Wen-Nung Lie

Robust and high-quality time-domain audio watermarking based on low-frequency amplitude modification

This work proposes a method of embedding digital watermarks into audio signals in the time domain. The proposed algorithm exploits differential average-of-absolute-amplitude relations within each group of audio samples to represent one-bit information. The principle of low-frequency amplitude modification is employed to scale amplitudes in a group manner (unlike the sample-by-sample manner as used in pseudonoise or spread-spectrum techniques) in selected sections of samples so that the time-domain waveform envelope can be almost preserved. Besides, when the frequency-domain characteristics of the watermark signal are controlled by applying absolute hearing thresholds in the psychoacoustic model, the distortion associated with watermarking is hardly perceivable by human ears. The watermark can be blindly extracted without knowledge of the original signal. Subjective and objective tests reveal that the proposed watermarking scheme maintains high audio quality and is simultaneously highly robust to pirate attacks, including MP3 compression, low-pass filtering, amplitude scaling, time scaling, digital-to-analog/analog-to-digital reacquisition, cropping, sampling rate change, and bit resolution transformation. Security of embedded watermarks is enhanced by adopting unequal section lengths determined by a secret key.

Multiple-image encryption and multiplexing using a modified Gerchberg-Saxton algorithm and phase modulation in Fresnel-transform domain

What we believe to be a new technique, based on a modified Gerchberg-Saxton algorithm (MGSA) and a phase modulation scheme in the Fresnel-transform domain, is proposed to reduce cross talks existing in multiple-image encryption and multiplexing. First, each plain image is encoded and multiplexed into a phase function by using the MGSA and a different wavelength/position parameter. Then all the created phase functions are phase modulated to result in different shift amounts of the reconstruction images before being combined together into a single phase-only function. Simulation results show that the cross talks between multiplexed images have been significantly reduced, compared with prior methods [Opt. Lett.30, 1306 (2005); J. Opt. A8, 391 (2006)], thus presenting high promise in increasing the multiplexing capacity and encrypting grayscale and color images.

A feature-based classification technique for blind image steganalysis

In contrast to steganography, steganalysis is focused on detecting (the main goal of this research), tracking, extracting, and modifying secret messages transmitted through a covert channel. In this paper, a feature classification technique, based on the analysis of two statistical properties in the spatial and DCT domains, is proposed to blindly (i.e., without knowledge of the steganographic schemes) to determine the existence of hidden messages in an image. To be effective in class separation, the nonlinear neural classifier was adopted. For evaluation, a database composed of 2088 plain and stego images (generated by using six different embedding schemes) was established. Based on this database, extensive experiments were conducted to prove the feasibility and diversity of our proposed system. It was found that the proposed system consists of: 1) a 90%/sup +/ positive-detection rate; 2) not limited to the detection of a particular steganographic scheme; 3) capable of detecting stego images with an embedding rate as low as 0.01 bpp; and 4) considering the test of plain images incurred low-pass filtering, sharpening, and JPEG compression.

Data hiding in images with adaptive numbers of least significant bits based on the human visual system

We propose in this paper a novel method for embedding multimedia data (including audio, image, video, or text; compressed or non-compressed) into a host image. The classical LSB concept is adopted, but with the number of LSBs adapting to pixels of different graylevels. A piecewise mapping function according to human visual sensitivity of contrast is used so that adaptivity can be achieved without extra bits for overhead. The leading information for data decoding is few, no more than 3 bytes. Experiments show that a large amount of bit streams (nearly 30%-45% of the host image) can be embedded without sever degradation of the image quality (33-40 dB, depending on the volume of embedded bits).

