Chin-Chen Chang and Yung-Chen Chou

With the advanced developments in information technology and networking, a user can easily communicate with others via the Internet. In daily life, users can make orders of products through the e-commerce market. Thus,how to protect users’ private information from being wiretapped over the Internet has become a very important research topic in recent years.

The objective of this special issue is to present up-to-date research and development activities in the areas of information security. We hope that this special issue will interest computer scientists to get involved in this promising and active research area. After carefully reviewing of many qualified submissions, the editorial committee accepted 9 outstanding papers to be included in this special issue.

To make sure data can be transmitted securely over the Internet, researchers have used various approaches,including cryptography, network security, steganography,and secret sharing. In cryptography, information is transformed into meaningless, undecipherable form using encryption algorithm, such as DES or RSA. The original information of these meaningless cipher texts can only be restored by using a decryption algorithm with a valid deciphering key. Because the cipher text is represented in a random stream of bits, it will attract attackers to pay special attraction to decipher it. Thus, the secret data delivery may fail due to attackers who try to decrypt a cipher text to reveal the original information.

Steganography is another way to achieve the goal of secret data delivery. Because digital media (e.g., audio,video, image, text, etc.) containing redundancy, the encrypted data can be concealed in the cover media.Considering the integrity of medium after data extraction,the data hiding technique can be classified into reversible data hiding and irreversible data hiding.

In order to ensure the security of secret image delivery over the public networks, Dr. Cheng-Hung Chuang at Asia University proposes an optical image encryption system with adaptive steganography using RGB channel integration. The secret data is embedded into the encrypted image with a specific hiding sequence generated by the zero-LSB sorting technique. That is a content-dependent and low distortion data embedding method.

On the other hand, reversible data hiding schemes not only can achieve secret data delivery, but also can restore the cover medium. Dr. Yung-Chen Chou and Dr.Huang-Ching Li at Asia University propose a reversible data hiding method using difference segmentation strategy and pseudo pixel generation to increase the height of peak in the prediction error histogram. Their proposed method successfully improves the performance in terms of embedding capacity.

Dr. Zhi-Hui Wang at Dalian University of Technology,Professor Chin-Chen Chang at Feng Chia University, and Mr. Ting-Yu Lin at National Chung Cheng University propose an efficient information hiding method based on closest paired tree structure vector quantization (CPTSVQ).Their proposed method makes the data embedding more practical for secret data delivery.

A new distortion-free data embedding scheme for high dynamic range (HDR) images is proposed by Professor Chin-Chen Chang, Mr. Thai-Son Nguyen at Feng Chia University, and Professor Chia-Chen Lin at Providence University. By using Cartesian product, their scheme can obtain higher embedding capacity while maintaining the exactly identical cover image and stego image when using the tone mapping algorithms.

Professor Chin-Feng Lee and Ming-Chi Shih at Chaoyang University of Technology propose a lossless data hiding scheme to improve Wanget al.’s method which is a lossless data hiding scheme to hide secret data in VQ indices. But, the encoding strategies adopted by their scheme expand the final codestream. Leeet al.’s method improves Wanget al.’s method to reduce the bit rates of the final codestream.

Authentication is the way for checking the integrity of received data. In 2011, Chan proposed an image authentication method by producing the parity check bits from pixels whose bits have been rearranged. With the help of the most-significant bit of the pixel, the pixel can be recovered by selecting two possible (7, 4) Hamming code words. Professor Chi-Shiang Chang, Professor Yuan-Yu Tsai, and Professor Chao-Liang Liu at Asia University propose an image authentication method which groups four most-significant bits into different groups to form a mapping codebook. The mapping codebook is used to produce authentication data instead of (7, 4) Hamming code book.

Hiding data in DNA can facilitate the authentication and annotation of important plant variety rights. Existing data hiding methods for DNA change the functionalities of DNA sequences, which induce morphological changes in biological patterns. Professor Wei-Liang Tai, and Mr.Charles C. N. Wang at Chinese Culture University, and Professors Phillip C. Y. Sheu and Jeffrey J. P. Tsai at Asia University propose a high capacity data hiding scheme for DNA without changing the functionalities of DNA sequences.

Recently, Changet al. proposed a Sudoku-based secret image sharing scheme. They utilized the Sudoku grid to generate meaningful shadow images, and their scheme satisfied all essential requirements. Based on Changet al.’s scheme, Dr. Zhi-Hui Wang at Dalian University of Technology, Dr. Cheng Guo at National Chung Cheng University, and Professor Chin-Chen Chang at Feng Chia University propose a novel (n,n) secret image sharing scheme based on Sudoku. In their proposed scheme, a secret image can be shared amongndifferent cover images by generatingnshadow images. The secret image can be reconstructed without distortion using only thesenshadow images.

Vector quantization (VQ) is a popular lossy image compression technique. VQ has good compression rate performance with acceptable visual quality of decompressed image. In order to improve the visual quality of decompression image, Professor Yung-Chen Chou at Asia University, Ms. Ya-Hsin Lo at National Chung Hsing University, and Professor Jau-Ji Shen at National Chung Hsing University propose a VQ like compression method to improve the visual quality of decompressed image. Their method applies VQ compression on image’s DWT (discrete wavelet transform) coefficients. The difference between image’s DWT coefficients and decompressed DWT coefficients is the adjustable basis of the decompressed image quality. By controlling the deviation of the difference matrix, it can be nearly lossless compression for VQ method.

On behalf of the editorial committee, we express our sincere thanks to all authors and reviewers for their great contribution to this special issue. Also, we thank the editorial committee members for their excellent assistance.Finally, we are grateful to the editorial staff for their help.Without all of the contributions of these hard-working,dedicated people, it would have been impossible to produce this special issue.