Optical Cryptosystems. Naveen K. Nishchal

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      “Appa Deepo Bhavah”

      Be a Light unto Yourself.

      Gautama Buddha

Preface

      In the digital era of contemporary society, information in any form, such as a message, text, data, image, audio, or video, can be treated as wealth. Therefore, securing information is as important as protecting property. In the history of the human race, the significance of security in one form or the other can easily be traced. Though cryptographic techniques have been in use for protecting information for thousands of years, the systematic study of cryptology as a science started around one hundred years ago. Julius Caesar (around 100 BC) was known to use a form of encryption to convey secret messages to his Army Generals. In modern times, digital techniques of information security are already in use wherein there exists scope for further improvements in terms of security level and computation cost.

      Owing to the unique features of light, such as parallel processing, high speed, and several degrees of freedom, it is envisaged that information can be highly secured and communicated to the intended recipients or authentic users employing optical technologies. It can be foreseen that with the multifaceted uses of advanced technologies, such as Artificial Intelligence, Big Data, Cloud Computing, and Internet-of-Things, security will always remain an important challenge. Technologies provide several opportunities, but, at the same time, they also pose threats to information theft or misuse. Searching for a cyber expert or the attackers who attacked the digital algorithm would be very hard, because they can exist in large numbers anywhere in the world. On the other hand, finding out an attacker in the optics domain would be relatively easier. The security can be in terms of storage, in dissemination of the message, communication/transmission over conventional channels, protection of copyright/ownership, and steganography. Therefore, developments of newer alternative technologies are required to meet the challenges in the domains of scientific investigation.

      This book intends to provide a collection of optical technologies for secure storage, secure communication, and the protection of copyright in terms of watermarking. Most of the optical techniques reported in literature can be traced around a double random phase encoding algorithm. Furthermore, many variants of this scheme have been proposed and demonstrated with improvements and different levels of complexity. This book aims to provide help to researchers in the field to get first-hand information of its progress.

      This book starts with a general discussion on digital algorithms already in use in chapter 1 with more emphasis on the principles of optical techniques for image/data security in chapter 2. The growth of literature on optical technologies has been exponential with the publication of the first report in 1995. A bar chart has been provided that shows the growth of the literature. Use of fully-phased data provides additional security and robustness against noise, therefore such techniques have been dealt with in chapter 3. There is another aspect associated with security that is called authentication, in which the retrieval of original information is not intended. This can be solved with the use of an optical correlator, called a joint transform correlator, which is discussed in chapter 4. Optical techniques of watermarking and hiding are discussed in chapter 5. Polarization is one of the important properties of light, which is suited to developing a practical system because in this case the parameter that is dealt with is intensity, not the phase. Therefore, storage and transmission of intensity data is easier than phase-only information. This has been detailed in chapter 6.

      Digital holography helps record 3D data and recording with digital sensors offers advantages in image/data security. The digital holograms can be stored in a personal СКАЧАТЬ