To provide a user registration method capable of ensuring the authentication of service users while protecting privacy information without being complex to users, and a proxy authentication method that is secure and easy for a service provider to use in terms of management of privacy information.

A proxy authentication agent 200 registers and records the biometric information of a user 100 in a database 230 together with the user's privacy information, creates a provider authentication code generation module for the service provider, and performs authentication as a proxy by causing an authentication code coming via a user authentication code generation module distributed to users to be collated with another authentication code coming via the provider authentication code generation module.