Glossary · Cryptography & authentication
PAKE (password-authenticated key exchange)
A PAKE is a cryptographic protocol in which two parties use a shared password to establish a strong session key — without ever transmitting the password or exposing it to offline guessing from intercepted traffic.
The problem PAKEs solve: passwords are low-entropy secrets, and anything derived from them naively (hashes, simple challenge-responses) can be brute-forced offline once observed. A PAKE binds the password into a key exchange such that an eavesdropper — or an active man-in-the-middle — learns nothing they can grind against a dictionary; each password guess costs a live protocol run.
PAKEs come in two families. In a balanced PAKE, both sides know the password. In an asymmetric or augmented PAKE (aPAKE) — the family relevant to client-server login — the server stores only derived material, never anything password-equivalent, so a database breach does not directly hand the attacker usable credentials. OPAQUE is the modern, IETF-standardized aPAKE; SRP is its widely deployed predecessor.