Abstract: An authentication system for use in a secure communication system having a verification means (6) for verifying the identity of a user attempting to access a database server (2). In order to complete authentication, the user is required to enter personal authentication data (PAD) into a client terminal (1). The PAD consists of a series of images and the client terminal (1) displays a login screen including a group of user selectable keys each associated with a respective image. At least one of the images associated with a user selectable key is an advertising image and the authentication system is adapted to generate revenue through the use of the advertising image in the login screen.