What does the TLS ServerKeyExchange message contain when using ECDHE?

• A. The elliptic curve parameters and the server's ECDH public point
• B. The server's certificate chain
• C. Application data
• D. Handshake alert

Answer: (A)

In TLS with ephemeral ECDH, the ServerKeyExchange message provides the data the client needs to compute the shared secret. It carries the elliptic curve parameters (which curve is being used) and the server’s ECDH public point on that curve. The client uses its own ephemeral private key, provided in the ClientKeyExchange, with the server’s public point to derive the premaster secret. The server’s certificate chain is delivered in a separate Certificate message earlier in the handshake, not here, and application data or alerts are not part of this handshake message.