Mandy needs to calculate how many keys must be generated for the 260 employees using the company’s PKI asymmetric algorithm. How many keys are required?

A.
33,670

B.
520

C.
67,340

D.
260

Explanation:
B: With asymmetric algorithms, every user must have at least one pair of keys (private and public). In public key systems, each entity has different keys, or asymmetric keys. The
two different asymmetric keys are mathematically related. If a message is encrypted by one key, the other key is required in order to decrypt the message. The formula for determining
the number of keys needed in this environment is N 2, which is the number of people (N) multiplied by the number of keys each person would need (2). In a public key system, the
pair of keys is made up of one public key and one private key. The public key can be known to everyone, and the private key must be known and used only by the owner.
A is incorrect because 33,670 is the number of keys needed in a symmetric key cryptosystem. Each pair of users who want to exchange data using symmetric key encryption must
have two instances of the same key. This means that if Dan and Bob want to communicate, both need to obtain a copy of the same key. If Dan also wants to communicate using
symmetric encryption with Norm and Dave, he needs to have three separate keys, one for each friend. This might not sound like a big deal until Dan realizes that he may communicate
with hundreds of people over a period of several months, and keeping track and using the correct key that corresponds to each specific receiver can become a daunting task. If ten
people needed to communicate securely with each other using symmetric keys, then 45 keys would need to be kept track of. If 100 people were going to communicate, then 4,950
keys would be involved. The equation used to calculate the number of symmetric keys needed is: N(N – 1) / 2 = number of keys.
C is incorrect because 67,340 is the total derived from N(N – 1), which is part of the formula used to determine the number of keys needed in a symmetric key cryptosystem. The
complete formula is N(N – 1) / 2. The question, however, asked for the number of keys that would be used in a public key infrastructure’s asymmetric algorithms. Asymmetricnot
symmetrickeys are used in a public key cryptosystem. The formula for determining the number of asymmetric keys that are needed is N 2.
D is incorrect because each user in a public key infrastructure requires at least one key paira public key and a private key. One key cannot encrypt and decrypt the same
message. So each user requires at least two keys. Thus, the formula for determining the number of asymmetric keys that are needed is N 2.