Blockchain has the potential to revolutionize the way we store, use, and process data. Information on most blockchains can be viewed by every node hosting the blockchain, which means that most blockchains cannot handle private data. Decentralized databases exist that guarantee privacy by encrypting user data with the user's private key, but this prevents easy data sharing. However, in many real world applications, from student data to medical records, it is desirable that user data is anonymously searchable. In this paper we present a novel system that gives users ownership over their data while at the same time enabling them to make their data searchable within previously agreed upon limits. Our system implements a strong notion of ownership using a self-sovereign identity system and a weak notion of ownership using multiple centralized databases together with a blockchain and a tumbling process. We discuss applications of our methods to university's student records and medical data.
We investigate a family of bugs in blockchain-based smart contracts, which we call event-ordering (or EO) bugs. These bugs are intimately related to the dynamic ordering of contract events, i.e., calls of its functions on the blockchain, and enable potential exploits of millions of USD worth of Ether. Known examples of such bugs and prior techniques to detect them have been restricted to a small number of event orderings, typicall 1 or 2. Our work provides a new formulation of this general class of EO bugs as finding concurrency properties arising in long permutations of such events. The technical challenge in detecting our formulation of EO bugs is the inherent combinatorial blowup in path and state space analysis, even for simple contracts. We propose the first use of partial-order reduction techniques, using happen-before relations extracted automatically for contracts, along with several other optimizations built on a dynamic symbolic execution technique. We build an automatic tool called ETHRACER that requires no hints from users and runs directly on Ethereum bytecode. It flags 7-11% of over ten thousand contracts analyzed in roughly 18.5 minutes per contract, providing compact event traces that human analysts can run as witnesses. These witnesses are so compact that confirmations require only a few minutes of human effort. Half of the flagged contracts have subtle EO bugs, including in ERC-20 contracts that carry hundreds of millions of dollars worth of Ether. Thus, ETHRACER is effective at detecting a subtle yet dangerous class of bugs which existing tools miss.
For decentralised P2P networks, it is very important to have a mechanism in place that allows the nodes to control resource usage and prevent flooding and denial-of-service attacks with spam. In this paper, we discuss and compare the different approaches to fully decentralised resource control that are used by projects in the cryptocurrency space. The introduced methods are then applied to design a decentralised exchange for Namecoin names (or more generally, crypto assets) as an example.
Internet of Things (IoT) is becoming necessities of people's daily life and establishing itself as an essential part of future Internet. One of the challenges for using IoT is the security of data collected by trillions of IoT devices and used by millions of services. Distributed ledger technology (DLT) provides a distributed security method which can benefit IoT. Yet challenges are put forward when integrating DLT with IoT, such as scalability and heterogeneous capability of IoT devices. In this paper, we propose a mechanism for integrating DLT in IoT by using edge computing technology, taking the scalability and heterogeneous capability of IoT devices into consideration. IoT devices are clustered dynamically into groups based on various proximity context information.
Implementation of Law Number 28 Year 2009 About Local Taxes and Levies and Qanun of Nagan Raya Regency Number 13 Year 2011 About Land Tax Rural and urban sector buildings have regulated the tax system of rural and urban land building taxes that were originally a central tax now become tax region, this is a form of follow-up of regional autonomy and existing fiscal decentralization. The result of the tax management 100% (one hundred percent) goes to the local treasury so that there is no more tax revenue sharing to the central government. One of the supporting aspects of success is through community participation. This study aims to determine how the role of government in every process of making policy, strategy, communication dispute resolution and role as therapy in society. This research uses qualitative descriptive method, based on the data obtained from the results of this study is described with the sentence according to the category to conclude, the data in the form of observation, interview and documentation.The results of this study indicate that the role of local government to increase the participation of the people paying the rural and urban land tax building is done through efforts such as improving the tax and retribution services through the simplification of administrative systems and procedures, raising public awareness through socialization approach, impose a 2% penalty per month for taxpayers who are late in paying taxes on PBB-P2, improving the quality of employees or tax collectors, improving and structuring the procedures of the financial administration system to prevent errors, leaks or deviations from the use of funds thereby through efforts made by the Regional Government Nagan Raya District is running well. This can be proven through data obtained by researchers through the Regional Finance Management Agency of Nagan Raya District, the increase of the number of taxpayers and the UN-P2 revenue from 2014-2016 in Nagan Raya District.Keywords : The role, local government, public participation, tax land sector buildingrural and urban areas
Abdalla Sid Ahmed Osman, Eiman Hag, Hind Amin Merghani, Naeema Al Gasseer
Primary health care (PHC) is high on the agenda of the ongoing health system reform. The health system in Sudan is decentralized with three levels of governance: federal, state, and locality. The interim Constitution of Sudan ensures the promotion of public health and guarantees equal access and free PHC to all its citizens. The government of Sudan is highly committed to achieving universal health coverage (UHC) by the year 2020. The higher authority in Sudan is the National Health Coordination Council chaired by the president of Sudan. This council is committed to UHC and endorses the family health policy. The PHC directorates, which receive the funds to facilitate the implementation of the PHC expansion, finance family health practice teams including the family medicine training programme in nine states in Sudan in addition to the in-service training of medical assistants and community health workers.
