Spread Spectrum Watermarking Research Articles

An interval centroid based spread spectrum watermarking scheme for multi-flow traceback

Network flow watermarking schemes have been proposed to trace network attacks in the presence of stepping stones or anonymized channels. Most existing interval-based watermarking schemes are not only ineffective in tracing multiple network flows in parallel due to severe inter-flow interference in practice but also vulnerable to the newly introduced watermarking attacks. By combining the Interval Centroid Based Watermarking (ICBW) modulation approach with the Spread Spectrum (SS) watermarking coding technique, we herein propose an Interval Centroid Based Spread Spectrum Watermarking scheme (ICBSSW) for efficiently tracing multiple network flows in parallel. Based on our proposed theoretical model, a statistical analysis of ICBSSW, with no assumptions or limitations concerning the distribution of packet times, proves its effectiveness and robustness against inter-flow interference. ICBSSW can thwart multi-flow attacks by utilizing multiple Pseudo-Noise (PN) codes as random seeds for randomizing the location of the embedded watermark across multiple flows. The experiments using a large number of synthetically generated secure shell (SSH) traffic flows demonstrate that ICBSSW can efficiently trace multiple flows simultaneously and achieve robustness against inter-flow interference. Furthermore, our approach can be applied to other interval-based flow watermarking schemes besides ICBW for effective and efficient multi-flow traceback.

Quantisation-based video watermarking in the wavelet domain with spatial and temporal redundancy

In this article we introduce a new public digital watermarking technique for video copyright protection working in the discrete wavelet transform domain. The scheme uses binary images as watermarks. These are embedded in the detail wavelet coefficients of the middle wavelet sub-bands. The method is a combination of spread spectrum and quantisation-based watermarking. Every bit of the watermark is spread over a number of wavelet coefficients with the use of a secret key. The resilience of the watermarking algorithm was tested against a series of eight different attacks using different videos. To improve the resilience of the algorithm we use error correction codes and embed the watermark with spatial and temporal redundancy. The proposed method achieves a very good perceptual quality with mean peak signal-to-noise ratio values of the watermarked videos of more than 40 dB and high resistance to a large spectrum of attacks.

Robust wavelet-based video watermarking scheme for copyright protection using the human visual system

The development of the information technology and computer networks facilitates easy duplication, manipulation, and distribution of digital data. Digital watermarking is one of the proposed solutions for effectively safeguarding the rightful ownership of digital images and video. We propose a public digital watermarking technique for video copyright protection in the discrete wavelet transform domain. The scheme uses binary images as watermarks. These are embedded in the detail wavelet coefficients of the middle wavelet subbands. The method is a combination of spread spectrum and quantization-based watermarking. Every bit of the watermark is spread over a number of wavelet coefficients with the use of a secret key by means of quantization. The selected wavelet detail coefficients from different subbands are quantized using an optimal quantization model, based on the characteristics of the human visual system (HVS). Our HVS-based scheme is compared to a non-HVS approach. The resilience of the watermarking algorithm is tested against a series of different spatial, temporal, and compression attacks. To improve the robustness of the algorithm, we use error correction codes and embed the watermark with spatial and temporal redundancy. The proposed method achieves a good perceptual quality and high resistance to a large spectrum of attacks.

Secure Spread-Spectrum Watermarking for Telemedicine Applications

This paper presents a secure spread-spectrum watermarking algorithm for digital images in discrete wavelet transform (DWT) domain. The algorithm is applied for embedding watermarks like patient identification /source identification or doctors signature in binary image format into host digital radiological image for potential telemedicine applications. Performance of the algorithm is analysed by varying the gain factor, subband decomposition levels, size of watermark, wavelet filters and medical image modalities. Simulation results show that the proposed method achieves higher security and robustness against various attacks.

Adaptive Multiwavelet-Based Watermarking Through JPW Masking

In this paper, a multibit, multiplicative, spread spectrum watermarking using the discrete multiwavelet (including unbalanced and balanced multiwavelet) transform is presented. Performance improvement with respect to existing algorithm is obtained by means of a new just perceptual weighting (JPW) model. The new model incorporates various masking effects of human visual perception by taking into account the eye's sensitivity to noise changes depending on spatial frequency, luminance and texture of all the image subbands. In contrast to conventional JND threshold model, JPW describing minimum perceptual sensitivity weighting to noise changes, is fitter for nonadditive watermarking. Specifically, watermarking strength is adaptively adjusted to obtain minimum perceptual distortion by employing the JPW model. Correspondingly, an adaptive optimum decoding is derived using a statistic model based on generalized-Gaussian distribution (GGD) for multiwavelet coefficients of the cover-image. Furthermore, the impact of multiwavelet characteristics on proposed watermarking scheme is also analyzed. Finally, the experimental results show that proposed JPW model can improve the quality of the watermarked image and give more robustness of the watermark as compared with a variety of state-of-the-art algorithms.

