In a brute-force attack, what percentage of the keyspace must an attacker generally search through until he or she finds the key that decrypts the data?

In a brute-force attack, what percentage of the keyspace must an attacker generally search through until he or she finds the key that decrypts the data?

A.
Roughly 66 percent

B.
Roughly 10 percent

C.
Roughly 75 percent

D.
Roughly 50 percent

Explanation:
All encryption algorithms are vulnerable to a brute-force attack. In this attack, an attacker
tries every possible key with the decryption algorithm. Generally, a brute-force attack
will succeed about 50 percent of the way through the keyspace. To defend against this
form of attack, modern cryptographers have to create a sufficiently large keyspace so that
attacking it in this way requires too much time and money to be practical.