Abstract: Authenticating an object includes marking the object with a mark containing at least two markers wherein each marker fluoresces when illuminated with one of UV and IR, but does not fluoresce when illuminated with visible light. The marking may be in the form of a bar code containing a number or alphanumeric codes uniquely identifying the object to be marked with the particular mixture of markers used. A spectral analysis of the marking ink or the code is used to define spectral peaks for use as part of the authentication signature. The authentication signature may be defined using the identified peaks and logical conditions imposed upon them such as minimum threshold amplitude values and ratio values among peaks.

Abstract: A composite authentication mark includes a bar code portion that is visible when illuminated with visible light and an invisible code portion that is not visible when illuminated with visible light, wherein the bar code portion includes a plurality of bars and spaces and the invisible code portion is arranged in at least one of the spaces of the bar code portion without overlapping any of the bars of the bar code portion. Because the invisible code portion does not overlap with any of the bars of the bar code portion, a single-step printing and reading processes may be used. More information can be coded by the composite authentication mark by using the relative location of the invisible code portion within the spaces of the bar code portion.