In the lesson’s description of Transport Layer Security (TLS) 1.3, which key-exchange method is associated with forward secrecy?

### Why this is right The lesson specifically associates ephemeral Diffie-Hellman with forward secrecy in Transport Layer Security (TLS) 1.3. The method helps establish temporary session key material rather than relying on one permanent shared session key. ### The concept Key exchange is the process of securely establishing cryptographic keys so encrypted communication can begin. TLS uses a hybrid approach: asymmetric methods support key establishment, and symmetric encryption protects the rest of the session. A certificate authority helps verify identity and reduce the risk of a man-in-the-middle attack. The question asks for the specific method named in the lesson, not for a general description of all key exchange. ### The other options - **B. A permanent shared key reused for every session**: This conflicts with the lesson’s description of ephemeral key exchange and temporary session keys. - **C. A hash used as a reversible encryption key**: Hashes are one-way fingerprints, not reversible encryption keys. - **D. A certificate authority’s private key used to decrypt all messages**: A certificate authority issues certificates; the lesson does not describe it as decrypting all communications. ### Terms - **TLS**: Transport Layer Security, a protocol used to secure communications such as web traffic. - **Ephemeral Diffie-Hellman**: A temporary key-agreement method identified in the lesson as supporting forward secrecy. - **Forward secrecy**: A property associated in the lesson with ephemeral key exchange. - **Certificate authority**: A trusted body that issues certificates linking identities and public keys. ### Remember For the lesson’s TLS 1.3 example, associate forward secrecy with ephemeral Diffie-Hellman.