Preuves à divulgation nulle de connaissance efficaces à base de réseaux euclidiens et applications Le chiffrement à base de réseaux euclidiens a connu un grand essor durant les vingt dernières années. Autant grâce à l’apparition de nouvelles primitives telles que le chiffrement complètement homomorphe, que grâce à l’amélioration des primitives existantes, comme le chiffrement á clef publique ou les signatures digitales, qui commencent désormais à rivaliser avec leurs homologues fondés sur la théorie des nombres. Cela dit les preuves à divulgation nulle de connaissance, bien qu’elles représentent un des piliers des protocols de confidentialité, n’ont pas autant progressé, que ce soit au niveau de leur expressivité que de leur efficacité. Cette thèse s’attelle dans un premier temps à améliorer l’état de l’art en matière de preuves à divulgation nulle de connaissance. Nous construisons une preuve d’appartenance à un sous ensemble dont la taille est indépendante de l’ensemble en question. Nous construisons de même une preuve de connaissance amortie qui est plus efficace et plus simple que toutes les constructions qui la précèdent. Notre second propos est d’utiliser ces preuves à divulgation nulle de connaissance pour construire de nouvelles primitives cryptographiques. Nous concevons une signature de groupe dont la taille est indépendante du groupe en question, ainsi qu’un schéma de vote électronique hautement efficace, y compris pour des élections à grand échelle.
Healthcare is a big application scenario of blockchain, and blockchains used in healthcare are called health blockchain. In general, blockchain blocks are open and the transactions in them are public. If some privacy data are involved in these transactions, they will be leaked. Owing to healthcare system involving a great deal of privacy data, certain security mechanisms must be built to protect these privacy data in health blockchain. Furthermore, because the core of security mechanisms is the key management schemes, the appropriate key management schemes should be designed before blockchains can be used in healthcare system. Here, according to the features of health blockchain, the authors use a body sensor network to design a lightweight backup and efficient recovery scheme for keys of health blockchain. The authors’ analyses show that the scheme has high security and performance, and it can be used to protect privacy messages on health blockchain effectively and to promote the application of health blockchain.
Many companies rely on Cloud infrastructures for their computation, communication and data storage requirements. While Cloud services provide some benefits, e.g., replacing high upfront costs for an IT infrastructure with a pay-as-you-go model, they also introduce serious concerns that are notoriously difficult to address. In essence, Cloud customers are storing data and running computations on infrastructures that they can not control directly. Therefore, when problems arise -- violations of Service Level Agreements, data corruption, data leakage, security breaches -- both customers and Cloud providers face the challenge of agreeing on which party is to be held responsible. In this paper, we review the challenges and requirements for enforcing accountability in Cloud infrastructures, and argue that smart contracts and blockchain technologies might provide a key contribution towards accountable Clouds.
Santiago Bragagnolo, Henrique Rocha, Marcus Denker, Sté́phane Ducasse
Blockchains store a massive amount of heterogeneous data which will only grow in time. When searching for data on the Ethereum platform, one is required to either access the records (blocks) directly by using a unique identifier, or sequentially search several records to find the desired information. Therefore, we propose the Ethereum Query Language (EQL), a query language that allows users to retrieve information from the blockchain by writing SQL-like queries. The queries provide a rich syntax to specify data elements to search information scattered through several records. We claim that EQL makes it easier to search, acquire, format, and present information from the blockchain.
During the normal operation of a Cloud solution, no one usually pays attention to the logs except technical department, which may periodically check them to ensure that the performance of the platform conforms to the Service Level Agreements. However, the moment the status of a component changes from acceptable to unacceptable, or a customer complains about accessibility or performance of a platform, the importance of logs increases significantly. Depending on the scope of the issue, all departments, including management, customer support, and even the actual customer, may turn to logs to find out what has happened, how it has happened, and who is responsible for the issue. The party at fault may be motivated to tamper the logs to hide their fault. Given the number of logs that are generated by the Cloud solutions, there are many tampering possibilities. While tamper detection solution can be used to detect any changes in the logs, we argue that critical nature of logs calls for immutability. In this work, we propose a blockchain-based log system, called Logchain, that collects the logs from different providers and avoids log tampering by sealing the logs cryptographically and adding them to a hierarchical ledger, hence, providing an immutable platform for log storage.
