Tamper Localization Research Articles

Semi-fragile watermarking algorithm for image tampers localization and recovery

Two watermarks are embedded into the original image. One is the authentication watermark generated by secret key, which is embedded into the sub-LSB (Least Significant Bit) of the original image for tamper localization; the other is the recovery watermark for tamper recovering. The original image is divided into 8×8 blocks and each block is transformed by Discrete Cosine Transform (DCT). For each block, some lower frequency DCT coefficients are chosen to be quantized and binary encoded so as to gain the recovery watermark of each block, and the recovery watermark is embedded into the LSB of another block by chaos encryption and authentication chain technology. After the two watermarks being detected, the location of any minute changes in image can be detected, and the tampered image data can be recovered effectively. In the paper, the number of coefficients and their bit lengths are carefully chosen in order to satisfy with the payload of each block and gain the capability of self-recovering. The proposed algorithm can well resist against possible forged attacks. Experimental results show that the watermark generated by the proposed algorithm is sensitive to tiny changes in images, and it has higher accuracy of tamper localization and good capability of the tamper recovery.

Multipurpose audio watermarking algorithm

To make audio watermarking accomplish both copyright protection and content authentication with localization, a novel multipurpose audio watermarking scheme is proposed in this paper. The zero-watermarking idea is introduced into the design of robust watermarking algorithm to ensure the transparency and to avoid the interference between the robust watermark and the semi-fragile watermark. The property of natural audio that the VQ indices of DWT-DCT coefficients among neighboring frames tend to be very similar is utilized to extract essential feature from the host audio, which is then used for watermark extraction. And, the chaotic mapping based semi-fragile watermark is embedded in the detail wavelet coefficients based on the instantaneous mixing model of the independent component analysis (ICA) system. Both the robust and semi-fragile watermarks can be extracted blindly and the semi-fragile watermarking algorithm can localize the tampering accurately. Simulation results demonstrate the effectiveness of our algorithm in terms of transparency, security, robustness and tampering localization ability.

A Sequential Quantization Strategy for Data Embedding and Integrity Verification

Quantization-based embedding has been used for integrity verification in semi-fragile watermarking. However, some of the illegal modifications cannot be detected in the normal quantization-based methods, especially when the host values (i.e., the values chosen in a host signal for data embedding) are independent from each other. In this paper, a sequential quantization strategy (SQS) is proposed to make the modulation of a host value dependent on a certain number of the previous ones. Therefore, a balance between security improvement and tamper localization can be achieved for integrity verification. Furthermore, the proposed SQS is incorporated with a reversible data hiding mechanism. A new watermarking algorithm is then generated for mesh authentication. The experimental results show that the chance to detect illegal modifications is increased by adopting the SQS while the property of reversibility is achieved.

A majority-voting based watermarking scheme for color image tamper detection and recovery

This paper presents a novel color image watermarking scheme for both tamper detection and tampered image recovery. The proposed scheme embeds watermarks consisting of the authentication data and the recovery data into image blocks. In the tamper detection process, instead of independently examining each embedded authentication data, we take all the authentication data embedded in an image into account and utilize a majority-voting technique to determine the legitimacy of image blocks. Experimental results show that the proposed scheme can effectively thwart collage attack and vector quantization (VQ) attack, while sustaining superior accuracy of tamper localization. Furthermore, the results reveal that the tampered images can be successfully recovered with acceptable visual quality.

A chaos-based self-embedding secure watermarking algorithm

This paper presents a novel chaos-based self-embedding secure watermarking algorithm based on the chaotic pseudorandom ness and sensitivity to initial value of chaotic map. In the proposed approach, the real-valued chaotic sequence, which is generated by the given initial value as secret key, is used to produce the ordered indices as the watermark embedding positions. The proposed algorithm has a larger key space than the existing self-embedding watermarking algorithms due to its watermark embedding positions being randomly selected by the secret key. Furthermore, the problem, how to locate the tampered image block in the self-embedding watermarking algorithm has been solved successfully. Theoretical analysis and simulation results show that our scheme not only improves the abilities of tamper localization, but also has better security against many attacks, including the vector quantization and synchronous counterfeiting attacks.

