Ja-Chen Lin

A simple and high-hiding capacity method for hiding digit-by-digit data in images based on modulus function

This study presents a simple method for high-hiding capacity. The basic concept uses a modulus operation. The proposed method has the following advantages: (1) the proposed method outperforms the simple LSB substitution method given the same range (0–m−1) of data digits in the embedded data; (2) the proposed method achieves good image vision quality without the need for post-processing; (3) the proposed method is almost as simple as the LSB method in both coding and decoding; (4) the smaller error advantage over the simple LSB substitution method can also be mathematically verified; (5) the error is smaller than ⌈(m−1)/2⌉ for almost every pixel; (6) the proposed method has high-hiding capacity (for example, the proposed method can hide a 256×256 or 256×512 image in a 512×512 host image).

Sharing and hiding secret images with size constraint

This paper presents a method for sharing and hiding secret images. The method is modified from the (t,n) threshold scheme. (Comput.Graph. 26(5)(2002)765) The given secret image is shared and n shadow images are thus generated. Each shadow image is hidden in an ordinary image so as not to attract an attackers attention. Any t of the n hidden shadows can be used to recover the secret image. The size of each stego image (in which a shadow image is hidden) is about 1/t of that of the secret image, avoiding the need for much storage space and transmission time (in the sense that the total size of t stego images is about the size of the secret image). Experimental results indicate that the qualities of both the recovered secret image and the stego images that contain the hidden shadows are acceptable. The photographers who work in enemy areas can use this system to transmit photographs.

Formation of crystalline silicon carbon nitride films by microwave plasma-enhanced chemical vapor deposition

We report that carbon nitride thin films can be formed by microwave plasma-enhanced chemical vapor deposition (PECVD). Gas mixtures containing CH4, H2, and NH3 in various ratios were tried as the precursors, and a Si(100) wafer was used as the substrate. The films were characterized by X-ray photoelectron spectroscopy (XPS), and electron microscopy (both SEM and TEM). A Si content of about half of the carbon content was observed when the substrate temperature exceeded 1000 °C. Microscopic investigation revealed the coexistence of large-grain (over 10 μm) and fine-grain (under 1 μm) crystals. We suggest the presence of a crystalline carbon nitride phase corresponding to an α-C3N4 structure (isomorphic to α-Si3N4), which may also be a stable hard material.

VCPSS: A two-in-one two-decoding-options image sharing method combining visual cryptography (VC) and polynomial-style sharing (PSS) approaches

This paper presents a novel method to combine two major branches of image sharing: VC and PSS. n transparencies are created for a given gray-valued secret image. If the decoding computer is temporarily not available at (or, not connected to) the decoding scene, we can still physically stack any t received transparencies (t≤n is a threshold value) to get a vague black-and-white view of the secret image immediately. On the other hand, when the decoding computer is finally available, then we can get a much finer gray-valued view of the secret image using the information hidden in the transparencies. In summary, each transparency is a two-in-one carrier of the information, and the decoding has two options.

Fragile watermarking for authenticating 3-D polygonal meshes

Designing a powerful fragile watermarking technique for authenticating three-dimensional (3-D) polygonal meshes is a very difficult task. Yeo and Yeung were first to propose a fragile watermarking method to perform authentication of 3-D polygonal meshes. Although their method can authenticate the integrity of 3-D polygonal meshes, it cannot be used for localization of changes. In addition, it is unable to distinguish malicious attacks from incidental data processings. In this paper, we trade off the causality problem in Yeo and Yeungs method for a new fragile watermarking scheme. The proposed scheme can not only achieve localization of malicious modifications in visual inspection, but also is immune to certain incidental data processings (such as quantization of vertex coordinates and vertex reordering). During the process of watermark embedding, a local mesh parameterization approach is employed to perturb the coordinates of invalid vertices while cautiously maintaining the visual appearance of the original model. Since the proposed embedding method is independent of the order of vertices, the hidden watermark is immune to some attacks, such as vertex reordering. In addition, the proposed method can be used to perform region-based tampering detection. The experimental results have shown that the proposed fragile watermarking scheme is indeed powerful.

Micro-Raman for diamond film stress analysis

Abstract The residual stress in microwave plasma-enhanced CVD diamond film was analyzed using a Raman spectrometer with micrometer spatial resolution. This enables effective study of isolated crystals grown in the same deposition run. A variation of the Raman line shape near 1332 cm −1 was observed from different crystals in the same sample. A phenomenological model was used to describe the shift and splitting of the diamond Raman line, from which the type and the magnitude of the stress in PECVD grown diamond can be assessed. The interrelationship and the origin of the stress in the film is discussed.

Visual cryptography with extra ability of hiding confidential data

We present a two-in-one visual cryptography (VC) scheme that not only shares an image of moderate confidentiality between two noisy transparencies, but also hides in these two transparencies a more confidential text file describing the image. None of the transparencies alone can reveal anything about the image or text. Later, people can view the image by simply stacking the two transparencies; on the other hand, after certain simple computations, the more confidential text data can also be extracted. We also introduce an alternative version in which the decoding of both the image and text requires no computer.

Progressive viewing and sharing of sensitive images

The paper proposes a progressive viewing method useful in sharing a sensitive image. As in visual cryptography, this method characterizes its ability to recover the image by stacking transparencies without any computation. However, the method balances the sensitivity and the daily-processing convenience of the image.

New approach to image encryption

A new cryptographic method for encrypting still images is proposed. This method is designed on the basis of the base- switching lossless image compression algorithm. The method there- fore simultaneously possesses both image encryption and lossless compression abilities. A given image is first partitioned into nonover- lapping fixed-size subimages, and each subimage will then have its own base value. These subimages are then encoded and encrypted one by one according to the base values. By choosing the function to encrypt the base value, there are (128!) t (or (128!) 3t ) possible ways to encrypt a gray-scaled (color) image if t layers are used in the encryption system. The theoretical analysis needed to support the proposed encryption method is provided, and the experimental results are also presented.

Universal principal axes: an easy-to-construct tool useful in defining shape orientations for almost every kind of shape

Abstract A convenient tool for defining shape orientations called universal principal axes is introduced. These axes are formed of half lines starting from the shape centroid, with their directional angles expressed as functions of the polar angle of the first non-zero complex number encountered in the sequence (∫ x + iy ) 1 d A with 1 = 2,3,4,..., provided that the integration domain is taken to be the given two-dimensional (2D) shape and the origin is assumed to be the shape centroid. Universal principal axes are shown to be independent of the translation, scaling, and rotation of the coordinate system used, and they are therefore qualified in defining shape orientations. A major benefit of using the proposed universal principal axes is that they exist for almost every kind of shape. Another benefit is that there is no need to judge in advance whether a given shape is mirror-symmetric, rotationally symmetric, irregular, etc. Moreover, in the case of rotationally symmetric shapes, the universal principal axes make the preprocessing procedure for detecting the number of folds contained in the given shape unnecessary although such procedure is essential for many existing tools designed to define orientations of rotationally symmetric shapes. Defining shape orientations by universal principal axes is therefore quite convenient. An algorithm describing the construction of universal principal axes and several examples showing the detected universal principal axes for some shapes of distinct types are given. The relationship between universal and conventional principal axes is also discussed.