Fergus Dall, Gabrielle De Micheli, Thomas Eisenbarth, Daniel Genkin · 7 authors
Intel Software Guard Extensions (SGX) allows users to perform secure computation on platforms that run untrusted software. To validate that the computation is correctly initialized and that it executes on trusted hardware, SGX supports attestation providers that can vouch for the user’s computation. Communication with these attestation providers is based on the Extended Privacy ID (EPID) protocol, which not only validates the computation but is also designed to maintain the user’s privacy. In particular, EPID is designed to ensure that the attestation provider is unable to identify the host on which the computation executes. In this work we investigate the security of the Intel implementation of the EPID protocol. We identify an implementation weakness that leaks information via a cache side channel. We show that a malicious attestation provider can use the leaked information to break the unlinkability guarantees of EPID. We analyze the leaked information using a lattice-based approach for solving the hidden number problem, which we adapt to the zero-knowledge proof in the EPID scheme, extending prior attacks on signature schemes.
Nguyen B. Truong, Tai‐Won Um, Bo Zhou, Gyu Myoung Lee
In recent years, Blockchain has been expected to create a secure mechanism for exchanging not only for cryptocurrency but also for other types of assets without the need for a powerful and trusted third-party. This could enable a new era of the Internet usage called the Internet of Value (IoV) in which any types of assets such as intellectual and digital properties, equity and wealth can be digitized and transferred in an automated, secure, and convenient manner. In the IoV, Blockchain is used to guarantee security of transactions that the transactions are nearly impossible to be altered; thus it is impractical to retract once a transaction is confirmed. Therefore, to strengthen the IoV, before making any transactions it is crucial to evaluate trust between participants for reducing the risk of dealing with malicious peers. In this article, we clarify the concept of IoV and propose a trust-based IoV model including a system architecture, components and features. Then, we present a trust platform in the IoV considering two concepts, Experience and Reputation, originated from Social Networks for evaluating trust between two any peers in the IoV. The Experience and Reputation are characterized and calculated using mathematical models with analysis and simulation in the IoV environment. We believe this paper consolidates the understandings about IoV technologies and demonstrates how trust is evaluated and used to strengthen the IoV. It also opens important research directions on both IoV and trust in the future.
Abstract The goal of the paper is to provide a vague summary of currently existing blockchain use cases in the information technology industry. Respective use cases have been examined in already existing scientific papers, Master Theses, industry white papers and blogs of industry experts. The paper also contains a description of blockchain main technological aspects and working principles, which allows making the assessment of the presented use cases. For each use case respective companies or organisations are added that are applying or testing the given solution. Due to research limitations the paper should not be considered an exhaustive blockchain use case description. The paper also provides short introduction into a feasibility analysis of specific blockchain use case. The authors describe the basic steps of potential idea evaluation with regards to blockchain main aspects. It helps understand the necessity for development of a detailed blockchain feasibility model.
Subasri Mathiyalahan, Shobana Manivannan, Mahalakshmi Nagasundaram, R. Ezhilarasie
Data integrity of outsourced data is main problem in CSP (cloud service provider). Space overhead and computation complexity are very high issue in recent PDP(Provable Data Possession) verification schemes. To overcome such issues MPDP (Mobile Provable Data Possession) schemes using hash tree data structure and Boneh-Lynn-Snacham short signature scheme have been used over decade. Data dynamics is well supported in MPDP scheme via block less verification, dynamic data operations, stateless verification, and verification out sourcing. But still there are some operations which can be performed much more efficiently in some other way than that of the two methods prescribed above. Operations in particular, data modification operations like insertion and deletion operations is somewhat difficult or in other words time consuming in hash tree data structure. In this paper, we have deployed an improved hash tree structure called MPT (Merkle Patricia Tree) for integrity checking.MPT is combination of MHT (Merkle Hash Tree) and patricia tree where each node consists of key-value pairs. As of now, MPT has been used only in block chain technology for providing authentication of transactions through Ethereum.
Abstract The recent advances in information technology for mobile devices have increased the work efficiency of users, the mobility of compact mobile devices, and the convenience of location independence. However, mobile devices have limited computing power and storage capacity, so mobile cloud computing is being researched to overcome these limitations in mobile devices. Mobile cloud computing is divided into two methods: the use of external cloud services and the use of mobile resource management without a cloud server (MRM), which integrates the computing and storage resources of nearby mobile devices. Because mobile devices can freely participate in MRM, it is critical to have authentication technology to determine the correctness of information regarding resources. Conventional technologies require strong authentication techniques because they have vulnerabilities that can easily be tampered with via man-in-the-middle (MITM) attacks. This paper proposes the Secure Authentication Management human-centric Scheme (SAMS) to authenticate mobile devices using blockchain for trusting resource information in the mobile devices that are participating in the MRM resource pool. The SAMS forms a blockchain based on the resource information of the subordinate client nodes around the master node in the MRM. Devices in the MRM that have not been authorized through the SAMS cannot access or falsify data. To verify the SAMS for application with MRM, it was tested for data falsification by a malicious user accessing the SAMS, and the results show that data falsification is impossible.
