Seung-Jin Ryu

Detection of copy-rotate-move forgery using Zernike moments

As forgeries have become popular, the importance of forgery detection is much increased. Copy-move forgery, one of the most commonly used methods, copies a part of the image and pastes it into another part of the the image. In this paper, we propose a detection method of copy-move forgery that localizes duplicated regions using Zernike moments. Since the magnitude of Zernike moments is algebraically invariant against rotation, the proposed method can detect a forged region even though it is rotated. Our scheme is also resilient to the intentional distortions such as additive white Gaussian noise, JPEG compression, and blurring. Experimental results demonstrate that the proposed scheme is appropriate to identify the forged region by copy-rotate-move forgery.

Estimation of linear transformation by analyzing the periodicity of interpolation

Linear transformation, such as rotation, scaling, or any combinations of geometric attacks, is among the most common forms of image manipulation. This letter proposes a forensic technique that estimates the linear transformation of an investigated image. We exploited the periodic properties of interpolation by the second-derivative of the transformed image in both the row and column directions. Both the magnitude and phase information of the derived signals were analyzed to estimate the transformation matrix accurately. Empirical evidence from a large database of manipulated images indicates the superior performance of the proposed method.

Electrophotographic printer identification by halftone texture analysis

Estimating printing source is applicable in many forensic situations. In this paper, we propose an electrophotographic printer identification scheme from its printed material, in which imperceptible halftone patterns are contained inherently. The halftone textures in each channel of CMYK domain are analyzed. We construct a histogram from angle values of linear features extracted by Hough transform. By averaging the histograms from multiple images, a printers reference pattern is identified. The soure printer is determined by a maximum correlation value between the reference patterns and the histogram of given image. Experiments are performed on 9,000 images made by 9 printers. The result supports that the presented scheme clearly recognizes different halftone textures.

Screenshot identification using combing artifact from interlaced video

As screenshots of copyrighted video contents are spreading through the Internet without any regulation, the copyright infringement arises gradually. However, there are still no techniques that prevent illegal screenshots from spreading out. Since most television systems use interlaced scanning mode and camcorders offer interlaced recording, many screenshots are interlaced. In this paper, we propose a screenshot identification scheme using unique characteristic of interlaced video, combing artifact. To do this, several blocks of the input image are selected for the significant combing artifact they have. In each block, eight features that represent the artifact are extracted. These extracted features are applied to train and test support vector machine for identifying whether the input image is a screenshot or not. In the experiments, the identification accuracy is measured when the input image is converted from and to common multimedia formats. The results prove that the proposed identification scheme performs well under the widely used image formats as JPEG, BMP, TIFF and video formats as MPEG-2, MPEG-4, H.264.

Forgery Detection for Surveillance Video

In many courts, surveillance videos are used as important legal evidence. Nevertheless, little research is concerned with forgery of surveillance videos. In this paper, we present a forgery detection system for surveillance videos. We analyze the characteristic of surveillance videos. Subsequently, forgeries mainly occur to the surveillance videos are investigated. To identify both RGB and infrared video, Sensor Pattern Noise (SPN) for each video is transformed by Minimum Average Correlation Energy (MACE) filter. Manipulations on the given video are detected by estimating scaling factor and calculating correlation coefficient. Experimental results demonstrate that the proposed scheme is appropriate to identify forgeries of surveillance video.

Document Forgery Detection with SVM Classifier and Image Quality Measures

This paper presents a detection scheme for a fraudulent document made by printers. The fraud document is indistinguishable by the naked eye from a genuine document because of the technological advances in printing methods. Even though we cannot find any visual evidence of forgery, the fraud document includes inherent device features. We propose a method to uncover these features. 17 image quality measures are applied to discriminate between genuine and fake documents. The results of each measure are used as training and testing parameters of SVM classifier to determine fake documents. Preliminary experimental results are presented based on the fraud gift voucher made by several color printers.

Vector Watermarking Robust to Both Global and Local Geometrical Distortions

A blind watermarking algorithm for vector graphic images is presented. The algorithm is resilient to both global and local geometrical distortions. The polygonal line is represented by the wavelet descriptor. An additive watermarking scheme is used to embed the watermark by slightly modifying the wavelet descriptor, and that causes invisible distortions to the coordinates of the vertices. The invariant properties of the wavelet descriptor ensure that the presented algorithm is resilient against both global and local geometrical distortions. Using vector graphic images from contour maps, we demonstrate that the presented algorithm outperforms the algorithm based on the Fourier descriptor.

Source camcorder identification from cropped and scaled videos

In the field of imaging device identification, the unique property of Photo-Response Non-Uniformity (PRNU) is widely employed. One of disadvantages of the PRNU based methods is sensitive to de-synchronization attacks. In this paper, we propose an improved PRNU based camcorder identification method which performs well with simultaneously cropped and scaled videos. The proposed method solves the out-of-sync problems by achieving downscale-tolerance of Minimum Average Correlation Energy Mellin Radial Harmonic (MACE-MRH) filter. The experimental results demonstrate that the proposed method identifies source devices faster and more accurate than the existing method.

Detecting re-captured videos using shot-based photo response non-uniformity

With advances in digital camcorders, re-capturing commercial videos called camcorder theft is getting a big problem. In this paper, we propose an automatic detection method for re-captured videos based on the photo response non-uniformity (PRNU). To discern a re-captured video, a given video is divided into shots first. Several usable shots are selected and PRNU is estimated from each of the shots. Using peak-to-correlation energy (PCE), a connection matrix, which indicates which shots were recorded with a specific camcorder, is constructed. Then, false negative connections are corrected by using Warshalls algorithm. With the number of connections from connection matrix, the given video is determined whether it was the re-captured or not. The experimental results show that the proposed method performs well even with compressed and scaled re-captured videos.

Improved Watermark Estimation Scheme Based on Neighborhood Filter

This paper introduces a new watermark estimation scheme for an additive watermark embedding model in spatial domain. Unlike traditional estimating filters only considering spatially adjacent pixels, the proposed method takes into account pixels which are both in close intensity value and spatially near distance. Thus, it is possible for the proposed method to estimate stably the watermark signal from a watermarked image that severely fluctuates in intensity value. Also, this paper proposes the preprocessing method that boosts the performance of our watermark estimation filter by suppressing host signal noises. Extensive experimental results show that the proposed method outperforms the traditional filters under various attacks.