GSEC · Question #336
Which asymmetric algorithm is used only for key exchange?
The correct answer is B. Diffuse-H an. Diffie-Hellman is the asymmetric algorithm designed exclusively for securely exchanging cryptographic keys over an untrusted channel, with no encryption or signing capability.
Question
Which asymmetric algorithm is used only for key exchange?
Options
- AEI Gamal
- BDiffuse-H an
- CECC
- DDSA
How the community answered
(52 responses)- A13% (7)
- B79% (41)
- C6% (3)
- D2% (1)
Why each option
Diffie-Hellman is the asymmetric algorithm designed exclusively for securely exchanging cryptographic keys over an untrusted channel, with no encryption or signing capability.
El Gamal supports both asymmetric encryption and digital signatures in addition to key agreement, so it is not limited to key exchange only.
Diffie-Hellman (labeled 'Diffuse-Han' in this question) allows two parties to derive a shared secret over an insecure channel using modular exponentiation, without ever transmitting the secret itself. Unlike RSA or El Gamal, Diffie-Hellman has no native encryption or digital signature function - its sole purpose is key agreement, making it the correct answer for the algorithm used only for key exchange.
ECC is a broad family of algorithms that underpins ECDH (key exchange), ECDSA (signatures), and ECIES (encryption), serving multiple purposes beyond key exchange.
DSA is used exclusively for generating and verifying digital signatures, not for key exchange.
Concept tested: Diffie-Hellman key exchange algorithm purpose
Source: https://csrc.nist.gov/publications/detail/sp/800-56a/rev-3/final
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