John Collomosse, Tu Bui, Alan Brown, John Sheridan · 9 authors
We present ARCHANGEL; a de-centralised platform for ensuring the long-term integrity of digital documents stored within public archives. Document integrity is fundamental to public trust in archives. Yet currently that trust is built upon institutional reputation --- trust at face value in a centralised authority, like a national government archive or University. ARCHANGEL proposes a shift to a technological underscoring of that trust, using distributed ledger technology (DLT) to cryptographically guarantee the provenance, immutability and so the integrity of archived documents. We describe the ARCHANGEL architecture, and report on a prototype of that architecture build over the Ethereum infrastructure. We report early evaluation and feedback of ARCHANGEL from stakeholders in the research data archives space.
Santiago Bragagnolo, Henrique Rocha, Marcus Denker, Sté́phane Ducasse
Solidity is a language used for smart contracts on the Ethereum blockchain. Smart contracts are embedded procedures stored with the data they act upon. Debugging smart contracts is a really difficult task since once deployed, the code cannot be reexecuted and inspecting a simple attribute is not easily possible because data is encoded. In this paper, we address the lack of inspectability of a deployed contract by analyzing contract state using decompilation techniques driven by the contract structure definition. Our solution, SmartInspect, also uses a mirror-based architecture to represent locally object responsible for the interpretation of the contract state. SmartInspect allows contract developers to better visualize and understand the contract stored state without needing to redeploy, nor develop any ad-hoc code.
Blockchain is a one of emerging technology for decentralized and sharing of transactional data across a large peer to peer network, where non-trusting members can interact with each other without an intermediary, in a verifiable manner. In this paper, we review the basics of Blockchain, its applications, types, and working of Blockchain. Behind this innovative technique, the security, privacy issues and Con-sensus mechanisms of this technology are also important and are a matter of concern. The problems associated with Blockchain technol-ogy are also discussed in this paper.
Initial Coin Offerings (ICO) are public offers of new cryptocurrencies in exchange of existing ones, aimed to finance projects in the blockchain development arena. In the last 8 months of 2017, the total amount gathered by ICOs exceeded 4 billion US$, and overcame the venture capital funnelled toward high tech initiatives in the same period. A high percentage of ICOS is managed through Smart Contracts running on Ethereum blockchain, and in particular to ERC-20 Token Standard Contract. In this work we examine 1388 ICOs, published on December 31, 2017 on icobench.com Web site, gathering information relevant to the assessment of their quality and software development management, including data on their development teams. We also study, at the same date, the financial data of 450 ICO tokens available on coinmarketcap.com Web site, among which 355 tokens are managed on Ethereum blochain. We define success criteria for the ICOs, based on the funds actually gathered, and on the behavior of the price of the related tokens, finding the factors that most likely influence the ICO success likeliness.
Blockchains have recently generated explosive interest from both academia and industry, with many proposed applications. But descriptions of many these proposals are more visionary projections than realizable proposals, and even basic definitions are often missing. We define "blockchain" and "blockchain network", and then discuss two very different, well known classes of blockchain networks: cryptocurrencies and Git repositories. We identify common primitive elements of both and use them to construct a framework for explicitly articulating what characterizes blockchain networks. The framework consists of a set of questions that every blockchain initiative should address at the very outset. It is intended to help one decide whether or not blockchain is an appropriate approach to a particular application, and if it is, to assist in its initial design stage.
With the development of marine observation technology and network technology, the volume of marine data growing rapidly. This brings new challenges for data storage and transmission. How to protect data security of marine big data has become an urgent problem. The traditional information security methods' characteristic is centralization. These technologies cannot provide whole process protection, e.g., data storage, data management and application of data. The blockchain technology is a novel technology, which can keep the data security and reliability by using decentralized methodology. It has aroused wide interest in the financial field. In this paper, we describe the concept, characteristics and key technologies of blockchain technology and introduce it into the field of marine data security.
