We’ve seen repeatedly that ideas in the research literature can be gradually forgotten or lie unappreciated, especially if they are ahead of their time, even in popular areas of research. Both practitioners and academics would do well to revisit old ideas to glean insights for present systems. Bitcoin was unusual and successful not because it was on the cutting edge of research on any of its components, but because it combined old ideas from many previously unrelated fields. This is not easy to do, as it requires bridging disparate terminology, assumptions, etc., but it is a valuable blueprint for innovation.
Distributed storage platforms draw much attention due to their high reliability and scalability for handling a massive amount of data. To protect user and data privacy, encryption is considered as a necessary feature for production systems like Storj. But it prohibits the nodes from performing content search. To preserve the functionality, we observe that a protocol of integration with searchable encryption and keyword search via distributed hash table allows the nodes in a network to search over encrypted and distributed data. However, this protocol does not address a practical threat in a fully distributed scenario. Malicious nodes would sabotage search results, and easily infiltrate the system as the network grows. Using primitives such as MAC and verifiable data structure may empower the users to verify the search result, but the robustness of the overall system can hardly be ensured. In this paper, we address this issue by proposing a protocol that is seamlessly incorporated to encrypted search in distributed network to attest and monitor nodes. From the moment a node joins the system, it will be attested and continuously monitored through verifiable search queries. The result of each attestation is determined via a standard quorum-based voting protocol, and then recorded on the blockchain as a consensus view of trusted nodes. Based on the proposed protocols, malicious nodes can be detected and removed by a majority of nodes in a self-determining manner. To demonstrate the security and efficiency, we conduct robustness analysis against several potential attacks, and perform performance and overhead evaluation on the proposed protocol.
In this paper, we propose a decentralized identity management system based on Blockchain. The function of the system mainly includes identity authentication and reputation management. The technical advantages of the Blockchain makes the data in the system safe and credible. In addition, we use smart contracts to write system rules to ensure the reliability of user information. We bind the user's entity information with the public key address and determine the true identity of a virtual user on the Blockchain. We use the token to represent the reputation which is shown to be an effective reputation model, making the participants in the system prefer to maintain and manage their personal reputation. Our system makes it possible for users to securely manage their identity and reputation on the Internet.
While Bitcoin (Peer-to-Peer Electronic Cash) [Nak]solved the double spend problem and provided work withtimestamps on a public ledger, it has not to date extendedthe functionality of a blockchain beyond a transparent andpublic payment system. Satoshi Nakamoto's original referenceclient had a decentralized marketplace service which was latertaken out due to a lack of resources [Deva]. We continued withNakamoto's vision by creating a set of commercial-grade ser-vices supporting a wide variety of business use cases, includinga fully developed blockchain-based decentralized marketplace,secure data storage and transfer, and unique user aliases thatlink the owner to all services controlled by that alias.
Rituparna Bhattacharya, Martin White, Natalia Beloff
Almost every traveller possesses some amount of leftover foreign currency, either as actual cash or on a travel currency card, at the end of any international trip. However, the means to exchange this leftover currency, coins in particular, is largely inconvenient often leading to considerable amounts discarded or left unused. In this paper, we explore how distributed ledger technology, i.e. blockchain, could be applied to the problem of utilizing this leftover foreign currency. We portray here the drawbacks of the existing systems of foreign currency exchange and delineate the requirements of a potential mobile web application for exchanging this currency by integrating smart kiosk based systems, particularly for handling cash, with a peer-to-peer currency exchange technique based on blockchain that could help to bring such currency back into circulation efficiently.
In the Bitcoin system, a peer-to-peer electronic currency system, the delay overhead in transaction verification prevents the Bitcoin from gaining increasing popularity nowadays as it makes the system vulnerable to double spend attacks. This paper introduces a proximity-aware extension to the current Bitcoin protocol, named Bitcoin Clustering Based Ping Time protocol (BCBPT). The ultimate purpose of the proposed protocol, that is based on how the clusters are formulated and the nodes define their membership, is to improve the transaction propagation delay in the Bitcoin network. In BCBPT, the proximity of connectivity in the Bitcoin network is increased by grouping Bitcoin nodes based on ping latencies between nodes. We show, through simulations, that the proximity base ping latency defines better clustering structures that optimize the performance of the transaction propagation delay. The reduction of the communication link cost measured by the information propagation time between nodes is mainly considered as a key reason for this improvement. Bitcoin Clustering Based Ping Time protocol is more effective at reducing the transaction propagation delay compared to the existing clustering protocol (LBC) that we proposed in our previous work.
Zhijie Ren, Kelong Cong, Johan Pouwelse, Zekeriya Erkin
Recently, the blockchain technique was put in the spotlight as it introduced a systematic approach for multiple parties to reach consensus without needing trust. However, the application of this technique in practice is severely restricted due to its limitations in throughput. In this paper, we propose a novel consensus model, namely the implicit consensus, with a distinctive blockchain-based distributed ledger in which each node holds its individual blockchain. In our system, the consensus is not on the transactions, but on a special type of blocks called Check Points that are used to validate individual transactions. Our system exploits the ideas of self-interest and spontaneous sharding and achieves unbounded throughput with the transaction reliability that equivalent to traditional Byzantine fault tolerance schemes.
