Simplified MAP Detector for Binary Fingerprinting Code Embedded by Spread Spectrum Watermarking Scheme

The ambiguity attack is to derive a valid watermark from a medium to defeat the ownership claim of the real owner. Most of the research suggests that it is difficult to design a provably secure non-ambiguity watermarking without a trusted third party. Recently, Li and Chang have provided a specific blind additive spread spectrum watermarking scheme as an example that is provably non-ambiguous. However, the proposed watermarking needs the length of watermark n > 3.07 × 10 9 according to our analysis. In this paper, a framework for quantization based watermarking schemes and non-blind spread spectrum watermarking scheme to achieve non-ambiguity is proposed. As a result, many of the existent watermarking schemes can achieve provable non-invertibility via using this framework, and an nonambiguity ownership verification protocol without a trusted third party may be constructed. We have obtained the close form solution of false positive rate for the underlying quantization based schemes and spread spectrum watermarking schemes (both blind and non-blind). The length of key of pseudo-random sequence generator (PRSG) is extended to m = c × n , the cardinality of the valid watermark set is extended to vWv = 2 m = 2 c,n , thus leading to more security to exhaustive searching attack than the Li and Chang's scheme, which has m = sn. In addition, the required length of watermark becomes much shorter than that required in the Li and Chang's scheme. At last, we propose a noninvertible and robust quantization-based watermarking scheme with the length of watermark being n=1024 .

The carrier of the digital watermark expands from audio signals to radio frequency (RF) signals. Unlike audio signals, RF signals, such as the watermark transmission carrier, must be correctly demodulated with the watermark signals so that the distortion of the digital carrier embedded with the watermark is associated with the change in bit error rate. Based on the spread spectrum watermarking scheme, the distortion of the digital carrier signal is redefined, and the channel capacity expression of the watermarking scheme is derived. In addition, the optimal parameters to achieve the maximal channel capacity are discussed, and the constraint relation between the channel capacity and the allowable distortion is investigated.

The relation between the digital watermarking and spread-spectrum is analyzed in this paper at the beginning. Then, a spread-spectrum adaptive digital watermarking scheme based on the wavelet transform is proposed and the system for this digital watermarking algorithm based on DSP is realized. Finally, a testing on the image digital watermarking processing system by DSP is conducted. The result from the testing approves that the system is flexible and can accomplish watermark embedding and detecting.

The paper presents a robust digital image watermarking scheme that uses both the characteristics of the human visual system (HVS) and statistical information measure. Spread transform approach is used where data is embedded through transform coefficients of both the cover and the watermark data. The spread transform watermarking technique yields better results in terms of imperceptibility, resiliency, capacity and cost compared to widely used spread spectrum watermarking schemes. Hadamard transformation is used not only for simpler implementation but also for its higher data hiding capacity (M. Ramkumar and AN Akansu, 2001). Experimental results show that the visual quality of the extracted watermark is good in spite of several external attacks. The fact is also supported by mutual information values used as objective measure.

Watermarking is a crucial technique for copyright protection of digital images. The most common spread-spectrum watermarking schemes suffer from host signal interference (HSI), which degrades the decode performance. Although this condition can be improved by increasing the embedding strength, it might make the embedded watermark perceptible. This paper solves these problems by proposing a novel blind spread-spectrum watermarking scheme with adaptive embedding strength (SSAES). A notion called the error threshold is introduced to analyze how HSI and distortions compromise robustness and imperceptibility of the spread-spectrum scheme, which motivates us to come up with our solutions. SSAES is HSI free by utilizing the priori knowledge of HSI and features an adjustable embedding strength derived from a theoretical equation related to peak signal-to-noise ratio (PSNR), which strikes a perfect balance between robustness and imperceptibility. SSAES can be easily applied to other watermarking frameworks. The experimental results demonstrate our scheme can ensure that the PSNR of each watermarked image is more than 40 dB and is superior to the state of the art method under the same watermarking framework in any simulation scenarios include image processing attacks and geometric attacks.

