catchword, motto, shibboleth, slogan - a favorite saying of a sect or political group

arcanum, secret - information known only to a special group; "the secret of Cajun cooking"

positive identification - evidence proving that you are who you say you are; evidence establishing that you are among the group of people already known to the system; recognition by the system leads to acceptance; "a system for positive identification can prevent the use of a single identity by several people"