1. A method for creating a one-dimensional iris string from an image of an eye of a subject, comprising: obtaining the image of the eye; detecting an iris region in the image of the eye, the iris region having an inner boundary and an outer boundary; and unfolding the iris region by employing a spiral sampling method to obtain sample pixels in the iris region, wherein the spiral sampling method chooses a spiral shape that obtains a selected number of turns on each side, wherein the spiral shape is a linear spiral, an Archimedean spiral, or a logarithmic spiral, and wherein the sample pixels are the one-dimensional iris string.