1. A method for marking for an object, comprising the steps of: encoding each symbol of a set of symbols using a mapping function to produce corresponding encoded functions, wherein the mapping function is continuous and values of the encoded functions are real and vary continuously; summing the encoded functions in a spatial domain to generate a summed function; adding a bias to the summed function to produce a biased function, wherein the values of the biased function are all positive and real; and altering a physical property of the object according the biased function to arrange a mark on the object.