A significant progress in modern power grids is witnessed by the tendency of becoming complex cyber‐physical systems. As a fundamental physical infrastructure, smart meter in the demand side provides real‐time energy consumption information to the utility. However, ensuring information security and privacy in the meter data aggregation process is a non‐trivial task. This study proposes a distributed, privacy‐preserving, and secure meter data aggregation framework, backed up by Blockchain and homomorphic encryption (HE) technologies. Meter data are aggregated and verified by a hierarchical Blockchain system, in which the consensus mechanism is supported by the practical Byzantine fault tolerance algorithm. On the top of the Blockchain system, HE technology is used to protect the privacy of individual meter data items during the aggregation process. Performance analysis is conducted to validate the proposed method.
Matteo Maffei, Giulio Malavolta, Manuel Reinert, Dominique Schröder
Cloud storage has rapidly become a cornerstone of many IT infrastructures, constituting a seamless solution for the backup, synchronization, and sharing of large amounts of data. Putting user data in the direct control of cloud service providers, however, raises security and privacy concerns related to the integrity of outsourced data, the accidental or intentional leakage of sensitive information, the profiling of user activities and so on. Furthermore, even if the cloud provider is trusted, users having access to outsourced files might be malicious and misbehave. These concerns are particularly serious in sensitive applications like personal health records and credit score systems. To tackle this problem, we present [Formula: see text], a definitional framework for Group Oblivious RAM, in which we formalize several security and privacy properties such as secrecy, integrity, anonymity, and obliviousness. [Formula: see text] allows per entry access control, as selected by the data owner. [Formula: see text] is the first framework to define such a wide range of security and privacy properties for outsourced storage. Regarding obliviousness, we tackle two different attacker models: our first definition protects against an honest-but-curious server while our second definition protects against such a server colluding with malicious clients. In the latter model, we prove a server-side computational lower bound of [Formula: see text] where n is the number of entries in the database, i.e., every operations requires to process a constant fraction of the database. Furthermore, we present two constructions: a pure cryptographic instantiation, which achieves an [Formula: see text] amortized communication and computation complexity and a construction based on a trusted proxy with logarithmic communication and server-side computational complexity. The second construction bypasses the previously established lower bound leveraging a trusted party. Both schemes achieve secrecy, integrity, and obliviousness with respect to a server colluding with malicious clients, but not anonymity due to the deployed access control mechanism. In the former model, we present a cryptographic system that achieves secrecy, integrity, obliviousness, and anonymity. In the process of designing an efficient construction, we developed three new, generally applicable cryptographic schemes, namely, batched zero-knowledge proof of shuffle correctness, the hash-and-proof paradigm, which even improves upon the former, and an accountability technique based on chameleon signatures, which we consider of independent interest. We implemented our constructions in Amazon Elastic Compute Cloud (EC2) and ran a performance evaluation demonstrating the scalability and efficiency of our construction.
