Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for receiving first user input by a primary device from a primary input device, where the user input is provided by a user to the primary input device that is coupled to a primary device. Receiving second user input provided by the user to a secondary input device that is in communication with the primary device. Determining a user credential based on the first user input and the second user input, where at least one or the first input and the second input includes at least a portion of the user credential. Receiving an indication that the user is authentic based on the user credential, and, in response, enabling the user to further interact with the primary device.