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).

A. PBKDF2
B. Symmetric encryption
C. Steganography
D. ECDHE
E. Diffie-Hellman

Answer: D,E

Explanation:
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.

CompTIA Security+ Question C-51

Which of the following represents a cryptographic solution where the encrypted stream cannot be captured by a sniffer without the integrity of the stream being compromised?

A. Elliptic curve cryptography.
B. Perfect forward secrecy.
C. Steganography.
D. Quantum cryptography.

Answer: D

Explanation:
Quantum cryptography is a cryptosystem that is completely secure against being compromised without knowledge of the sender or the receiver of the messages.

CompTIA Security+ Question B-99

Matt, a security analyst, needs to select an asymmetric encryption method that allows for the same level of encryption strength with a lower key length than is typically necessary. Which of the following encryption methods offers this capability?

A. Twofish
B. Diffie-Hellman
C. ECC
D. RSA

Answer: C

Explanation:
Elliptic curve cryptography (ECC) is an approach to public-key cryptography based on the algebraic structure of elliptic curves over finite fields. One of the main benefits in comparison with non-ECC cryptography (with plain Galois fields as a basis) is the same level of security provided by keys of smaller size.

CompTIA Security+ Question A-22

Which of the following types of cryptography should be used when minimal overhead is necessary for a mobile device?

A. Block cipher
B. Elliptical curve cryptography
C. Diffie-Hellman algorithm
D. Stream cipher

Answer: B

Explanation:
Regarding the performance of ECC applications on various mobile devices, ECC is the most suitable PKC (Public-key cryptography) scheme for use in a constrained environment. Note: Elliptic curve cryptography (ECC) is an approach to public-key cryptography based on the algebraic structure of elliptic curves over finite fields. One of the main benefits in comparison with non-ECC cryptography (with plain Galois fields as a basis) is the same level of security provided by keys of smaller size. Using smaller key size would be faster.