Examkin

Question

Difficulty: MediumCryptographic Concepts and Algorithms

A security analyst is selecting a key exchange mechanism for lightweight microservices communicating over an untrusted enterprise network. The solution must allow the services to negotiate shared symmetric session keys, ensure that compromise of a long-term private key does not expose past session traffic (perfect forward secrecy), and minimize CPU computational overhead on the constrained nodes. Which of the following algorithms or protocols best fulfills these requirements?

  1. ECDHE (Elliptic Curve Diffie-Hellman Ephemeral)Answer
  2. B
    Static RSA key exchange
  3. C
    AES-256-GCM (Galois/Counter Mode)
  4. D
    HMAC-SHA256

Answer

ECDHE (Elliptic Curve Diffie-Hellman Ephemeral) is the correct choice because it enables key agreement with perfect forward secrecy using lower computational overhead than traditional asymmetric methods.
ECDHE (Elliptic Curve Diffie-Hellman Ephemeral) uses temporary, ephemeral keys generated for each session to ensure perfect forward secrecy. Because it uses elliptic curve cryptography, it requires substantially less processing power and memory than traditional finite-field Diffie-Hellman or static RSA.

Step-by-Step Solution

1
Identify the primary cryptographic requirement
The scenario requires key exchange with perfect forward secrecy (PFS) and high computational efficiency.
Session keys must be dynamically negotiated without relying on static long-term private keys for decryption.
2
Evaluate key agreement protocols against constraints
Diffie-Hellman with ephemeral keys (DHE) provides PFS. Adding Elliptic Curve Cryptography (ECDHE) reduces resource consumption.
ECC achieves equivalent key strength with significantly shorter key lengths compared to standard Diffie-Hellman or RSA.
3
Eliminate non-key-exchange mechanisms
Discard symmetric ciphers (AES-GCM) and hash authentication mechanisms (HMAC) as they do not perform key negotiation.
Selecting symmetric ciphers or hashes mistakes bulk data protection for key establishment protocols.

Key Concept

Diffie-Hellman Ephemeral and Perfect Forward Secrecy
Rate this question

Topics

Cryptographic Concepts and Algorithms

More questions from this topic