. It
goes something like this: How many people must be in the same room for the chance to be greater
than even that another person has the same birthday as you?

that at least two people share the same birthday?

looking for someone with a specific birthday date, which matches yours. In the second instance, you
are looking for any two people who share the same birthday. There is a higher probability of finding
two people who share a birthday than you finding another person sharing your birthday — thus, the
birthday paradox. This means that if an attacker has one hash value and wants to find a message
that hashes to the same hash value, this process could take him years. However, if he just wants to
find any two messages with the same hashing value, it could take him only a couple hours. …..The
main point of this paradox and this section is to show how important longer hashing values truly are.
A hashing algorithm that has a larger bit output is stronger and less vulnerable to brute force attacks
like a birthday attack. Pg 554-555 Shon Harris: All-In-One Certification Exam Guide