210-250 · Question #199
The ECDHE_ECDSA part of the cipher list identifies which one of the following algorithms?
The correct answer is A. authentication and key exchange. In a TLS cipher suite name, ECDHE identifies the key exchange method and ECDSA identifies the authentication mechanism, so ECDHE_ECDSA covers both key exchange and authentication.
Question
The ECDHE_ECDSA part of the cipher list identifies which one of the following algorithms?
Options
- Aauthentication and key exchange
- Bencryption
- Cmessage authentication code
- Dpseudorandom function
How the community answered
(16 responses)- A94% (15)
- C6% (1)
Why each option
In a TLS cipher suite name, ECDHE identifies the key exchange method and ECDSA identifies the authentication mechanism, so ECDHE_ECDSA covers both key exchange and authentication.
ECDHE_ECDSA represents two combined functions - ECDHE (Elliptic Curve Diffie-Hellman Ephemeral) handles ephemeral key exchange to establish the session secret, while ECDSA (Elliptic Curve Digital Signature Algorithm) handles server authentication by verifying the certificate signature, as defined in RFC 4492.
Encryption is identified by the bulk cipher component of the suite name (e.g., AES_256_GCM), not by ECDHE_ECDSA.
The message authentication code is identified by the hash algorithm component at the end of the cipher suite name (e.g., SHA384), not by ECDHE_ECDSA.
The pseudorandom function is an internal TLS key derivation mechanism tied to the negotiated hash algorithm, not directly represented by the ECDHE_ECDSA portion of the cipher suite name.
Concept tested: TLS cipher suite ECDHE ECDSA key exchange and authentication roles
Source: https://www.rfc-editor.org/rfc/rfc4492
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