Patent attributes
Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for authorizing actions of a service provider. In one aspect, a method includes providing a user security key to a mobile device of a user. A request is received from a client device distinct from the mobile device to perform an action. A challenge token including a security signature matched to a service security key is generated, and the challenge token is provided to the mobile device. An approval value is received from the client device. The approval value is determined to be valid in reference to the challenge token and the user security key previously provided to the mobile device and to indicate approval to perform the action for the user. The action is performed in response to receiving the approval value.