Dinesh Verma, Nirmit Desai, Alun Preece, Ian Taylor
To support dynamic communities of interests in coalition operations, new architectures for efficient sharing of ISR assets are needed. The use of blockchain technology in wired business environments, such as digital currency systems, offers an interesting solution by creating a way to maintain a distributed shared ledger without requiring a single trusted authority. In this paper, we discuss how a blockchain-based system can be modified to provide a solution for dynamic asset sharing amongst coalition members, enabling the creation of a logically centralized asset management system by a seamless policy-compliant federation of different coalition systems. We discuss the use of blockchain for three different types of assets in a coalition context, showing how blockchain can offer a suitable solution for sharing assets in those environments. We also discuss the limitations in the current implementations of blockchain which need to be overcome for the technology to become more effective in a decentralized tactical edge environment.
Despite a great deal of work to improve the TLS PKI, CA misbehavior continues to occur, resulting in unauthorized certificates that can be used to mount man-in-the-middle attacks against HTTPS sites. CAs lack the incentives to invest in higher security, and the manual effort required to report a rogue certificate deters many from contributing to the security of the TLS PKI. In this paper, we present IKP, a platform that automates responses to unauthorized certificates and provides incentives for CAs to behave correctly and for others to report potentially unauthorized certificates. Domains in IKP specify criteria for their certificates, and CAs specify reactions such as financial penalties that execute in case of unauthorized certificate issuance. By leveraging smart contracts and blockchain-based consensus, we can decentralize IKP while still providing automated incentives. We describe a theoretical model for payment flows and implement IKP in Ethereum to show that decentralizing and automating PKIs with financial incentives is both economically sound and technically viable.
The delay overhead of transaction verification in Bitcoin, a peer-to-peer electronic currency system, is a complicated issue which makes the system vulnerable to double spend attacks. In this paper, we propose a new approach, that is based on how the clusters are formulated and the nodes define their membership, to improve the transaction propagation delay in the Bitcoin network. In this approach, the locality of connectivity in the Bitcoin network is increased by grouping Bitcoin nodes based on their geographical location. We show, through simulations, that location based-distance better defines clustering structures that optimize the performance of the transaction propagation delay. A key reason behind this improvement is mainly due to the reduction of the communication link cost measured by the distance between nodes. Compared to the existing clustering protocol (BCBSN) that we proposed in our previous work, location based clustering is more effective at reducing the transaction propagation delay.
M. J. G. Borge, Eleftherios Kokoris-Kogias, Philipp Jovanovic, Linus Gasser · 6 authors
Permissionless blockchain-based cryptocurrencies commonly use proof-of-work (PoW) or proof-of-stake (PoS) to ensure their security, e.g. to prevent double spending attacks. However, both approaches have disadvantages: PoW leads to massive amounts of wasted electricity and re-centralization, whereas major stakeholders in PoS might be able to create a monopoly. In this work, we propose proof-of-personhood (PoP), a mechanism that binds physical entities to virtual identities in a way that enables accountability while preserving anonymity. Afterwards we introduce PoPCoin, a new cryptocurrency, whose consensus mechanism leverages PoP to eliminate the dis-advantages of PoW and PoS while ensuring security. PoPCoin leads to a continuously fair and democratic wealth creation process which paves the way for an experimental basic income infrastructure.
Bitcoin is a popular alternative to fiat money, widely used for its perceived anonymity properties. However, recent attacks on Bitcoin's peer-to-peer (P2P) network demonstrated that its gossip-based flooding protocols, which are used to ensure global network consistency, may enable user deanonymization---the linkage of a user's IP address with her pseudonym in the Bitcoin network. In 2015, the Bitcoin community responded to these attacks by changing the network's flooding mechanism to a different protocol, known as diffusion. However, no systematic justification was provided for the change, and it is unclear if diffusion actually improves the system's anonymity. In this paper, we model the Bitcoin networking stack and analyze its anonymity properties, both pre- and post-2015. In doing so, we consider new adversarial models and spreading mechanisms that have not been previously studied in the source-finding literature. We theoretically prove that Bitcoin's networking protocols (both pre- and post-2015) offer poor anonymity properties on networks with a regular-tree topology. We validate this claim in simulation on a 2015 snapshot of the real Bitcoin P2P network topology.
