A graphical user interface supports an interactive client-server authentication based on Random Partial Pattern Recognition algorithm (RPPR). In RPPR, an ordered set of data fields is stored for a client to be authenticated in secure memory on the server side. A graphical user interface presents a clue generated at the server to the client, such positions in the ordered set of a random subset of data fields from the ordered set. The client enters input data in multiple fields of the interface according to the clue, and the server accepts the input data from the client. The input data includes storage units representing alpha-numeric characters, images and colors corresponding to the field contents for the data fields. The interface includes indicators for elapsed time and status of the authentication session.