A Set Theoretic Framework for Watermarking and Its Application to Semifragile Tamper Detection

We introduce a set theoretic framework for watermarking. Multiple requirements, such as watermark embedding strength, imperceptibility, robustness to benign signal processing, and fragility under malicious attacks are described as constraint sets and a watermarked image is determined as a feasible solution satisfying these constraints. We illustrate that several constraints can be formulated as convex sets and develop a watermarking algorithm based on the method of projections onto convex sets. The framework allows flexible incorporation of different constraints, including embedding strength requirements for multiple watermarks that share the same spatial context and different imperceptibility requirements based on frequency-weighted error and local texture perceptual models. We illustrate the effectiveness of the framework by designing a hierarchical semifragile watermark that is tolerant to mild compression, allows tamper localization, and is fragile under aggressive compression. Using a quad-tree representation, a spatial resolution hierarchy is established on the image and a watermark is embedded corresponding to each node of the hierarchy. The spatial hierarchy of watermarks provides a graceful tradeoff between robustness and localization under mild JPEG compression, where watermarks at coarser levels demonstrate progressively higher immunity to JPEG compression. Under aggressive compression, watermarks at all hierarchy levels vanish, indicating a lack of trust in the image data. The constraints implicitly partition watermark power in the resolution hierarchy as well as among image regions based on robustness and invisibility requirements. Experimental results illustrate the flexibility and effectiveness of the method

Digital watermarking scheme exploiting nondeterministic dependence for image authentication

Watermarking schemes for authentication purposes are characterized by three factors: security, resolution of tamper localization, and embedding distortion. Since the requirements of high security, high localization resolution, and low distortion cannot be fulfilled simultaneously, the relative importance of a particular factor is application-dependent. Moreover, blockwise dependence is recognized as a key requirement for fragile watermarking schemes to thwart the Holliman-Memon counterfeiting attack. However, it has also been observed that deterministic dependence is still susceptible to transplantation attack or even simple cover-up attack. This work proposes a fragile watermarking scheme for image authentication, which exploits nondeterministic dependence and provides the users with freedom of making trade-offs among the three factors according to the needs of their applications.

Secure authentication watermarking for localization against the Holliman–Memon attack

Authentication watermarking schemes using block-wise watermarks for tamper localization are vulnerable to the Holliman---Memon attack. In this paper, we propose a novel method based on the Wong's localization scheme (Proceedings of the IS&T PIC, Portland) to resist this attack. A unique image index scheme is used for computing the authentication signature that is embedded in the least significant bit-plane of the block. The informed detector estimates the correct image index by using the side information about the watermarked image. The image index estimation from the fake image can definitely be an alternative to keeping a directory of image indices. So it is not necessary to manage the database of image indices for the verification purpose. The authenticity measure is defined to quantify the attack severity by taking the connectivity among possible authentic blocks into consideration. There are more blocks verified as authentic when this measure is high for a fake image constructed using this attack. As such, the blocks for a fake image can be chosen from a reduced number of database images. The blocks from any such image are to be connected with each other to maximize the authenticity measure. Thus, the attacker's task to generate a fake image of reasonable perceptual quality becomes increasingly difficult. With the proposed method there is no loss or ambiguity in localization after the Holliman---Memon attack and content tampering in an image. The localization accuracy in the proposed method is demonstrated by the simulation results and is equal to the chosen block size, similar to the Wong's scheme.

Joint near-lossless compression and watermarking of still images for authentication and tamper localization

A system is presented to jointly achieve image watermarking and compression. The watermark is a fragile one being intended for authentication purposes. The watermarked and compressed images are fully compliant with the JPEG-LS standard, the only price to pay being a slight reduction of compression efficiency and an additional distortion that can be anyway tuned to grant a maximum preset error. Watermark detection is possible both in the compressed and in the pixel domain, thus increasing the flexibility and usability of the system. The system is expressly designed to be used in remote sensing and telemedicine applications, hence we designed it in such a way that the maximum compression and watermarking error can be strictly controlled (near-lossless compression and watermarking). Experimental results show the ability of the system to detect tampering and to limit the peak error between the original and the processed images.

