A computer-readable medium may include one or more instructions for providing sub-images, one or more instructions for receiving selection of a plurality of sub-images, one or more instructions for constructing a first image, the first image being a unified image including the selected plurality of sub-images, one or more instructions for comparing at the selected plurality of sub-images with previously selected sub-images, and one or more instructions for providing access to at least one of a device, a service, or a function when the selected plurality of sub-images match the previously selected sub-images.