OPAQUE
Asymmetric PAKE: password-authenticated key exchange where the server never sees the password. Jarecki + Krawczyk + Xu, 2018. RFC in progress. Distinct from classic authentication: server compromise doesn't leak passwords even hashed.
How: client runs OPRF (Oblivious Pseudo-Random Function) with server → output = key derived from password but server can't calculate password from it. Logs in via challenge-response on this key. Adoption: WhatsApp encrypted backups, Facebook Cloud WiFi passwords. Modern post-password movement: WebAuthn/passkeys are a cleaner approach but require hardware support. OPAQUE is backward-fit for password-based flows.