Cryptographic accumulators are a tool for compact set representation and secure set membership proofs. When an element is added to a set by means of an accumulator, a membership witness is generated. This witness can later be used to prove the membership of the element. Typically, the membership witness has to be synchronized with the accumulator value, and to be updated every time another element is added to the accumulator. In this work we propose an accumulator that, unlike any prior scheme, does not require strict synchronization. In our construction a membership witness needs to be updated only a logarithmic number of times in the number of subsequent element additions. Thus, an out-of-date witness can be easily made current. Vice versa, a verifier with an out-of-date accumulator value can still verify a current membership witness. These properties make our accumulator construction uniquely suited for use in distributed applications, such as blockchain-based public key infrastructures.

No description available.

No description available.

No description available.

With the issuance of the Notice of Proposed Rule Making (NPRM) for Vehicle to Vehicle (V2V) communications by the United States National Highway Tra c Safety Administration (NHTSA), the goal of the widespread deployment of vehicular networking has taken a signi cant step towards becoming a reality. In order for consumers to accept the technology, it is expected that reasonable mechanisms will be in place to protect their privacy. Cooperative Caching has been proposed as an approach that can be used to improve privacy by distributing data items throughout the mobile network as they are requested. With this approach, vehicles rst attempt to retrieve data items from the mobile network, alleviating the need to send all requests to a centralized location that may be vulnerable to an attack. However, with this approach, a requesting vehicle may expose itself to many unknown vehicles as part of the cache discovery process. In this work we present a Public Key Infrastructure (PKI) based Cooperative Caching system that utilizes a genetic algorithm to selectively choose members of the mobile network to query for data items with a focus on improving overall privacy. The privacy improvement is achieved by avoiding those members that present a greater risk of exposing information related to the request and choosing members that have a greater potential of having the needed data item. An Agent Based Model is utilized to baseline the privacy concerns when using a broadcast based approach to cache discovery. In addition, an epidemiology inspired mathematical model is presented to illustrate the impact of reducing the number of vehicles queried during cache discovery. Periodic reports from neighboring vehicles are used by the genetic algorithm to identify which neighbors should be queried during cache discovery. In order for the system to be realistic, vehicles must trust the information in these reports. A PKI based approach used to evaluate the trustworthiness of each vehicle in the system is also detailed. We have conducted an in-depth performance study of our system that demonstrates a signi cant reduction in the overall risk of exposure when compared to broadcasting the request to all neighbors. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Les schémas de Chiffrement Complètement Homomorphe (FHE) permettent de manipuler des données chiffrées avec grande flexibilité : ils rendent possible l'évaluation de fonctions à travers les couches de chiffrement. Depuis la découverte du premier schéma FHE en 2009 par Craig Gentry, maintes recherches ont été effectuées pour améliorer l'efficacité, atteindre des nouveaux niveaux de sécurité, et trouver des applications et liens avec d'autres domaines de la cryptographie. Dans cette thèse, nous avons étudié en détail ce type de schémas. Nos contributions font état d'une nouvelle attaque de récuperation des clés au premier schéma FHE, et d'une nouvelle notion de sécurité en structures hierarchiques, évitant une forme de trahison entre les usagers tout en gardant la flexibilité FHE. Enfin, on décrit aussi des implémentations informatiques. Cette recherche a été effectuée au sein du Laboratoire de Mathématiques de Versailles avec le Prof. Louis Goubin. / Fully Homomorphic Encryption schemes allow public processing of encrypted data. Since the groundbreaking discovery of the first FHE scheme in 2009 by Craig Gentry, an impressive amount of research has been conducted to improve efficiency, achieve new levels of security, and describe real applications and connections to other areas of cryptography. In this Dissertation, we first give a detailed account on research these past years. Our contributions include a key-recovery attack on the ideal lattices FHE scheme and a new conception of hierarchic encryption, avoiding at some extent betrayal between users while maintaining the flexibility of FHE. We also describe some implementations. This research was done in the Laboratoire de Mathématiques de Versailles, under supervision of Prof. Louis Goubin.

The emerging Blockchain technology has the potential to shift the traditional centralized systems to become more flexible, efficient and decentralized. An important area to apply this capability is supply chain. Supply chain visibility and transparency has become an important aspect of a successful supply chain platform as it becomes more complex than ever before. The complexity comes from the number of participants involved and the intricate roles and relations among them. This puts more pressure on the system and the customers in terms of system availability and tamper-resistant data. This thesis presents a private and permisioned application that uses Blockchain and aims to automate the shipping processes among different participants in the supply chain ecosystem. Data in this private ledger is governed with the participants’ invocation of their smart contracts. These smart contracts are designed to satisfy the participants’ different roles in the supply chain. Moreover, this thesis discusses the performance measurements of this application results in terms of the transaction throughput, transaction average latency and resource utilization. / Graduate

Thesis (Ph.D.)--University of Wollongong, 2009. / Typescript. Includes bibliographical references (leaf 130-140) and index.

M. Tech. Electrical Engineering. / Proposes a public-key encryption scheme based on Qi hyperchaos, which is considered much better than chaos and other hyperchaos in terms of pseudo-randomness. In an environment where digital information is being extensively used, a cat map based hyperchaotic system is proposed. This map is used to design the public key encryption scheme that uses private keys, public keys and shared private keys. This encryption is tested successfully on text messages and images. The application of the hyperchaos-based scheme on a web server client platform concludes this work. MATLAB is used for simulation. PHP, HTML, and C are used in the development of the web form and the chat application.

During the modern times, innovators and researchers developed a key technology known as Artificial Intelligence (AI) Marketplace which leverages the power of AI to efficiently utilize the data generated by millions of devices to create new and better services and software products. H2020 Bonseyes is one such project that provides us a collaborative cloud based model of the AI marketplace for the users who generally don’t have access to large data sets, algorithms etc by allowing them to collaborate which each other and exchange the software artifacts. Collaboration leads to issues related to authentication and authorization which are addressed by Public Key In- frastructure(PKI).The main component of the PKI is the Certificate Authority which acts a anchor of trust, whose architecture is designed to be centralized. Centralized architecture is prone to many attacks and also failures which makes it vulnerable and weak.The adverse effects of the CA based PKI can be avoided by implementing a distributed PKI.This thesis focuses on a hybrid methodology consisting of Qualitative and Quanti- tative analysis by performing a literature review for accumulating knowledge from the Ocean Protocol which is a decentralized AI marketplace.The thesis aims to design and implement the framework used in the ocean protocol and evaluate its performance.The thesis also aims to develop a reference framework to be compatible with the Bonseyes Project. Moreover, our research also provides the reader with the concepts and technologies used in other implementations of distributed PKI.