Abstract: An initiating user receives an authentication code and an associated confirmation word from a server system in response to an authentication code request. The initiating user initiates a communication session with an authenticating user and provides the authentication code to the authenticating user without providing the associated confirmation word to the authenticating user. The authenticating user is only able to obtain the associated confirmation word if the authentication code corresponds to an authentication code previously generated by the server system for the initiating user and no usage limitation on the authentication code has been reached. Subsequently, the initiating user receives a confirmation word from the authenticating user. The initiating user provides action instructions to the authenticating user when the confirmation word provided by the authenticating user corresponds to the associated confirmation word.