A rate-compatible puncturing scheme for LDPC codes is proposed based on the fact that a one-step recoverable (1-SR) node is more reliable than a k-SR node (k>;1) and a 1-SR node with more survived check nodes can be recovered more reliably in a recovery tree, so the scheme tries to obtain 1-SR nodes which have multiple survived check nodes as many as possible. Simulation results show that the puncturing scheme has better performance than both the random puncturing scheme and the novel method in [5].

By combining an algebraic method and a random method, a hybrid method is proposed to construct LDPC codes, which can easily ensure the girth is at least six. The complexity of construction for the hybrid code is only a fraction of that for PEG code, which facilitates the construction of long LDPC codes with very low density. Simulation results show that the hybrid code from EG-LDPC code and PEG code has the identical error performance and convergence rate to the PEG code with the same length.

The rapid advancement of digital scanner, digital camera and digital video recorder technologies has created a huge market for digital multi-media, such as documents, photos and videos, storage, retrieval and reproduction market. The ease of modifications using editing tools makes the identification of original masterpiece difficult and these forgeries sometimes become an important issue for identification, authentication and law enforcement. The demand of a security protection chip increases as digital documents in form of digital video became popular and forensic approaches for detecting forgery evident became vital. In this paper, a real time forensic chip is designed and implemented. This Chip captures real time video frames and encodes forensic mark into the video frame. The video frame with forensic mark embedded is then transmitted to remote host through TCP/IP. On the remote host, the same Chip can be used to decode the stored forensic mark from the received video frame. Any modifications to the original captured video can immediately be detected by the chip in real time.

Based on curvelet transform this paper embeds one leveled watermark onto significant coefficients by quantization in individual frequency scales. Watermark bits come from image HASH, which is defined in the paper. Bigger coefficients are used for watermarking for the conception that coefficient energy is proportion to its directional sensitivity and bigger coefficients are more stable. Watermark is extracted without resort to the original image. The proposed watermarking can realize multifunction of content authentication and copyright protection the same time.

Multipurpose watermarking for content authentication and copyright verification are accomplished by using the multiscale curvelet transform. A curvelet transform gains better and sparser representation than most traditional multiscale transforms. In this paper, an image is decomposed into multiscale coefficients with a dyadic number of wedges constructed from a variety of neighboring scales. Image hash is designed to extract image features from an approximate scale. The image features represented in the form of bit sequences are then embedded onto the wedges by a quantization based on human visual system behavior. The implementation strategy achieves content authentications for fatigue watermarking and copyright verifications for robust watermarking. The experiments demonstrate good results to support the feasibility of using this method in multipurpose applications.

In this paper, we propose a novel digital watermarking to hide a trademark into a host-image such that an unintended observer will not be aware of the watermarking. By inserting the watermarking information into the random positioning location of a DCT image, the image capability against median filtering can be greatly improved. Experimental results demonstrate that the resulting proposed digital watermarking scheme has a higher peak signal-to-noise ratio and the visual quality of the digital watermarked image is indistinguishable from the original unmarked image.

Based on the construction of linear codes proposed by Niederriter and Xing (see Applicable Algebra in Engineering, Communication and Computing, vol.10, p.425-32, 2000), a corresponding generator matrix is derived. The duality operator and the propagation operator of these extended linear codes are studied. A sufficient and necessary condition under which these two operators are commutative is obtained. This commutative property is found useful for constructing the corresponding parity-check matrix and, thus, the error detection/recovery codes.