Originally published in Journal of Computers: http://www.academypublisher.com/jcp/index.htmlIt is easy for humans to design passwords that are easily remembered. However, such passwords may have a predictable structure, making exhaustive search feasible. We have divided human-generated passwords into three categories: Non-word passwords, Mixture passwords, and Word passwords; depending on their overall structure. Within these categories, we have analyzed the search-space reduction of several common password sub-structures. From this analysis, we have derived guidelines that yield strong passwords within in each password category. Our results contribute towards the goal of achieving both strong and memorable passwords
