If the application of a hash function results in an m-bit fixed length
output, an attack on the hash function that attempts to achieve a
collision after 2 m/2 possible trial input values is called a(n):

A.
Birthday attack

B.
Meet-in-the-middle attack

C.
Chosen-ciphertext attack

D.
Adaptive-chosen-plaintext attack

Explanation:
This problem is analogous to asking the question How many
people must be in a room for the probability of two people having
the same birthday to be equal to 50%? The answer is 23. Thus,
trying 2m/2 possible trial inputs to a hash function gives a 50%
chance of finding two inputs that have the same hash value. Answer
a, describes an attack in which the attacker can choose the plaintext
to be encrypted and can modify his/her choice based on the results
of a previous encryption.
* Answer the chosen-cipher text attack is where the attacker can select different ciphertexts to be
decrypted and has the decrypted plaintext available. This attack is used to determine the key or
keys being used. Answer d is an attack against
double encryption. This approach shows that for a key length of k
bits, a chosen-plaintext attack could find the key after 2k+1 trials
instead of 22k attempts. In this attack on double encryption, one
encrypts from one end, decrypts from the other and compares the
results in-the-middle.