Password-based cryptography

Password-based cryptography is the study of password-based key encryption, decryption, and authorization. It generally refers two distinct classes of methods:

Single-party methods
Multi-party methods

Single party methods

Some systems attempt to derive a cryptographic key directly from a password. However, such practice is generally ill-advised when there is a threat of brute-force attack. Techniques to mitigate such attack include passphrases and iterated password-based key derivation functions such as PBKDF2.

Multi-party methods

Password-authenticated key agreement systems allow two or more parties that agree on a password to derive shared keys without exposing the password or keys to network attack. Earlier generations of challenge–response authentication systems have also been used with passwords, but these have generally been subject to eavesdropping and/or brute-force attacks on the password.