Protected Login.

Despite known problems with their security and ease-of-use, passwords will likely continue to be the main form of web authentication for the foreseeable future. We define a certain class of password-based authentication protocols and call them protected login . Protected login mechanisms present reasonable security in the face of real-world threat models. We find that some websites already employ protected login mechanisms, but observe that they struggle to protect first logins from new devices --- reducing usability and security. Armed with this insight, we make a recommendation for increasing the security of web authentication: reduce the number of unprotected logins, and in particular, offer opportunistic protection of first logins. We provide a sketch of a possible solution.