The brave new world of blockchain potentially transforms the financial structures we have come to know and feel ambivalent about. What does a decentralized, secure system mean for our society?
The emergence of distributed ledger technology (DLT) based upon a blockchain data structure, has given rise to new approaches to identity management that aim to upend dominant approaches to providing and consuming digital identities. These new approaches to identity management (IdM) propose to enhance decentralisation, transparency and user control in transactions that involve identity information; but, given the historical challenge to design IdM, can these new DLT-based schemes deliver on their lofty goals? We introduce the emerging landscape of DLT-based IdM, and evaluate three representative proposals: uPort; ShoCard; and Sovrin; using the analytic lens of a seminal framework that characterises the nature of successful IdM schemes.
Systems that use blockchain technology to improve the know-your-customer (KYC) process have only been proposed at a conceptual level and all share certain attributes that make their adoption very difficult. We propose and program a blockchain-based system that reduces and shares out among the financial institutions (FIs) that work with a customer the costs of the KYC process and also makes it possible for FIs to dynamically update information related to customers and disseminates this information among participating FIs. Additionally, our system addresses some of the attributes that hinder the adoption of previously proposed solutions by FIs. The result is a stand-alone solution that reduces the cost of the KYC process without requiring any central instance to store the customer's data, and in which FIs share the initial costs of the KYC process as well as the running costs of keeping the information about customers up to date.
Virtual machine (VM) measurements data in IaaS cloud play a crucial role in integrity evaluation and decision making. Hence, the secure storage for these data has attracted more attention recently. This paper proposes a novel approach, named Mchain, to enhance the integrity and controllability of the secure storage. Especially, to enhance the integrity, a two-layer blockchain network is introduced. In the first layer, after the production, the data packages are first verified by leveraging a correspondence between a package and a policy, and a one-to-one relation among a VM, a user, and a node. After that, we propose a consensus achievement algorithm to construct a semi-finished block on a candidate block arranged by data packages. Meanwhile, the semi-finished block is distributed to all nodes, which can provide a certain integrity. In the second-layer, tamper-resistant metadata is generated by performing PoW tasks on the semi-finished block, resulting in strong integrity. Further, to enhance the controllability, a revisable user-defined policy-based encryption method with KP-ABE is proposed. It helps to flexibly control the scope of authorized verifiers. The experimental results on six scenarios with simulated data set show that the proposed approach is appealing in integrity and controllability, and the time overhead of data storage.
Recently we presented a single-party cryptographic timestamping mechanism based on proof-of-sequential-work, which we proved secure in the universal composability framework [16]. This paper describes this construction and its security claims and uses it to construct a multi-party permissioned blockchain protocol and show that it achieves an immutability notion. Finally we discuss applications of this protocol, including unpermissioned blockchains, and how these may benefit.
In recent years, there has been an upsurge of researching and learning the Amoeba management model in China. Amoeba management model is a business model created by INAMORI KAZUO in KYOCERA, and then many enterprises have achieved unprecedented success. At present, a large number of scholars have studied the amoeba management model, but the exploration of the operation mechanism of the amoeba management model has not yet appeared. As for an organization management model, it is very important to explore the mechanism for its normal operation, which provides the research question for this article, namely, the operation mechanism of amoeba organization model. Therefore, based on the characteristics of Amoeba organization, this paper explores the operation mechanism of Amoeba’s organizational model, which provides reference for other enterprises that want to implement the Amoeba organization model. The research found that the operation mechanism of Amoeba’s organizational model mainly includes Amoeba’s team relationship, team incentive mechanism, team accounting mechanism and team evaluation mechanism. The Amoeba team broke the traditional relationship between the corporate sector and the traditional relationship resulting in low efficiency of the enterprise, while the amoeba organization leads the trading relationship into the enterprise Amoeba teams, the trading between teams, and self-financing of each team resulting in the active communication between teams and the actively cooperate. The Incentive mechanism is mainly for the amoeba team decentralization, the establishment of a strict responsibility and profit mechanism for each team, the division of power and responsibility, so that each team has its own power. The accounting mechanism and the accounting of Amoeba organization model mainly introduce the independent accounting mechanism; each team is responsible for its own profit and loss, independent accounting, and uses the unit time accounting system to calculate the team. The Evaluation mechanism rigorously assesses the amoeba team. In the light of the strategy at this stage of the company, we need to build a guiding evaluation system so that the team goals and corporate goals become same, and commonly achieve the enterprise strategies.