A method and computing system are proposed for producing an authenticable security device with two sides. The verso side is covered with a luminescent emissive variable intensity layer formed for example by invisible luminescent ink halftones and the recto side is covered with transmissive non-luminescent ink halftones. The backlit colors resulting from the emissions of the luminescent layer or resulting from illumination by normal white light through the transmissive non-luminescent ink halftones are predicted by a backlighting model. This model enables computing the surface coverages of the luminescent and/or non-luminescent ink halftones in order to obtain a desired color either under excitation light (UV light) or under normal white light. This enable creating authenticable backlit images substantially similar to pre-stored reference images, either under normal white light, under excitation light, or under both the normal white light and the excitation light.