In the irrigated agricultural areas of Pakistan, the major sources of irrigation are canal water and groundwater. Due to the scarcity of canal water the dependency on groundwater is rapidly increasing in many areas of Pakistan. The groundwater is not only expensive, inadequate, and non-affordable for the small farmers but also of inferior quality. Much of the wastewater which is produced in urban and peri-urban areas is directly or indirectly used for irrigation without any kind of treatment. It appears that suitable technologies for decentralized treatment are avoided but other barriers to the wide adoption of the decentralized approach also exists. These barriers include lack of finance and suitable land, devoid of knowledge and skills and a lack of flexibility in official design standards. This study is an effort to check the status of treatment of the wastewater generated in Faisalabad: The area irrigated with wastewater in and around Faisalabad, quality of wastewater used to grow crops in wastewater irrigated areas, types of crops grown with wastewater, mechanism and composition of wastewater used and supplied to the farmers and farmer’s perception about the social and adverse impacts on human health and constraints in wastewater irrigation. To reduce these barriers several opportunities for improving wastewater management are to be considered via improved policies, institutional dialogues and financial mechanisms, which would reduce the risks in food chain contamination in agriculture practices. Effluent standards combined with incentives or enforcement can motivate improvements in water management by household and industrial sectors discharging wastewater from point sources. Segregation of chemical pollutants from urban wastewater facilitates treatment and reduces risk. Strengthening institutional capacity and establishing links between water delivery and sanitation sectors through inter-institutional coordination leads to more efficient management of wastewater and risk reduction. Key words: Wastewater irrigation, wastewater implication, constraints, farmer ‘perception, food chain contamination.
Attribute-based encryption (ABE) offers a promising solution for flexible access control over sensitive personal health records in a mobile healthcare system on top of a public cloud infrastructure. However, ABE cannot be simply applied to lightweight devices due to its substantial computation cost during decryption. This problem could be alleviated by delegating significant parts of the decryption operations to computationally powerful parties, such as cloud servers, but the correctness of the delegated computation would be at stake. Thus, previous works enabled users to validate the partial decryption by employing a cryptographic commitment or message authentication code (MAC). This paper demonstrates that the previous commitment or MAC-based schemes cannot support verifiability in the presence of potentially malevolent cloud servers. We propose two concrete attacks on previous commitment or MAC-based schemes. We propose an effective countermeasure scheme for securing resource-limited mobile healthcare systems and provide a rigorous security proof in the standard model, demonstrating that the proposed scheme is secure against our attacks. The experimental analysis shows that the proposed scheme provides the similar performance compared with the previous commitment-based schemes and outperforms the MAC-based scheme.
Currently, the number of Internet of Thing (IoT) devices making up the IoT is more than 11 billion and this number has been continuously increasing. The prevalence of these devices leads to an emerging IoT business model called Device-as-a-service(DaaS), which enables sensor devices to collect data disseminated to all interested devices. The devices sharing data with other devices could receive some financial reward such as Bitcoin. However, side-channel attacks, which aim to exploit some information leaked from the IoT devices during data trade execution, are possible since most of the IoT devices are vulnerable to be hacked or compromised. Thus, it is challenging to securely realize data trading in IoT environment due to the information leakage such as leaking the private key for signing a Bitcoin transaction in Bitcoin system. In this paper, we propose LRCoin, a kind of leakage-resilient cryptocurrency based on bitcoin in which the signature algorithm used for authenticating bitcoin transactions is leakage-resilient. LRCoin is suitable for the scenarios where information leakage is inevitable such as IoT applications. Our core contribution is proposing an efficient bilinear-based continual-leakage-resilient ECDSA signature. We prove the proposed signature algorithm is unforgeable against adaptively chosen messages attack in the generic bilinear group model under the continual leakage setting. Both the theoretical analysis and the implementation demonstrate the practicability of the proposed scheme.
Open access
3 source records
Blockchain Technology Applications and Security
Cryptography and Data Security
Advanced Steganography and Watermarking Techniques
Blockchain technology is swiftly entering the fields of humanitarian and development aid. While it has the potential to revolutionize the aid sector, e.g., through pairing smart contracts with forecast-based financing, it also has the potential to perpetuate societal problems and add new risks. This essay outlines the use cases of Blockchain technology for the humanitarian and development sectors and reflects on potentials and pitfalls that come with the adaptation of this new technology.
