Techniques are described for identifying and validating security documents according to an Eigen image process method. For example, a security document authentication device selects one or more reference documents of different document types, calculates, from the reference documents, one or more Eigen images and Eigen values for the plurality of different document types, and calculates a reference weight coefficient vector of each of the plurality of document types. Upon receiving at least one captured image of an unknown document, the device calculates a weight coefficient vector of the captured image, compares the weight coefficient vector of the captured image and each of the reference weight coefficient vectors of the document types to calculate a plurality of distances, and, based on the plurality of distances, identifies the unknown document as one of the plurality of document types.