Five Word Password Composition Policy

Password composition policies (PCPs) are critical security rules that govern how users create passwords for online authentication.Despite passwords remaining the primary authentication method online, there is significant disagreement among experts, regulatory bodies, and researchers about what constitutes effective password policies.This lack of consensus has led to high variance in PCP implementations across websites, leaving both developers and users uncertain.Current approaches lack a theoretical foundation for evaluating and comparing different password composition policies.We show that a structurebased policy, such as the three-random words recommended by UK's National Cyber Security Centre (NCSC), can improve password security.We demonstrate this using an empirical evaluation of labelled password datasets and a new theoretical framework.Using these methods we demonstrate the feasibility and security of multi-word password policy and extend the NCSC's recommendation to five words to account for nonuniform word selection.These findings provide an evidence-based framework for password policy development and suggest that current web authentication systems should adjust their minimum word requirements upward while maintaining usability.This work addresses core areas of web security, and our results provide actionable insights for improving password policies across web platforms while maintaining usability.Our findings and insights provide immediate applications for system and web admins.Our work also provides a theoretical and reasoning basis for future password composition policy development and research.