Blockchain is a data structure of data blocks arranged in chronological order. It is featured by decentralization, trustworthiness, data sharing, security, etc. It has been widely used in digital currency, smart contract, credit encryption and other fields. With the development of the Internet technology, online education, a novel education mode, has been greatly popularized. However, this education mode still faces many problems in course credibility, credit and certificate certification, stu-dent privacy, and course sharing. Through literature review and case analysis, this paper discusses the basic technical principles and application features of blockchain technology, and proposes a solution to the problems of online educa-tion based on blockchain technology. The blockchain technology can store learn-ing records in a trusted, distributed manner, provide credible digital certificates, realize learning resource sharing with smart contract, and protect intellectual property through data encryption. The research shows that the integration of blockchain technology is a promising trend in the development of online educa-tion.
Blockchain and distributed ledger technology (DLT) research encompasses use cases ranging from social innovation to banking, and technical developments ranging from cryptography to semantics of legal text. Research in both academia and industry is highly interdisciplinary across domains such as computer science, linguistics, law, cryptography, banking, economics, and social sciences. The growing complexity of blockchain science and use cases, coupled with the interdisciplinary nature of the research, poses new challenges to our community. Research publication plays a key role in supporting this highly interdisciplinary work: supporting the need for rapid and reliable dissemination of preliminary and final results, and the need for longevity of results beyond the end of financial or management support for a research project. Industry teams rarely have subscriptions to academic journals, and an open access journal adds substantial value in supporting the research community. The field is young, with many research challenges to be addressed. One “grand challenge” for our research community is the implementation of high-value, long-lived, financial derivatives transactions running as smart contracts on DLT (“smart financial derivatives”). This is currently being explored by academia, banking practitioners, trade associations and technology vendors, and is driving research across a wide range of research groups, each focusing on a different aspect. What makes this a “grand” challenge is the need for a large number of diverse research problems to be solved simultaneously. The following outlines a few of the major research questions being investigated: some of these are general research problems that affect blockchain/DLT development broadly, whereas others are very specific to financial derivatives, but all of these aspects must be solved, and their solutions combined effectively, to provide efficient and resilient solutions to the grand challenge.
Oct 26, 2018·Proceedings of the 2018 26th ACM Joint Meeting on European Software Engineering Conference and Symposium on the Foundations of Software Engineering
The Ethereum ecosystem has created a prosperity of smart contract applications in public blockchains, with transparent, traceable and programmable transactions. However, the flexibility that everybody can write and deploy smart contracts on Ethereum causes a large collection of similar contracts, i.e., clones. In practice, smart contract clones may amplify severe threats like security attacks, resource waste etc.
Oct 26, 2018·Proceedings of the 2018 26th ACM Joint Meeting on European Software Engineering Conference and Symposium on the Foundations of Software Engineering
Daejun Park, Yi Zhang, Manasvi Saxena, Philip Daian · 5 authors
In this paper, we present a formal verification tool for the Ethereum Virtual Machine (EVM) bytecode. To precisely reason about all possible behaviors of the EVM bytecode, we adopted KEVM, a complete formal semantics of the EVM, and instantiated the K-framework's reachability logic theorem prover to generate a correct-by-construction deductive verifier for the EVM. We further optimized the verifier by introducing EVM-specific abstractions and lemmas to improve its scalability. Our EVM verifier has been used to verify various high-profile smart contracts including the ERC20 token, Ethereum Casper, and DappHub MakerDAO contracts.
Nelson Kibichii Bore, Ravi Kiran Raman, Isaac M. Markus, Sekou L. Remy · 11 authors
Policy decisions are increasingly dependent on the outcomes of simulations and/or machine learning models. The ability to share and interact with these outcomes is relevant across multiple fields and is especially critical in the disease modeling community where models are often only accessible and workable to the researchers that generate them. This work presents a blockchain-enabled system that establishes a decentralized trust between parties involved in a modeling process. Utilizing the OpenMalaria framework, we demonstrate the ability to store, share and maintain auditable logs and records of each step in the simulation process, showing how to validate results generated by computing workers. We also show how the system monitors worker outputs to rank and identify faulty workers via comparison to nearest neighbors or historical reward spaces as a means of ensuring model quality.
