A Multi Way Tree for Token Based Authentication

Tokens are popular in two factor authentication, where the first authentication credential is a fixed secret key s
₁
associated with the user and the second authentication credential is a dynamic secret key s
₂
generated by the token assigned to the user. Popular hardware tokens use a synchronized clock T along with a static secret key encoded into the token to generate a one time secret s
₂
. The contribution of the paper is to eliminate this clock synchronization with the authentication server S and to detect unauthorized login attempts when an intruder is in possession of s
₁
or s
₂
but not both, with a high degree of certainty.