Techniques for authenticating a user are described. In one implementation, a user requests access to protected information or resources by providing a user name and a password to a web server that controls access to the information or resources. If the user name and password match a known user profile, the web server retrieves a user identifier (e.g., a personal identification number) and constructs a translation table around the user identifier. The translation table includes the values that constitute the user identifier, random representations of each value, visual images that represent each value, and random image names for each visual image. The information in the translation table is then used to generate a user interface that allows the user to enter his or her user identifier via the user's computing device without exposing the actual user identifier values to the computing device.