Authentication with Distortion Criteria

In a variety of applications, there is a need to authenticate content that has experienced legitimate editing in addition to potential tampering attacks. We develop one formulation of this problem based on a strict notion of security, and characterize and interpret the associated information-theoretic performance limits. The results can be viewed as a natural generalization of classical approaches to traditional authentication. Additional insights into the structure of such systems and their behavior are obtained by further specializing the results to Bernoulli and Gaussian cases. The associated systems are shown to be substantially better in terms of performance and/or security than commonly advocated approaches based on data hiding and digital watermarking. Finally, the formulation is extended to obtain efficient layered authentication system constructions.Comment: 22 pages, 10 figure

Print-Scan Resilient Text Image Watermarking Based on Stroke Direction Modulation for Chinese Document Authentication

Print-scan resilient watermarking has emerged as an attractive way for document security. This paper proposes an stroke direction modulation technique for watermarking in Chinese text images. The watermark produced by the idea offers robustness to print-photocopy-scan, yet provides relatively high embedding capacity without losing the transparency. During the embedding phase, the angle of rotatable strokes are quantized to embed the bits. This requires several stages of preprocessing, including stroke generation, junction searching, rotatable stroke decision and character partition. Moreover, shuffling is applied to equalize the uneven embedding capacity. For the data detection, denoising and deskewing mechanisms are used to compensate for the distortions induced by hardcopy. Experimental results show that our technique attains high detection accuracy against distortions resulting from print-scan operations, good quality photocopies and benign attacks in accord with the future goal of soft authentication

Validation and Data Repairing of Document Image using Steganography Method

This paper attempts to propose a novel technique of blind authentication based on the method of secret in addition to data repair capability for grayscale document images through the use of the Portable Network Graphics (PNG) image. For every block of a grayscale document image, an authentication signal is generated, which, along with the block content in binary, is transformed into numerous shares using the Shamir secret sharing scheme. The parameters involved are carefully selected so that as many shares as possible can be generated and embedded into an alpha channel plane. After this, the alpha channel plane is combined with the original grayscale image to yield a PNG image. During this process, the computed share values are recorded as a range of alpha channel values near their maximum value of 255 to return a transparent stego-image with a disguised effect. In the image authentication process, marking of an image block is done as tampered, if the authentication signal computed from the current block content does not match the one extracted from the shares embedded in the alpha channel plane. Each tampered block is then subjected to data repairing by a reverse Shamir scheme after collecting two shares from unmarked blocks. Procedures to protect the safety of the data that lies concealed in the alpha channel have been proposed. Decent experimental results demonstrate the efficiency of the proposed method

A Framework for Multimedia Data Hiding (Security)

With the proliferation of multimedia data such as images, audio, and video, robust digital watermarking and data hiding techniques are needed for copyright protection, copy control, annotation, and authentication. While many techniques have been proposed for digital color and grayscale images, not all of them can be directly applied to binary document images. The difficulty lies in the fact that changing pixel values in a binary document could introduce Irregularities that is very visually noticeable. We have seen but limited number of papers proposing new techniques and ideas for document image watermarking and data hiding. In this paper, we present an overview and summary of recent developments on this important topic, and discuss important issues such as robustness and data hiding capacity of the different techniques