What is OPIE Authentication System?

OPIE is the initialism of "One time Passwords In Everything". Opie is a mature, Unix-like login and password package installed on the server and the client which makes untrusted networks safer against password-sniffing packet-analysis software like dSniff and safe against Shoulder surfing.It works by circumventing the delayed attack method because the same password is never used twice after installing Opie. OPIE implements a one-time password scheme based on S/KEY, which will require a secret passphrase to generate a password for the current session, or a list of passwords you can print and carry on your person.