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?
How many people must be in the same room for the chance to be greater than even that at least
two people share the same birthday?
This seems a bit backwards, but the difference is that in the first instance, you are 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