Effects of Password Permutation on Subjective Usability Across Platforms

Kristen K. Greene

Abstract: The current work examines the effects of password permutation on subjective usability across platforms, using system-generated passwords that adhere to the password requirements found in higher-security enterprise environments. This research builds upon a series of studies at the National Institute of Standards and Technology by testing a previously proposed idea of password permutation: grouping like character classes together in order to improve password usability. Password permutation improves mobile device entry by reducing the number of keystrokes required to enter numbers and symbols. Across platforms (smartphone, tablet, and desktop computer) participants rated the longer (length 14) permuted passwords as easier to type than the shorter (length 10) non-permuted passwords. This demonstrates that the composition and structure of a password are important; people are sensitive to factors beyond simple password length. By combining qualitative and quantitative research, we will ultimately arrive at a more complete understanding of how password construction impacts usability.