Popularity Is Everything a New Approach to Protecting Passwords From Statistical-Guessing Attacks

The authors propose to strengthen user-selected passwords against statistical-guessing attacks by allowing users of Internet-scale systems to choose any password they want-so long as it's not already too popular with other users. They create an oracle to identify undesirably popular passwords using an existing data structure known as a count-min sketch, which they populate with existing users' passwords and update with each new user password. Unlike most applications of probabilistic data structures, which seek to achieve only a maximum acceptable rate false-positives, they set a minimum acceptable false-positive rate to confound attackers who might query the oracle or even obtain a copy of it.