A birthday attack is somewhat complicated and would require an attacker to be dedicated to be successful. What is the usual goal of this type of attack?

A.
Gaining access to confidential data in an unauthorized manner

B.
Authenticating to a system through a replay attack

C.
Modifying an original document without the receiver detecting it

D.
Injecting sensitive data into a non-sensitive document

Explanation:
A birthday attack takes place when there is a collision in message
digest values. If there just happen to be two documents that create the same message
digest value when hashed, this is not really a big security issue. It is when an
attacker can modify a document or message and generate the same message digest value
of the original so that no one will know that a modification took place.