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2020 | Book

Introduction Read chapter Read first chapter

Improving Image Quality in Visual Cryptography

Authors: Bin Yan, Prof. Dr. Yong Xiang, Prof. Guang Hua

Publisher: Springer Singapore

Book Series : Signals and Communication Technology

Part of: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

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About this book

This book comprehensively covers the important efforts in improving the quality of images in visual cryptography (VC), with a focus on cases with gray scale images. It not only covers schemes in traditional VC and extended VC for binary secret images, but also the latest development in the analysis-by-synthesis approach.

This book distinguishes itself from the existing literature in three ways. First, it not only reviews traditional VC for binary secret images, but also covers recent efforts in improving visual quality for gray scale secret images. Second, not only traditional quality measures are reviewed, but also measures that were not used for measuring perceptual quality of decrypted secret images, such as Radially Averaged Power Spectrum Density (RAPSD) and residual variance, are employed for evaluating and guiding the design of VC algorithms. Third, unlike most VC books following a mathematical formal style, this book tries to make a balance between engineering intuition and mathematical reasoning. All the targeted problems and corresponding solutions are fully motivated by practical applications and evaluated by experimental tests, while important security issues are presented as mathematical proof. Furthermore, important algorithms are summarized as pseudocodes, thus enabling the readers to reproduce the results in the book. Therefore, this book serves as a tutorial for readers with an engineering background as well as for experts in related areas to understand the basics and research frontiers in visual cryptography.

Table of Contents

Frontmatter
Chapter 1. Introduction
Abstract
The purpose of this chapter is to lead the readers from applications to research problems. We start the book by briefly reviewing the history of VC, in order to give the reader a general idea of this topic. Then, we identify some important applications of VC. Here, we also discuss in which applications visual cryptography is suitable and in which applications classical cryptography is preferable, in order to guide the reader to select appropriate cryptographic tools according to their intended security services. From these applications, the existing algorithms can be classified into several categories.
Bin Yan, Yong Xiang, Guang Hua
Chapter 2. Basic Visual Cryptography Algorithms
Abstract
This chapter aims to help the readers to get familiar with the classical VC algorithms. These algorithms are also stepstones for developing more complicated algorithms in later chapters. First, we introduce the general framework of VC, such as access structure and general requirements (security and contrast). Then, we introduce the classical deterministic VC with pixel expansion as developed in Naor and Shamir’s seminal work. Next, the size-invariant algorithms are summarized, including the probabilistic VC and random grid VC. Some examples will be discussed for the readers that are new to this topic. Finally, various security levels in visual cryptography will be discussed, including strong security and several weak securities.
Bin Yan, Yong Xiang, Guang Hua
Chapter 3. Digital Halftoning
Abstract
Chapter 2 focuses on binary secret image. In the next four chapters, we move further to grayscale secret images and cover images. For this case, the shares and the decrypted images are halftone images. This chapter will equip the readers with necessary background knowledge of digital halftoning. First, the problem of halftoning and its classification are introduced. Then, we review three popular halftoning frameworks, including ordered dithering, error diffusion, and direct binary search (DBS). The mathematical models for error diffusion are also discussed. Finally, some commonly used perceptual quality measures for halftone images are introduced. These measures are particularly useful when developing algorithms for grayscale images in later chapters.
Bin Yan, Yong Xiang, Guang Hua
Chapter 4. Improving Visual Quality for Share Images
Abstract
In this chapter, we focus on improving visual quality for extended VC, i.e., VC with meaningful shares. First, we discuss the case with binary secret images and cover images. Then we extend it to halftone cover images, in order to produce share images with better visual quality based on error diffusion. Finally, we extend the design to include a hidden watermark that can serve the authentication purpose.
Bin Yan, Yong Xiang, Guang Hua
Chapter 5. Improving Visual Quality for Probabilistic and Random Grid Schemes
Abstract
This chapter focuses on improving visual quality for grayscale secret images. First, we review available designs of VC for grayscale secret image. Then we provide a new design for (n, n)-threshold VC based on an Analysis-by-Synthesis (AbS) framework. The AbS-based probabilistic VC and AbS-based random grid VC will be elaborated in full detail.
Bin Yan, Yong Xiang, Guang Hua
Chapter 6. Improving Visual Quality for Vector Schemes
Abstract
To further improve the visual quality for grayscale secret images, we introduce the vector VC approach that encodes one block as a unit. First, we outline the basic vector VC for binary secret images. Then, we combine the AbS framework with vector VC to get better visual quality than AbS-based probabilistic VC and AbS-based random grid VC. For separate halftoning and VC encryption, we use the blackness preserving algorithm. For grayscale secret image, we develop an AbS-based vector VC algorithm.
Bin Yan, Yong Xiang, Guang Hua
Chapter 7. Conclusion and Future Works
Abstract
This chapter summarizes the whole book. After a brief review of the topics covered, several conclusions will be drawn. Guided with these conclusions, it is worth exploring several possible topics in the future.
Bin Yan, Yong Xiang, Guang Hua
Metadata
Title
Improving Image Quality in Visual Cryptography
Authors
Bin Yan
Prof. Dr. Yong Xiang
Prof. Guang Hua
Copyright Year
2020
Publisher
Springer Singapore
Electronic ISBN
978-981-13-8289-5
Print ISBN
978-981-13-8288-8
DOI
https://doi.org/10.1007/978-981-13-8289-5