Lightweight Detection of Additive Watermarking in the DWT-Domain

This article aims at lightweight, blind detection of additive spread-spectrum watermarks in the DWT domain. We focus on two host signal noise models and two types of hypothesis tests for watermark detection. As a crucial point of our work we take a closer look at the computational requirements of watermark detectors. This involves the computation of the detection response, parameter estimation and threshold selection. We show that by switching to approximate host signal parameter estimates or even fixed parameter settings we achieve a remarkable improvement in runtime performance without sacrificing detection performance. Our experimental results on a large number of images confirm the assumption that there is not necessarily a tradeoff between computation time and detection performance.

Multicarrier spread spectrum watermarking for secure error concealment in fading channel

This paper proposes a novel multicarrier spread spectrum (SS) watermarking scheme for the application of image error concealment using multicarrier-code division multiple access (MC-CDMA) with binary phase shift keying (BPSK) transmission in Rayleigh fading channel. The goal is achieved by embedding important information (image digest) which is extracted from the original image itself, and is used to introduce sufficient redundancy in the transmitted image. Half-toning technique is applied to obtain image digest from its low-resolution version. At the decoder side, data demodulation as well as watermark decoding are done using minimum mean square error combining (MMSEC) strategy. The extracted image digest is used to correct the damaged regions. The integration of SS watermarking with the existing SS modulation not only simplifies the design but also offers significant performance improvement for error concealment in fading channel. Authorized users having the knowledge of code patterns for SS watermarking can only perform the error concealment operation and the method is secured. Experimental results duly support the effectiveness of the proposed scheme.

Secure Client-Side ST-DM Watermark Embedding

Client-side watermark embedding systems have been proposed as a possible solution for the copyright protection in large-scale content distribution environments. In this framework, we propose a new look-up-table-based secure client-side embedding scheme properly designed for the spread transform dither modulation watermarking method. A theoretical analysis of the detector performance under the most known attack models is presented and the agreement between theoretical and experimental results verified through several simulations. The experimental results also prove that the advantages of the informed embedding technique in comparison to the spread-spectrum watermarking approach, which are well known in the classical embedding schemes, are preserved in the client-side scenario. The proposed approach permits us to successfully combine the security of client-side embedding with the robustness of informed embedding methods.

Selective correlation detector for additive spread spectrum watermarking in transform domain

As an improvement on additive spread spectrum (ASS) watermarking, this paper proposes the selective correlation detector (SCD), which performs correlation detection on a portion rather than the whole block of the signal. The portion is determined based on the watermark-to-cover signal power ratio (WCR) and the estimated variance of the correlation. A similar improvement has been obtained by improved spread spectrum (ISS) watermarking [6] (Malvar and Florencio, 2003), but we show that a better performance can be achieved by combining both algorithms. Experiments with or without a psychoacoustic model are conducted on several audio signals, and confirm the improvements by the SCD and by the combined ISS and SCD.

On the Implementation of Spread Spectrum Fingerprinting in Asymmetric Cryptographic Protocol

Digital fingerprinting of multimedia contents involves the generation of a fingerprint, the embedding operation, and the realization of traceability from redistributed contents. Considering a buyer's right, the asymmetric property in the transaction between a buyer and a seller must be achieved using a cryptographic protocol. In the conventional schemes, the implementation of a watermarking algorithm into the cryptographic protocol is not deeply discussed. In this paper, we propose the method for implementing the spread spectrum watermarking technique in the fingerprinting protocol based on the homomorphic encryption scheme. We first develop a rounding operation which converts real values into integer and its compensation, and then explore the tradeoff between the robustness and communication overhead. Experimental results show that our system can simulate Cox's spread spectrum watermarking method into asymmetric fingerprinting protocol.

Evaluation model for robustness of digital watermarking

Robustness is one of the most important requirements when digital watermarking is applied. Different from the StirMark test and various simulation tests, a mutual information function is defined as a criterion to measure the robustness of watermarking algorithm. Taking the additive spread spectrum watermarking scheme and quantization index modulation (QIM) watermarking scheme as two examples, the calculation formulas of mutual information function are derived to evaluate the robustness of the algorithms. Numerical computation of mutual information is performed with change of watermark noise rate (WNR). In the experiment, spread spectrum watermarking is implemented in discrete cosine transform (DCT) and QIM watermarking is implemented in discrete wavelet transform (DWT). The statistic bit error rate (BER) is derived against Gaussian distribution noise and JPEG compression. Experiment results show that the evaluation conclusion of mutual information method is in accordance with the empirical BER. Mutual information can be selected as a cost function to predict the BER.

