Which one of the following is a key agreement protocol used to enable two entities to agree and generate a
session key (secret key used for one session) over an insecure medium without any prior secrets or
communications between the entities? The negotiated key will subsequently be used for message encryption
using Symmetric Cryptography.

A.
RSA

B.
PKI

C.
Diffie_Hellmann

D.
3DES

Explanation:
Diffie–Hellman key exchange (D–H) is a specific method of securely exchanging cryptographic keys over a
public channel and was one of the first public-key protocols as originally conceptualized by Ralph Merkle. D–H
is one of the earliest practical examples of public key exchange implemented within the field of cryptography.
Traditionally, secure encrypted communication between two parties required that they first exchange keys by
some secure physical channel, such as paper key lists transported by a trusted courier. The Diffie–Hellman key
exchange method allows two parties that have no prior knowledge of each other to jointly establish a shared
secret key over an insecure channel. This key can then be used to encrypt subsequent communications using a
symmetric key cipher.
Incorrect Answers:
A: RSA is not the key agreement protocol described in the question.
B: PKI is not the key agreement protocol described in the question.
D: 3DES is not the key agreement protocol described in the question.

https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange