Classical Cryptographic Protocols in a Quantum World

Cryptographic protocols, such as protocols for secure function evaluation (SFE), have played a crucial role in the development of modern cryptography. The extensive theory of these protocols, however, deals almost exclusively with classical attackers. If we accept that quantum information processing is the most realistic model of physically feasible computation, then we must ask: what classical protocols remain secure against quantum attackers? Our main contribution is showing the existence of classical two-party protocols for the secure evaluation of any polynomial-time function under reasonable computational assumptions (for example, it suffices that the learning with errors problem be hard for quantum polynomial time). Our result shows that the basic two-party feasibility picture from classical cryptography remains unchanged in a quantum world.Comment: Full version of an old paper in Crypto'11. Invited to IJQI. This is authors' copy with different formattin

Quantum Cryptography Beyond Quantum Key Distribution

Quantum cryptography is the art and science of exploiting quantum mechanical effects in order to perform cryptographic tasks. While the most well-known example of this discipline is quantum key distribution (QKD), there exist many other applications such as quantum money, randomness generation, secure two- and multi-party computation and delegated quantum computation. Quantum cryptography also studies the limitations and challenges resulting from quantum adversaries---including the impossibility of quantum bit commitment, the difficulty of quantum rewinding and the definition of quantum security models for classical primitives. In this review article, aimed primarily at cryptographers unfamiliar with the quantum world, we survey the area of theoretical quantum cryptography, with an emphasis on the constructions and limitations beyond the realm of QKD.Comment: 45 pages, over 245 reference

Composable security of delegated quantum computation

Delegating difficult computations to remote large computation facilities, with appropriate security guarantees, is a possible solution for the ever-growing needs of personal computing power. For delegated computation protocols to be usable in a larger context---or simply to securely run two protocols in parallel---the security definitions need to be composable. Here, we define composable security for delegated quantum computation. We distinguish between protocols which provide only blindness---the computation is hidden from the server---and those that are also verifiable---the client can check that it has received the correct result. We show that the composable security definition capturing both these notions can be reduced to a combination of several distinct "trace-distance-type" criteria---which are, individually, non-composable security definitions. Additionally, we study the security of some known delegated quantum computation protocols, including Broadbent, Fitzsimons and Kashefi's Universal Blind Quantum Computation protocol. Even though these protocols were originally proposed with insufficient security criteria, they turn out to still be secure given the stronger composable definitions.Comment: 37+9 pages, 13 figures. v3: minor changes, new references. v2: extended the reduction between composable and local security to include entangled inputs, substantially rewritten the introduction to the Abstract Cryptography (AC) framewor

Quantum cryptography: key distribution and beyond

Uniquely among the sciences, quantum cryptography has driven both foundational research as well as practical real-life applications. We review the progress of quantum cryptography in the last decade, covering quantum key distribution and other applications.Comment: It's a review on quantum cryptography and it is not restricted to QK

Composable and Efficient Mechanisms

We initiate the study of efficient mechanism design with guaranteed good properties even when players participate in multiple different mechanisms simultaneously or sequentially. We define the class of smooth mechanisms, related to smooth games defined by Roughgarden, that can be thought of as mechanisms that generate approximately market clearing prices. We show that smooth mechanisms result in high quality outcome in equilibrium both in the full information setting and in the Bayesian setting with uncertainty about participants, as well as in learning outcomes. Our main result is to show that such mechanisms compose well: smoothness locally at each mechanism implies efficiency globally. For mechanisms where good performance requires that bidders do not bid above their value, we identify the notion of a weakly smooth mechanism. Weakly smooth mechanisms, such as the Vickrey auction, are approximately efficient under the no-overbidding assumption. Similar to smooth mechanisms, weakly smooth mechanisms behave well in composition, and have high quality outcome in equilibrium (assuming no overbidding) both in the full information setting and in the Bayesian setting, as well as in learning outcomes. In most of the paper we assume participants have quasi-linear valuations. We also extend some of our results to settings where participants have budget constraints

JSB Composability and Web Services Interoperability Via Extensible Modeling & Simulation Framework (XMSF), Model Driven Architecture (MDA), Component Repositories, and Web-based Visualization

Study Report prepared for the U. S. Air Force, Joint Synthetic Battlespace Analysis of Technical Approaches (ATA) Studies & Prototyping Overview: This paper summarizes research work conducted by organizations concerned with interoperable distributed information technology (IT) applications, in particular the Naval Postgraduate School (NPS) and Old Dominion University (ODU). Although the application focus is distributed modeling & simulation (M&S) the results and findings are in general easily applicable to other distributed concepts as well, in particular the support of operations by M&S applications, such as distributed mission operations. The core idea of this work is to show the necessity of applying open standards for component description, implementation, and integration accompanied by aligned management processes and procedures to enable continuous interoperability for legacy and new M&S components of the live, virtual, and constructive domain within the USAF Joint Synthetic Battlespace (JSB). JSB will be a common integration framework capable of supporting the future emerging simulation needs ranging from training and battlefield rehearsal to research, system development and acquisition in alignment with other operational requirements, such as integration of command and control, support of operations, integration of training ranges comprising real systems, etc. To this end, the study describes multiple complementary Integrated Architecture Framework approaches and shows, how the various parts must be orchestrated in order to support the vision of JSB effectively and efficiently. Topics of direct relevance include Web Services via Extensible Modeling & Simulation Framework (XMSF), the Object Management Group (OMG)’s Model Driven Architecture (MDA), XML-based resource repositories, and Web-based X3D visualization. To this end, the report shows how JSB can − Utilize Web Services throughout all components via XMSF methodologies, − Compose diverse system visualizations using Web-based X3D graphics, − Benefit from distributed modeling methods using MDA, and − Best employ resource repositories for broad and consistent composability. Furthermore, the report recommends the establishment of necessary management organizations responsible for the necessary alignment of management processes and procedures within the JSB as well as with neighbored domains. Continuous interoperability cannot be accomplished by technical standards alone. The application of technical standards targets the implementation level of the system of systems, which results in an interoperable solution valid only for the actual 2 implementation. To insure continuity, the influence of updates, upgrades and introduction of components on the system of systems must be captured in the project management procedures of the participating systems. Finally, the report proposes an exemplifying set of proof-of-capability demonstration prototypes and a five-year technical/institutional transformation plan. All key references are online available at http://www.movesinstitute.org/xmsf/xmsf.html (if not explicitly stated otherwise)