Which authentication method relies on a password-based authentication and key agreement that provides forward secrecy?

• A. OAuth 2.0
• B. Simultaneous authentication of equals (SAE)
• C. Kerberos
• D. TLS

Answer: (B)

Simultaneous Authentication of Equals is a password-authenticated key exchange. It uses a shared password to perform mutual authentication and to derive a fresh, common session key through a PAKE (password‑based key exchange) process. The key point is that the handshake does not reveal enough information for an offline attacker to test guesses for the password, and the resulting session key is ephemeral, providing forward secrecy. In practice, this makes it ideal for password-based wireless authentication (as in WPA3), because each connection establishes a unique key that isn’t compromised by later exposure of the password.

OAuth 2.0 is an authorization framework, not a password‑based key exchange. Kerberos relies on tickets issued by a Key Distribution Center and doesn’t perform a password‑based mutual key exchange with forward secrecy. TLS can provide forward secrecy with ephemeral key exchanges, but it is primarily certificate-based authentication rather than password‑based; it’s not the typical password‑based PAKE described here.