Lossless watermarking for image authentication: a new framework and an implementation

We present a novel framework for lossless (invertible) authentication watermarking, which enables zero-distortion reconstruction of the un-watermarked images upon verification. As opposed to earlier lossless authentication methods that required reconstruction of the original image prior to validation, the new framework allows validation of the watermarked images before recovery of the original image. This reduces computational requirements in situations when either the verification step fails or the zero-distortion reconstruction is not needed. For verified images, integrity of the reconstructed image is ensured by the uniqueness of the reconstruction procedure. The framework also enables public(-key) authentication without granting access to the perfect original and allows for efficient tamper localization. Effectiveness of the framework is demonstrated by implementing the framework using hierarchical image authentication along with lossless generalized-least significant bit data embedding.

A hierarchical digital watermarking method for image tamper detection and recovery

In this paper, we present an efficient and effective digital watermarking method for image tamper detection and recovery. Our method is efficient as it only uses simple operations such as parity check and comparison between average intensities. It is effective because the detection is based on a hierarchical structure so that the accuracy of tamper localization can be ensured. That is, if a tampered block is not detected in level-1 inspection, it will be detected in level-2 or level-3 inspection with a probability of nearly 1. Our method is also very storage effective, as it only requires a secret key and a public chaotic mixing algorithm to recover a tampered image. The experimental results demonstrate that the precision of tamper detection and localization is 99.6% and 100% after level-2 and level-3 inspection, respectively. The tamper recovery rate is better than 93% for a less than half tampered image. As compared with the method in Celik et al. [IEEE Trans. Image Process. 11(6) (2002) 585], our method is not only as simple and as effective in tamper detection and localization, it also provides with the capability of tamper recovery by trading off the quality of the watermarked images about 5 dB.

An ill-posed operator for secure image authentication

Many problems in science and technology are modeled by ill-posed operators and the main difficulty in obtaining accurate solutions is caused by the high instability of such operators. The paper introduces a new schema for secure image authentication. It is based on a rather unconventional approach - the extremely high sensitivity of ill-posed operators to any change in the input data is turned into a tool to achieve fragile watermarking for secure image verification. The ill-posed operator of concern is based on a highly ill-conditioned matrix interrelating the watermark and the original image. Authentication is achieved by solving the least squares problem associated with the underlying linear operator. Regarding general requirements for secure watermark-based authentication, analytical and practical aspects of the introduced technique are discussed. It is shown that the proposed authentication schema is highly secure while providing excellent tamper localization. Several experiments were conducted to demonstrate the effectiveness of the technique when it is subjected to different attacks, including vector quantization counterfeiting and cropping.

Wavelet packets-based digital watermarking for image verification and authentication

In this paper, we present a novel watermarking scheme to ensure the authenticity of digital images. Our authentication technique is able to detect malicious tampering of images even if they have been incidentally distorted by basic image processing operations. The image protection is achieved by the insertion of a secret author's identification key in the image wavelet coefficients by their selective quantization. Our system uses characteristics of the human visual system to maximize the embedding weights while keeping good perceptual transparency. We develop an image-dependent method to evaluate, in the wavelet domain, the optimal quantization step allowing the tamper proofing of the image. The nature of multiresolution discrete wavelet decomposition allows the spatial and frequency localization of image tampering. Experimental results are presented to demonstrate the capacity of our system to detect unauthorized modification of images, to show its robustness to image compression and high security levels and to compare it with publicly available image authentication software.

Hierarchical watermarking for secure image authentication with localization

Several fragile watermarking schemes presented in the literature are either vulnerable to vector quantization (VQ) counterfeiting attacks or sacrifice localization accuracy to improve security. Using a hierarchical structure, we propose a method that thwarts the VQ attack while sustaining the superior localization properties of blockwise independent watermarking methods. In particular, we propose dividing the image into blocks in a multilevel hierarchy and calculating block signatures in this hierarchy. While signatures of small blocks on the lowest level of the hierarchy ensure superior accuracy of tamper localization, higher level block signatures provide increasing resistance to VQ attacks. At the top level, a signature calculated using the whole image completely thwarts the counterfeiting attack. Moreover, "sliding window" searches through the hierarchy enable the verification of untampered regions after an image has been cropped. We provide experimental results to demonstrate the effectiveness of our method.