A new spread spectrum watermarking method using two levels DCT

In this paper, a discrete cosine transform (DCT) based blind watermarking scheme based on spread spectrum communications is proposed. We perform block-based DCT (BDCT) on the host image; then using the DC coefficients of each block, we construct a low-resolution approximation image. We apply BDCT on this approximation image, then watermark is embedded by adding a pseudo random noise sequence into its high frequencies. In detection stage, we extract the approximation image from the watermarked image, then the same pseudo random noise sequence is generated, and its correlation is computed with high frequencies of the watermarked approximation image. In our method, higher robustness is obtained because of embedding the watermark in low frequencies. In addition, higher imperceptibility is gained by scattering the watermark's bit in different blocks. Compared with related works, our method proved to be highly resistant in cases of many common attacks, while preserving high peak signal to noise ratio for the watermarked images.

Evolutionary hidden information detection by granulation-based fitness approximation

Spread spectrum watermarking (SSW) is one of the most powerful techniques for secure audio or image watermarking. SSW hides information by spreading the spectrum. The hidden information is called the ‘watermark’ and is added to a host signal, making the latter a watermarked signal. The spreading of the spectrum is carried out by using a pseudorandom noise (PN) sequence. In conventional SSW approaches, the receiver must know both the PN sequence used at the transmitter and the location of the watermark in the watermarked signal for detecting the hidden information. This method has contributed much to secure audio watermarking in that any user, who is not able to access this secrete information, cannot detect the hidden information. Detection of the PN sequence is the key issue of hidden information detection in SSW. Although the PN sequence can be reliably detected by means of heuristic approaches, due to the high computational cost of this task, such approaches tend to be too computationally expensive to be practical. Evolutionary Algorithms (EAs) belong to a class of such approaches. Most of the computational complexity involved in the use of EAs arises from fitness function evaluation that may be either very difficult to define or computationally very expensive to evaluate. This paper proposes an approximate model, called Adaptive Fuzzy Fitness Granulation with Fuzzy Supervisor (AFFG-FS), to replace the expensive fitness function evaluation. First, an intelligent guided technique via an adaptive fuzzy similarity analysis for fitness granulation is used for deciding on the use of exact fitness function and dynamically adapting the predicted model. Next, in order to avoid manually tuning parameters, a fuzzy supervisor as auto-tuning algorithm is employed. Its effectiveness is investigated with three traditional optimization benchmarks of four different choices for the dimensionality of the search space. The effect of the number of granules on the rate of convergence is also studied. The proposed method is then extended to the hidden information detection problem to recover a PN sequence with a chip period equal to 63, 127 and 255 bits. In comparison with the standard application of EAs, experimental analysis confirms that the proposed approach has an ability to considerably reduce the computational complexity of the detection problem without compromising performance. Furthermore, the auto-tuning of the fuzzy supervisor removes the need of exact parameter determination.

Comparison of secure spread-spectrum modulations applied to still image watermarking

This article shows the results obtained when using secure spread-spectrum watermarking on gray-scale images in the watermark only attack (WOA) framework. Two secure modulations, natural watermarking (NW) and circular watermarking (CW), are compared with classical insecure modulations, spread spectrum (SS) and improved spread spectrum (ISS), from distortion, robustness, and security points of view. Implementations of CW and NW for still images are proposed: they use a wavelet transform and variable strength embedding with bounded distortion. Robustness of these schemes is assured by using JPEG compression and security is quantified by using a source separation technique: independent component analysis (ICA). Finally, tests are conducted on 2,000 natural images. They allow to distinguish between WOA security classes.

Multistage Spread Spectrum Watermark Detection Technique Using Fuzzy Logic

In this letter, a new model of spread spectrum (SS) watermarking is proposed where each watermark bit is spread using a distinct code pattern over N-mutually orthogonal signal points. Decision variable for each bit of watermark decoding is formed from the weighted average of N-decision statistics. Multiple detection stages are applied where the detected bit patterns of one stage are used in the immediate subsequent stage to cancel the multiple bit interference (MBI) effect experienced by the individual bit. Fuzzy logic is used to beat the effect of such MBI through Multiple Group Combined Interference Cancelation (MGCIC) technique in the intermediate stage(s). The group is formed from the decision magnitudes corresponding to a group of code patterns and the ensemble of code patterns are classified in different groups like very strong, strong, weak and very weak based on fuzzy membership function derived from the magnitude of the decision variables. Attack channel is modeled as Rayleigh distribution followed by AWGN (additive white Gaussian noise). Simulation results show that BER (bit error rate) value is reduced more, of course, at the cost of slight increase in computational complexity if the code patterns are classified in a greater number of groups.

