Kuo-Nan Chen

A secure fragile watermarking scheme based on chaos-and-hamming code

In this work, a secure fragile watermarking scheme is proposed. Images are protected and any modification to an image is detected using a novel hybrid scheme combining a two-pass logistic map with Hamming code. For security purposes, the two-pass logistic map scheme contains a private key to resist the vector quantization (VQ) attacks even though the embedding scheme is block independent. To ensure image integrity, watermarks are embedded into the to-be-protected images which are generated using Hamming code technique. Experimental results show that the proposed scheme has satisfactory protection ability and can detect and locate various malicious tampering via image insertion, erasing, burring, sharpening, contrast modification, and even though burst bits. Additionally, experiments prove that the proposed scheme successfully resists VQ attacks.

Adaptive self-recovery for tampered images based on VQ indexing and inpainting

In this paper, we propose a novel self-recovery scheme for tampered images using vector quantization (VQ) indexing and image inpainting. Cover image blocks are classified into complex blocks and smooth blocks according to the distribution characteristics. Due to the good performance of the compressed representation of VQ and the automatic repairing capability of image inpainting, the recovery-bits of each cover block are generated by its VQ index and the inpainting indicator. Recovery-bits and authentication-bits are embedded into the LSB planes of the cover image to produce the watermarked image. On the receiver side, after tampered blocks are all localized, the extracted recovery-bits are used to judge the classification of each tampered block. By analyzing the validity of the VQ indices and the damaged degree of the neighboring regions, the adaptive recovery mechanism can be utilized to restore all the tampered blocks by using VQ index and image inpainting. Experimental results demonstrate the effectiveness of the proposed scheme.

Lossless Data Hiding Based on Histogram Modification for Image Authentication

Lossless data hiding enables the embedding of messages in a host image without any loss of content. In this paper, we present a lossless data hiding technique based on histogram modification for image authentication that is lossless in the sense that if the marked image is deemed authentic, the embedding distortion can be completely removed from the marked image after the embedded message has been extracted. This technique uses characteristics of the pixel difference to embed more data than other histogram-based lossless data hiding algorithms. We also present a histogram shifting technique to prevent overflow and underflow problems. Performance comparisons with other existing lossless data hiding schemes are provided to demonstrate the superiority of the proposed scheme.

An encoding method for both image compression and data lossless information hiding

Reversible image data hiding technology means the cover image can be totally recovered after the embedded secret data is extracted. In this paper, we propose a reversible image data hiding scheme based on vector quantization (VQ) compressed images. The secret bits are embedded into the VQ index table by modifying the index value according to the difference of neighboring indices. The data hiding capacity and the size of the final codestream (embedded result) are a trade-off, and it can be decided by users. In other words, the proposed scheme has flexible hiding capacity ability. To estimate the performance, the proposed scheme was compared with the scheme proposed by Wang and Lu (2009). The results of the comparison showed that our proposed scheme is superior to the scheme proposed by Wang and Lu in both data hiding capacity and bit rate.

Improvements of EMD Embedding for Large Payloads

A novel steganographic method by exploiting modification direction in digital images was proposed by Zhang et al, in which each secret digit in a (2n+1)- ary notational system is carried by n cover pixels, and only one cover pixel increases or decreases by 1 at most. In other words, the (2n+1) possible values of a secret digit correspond to (2n+1) possible ways of modification to the cover pixels. It can provide higher embedding efficiency and embedding rate than those of matrix embedding. In this paper, we propose an improved EMD embedding method to increase the embedding rate (number of secret bits embedded in each cover pixel). And from the experiments, we show that our improved method still can preserve good stego image quality.

A Large Payload EMD Embedding Scheme with High Stego-image Quality

In this paper, we propose an efficient EMD-based data hiding scheme. To avoid the serious, but usually disregarded, overflow problem in the embedding process, the danger cover pixels, which may result in overflow problem, are modified to safe area. However, the modification will not influence the stego image quality. Comparing to Hong et al.’s scheme proposed in 2008 and Lee et al.’s scheme proposed in 2010, our proposed scheme outperforms these two previous scheme in stego image quality.

Reversible Data Hiding Scheme Based on Image Inpainting

Reversible/lossless image data hiding schemes provide the capability to embed secret information into a cover image where the original carrier can be totally restored after extracting the secret information. This work presents a high performance reversible image data hiding scheme especially in stego image quality control using image inpainting, an efficient image processing skill. Embeddable pixels chosen from a cover image are initialized to a fixed value as preprocessing for inpainting. Subsequently, these initialized pixels are repaired using inpainting technique based on partial differential equations PDE. These inpainted pixels can be used to carry secret bits and generate a stego image. Experimental results show that the proposed scheme produces low distortion stego images and it also provides satisfactory hiding capacity.

A Robust Public Watermarking Scheme Based on DWT

Watermarking is a simple and effective method that is frequently used to protect the copyright of an image. However, watermarks must be strong enough to resist various attacks. In this paper, two-level Discrete Wavelet Transform (DWT) and a trusted third party are applied to ensure the robustness of the watermarks and protect the copyright of an image. The experimental results showed that our proposed scheme can resist various attacks successfully, such as JPEG compression attacks, filtering attacks, and sharpening attacks. Consequently, our scheme is a method that ensures the robustness of the watermark and protects the copyright of a grayscale image.

Embedding secret messages based on chaotic map and Huffman coding

In this paper, an efficient and secure data hiding scheme is proposed. The cover medium is compressed by a revised Huffman coding. Based on the lossless Huffman coding, not only images but also text files can be used as the cover media. The secret information is embedded into the compressed code by using the revised Huffman coding. Before embedding, the secret information is rearranged by a logistic map with a private key for achieving the purpose of security. The experimental results show that our proposed scheme is secure because only the receiver who owns the private key can decrypt the secert information.

A quadratic-residue-based fragile watermarking scheme

A new fragile watermarking scheme for image authentication and location of areas that have been tampered with is proposed in this paper. Based on a quadratic-residue theorem, the proposed scheme generates the watermark block-by-block in the cover image. To improve security by preventing malicious attacks, such as the vector quantization attack, a pseudo-random number generator using a private key as a seed is applied in the embedding process. The experimental results show that our proposed scheme is effective in image authentication and maintains high image quality in the watermarked images. In addition, areas that have been tampered with can be located and at least approximately recovered.