An authentication or authorization system to facilitate electronic transactions uses simultaneous or substantially simultaneous communications on two different networks to verify a user's identity. When a user logs onto a site, via the internet, a telephone number, either pre-stored or obtained in real time from the visitor, where the visitor can be called essentially immediately is used to set up, via the switched telephone network another communication link. Where the user has multiple communication links available, the telephone call is automatically placed via the authentication or authorization software simultaneously while the user is on-line. In the event that the user has only a single communication link, that individual will have to log off temporarily for purposes of receiving the telephone call. Confirmatory information is provided via the internet to the user. The automatically placed telephone call requests that the user feed back this confirmatory information for verification purposes. The telephone number which is being called is adjacent to the user's internet terminal. The user's response, via the telephone network, can be compared to the originally transmitted confirmatory information to determine whether the authentication or authorization process should go forward.