Public-key-based optical image cryptosystem based on data embedding techniques

We propose a public-key-based optical image cryptosystem for practical secure communications since conventional optical crypto- systems that use a symmetric algorithm are confronted by the problem of key delivery. The proposed system employs a hybrid architecture in which a double-random-phase encoding is used to cipher and decipher an image and an asymmetric algorithm is used for ciphering and deci- phering the session key. To solve this problem of key delivery, the double-random-phase encoding algorithm is analyzed to establish a co- vert channel and therefore elucidate the phenomenon that the amplitude part of the ciphered image is less sensitive to quantization error than the other parts in the Fourier and output planes. The session key is then hidden in the covert channel setup in the ciphered image and extracted at the receiver side. Experimental results demonstrate that the amplitude parts in the Fourier and output planes are better suited to convey the session key because they enable reconstructed images with a higher visual quality to be obtained.

Fast double-phase retrieval in Fresnel domain using modified Gerchberg-Saxton algorithm for lensless optical security systems

A novel fast double-phase retrieval algorithm for lensless optical security systems based on the Fresnel domain is presented in this paper. Two phase-only masks are efficiently determined by using a modified Gerchberg-Saxton algorithm, in which two cascaded Fresnel transforms are replaced by one Fourier transform with compensations to reduce the consumed computations. Simulation results show that the proposed algorithm substantially speeds up the iterative process, while keeping the reconstructed image highly correlated with the original one.

Robust and high-quality time-domain audio watermarking subject to psychoacoustic masking

We propose in this paper a new method for embedding digital watermarks into audio signals in the time domain. By testing frequency domain characteristics (i.e., the psychoacoustic model) and making appropriate adjustments, our algorithm is capable of preventing watermark disturbance from human perception. A watermark can be extracted without the knowledge of original audio signals. Experiments show that our watermarking scheme leads to results with good audio quality (comparable to the original ones, according to some subjective tests) and is robust (more than 98% of survival rate) to pirate attacks, such as MP3 compression, low-pass filtering, amplitude normalization, DAVAD same-rate reacquisition, and cropping.

A robust dynamic programming algorithm to extract skyline in images for navigation

In this paper, a skyline image detection algorithm is proposed for navigation of mobile vehicles or planes in mountainous environments. First, edge detection and subsequent binary thresholding are applied on the luminance component to obtain the edge map, from which a multi-stage graph is constructed for determining the skyline curve by using the dynamic programming (DP) algorithm. In optimal DP search, characteristics (e.g., preferred position and orientation) of the skyline are utilized to help in correct linking of curves. The tolerance in short breakage of skyline curve is considered for robustness consideration. Experiments show that the processing speed is fast (approximately 0.12-0.21 s for a 352x240 pixel image on a Pentium-M 1.3 GHz CPU) and promising for real-time applications.

Robust image watermarking on the DCT domain

This paper proposes two simple DCT-domain-based schemes to embed single or multiple watermarks into an image for copyright protection and data monitoring and tracking. The watermark data are essentially embedded in the middle band of the DCT domain to make a tradeoff between visual degradation and robustness. The proposed schemes are simple and no original host image is required for watermark extraction. The algorithm also features the capability of embedding multiple orthogonal watermarks into an image simultaneously. A set of systematic experiments, including Gaussian smoothing, JPEG compression, and image cropping are performed to prove the robustness of our algorithms.

Dual protection of JPEG images based on informed embedding and two-stage watermark extraction techniques

In this paper, the authors propose a watermarking scheme that embeds both image-dependent and fixed-part marks for dual protection (content authentication and copyright claim) of JPEG images. To achieve the goals of efficiency, imperceptibility, and robustness, a compressed-domain informed embedding algorithm, which incorporates the Lagrangian multiplier optimization approach and an adjustment procedure, is developed. A two-stage watermark extraction procedure is devised to achieve the functionality of dual protection. In the first stage, the semifragile watermark in each local channel is extracted for content authentication. Then, in the second stage, a weighted soft-decision decoder, which weights the signal detected in each channel according to the estimated channel condition, is used to improve the recovery rate of the fixed-part watermark for copyright protection. The experiment results manifest that the proposed scheme not only achieve dual protection of the image content, but also maintain higher visual quality (an average of 6.69 dB better than a comparable approach) for a specified level of watermark robustness. In addition, the overall computing load is low enough to be practical in real-time applications