One-Time Passwords in Everything (OPIE): Experiences with Building and Using Strong Authentication

The U. S. Naval Research Laboratory's OPIE (One-time Passwords In Everything) Software Distribution is an enhancement of Bellcore's S/Key(TM) 1.0 package. OPIE improves on S/Key in several areas, including FTP service with one-time passwords, and a stronger algorithm for generating one-time passwords. OPIE diverges from S/Key in select design decisions and in the behavior of certain programs. While not a total security solution, OPIE can be an important part of one. OPIE and its evolutionary predecessors have been used for over a year in parts of NRL. Its use has taught the authors lessons on implementation, usability, deployment, and future directions for improvement.