In this paper we propose robust watermarking schema for video files based on spread spectrum theory. The main concept relies on utilization of time as temporal dimension for spreading of watermark bits that are assigned to video frames. The second level spreading that is impartial to first level, uses different set of PN sequences within the video frames what allows to utilize multiple watermarking methods designed for still images simultaneously. Two dimensional spread spectrum watermarking framework allows acquiring a high level of robustness with desired imperceptibility of hidden watermark. Two independent embedding methods LSB and DCT were tested during embedding as representative techniques of different embedding domain. The presented results show that proposed watermarking schema is able to withstand intentional attacks. The proposed system is robust and adaptive to recent and newly developed embedding technique, which could provide a requisite of robustness and protection against copyright infringement.

Digital watermarking is a technique that aims at hiding a message signal in a multimedia signal for copyright claim, authentication, device control, or broadcast monitoring, etc. We focus on embedding watermarks into still images. We propose to scramble the watermark with pseudo-noise (PN) or orthogonal codes before it is embedded into an image. We also try to incorporate error correction coding (ECC) into the watermarking scheme, anticipating reduction of the watermark bit error rate (WBER). We consider to adopt trellis-based schemes (including trellis-code modulation (TCM) and turbo codes) to improve the WBER. Due to the similarity between the PN/orthogonal coded watermarking and the spread spectrum communication, it is natural that, following similar derivations regarding data BER, we derive certain explicit quantitative relationship regarding the trade-off between the WBER and the distortion suffered by the original image, which is measured in terms of the embedded image's signal-to-noise ratio (abbreviated as ISNR).

At present, the spread spectrum (SS) sequences used in watermark include i.i.d. random sequences and the sequences used in SS communications. They appear earlier than digital watermark. Almost no researchers pay attention to whether they are really fit for watermark. In this paper, we compare the SS watermark channel and the traditional SS communication channel. We find out that their correlation property is different. Considering cropping and translation attacks, we define watermark auto- and cross-correlation and propose Loose Autocorrelation and Tight Cross-Correlation (LAC&TCC) properties for SS watermark. The LAC&TCC properties are that, whether or not synchronized, the autocorrelation is equal or close to 1 and the cross-correlation is equal or close to 0. Accordingly, the peak correlation is divided into the peak autocorrelation Ra(l) and the peak cross-correlation Rc(l). We establish the lower bound of Rc(l) and the higher bound of Ra(l), respectively. The two bounds indicate that, no matter how small the cover is reserved, the extractor can always find a threshold to distinguish auto- and cross-correlation in theory.

Spread spectrum watermarking (SSW) is one of the most widespread watermarking methods. In this paper, the characterization of the SSW from the information theoretic point of view is performed. Previous works on channel capacity analysis of watermarking systems are reviewed. Since SSW method is designed so that the host signal is unknown to the embedding encoder, Costa's results for capacity analysis of watermarking systems are not directly applicable. In this paper, watermarking embedding and detection is modeled as a channel that transmits information in the presence of noise of host and channel capacity analysis of that model is derived and the most reliable transmission rate of hidden information obtained. In addition, channel capacity for the case of presence of additive noise in the watermark channel is derived and robustness of the SSW against additive noise examined

Secure watermark embedding allows to securely embed a watermark into a piece of content at an untrusted user device without compromising the security of the watermark key, the watermark or the original. In this paper, we show how secure embedding can be achieved by using traditional watermarking schemes in conjunction with partial encryption techniques, which were primarily developed to facilitate fast encryption of media content. Based on this concept, we develop two new efficient secure embedding mechanisms, one for the MASK watermarking scheme operating on baseband audio and one for a spread spectrum watermarking scheme operating on MPEG-2 encoded video streams.

