Password Strength Estimation

Dropbox developed zxcvbn, an open-source password strength estimator that goes beyond naive entropy calculations to account for common password patterns (dictionary words, spatial patterns, sequences, etc.). This system aims to provide more accurate feedback to users, encouraging stronger password choices and better security. The initial implementation was used on dropbox.com/register and made available on GitHub. This post details the algorithm and compares its output to other password strength meters.