A Photo Certificate-A Framework for Generating Visualized Public Key Certificates

In the proposed photo certificate, the principal component is the image, for example, the user＇s photo. User-related fields, such as the subject＇s name, the issuer＇s name, and the expiration period, which are meaningful to users, are embedded into the surface of the photo by using a visible watermark algorithm, so that the reader can capture this information without the requirement for special software. The remaining fields in the certificate are embedded into a marked photo. Later, the whole photo certificate is eryptographically signed by certification authority （CA） private key to guarantee the integrity of our photo certificate. By such arrangement, the eertificate＇s verification is divided into two layers. The first layer is human visual system oriented and the second layer is the software-oriented. User can determine whether the user＇s photo and its subject＇s name are consistent and cheek whether the expired period is valid first. The second layer＇s verification is lunched only when the first layer＇s verification is passed. To sum up, the proposed photo certificate not only inherits the functions of a traditional certificate, but also provides a friendlier operational environment of X.509 certificate.

Distortion-Free Data Embedding Scheme for High Dynamic Range Images

Distortion-free data embedding is a technique which can assure that not only the secret data is correctly extracted but also the cover media is recovered without any distortion after secret data is extracted completely. Because of these advantages, this technique attracts the attention of many researchers. In this paper, a new distortion-free data embedding scheme for high dynamic range （HDR） images is proposed. By depending on Cartesian product, this scheme can obtain higher embedding capacity while maintaining the exactly identical cover image and stego image when using the tone mapping algorithms. In experimental results, the proposed scheme is superior to Yu et aL＇s scheme in regard to the embedding rate——an average embedding rate of 0.1355 bpp compared with Yn et aL＇s scheme （0.1270 bpp）.

Reversible Data Embedding Scheme Using Relationships between Pixel-Values and Their Neighbors

Reversible data embedding is becoming a very important issue in securing images transmitted over the Internet, especially in dealing with sensitive images such as those created for military data and medical data. Based on the relationships between pixels and their neighbors, we propose a reversible data embedding scheme to embed hidden messages into an original image. In our proposed scheme, a two-layer data embedding approach is used for our proposed data embedding phase. Layer-1 embedding is used to hide secret data. Layer-2 embedding, which is an embedding variant of the proposed layer-1 embedding, is used to hide side information, such as the parameters required to restore the marked image. In our layer-1 embedding, the value of an embedded pixel is determined according to a predetermined threshold and the relationship between the pixel and its neighbors. In our layer-2 embedding, the similar data embedding concept is expanded to the block-based. Experimental results provide supportive data to show that the proposed scheme can provide greater hiding capacity while preserving the image quality of a marked image in comparison with previous work.

Guest Editorial Special Issue on Information Security

The Intemet is a popular channel for allowing more and more users to exchange information without geographical limitations and time restrictions. Therefore, a large amount of digital data, such as digital images, text, audio, and video, is transmitted over the Intemet. Unfortunately, sensitive digital data can be intercepted by malicious users of the Internet, so the development of techniques for ensuring the secrecy and security of data during transmission has become a top priority.

Multiple Perspective of Multipredictor Mechanism and Multihistogram Modification for High-Fidelity Reversible Data Hiding

Reversible data hiding is a confidential communication technique that takes advantage of image file characteristics,which allows us to hide sensitive data in image files.In this paper,we propose a novel high-fidelity reversible data hiding scheme.Based on the advantage of the multipredictor mechanism,we combine two effective prediction schemes to improve prediction accuracy.In addition,the multihistogram technique is utilized to further improve the image quality of the stego image.Moreover,a model of the grouped knapsack problem is used to speed up the search for the suitable embedding bin in each sub-histogram.Experimental results show that the quality of the stego image of our scheme outperforms state-of-the-art schemes in most cases.