A zero-knowledge proof of knowledge allows one party to convince another party that it knows a secret piece of information without revealing anything about it. Such protocols are important building blocks for many interesting higher-level cryptographic applications, such as e-voting and e-cash systems, digital signature and identification schemes, or anonymous credential systems. Unfortunately, their high computational costs, as well as long and error-prone implementation cycles, are major hurdles on their way to real-world usage. This thesis contributes to overcoming these restrictions. On the practical side, we introduce a compiler which automatically translates natural specifications of zero-knowledge proofs into concrete implementations. In addition, it generates formal proofs that the generated protocols are indeed sound. On the theoretical side, we analyze inherent efficiency limitations of igma-protocols, proving the optimality of currently known protocols. Finally, we consider zero-knowledge proofs in the Universal Composability framework. By enabling UC-compliant proofs of existence for the first time, we are able to decrease the computational complexity of many practically relevant UC-secure zero-knowledge protocols to an acceptable level.

This book constitutes the thoroughly refereed post-proceedings of the 17th International Workshop on Security Protocols, SP 2009, held in Cambridge, UK, in April 2009. The 17 revised full papers presented together with edited transcriptions of some of the discussions following the presentations have gone through multiple rounds of reviewing, revision, and selection. The theme of this workshop was "Brief Encounters". In the old days, security protocols were typically run first as preliminaries to, and later to maintain, relatively stable continuing relationships between relatively unchanging individual entities. Pervasive computing, e-bay and second life have shifted the ground: we now frequently desire a secure commitment to a particular community of entities, but relatively transient relationships with individual members of it, and we are often more interested in validating attributes than identity. The papers and discussions in this volume examine the theme from the standpoint of various different applications and adversaries.

This book constitutes the refereed proceedings of the 18th International Conference on Practice and Theory in Public-Key Cryptography, PKC 2015, held in Gaithersburg, MD, USA, in March/April 2015. The 36 papers presented in this volume were carefully reviewed and selected from 118 submissions. They are organized in topical sections named: public-key encryption; e-cash; cryptanalysis; digital signatures; password-based authentication; pairint-based cryptography; efficient constructions; cryptography with imperfect keys; interactive proofs; lattice-based cryptography; and identity-based, predicate, and functional encryption.

The two volume-set, LNCS 8042 and LNCS 8043, constitutes the refereed proceedings of the 33rd Annual International Cryptology Conference, CRYPTO 2013, held in Santa Barbara, CA, USA, in August 2013. The 61 revised full papers presented in LNCS 8042 and LNCS 8043 were carefully reviewed and selected from numerous submissions. Two abstracts of the invited talks are also included in the proceedings. The papers are organized in topical sections on lattices and FHE; foundations of hardness; cryptanalysis; MPC - new directions; leakage resilience; symmetric encryption and PRFs; key exchange; multi linear maps; ideal ciphers; implementation-oriented protocols; number-theoretic hardness; MPC - foundations; codes and secret sharing; signatures and authentication; quantum security; new primitives; and functional encryption.

Enables readers to understand applications of attribute-based encryption schemes in cloud computing with the support of blockchain technology With a focus on blockchain technology, Attribute-based Encryption (ABE) provides insight into the application of attribute-based encryption (ABE) schemes with blockchain, discussing types of blockchains, fundamentals of blockchain, and how blockchains are constructed. Comprised of 16 chapters, the text provides readers with an overview of the components that go into creating a dual ABE system of encryption proofs within the following: composite bilinear groups, dual pairing vector space framework, matrix pairing framework, framework for matrix pairing, and the application of cryptographic scheme on blockchain. The team of authors discuss the basic construction components of ABE and share the security models, including the selective and semi-adaptive security models, applying these to either prime order or composite order groups. This book also discusses the tools used for converting a composite order ABE scheme to prime order and an adaptive secure ABE scheme based on prime order. In Attribute-based Encryption (ABE), readers can expect to find information on: Mathematical background of ABE, covering group and cyclic group, elliptic curves, curve selection, supersingular curves, ordinary curves, and weil and tate pairing Basic construction components of ABE, covering access structure, monotone boolean formula, linear secret-sharing scheme, and ordered binary decision diagram Tools for converting composite order ABE schemes to prime order, covering security assumptions and conversion based on vectors for preliminaries, scheme construction, and security proof technique Foundations of blockchain technology, covering blocks, miners, hash functions, and public key cryptography Attribute-based Encryption (ABE) is an essential resource for professionals working in the field of design and cybersecurity who wish to understand how to use blockchain and the ABE scheme to provide fine-grained access control in outsourced data on third-party cloud servers.

