Distortion metrics for predicting authentication functionality of printed security deterrents

Document authentication is the process by which a unique identifier is assigned to each version of a printed document and is verified via an inspection procedure. One type of approach that has proven successful involves printing overt color-tile security deterrents, which can be scanned and analyzed to provide authenticity. For a variety of reasons discussed herein, it is advantageous to estimate whether or not a printed deterrent will authenticate without invoking the actual authentication process. Several algorithms are presented to predict the outcome of the authentication process. The area-over-the-curve (AOC) statistic is one of the tools used to characterize how well each candidate algorithm estimates authentication performance in the presence of distortions introduced via different print+scan paths. A surprising but useful result is that a no-reference metric yields the best performance: the AOC is approximately half that of all other tested methods, and is over five times smaller than the AOC achieved by state-of-the-art algorithms SSIM and VIF.