Chao Qiu, F. Richard Yu, Fangmin Xu, Haipeng Yao · 5 authors
Nowadays, in order to support flexibility, agility, and ubiquitous accessibility among vehicles, software defined networking has been proposed to integrate with vehicular networks, known as software defined vehicular network (SDVN). Due to a variety of data, flows, and vehicles in SDVN, a distributed SDVN is necessary. However, how to reach consensus in distributed SDVN efficiently and safely is an intractable problem. In this paper, we use a permissioned blockchain approach to reach consensus in distributed SDVN. The existing permissioned blockchain has a number of drawbacks, such as low throughput. We virtualize the underlying resources (e.g., computing resources and networking resources), jointly considering the trust features of blockchain nodes to improve the throughput. Accordingly, we formulate view change, computing resources allocation, and networking resources allocation as a joint optimization problem. In order to solve this joint problem, we use a novel deep Q-learning approach. Simulation results show the effectiveness of our proposed scheme.
Antônio Unias de Lucena, Marco Aurélio Amaral Henriques
Um computador quântico com alta capacidade de processamento quebrará as assinaturas digitais utilizadas nos principais blockchains. Este trabalho traz um estudo preliminar sobre a adoção de assinaturas baseadas em hash no blockchain do Bitcoin para torná-lo resistente ao computador quântico. O estudo mostra os pontos a serem modificados e seus impactos. O maior deles refere-se ao tamanho da assinatura digital, que influencia no tamanho de uma transação e diminui o número de transações por bloco. Soluções para este problema incluem o aumento do tamanho do bloco, a diminuição do tamanho das assinaturas baseadas em hash e/ou a adoção de algoritmos pós-quânticos que produzam assinaturas digitais menores.
Considered within the history of documenting welfare beneficiaries in India, the <italic>Aadhaar</italic> is unprecedented in that the unique number is a digital, portable identity and part of ‘a larger administrative and technological regime’ (Bennett and Lyon 2008) of cloud-based authentication. This chapter argues, however, that the production of this identifier has necessitated miming existing bureaucratic habits of inscription and mobilizing the rhetoric, ritualism and the materiality common to processes of issuing and verifying identification documents. Far from being an ID that is insulated from the host of administratively restrictive genres of identification documents like ration cards and caste certificates, the <italic>Aadhaar</italic> is relevant only within a paper-based matrix of elite norms of proof, urban spatiality of power brokerage, and the politics of staking out regional identities. Based on an intensive ethnography around a rural poor community, the chapter shows that the current welfare ecology still contingent on address norms requires not so much an electronic number identifier but rather a dynamic interplay of popular, quasi-legal, and legal documents of identity.
This chapter analyzes how multilevel elections, strong subnational governments, and decentralized electoral rules shape the workings of Brazil’s democratic institutions. I seek to answer two major questions. First, to what extent have institutions adopted by the 1988 Constitution created effective incentives for party nationalization and integration and, therefore, for organization of party competition around the dispute over the national executive? Second, what is the impact of multilevel elections on electoral coordination and party fragmentation in congressional races? The core argument is that the institutional mix chosen by the drafters of the 1988 Constitution created cross-cutting incentives. Concurrent presidential, national legislative, and state elections since 1994 have tended to strengthen presidential coattails and the related incentives for party coordination around presidential campaigns, and extensive presidential legislative powers facilitate centralization of the policy-making process. But, although these institutions foster the organization of a nationalized party system and effective intergovernmental coordination, incentives and opportunities provided by multilevel elections in the context of autonomous subnational party branches and highly permissive electoral rules allow for the survival and growth of poorly integrated, office-seeking party organizations organized around subnational races. The chapter concludes that Brazil’s federalism weakens the connection between presidential and legislative races, while at the same time fostering high levels of party fragmentation, therefore increasing the costs of coalition formation.
Davi R. Ortega, Catherine M. Oikonomou, H. Ding, Prudence Rees-Lee · 6 authors
Abstract Three-dimensional electron microscopy techniques like electron tomography provide valuable insights into cellular structures, and present significant challenges for data storage and dissemination. Here we explored a novel method to publicly release more than 11,000 such datasets, more than 30 TB in total, collected by our group. Our method, based on a peer-to-peer file sharing network built around a blockchain ledger, offers a distributed solution to data storage. In addition, we offer a user-friendly browser-based interface, https://etdb.caltech.edu , for anyone interested to explore and download our data. We discuss the relative advantages and disadvantages of this system and provide tools for other groups to mine our data and/or use the same approach to share their own imaging datasets.
Open access
2 source records
Innovative Microfluidic and Catalytic Techniques Innovation