Digital image forensics

The article explains how photo-response nonuniformity (PRNU) of imaging sensors can be used for a variety of important digital forensic tasks, such as device identification, device linking, recovery of processing history, and detection of digital forgeries. The PRNU is an intrinsic property of all digital imaging sensors due to slight variations among individual pixels in their ability to convert photons to electrons. Consequently, every sensor casts a weak noise-like pattern onto every image it takes. This pattern, which plays the role of a sensor fingerprint, is essentially an unintentional stochastic spread-spectrum watermark that survives processing, such as lossy compression or filtering. This tutorial explains how this fingerprint can be estimated from images taken by the camera and later detected in a given image to establish image origin and integrity. Various forensic tasks are formulated as a two-channel hypothesis testing problem approached using the generalized likelihood ratio test. The performance of the introduced forensic methods is briefly illustrated on examples to give the reader a sense of the performance.

Non-ambiguity of blind watermarking: a revisit with analytical resolution

Resistance to ambiguity attack is an important requirement for a secure digital rights management (DRM) system. In this paper, we revisit the non-ambiguity of a blind watermarking based on the computational indistinguishability between pseudo random sequence generator (PRSG) sequence ensemble and truly random sequence ensemble. Ambiguity attacker on a watermarking scheme, which uses a PRSG sequence as watermark, is viewed as an attacker who tries to attack a noisy PRSG sequence. We propose and prove the security theorem for binary noisy PRSG sequence and security theorem for general noisy PRSG sequence. It is shown that with the proper choice of the detection threshold Th = a√n (a is a normalized detection threshold; n is the length of a PRSG sequence) and n ⩾ 1.39 × m/a2 (m is the key length), the success probability of an ambiguity attack and the missed detection probability can both be made negligibly small thus non-ambiguity and robustness can be achieved simultaneously for both practical quantization-based and blind spread spectrum (SS) watermarking schemes. These analytical resolutions may be used in designing practical non-invertible watermarking schemes and measuring the non-ambiguity of the schemes.

Optimal Spread Spectrum Watermark Embedding via a Multistep Feasibility Formulation

We consider optimal formulations of spread spectrum watermark embedding where the common requirements of watermarking, such as perceptual closeness of the watermarked image to the cover and detectability of the watermark in the presence of noise and compression, are posed as constraints while one metric pertaining to these requirements is optimized. We propose an algorithmic framework for solving these optimal embedding problems via a multistep feasibility approach that combines projections onto convex sets (POCS) based feasibility watermarking with a bisection parameter search for determining the optimum value of the objective function and the optimum watermarked image. The framework is general and can handle optimal watermark embedding problems with convex and quasi-convex formulations of watermark requirements with assured convergence to the global optimum. The proposed scheme is a natural extension of set-theoretic watermark design and provides a link between convex feasibility and optimization formulations for watermark embedding. We demonstrate a number of optimal watermark embeddings in the proposed framework corresponding to maximal robustness to additive noise, maximal robustness to compression, minimal frequency weighted perceptual distortion, and minimal watermark texture visibility. Experimental results demonstrate that the framework is effective in optimizing the desired characteristic while meeting the constraints. The results also highlight both anticipated and unanticipated competition between the common requirements for watermark embedding.

A robust spread spectrum watermarking method using two levels DCT

In this paper, a discrete cosine transform (DCT) based blind watermarking scheme based on spread spectrum communications is proposed. We perform block-based DCT (BDCT) on the host image; then using the DC coefficients of each block, we construct a low-resolution approximation image. We apply BDCT on this approximation image, then watermark is embedded by adding a pseudo random noise sequence into its high frequencies. In detection stage, we extract the approximation image from the watermarked image, then the same pseudo random noise sequence is generated, and its correlation is computed with high frequencies of the watermarked approximation image. In our method, higher robustness is obtained because of embedding the watermark in low frequencies. In addition, higher imperceptibility is gained by scattering the watermark's bit in different blocks. Compared with related works, our method proved to be highly resistant in cases of many common attacks, while preserving high peak signal to noise ratio for the watermarked images.

Robust audio watermarking using frequency-selective spread spectrum

A novel audio watermarking scheme based on frequency-selective spread spectrum (FSSS) technique is presented. Unlike most of the existing spread spectrum (SS) watermarking schemes that use the entire audible frequency range for watermark embedding, the proposed scheme randomly selects subband(s) signal(s) of the host audio signal for watermark embedding. The proposed FSSS scheme provides a natural mechanism to exploit the band-dependent frequency-masking characteristics of the human auditory system to ensure the fidelity of the host audio signal and the robustness of the embedded information. Key attributes of the proposed scheme include reduced host interference in watermark detection, better fidelity, secure embedding and improved multiple watermark embedding capability. To detect the embedded watermark, two blind watermark detection methods are examined, one based on normalised correlation and the other based on estimation correlation. Extensive simulation results are presented to analyse the performance of the proposed scheme for various signal manipulations and standard benchmark attacks. A comparison with the existing full-band SS-based schemes is also provided to show the improved performance of the proposed scheme.