US Patent 9075979 Authentication based on proximity to mobile device

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for performing multi-factor authentication. In one aspect, a method includes determining that a user has successfully completed an authentication factor, determining whether a mobile device associated with the user is proximate to a computer; and authenticating the user based on determining that the user has successfully completed the authentication factor, and that the mobile device is proximate to the computer.