The print-scan problem in printed steganography of face images

Abstract

The use of steganography and watermarking techniques for a secure identification and automatic authentication of the holder's photo in an ICAO-consistent (travel) document is proposed. A specific distortion of the hidden watermarks is caused by the print-scan process, as a printed photo is scanned to constitute the reference pattern in face verification. The main distortions induced by this process are identified - image rotation and cropping, nonlinear intensity change and additive color quantization noise. Three steganography methods are selected and adapted for this application. They provide hidden watermark insertion in the image domain, the Fourier-Mellin transform domain or in a net of normalized triangle regions. Test results induce the conditions for the proper use of these methods. © Springer International Publishing Switzerland 2013.