A framework to jointly halftone and watermark a grayscale images is presented. The framework needs the definition of three components: a human visual system (HVS)-based error metric between the continuous-tone image and a halftone, a watermarking scheme with a corresponding watermark detection measure, and a search strategy to traverse the space of halftones. We employ the HVS-based error metric used in the direct binary search (DBS) halftoning algorithm, and we use a block-based spread spectrum watermarking scheme and the toggle and swap search strategy of DBS. The halftone is printed on a desktop printer and scanned using a flatbed scanner. The watermark is detected from the scanned image and a number of post-processed versions of the scanned image, including one restored in Adobe PhotoShop. The results show that the watermark is extremely resilient to printing, scanning, and post-processing; for a given baseline image quality, joint optimization is better than watermarking and halftoning independently. For this particular algorithm, the original continuous-tone image is required to detect the watermark.

Fingerprinting for multimedia content broadcasting system

Ultrasound Transmission Loss Across Transverse and Oblique Bone Fractures: An In Vitro Study

Periodic tidal ocean currents induce electric currents and, therefore, magnetic field signals that are observable using spaceborne and ground-based observation techniques. In theory, the signals can be used to monitor oceanic temperature and salinity variations. Tidal magnetic field amplitudes and phases have been extracted from magnetometer measurements in the past. However, due to uncertainties caused by a plentitude of influencing factors, the shape and temporal variation of these signals are only known to a limited extent. This study uses past extraction methods to characterize seasonal variations and long-term trends in the ten year magnetometer time series of three coastal island observatories. First, we assess data processing procedures used to prepare ground-based magnetometer observations for tidal ocean dynamo signal extraction to demonstrate that existing approaches, i.e., subtraction of core field models or first-order differencing, are unable to reliably remove low-frequency contributions. We hence propose low-frequency filtering using smoothing splines and demonstrate the advantages over the existing approaches. Second, we determine signal and side peak magnitudes of the M2 tide induced magnetic field signal by spectral analysis of the processed data. We find evidence for seasonal magnetic field signal variations of up to 25% from the annual mean. Third, to characterize the long-term behavior of tidal ocean dynamo signal amplitudes and phases, we apply different signal extraction techniques to identify tidal ocean-dynamo signal amplitudes and phases in sub-series of the ten-year time series with incrementally increasing lengths. The analyses support three main findings: (1) trends cause signal amplitude changes of up to approx 1~nT and phase changes are in the order of {mathcal {O}}(10^{circ }) within the observation period; (2) at least four years of data are needed to obtain reliable amplitude and phase values with the extraction methods used and (3) signal phases are a less dependent on the chosen extraction method than signal amplitudes.Graphical

<sec>This paper aims to analyze the failure mechanism of the two-stage PIN limiter after having been injected by a microwave pulse. A two-stage PIN limiter model with high computational efficiency and accuracy is built by using the method of field-circuit collaborative simulation. Using this model, the temperature change of the PIN diodes during the injection of microwave pulse is simulated. The melting temperature of the PIN diode is selected as the failure criterion of the PIN limiter. The time and energy required for the failure of the PIN limiter under injection of microwave pulses with different frequencies and amplitudes are simulated. Furthermore, the mechanisms that trigger off these effects are analyzed. The relationship between the microwave pulse parameters and the PIN limiter failure time is summarized by using an empirical formula.</sec><sec>According to the simulation results, the temperature change of the second-stage PIN diode is relatively small compared with that of the first-stage. During the injection of the microwave pulse, the failure time and energy consumption of limiter show a certain regularity with the variation of microwave pulse amplitude and frequency, and this work discusses this regularity from the following three aspects. Firstly, the failure time and energy consumption decrease in a similar trend with frequency increasing. And with the increase in signal amplitude, the failure time and energy consumption tend to stabilize. Secondly, the increase in the signal amplitude leads failure time to decrease, which is similar to the relationship between failure time and the signal frequency mentioned before. But as the signal’s amplitude increases, the energy consumption first increases and then decreases slightly when the amplitude reaches about 900 V. Based on the theoretical analysis and the physical image of the two-stage PIN limiter, the reasons for these effects can be explained as the changes in the I-region's impedance and heat distribution change caused by electric field changes. Thirdly, the failure time and energy consumption show different sensitivities to different parameters of the microwave pulse. The signal frequency change has greater influence on the energy consumption than the signal amplitude change, while the amplitude change can exert a greater influence on the failure time than the frequency change.</sec>