Introduction to Cryptography with Coding Theory, 3rd Edition

12.6 Password Protocols

We now look at how the communications take place in a password-based authentication protocol, as is commonly used to log onto computer systems. Password-based authentication is a popular approach to authentication because it is much easier for people to remember a phrase (the password) than it is to remember a long, cryptographic response.

In a password protocol, we have a user, Alice, and a verifier, Veronica. Veronica is often called a host and might, for example, be a computer terminal or a smartphone or an email service. Alice and Veronica share knowledge of the password, which is a long-term secret that typically belongs to a much smaller space of possibilities than cryptographic keys and thus passwords have small ...