This textbook introduces the non-specialist reader to the concepts of quantum key distribution and presents an overview of state-of-the-art quantum communication protocols and applications. The field of quantum cryptography has advanced rapidly in the previous years, not least because with the age of quantum computing drawing closer, traditional encryption methods are at risk. The textbook presents the necessary mathematical tools without assuming much background, making it accessible to readers without experience in quantum information theory. In particular, the topic of classical and quantum entropies is presented in great detail. Furthermore, the author discusses the different types of quantum key distribution protocols and explains several tools for proving the security of these protocols. In addition, a number of applications of quantum key distribution are discussed, demonstrating its value to state-of-the-art cryptography and communication. This book leads the reader through the mathematical background with a variety of worked-out examples and exercises. It is primarily targeted at graduate students and advanced undergraduates in theoretical physics. The presented material is largely self-contained and only basic knowledge in quantum mechanics and linear algebra is required.

Rising concerns about the security of our data have made quantum cryptography a very active research field in recent years. Quantum cryptographic protocols promise everlasting security by exploiting distinctive quantum properties of nature. The most extensively implemented protocol is quantum key distribution (QKD), which enables secure communication between two users. The aim of this book is to introduce the reader to state-of-the-art QKD and illustrate its recent multi-user generalization: quantum conference key agreement. With its pedagogical approach that doesn’t disdain going into details, the book enables the reader to join in cutting-edge research on quantum cryptography.

This textbook integrates the most advanced topics of physical-layer security, cryptography, covert/stealth communications, quantum key distribution (QKD), and cyber security to tackle complex security issues. After introducing the reader to various concepts and practices, the author addresses how these can work together to target problems, rather than treating them as separate disciplines. This book offers students an in-depth exposition on: cryptography, information-theoretic approach to cryptography, physical-layer security, covert/stealth/low-probability of detection communications, quantum information theory, QKD, and cyber security; to mention few. The goal is to provide a unified description of the most advanced topics related to: (i) modern cryptography, (ii) physical-layer security, (iii) QKD, (iv) covert communications, and (v) cyber security. Each chapter is followed by a set of problems. Also, for readers to better understand the book, an appendix covers all needed background. Homework problems and lecture notes are available online. The book does not require any prior knowledge or prerequisite material.

Using the quantum properties of single photons to exchange binary keys between two partners for subsequent encryption of secret data is an absolutely novel te- nology. Only a few years ago quantum cryptography – or better Quantum Key Distribution – was the domain of basic research laboratories at universities. But during the last few years things changed. Quantum Key Distribution or QKD left the laboratories and was picked up by more practical-oriented teams that worked hard to develop a practically applicable technology out of the astonishing results of basic research. One major milestone toward a QKD technology was a large research and dev- opment project funded by the European Commission that aimed at combining qu- tum physics with complementary technologies that are necessary to create a tech- cal solution: electronics, software, and network components were added within the project SECOQC (Development of a Global Network for Secure Communication based on Quantum Cryptography) that teamed up all expertise on European level to get a technology for future cryptography.

The shortcomings of modern cryptography and its weaknesses against computers that are becoming more powerful necessitate serious consideration of more robust security options. Quantum cryptography is sound, and its practical implementations are becoming more mature. Many applications can use quantum cryptography as a backbone, including key distribution, secure direct communications, large prime factorization, e-commerce, e-governance, quantum internet, and more. For this reason, quantum cryptography is gaining interest and importance among computer and security professionals. Quantum Cryptography and the Future of Cyber Security is an essential scholarly resource that provides the latest research and advancements in cryptography and cyber security through quantum applications. Highlighting a wide range of topics such as e-commerce, machine learning, and privacy, this book is ideal for security analysts, systems engineers, software security engineers, data scientists, vulnerability analysts, professionals, academicians, researchers, security professionals, policymakers, and students.

This self-contained 2006 text introduces the principles and techniques of quantum cryptography, with specific focus on secret-key distillation. With its blend of fundamental theory, implementation techniques, and details of recent protocols, this book will be of interest to graduate students, researchers, and practitioners in electrical engineering, physics, and computer science.

QUANTUMCOMM 2009––the International Conference on Quantum Communi- tion and Quantum Networking (from satellite to nanoscale)––took place in Vico Equense near Naples, Italy, during October 26–30, 2009. The conference made a significant step toward stimulating direct dialogue between the communities of quantum physics and quantum information researchers who work with photons, atoms, and electrons in pursuit of the common goal of investigating and utilizing the transfer of physical information between quantum systems. This meeting brought together experts in quantum communication, quantum inf- mation processing, quantum nanoscale physics, quantum photonics, and networking. In the light of traditional approaches to quantum information processing, quantum communication mainly deals with encoding and securely distributing quantum states of light in optical fiber or in free space in order to provide the technical means for quantum cryptography applications. Exciting advances in the area of quantum c- munication over the last decade have made the metropolitan quantum network a re- ity. Several papers presented at this meeting have demonstrated that quantum crypt- raphy is approaching the point of becoming a high-tech application rather than a - search subject. The natural distance limitation of quantum cryptography has been significantly augmented using ideas of global quantum communication with stab- orbit satellites. The results presented at this conference demonstrated that practical secure satellite communication is clearly within reach.

This open access State-of-the-Art Survey presents the main recent scientific outcomes in the area of reversible computation, focusing on those that have emerged during COST Action IC1405 "Reversible Computation - Extending Horizons of Computing", a European research network that operated from May 2015 to April 2019. Reversible computation is a new paradigm that extends the traditional forwards-only mode of computation with the ability to execute in reverse, so that computation can run backwards as easily and naturally as forwards. It aims to deliver novel computing devices and software, and to enhance existing systems by equipping them with reversibility. There are many potential applications of reversible computation, including languages and software tools for reliable and recovery-oriented distributed systems and revolutionary reversible logic gates and circuits, but they can only be realized and have lasting effect if conceptual and firm theoretical foundations are established first.

All current methods of secure communication such as public-key cryptography can eventually be broken by faster computing. At the interface of physics and computer science lies a powerful solution for secure communications: quantum cryptography. Because eavesdropping changes the physical nature of the information, users in a quantum exchange can easily detect eavesdroppers. This allows for totally secure random key distribution, a central requirement for use of the one-time pad. Since the one-time pad is theoretically proven to be undecipherable, quantum cryptography is the key to perfect secrecy. Quantum Communications and Cryptography is the first comprehensive review of the past, present, and potential developments in this dynamic field. Leading expert contributors from around the world discuss the scientific foundations, experimental and theoretical developments, and cutting-edge technical and engineering advances in quantum communications and cryptography. The book describes the engineering principles and practical implementations in a real-world metropolitan network as well as physical principles and experimental results of such technologies as entanglement swapping and quantum teleportation. It also offers the first detailed treatment of quantum information processing with continuous variables. Technologies include both free-space and fiber-based communications systems along with the necessary protocols and information processing approaches. Bridging the gap between physics and engineering, Quantum Communications and Cryptography supplies a springboard for further developments and breakthroughs in this rapidly growing area.

This book explores both the state of the art and the latest developments in QKD. It describes the fundamental concepts and practical aspects of QKD from a viewpoint of information security and quantum channel efficiency improvement. The purpose of this book is to extend and update the knowledge of the readers in the dynamically changing field of QKD. The authors attempt to present in detail their results of scientific research, which is divided into two sections - Modern QKD Technologies and Quantum Channel Construction. It will be useful for researchers, engineers, graduates, and doctoral students working in quantum cryptography and information security-related areas.