An approach for authenticating parties engaged in a web-based transaction without compromising the integrity or anonymity of the parties is described. An authentication platform receives, from a first application associated with a first party, an authentication request that has been redirected in response to a transaction initiated with a second application associated with a second party. The authentication platform forwards knowledge based assessment information to the first application that is based on determined behavioral information for authenticating the second party to the first party. A valid response to the knowledge based assessment information by the first application provides authentication of the first party to the second party.