CompTIA Security+ Question E-74

A security administrator must implement a system to allow clients to securely negotiate encryption keys with the company’s server over a public unencrypted communication channel.
Which of the following implements the required secure key negotiation? (Select TWO).

B. Symmetric encryption
C. Steganography
E. Diffie-Hellman

Answer: D,E

Elliptic curve Diffie–Hellman (ECDH) is an anonymous key agreement protocol that allows two parties, each having an elliptic curve public-private key pair, to establish a shared secret over an insecure channel. This shared secret may be directly used as a key, or better yet, to derive another key which can then be used to encrypt subsequent communications using a symmetric

key cipher. It is a variant of the Diffie–Hellman protocol using elliptic curve cryptography. Note: Adding an ephemeral key to Diffie-Hellman turns it into DHE (which, despite the order of the acronym, stands for Ephemeral Diffie-Hellman). Adding an ephemeral key to Elliptic Curve Diffie-Hellman turns it into ECDHE (again, overlook the order of the acronym letters; it is called Ephemeral Elliptic Curve Diffie-Hellman). It is the ephemeral component of each of these that provides the perfect forward secrecy.