What keys are transmitted from the server to the client?

During a standard HTTPS connection from server to client, the following keys are transmitted:

• Server Certificate (Certificate): Contains the server's public key, owner information, validity period, and the signature of the certification authority. It is used by the client to verify the server's authenticity and obtain its public key.
• DHE/ECDHE parameters (when using ephemeral Diffie-Hellman keys): Parameters g, p (for DHE) or curve parameters (for ECDHE), which allow the client and server to jointly compute a shared secret for subsequent session encryption. These keys are temporary and generated for each session, ensuring Forward Secrecy.

It is important to note that the server's private key is never transmitted to the client. It is stored only on the server.

After the key exchange, the client and server use the agreed-upon shared secret to generate session keys (Session Key / Symmetric Key), which are used for encrypting and decrypting transmitted data during the session. The session key itself is never transmitted in plain text but is generated independently by both parties based on the shared secret.