Ben has been tasked with developing a new application with a global user base that will enable users to sign up and access their existing data. He wants to implement an authentication method that can verify that the users are the right individuals to be linked with their respective accounts. What methods can he use to authenticate these users?

Knowledge-based authentication is a type of authentication that relies on information that only the user is likely to know, such as past tax payments, bill amounts, or similar information. While requesting a Social Security number is less secure and only applicable to users in the United States, federated identity via Google accounts is not suitable for this purpose as Google accounts do not have a user validation requirement. Validation emails, on the other hand, only demonstrate that the user has access to an account they provide, rather than verifying their identity as a specific individual.