Outline the design of an authentication scheme.
The authentication scheme would start with certain primitive information about a user, such as name and password.
As the use of the computing system continued, the authentication system would gather such information as commonly used programming languages; dates, times, and lengths of computing sessions; and use of distinctive resources.
The authentication challenges would become more individualized as the system learned more information about the user.
The design should include a list of many pieces of information about a user that the system could collect. It is permissible for the system to ask an authenticated user for certain additional information, such as a favorite book, to use in subsequent challenges.
The design should also consider the problem of presenting and validating these challenges: Does the would-be user answer a true-false or a multiple-choice question? Does the system interpret natural language prose?