Abstract: An identification label with a three-dimensional wrinkled structure may be formed by depositing a hard film with a high elastic modulus on an elongated substrate of a lower elastic modulus. Wrinkles with defects develop as the substrate is subsequently allowed to relax. Defects such as ridge endings and ridge bifurcations are randomly distributed over the wrinkled surface, and allow to uniquely identify any given identification label with the high degree of accuracy. Since the formation of defects is a random process, the wrinkled structure cannot be reproduced or counterfeited. The labels are thus forgery-proof.