End users of a multi-factor authentication service can utilize an account management service, and third-party website can register to utilize the multi-factor authentication service. Registering a third-party website can comprise the multi-factor authentication service receiving a valid digital identity certificate for the third-party website, and receiving an agreement to terms of use of the multi-factor authentication service for the third-party website. Once received, the multi-factor authentication service can enable the third-party website to utilize the service (e.g., switch the service on, or send an authorization key to the third-party website). Further, registering a user to the multi-factor authentication service can comprise determining availability of service, and providing a location-specific access code. Additionally, registering the user can comprise registering the user's mobile device, for example, to provide multi-factor authentication. Also, an Internet-based user account management user interface can be provided that allows a user to view transactions on their account, and an ability to shut off a designated mobile device's ability to authenticate.