| Summary: | 博士 === 國立交通大學 === 資訊科學與工程研究所 === 100 === Image authentication is an effective technique to protect digital image content and the goal of such techniques is to check the integrity and fidelity of a digital image. It means that image authentication techniques are capable of providing the function of tempering detection and tampering localization when an image has been tampered with. In this dissertation, repairable image authentication methods for grayscale document images, binary images and grayscale images are proposed, respectively. The proposed methods can not only detect and localize the tampered region but further repair the tampered region for an attacked image. For authentication of grayscale document images and binary images, an input cover image is first transformed into a stego-image in the PNG format with an alpha channel plane. Subsequently, the information used for authentication and image repairing are transformed into partial shares by the Shamir’s secret sharing method, which are then distributed in a well-designed manner into an alpha channel plane to create a stego-image in the PNG format. In this way, data repairing can be applied to tampered region by a reverse Shamir scheme after collecting enough shares from the alpha channel plane. In addition, a color image authentication method which is based on a new data hiding method proposed is developed in this dissertation. The data hiding method conceals data by utilizing the character of the transparency of the alpha channel plane. For authentication of grayscale images, a method which is based on the concept of compressing a number of the most significant bits of a pixel’s gray value into a shorter “bin code” is proposed. The bin code is for use both as an authentication signal for the pixel and as an index for generating the data for repairing the pixel when it is authenticated to have been tampered with.
In the aspect of multimedia security, a new covert communication method which takes Spreadsheets as the cover medium and applies Secret Sharing method to yield a self-authentication capability is proposed. Through checking the consistency of the copies in value computed from secret shares, the proposed covert communication has the capability of self-authentication. In the field of reversible data hiding, a blind two-phase reversible data hiding method based on histogram shifting is proposed. Two types of histogram-shifting techniques are executed in two phases such that the proposed method can be performed iteratively during the data embedding process and blindly during the data extraction process.
The feasibility and effectiveness of all the above proposed method have been demonstrated by theoretical analyses and experiments.
|
|---|