"A staggeringly comprehensive review of the state of modern cryptography. Essential for anyone getting up to speed in information security." - Thomas Doylend, Green Rocket Security An all-practical guide to the cryptography behind common tools and protocols that will help you make excellent security choices for your systems and applications. In Real-World Cryptography, you will find: Best practices for using cryptography Diagrams and explanations of cryptographic algorithms Implementing digital signatures and zero-knowledge proofs Specialized hardware for attacks and highly adversarial environments Identifying and fixing bad practices Choosing the right cryptographic tool for any problem Real-World Cryptography reveals the cryptographic techniques that drive the security of web APIs, registering and logging in users, and even the blockchain. You’ll learn how these techniques power modern security, and how to apply them to your own projects. Alongside modern methods, the book also anticipates the future of cryptography, diving into emerging and cutting-edge advances such as cryptocurrencies, and post-quantum cryptography. All techniques are fully illustrated with diagrams and examples so you can easily see how to put them into practice. Purchase of the print book includes a free eBook in PDF, Kindle, and ePub formats from Manning Publications. About the technology Cryptography is the essential foundation of IT security. To stay ahead of the bad actors attacking your systems, you need to understand the tools, frameworks, and protocols that protect your networks and applications. This book introduces authentication, encryption, signatures, secret-keeping, and other cryptography concepts in plain language and beautiful illustrations. About the book Real-World Cryptography teaches practical techniques for day-to-day work as a developer, sysadmin, or security practitioner. There’s no complex math or jargon: Modern cryptography methods are explored through clever graphics and real-world use cases. You’ll learn building blocks like hash functions and signatures; cryptographic protocols like HTTPS and secure messaging; and cutting-edge advances like post-quantum cryptography and cryptocurrencies. This book is a joy to read—and it might just save your bacon the next time you’re targeted by an adversary after your data. What's inside Implementing digital signatures and zero-knowledge proofs Specialized hardware for attacks and highly adversarial environments Identifying and fixing bad practices Choosing the right cryptographic tool for any problem About the reader For cryptography beginners with no previous experience in the field. About the author David Wong is a cryptography engineer. He is an active contributor to internet standards including Transport Layer Security. Table of Contents PART 1 PRIMITIVES: THE INGREDIENTS OF CRYPTOGRAPHY 1 Introduction 2 Hash functions 3 Message authentication codes 4 Authenticated encryption 5 Key exchanges 6 Asymmetric encryption and hybrid encryption 7 Signatures and zero-knowledge proofs 8 Randomness and secrets PART 2 PROTOCOLS: THE RECIPES OF CRYPTOGRAPHY 9 Secure transport 10 End-to-end encryption 11 User authentication 12 Crypto as in cryptocurrency? 13 Hardware cryptography 14 Post-quantum cryptography 15 Is this it? Next-generation cryptography 16 When and where cryptography fails

Secure two-party computation, called secure function evaluation (SFE), enables two mutually mistrusting parties, the client and server, to evaluate an arbitrary function on their respective private inputs while revealing nothing but the result. Originally the technique was considered to be too inefficient for practical privacy-preserving applications, but in recent years rapid speed-up in computers and communication networks, algorithmic improvements, automatic generation, and optimizations have enabled their application in many scenarios. The author offers an extensive overview of the most practical and efficient modern techniques used in the design and implementation of secure computation and related protocols. After an introduction that sets secure computation in its larger context of other privacy-enhancing technologies such as secure channels and trusted computing, he covers the basics of practically efficient secure function evaluation, circuit optimizations and constructions, hardware-assisted garbled circuit protocols, and the modular design of efficient SFE protocols. The goal of the author's research is to use algorithm engineering methods to engineer efficient secure protocols, both as a generic tool and for solving practical applications, and he achieves an excellent balance between the theory and applicability. The book is essential for researchers, students and practitioners in the area of applied cryptography and information security who aim to construct practical cryptographic protocols for privacy-preserving real-world applications.