Distributed ledger technology, a method of storing and maintaining the integrity of multiple copies of critical data using a massively redundant network of participating machines, has found a “killer application” in blockchain, a type of distributed ledger. A blockchain consists of sequential blocks that may never be modified or reordered, leaving a public, auditable record that is consistent and highly resistant to tampering and deletion. These qualities make blockchain eminently suitable for its most common use, cryptocurrency, and its occasional variants in the form of cryptocurrency tokens, used to represent ownership or some other right to virtual or physical goods and capabilities. Blockchain also enables smart contracts, discrete bodies of software written to serve both as the memorial and the means of execution of an agreement between parties. Smart contracts can have all the elements of a traditional contract, and as jurisdictions legislate or jurists rule on the fine points of enforceability and the acceptability of smart contracts as traditional contracts, applications in nearly every area of commerce have emerged. Digital lawyers may not need to become software developers, but deepening their understanding of the capabilities and limitations of the technology, developing a keen awareness of the issues at the intersection between code and the law, as well as the law’s readiness in this area, will be of great advantage to them and their clients in this rapidly evolving area at the intersection of technology, commerce and law.
There exist many unsolved problems in the traditional digital rights management of network media. For example, in the traditional management system it is hard to guarantee the quality of media works, to protect the copyrights, to find the effective profit model and so on. To solve these problems, we propose in this paper a network media's digital rights management scheme based on blockchain. Blockchain is a technology that makes use of cryptographic algorithm, hash chains and consensus mechanism to implement consensus, irreversibility and traceability for online data. The proposed scheme can use these functionalities of blockchain to implement the effective production management, copyright management, transaction management and users' behavior management for network media. Furthermore, our proposed scheme can predictively provide an important support for the network media platform to build a sustainable development of benign ecological environment.
The last step turned the blockchain data structure into an immutable, append-only data store that can serve as a tamper-resistant ledger for transaction data. Having a single, immutable, append-only history of transaction data in isolation may be of limited value for our goal of clarifying ownership based on a group of computers that serve as witnesses to ownership-related events. Hence, this step focuses on establishing a purely distributed peer-to-peer system that shares transaction information.
Marco Baldi, Franco Chiaraluce, Emanuele Frontoni, Giuseppe Gottardi · 6 authors
Public key infrastructures (PKIs) are of crucial importance for the life of online services relying on certificate-based authentication, like e-commerce, e-government, online banking, as well as e-mail, social networking, cloud services and many others. One of the main points of failure (POFs) of modern PKIs concerns reliability and security of certificate revocation lists (CRLs), that must be available and authentic any time a certificate is used. Classically, the CRL for a set of certificates is maintained by the same (and sole) certification authority (CA) that issued the certificates, and this introduces a single POF in the system. We address this issue by proposing a solution in which multiple CAs share a public, decentralized and robust ledger where CRLs are collected. For this purpose, we consider the model of public ledgers based on blockchains, introduced for the use in cryptocurrencies, that is becoming a widespread solution for many online applications with stringent security and reliability requirements.
Digital infrastructures play an increasingly central role in shaping existing organisations and creating new ones. Research on digital infrastructure has rested on the assumption that infrastructures are developed to support pre-existing organised activities. However, with new digital infrastructures supporting open source projects and blockchain communities such as Bitcoin, development of the technological infrastructure also gives rise to a new way of self-organising. Specifically, forking of the underlying source code and subsequent community adoption is increasingly observed to trigger new patterns of self-organising. In order to explore and develop this concept, this paper investigates a case of such distributed digital community: the emergence of the Bitcoin community around a specific instantiation of the Blockchain infrastructure. Our study examines how the community emerges, and how changes in the source code lead to different patterns of self-organising. The paper develops a conceptual framework of self-organising in distributed communities emerging around digital infrastructures.
Over past decade cloud services have enabled individuals and organizations to perform different types of tasks such as online storage, email services, on-demand movies and TV shows. The cloud services has also enabled on-demand deployment of applications, at cheap cost with elastic and scalable, fault tolerant system. These cloud services are offered by cloud providers who use authentication, authorization and accounting framework based on client-server model. Though this model has been used over decades, study shows it is vulnerable to different hacks and it is also inconvenient to use for the end users. In addition, the cloud provider has total control over user data which they are able to monitor, trace, leak and even modify at their will. Thus, the user data ownership, digital identity and use of cloud services has raised privacy and security concern for the users. In this thesis, Blockchain and its applications are studied and alternative model for authentication, authorization and accounting is proposed based on Ethereum Blockchain. Furthermore, a prototype is developed which enables users to consume cloud services by authenticating, authorizing and accounting with a single identity without sharing any private user data. Experiments are run with the prototype to verify that it works as expected. Measurements are done to assess the feasibility and scalability of the solution. In the final part of the thesis, pros and cons of the proposed solution are discussed and perspectives for further research are sketched.
The Bitcoin protocol allows to save arbitrary data on the blockchain through a special instruction of the scripting language, called OP_RETURN. A growing number of protocols exploit this feature to extend the range of applications of the Bitcoin blockchain beyond transfer of currency. A point of debate in the Bitcoin community is whether loading data through OP_RETURN can negatively affect the performance of the Bitcoin network with respect to its primary goal. This paper is an empirical study of the usage of OP_RETURN over the years. We identify several protocols based on OP_RETURN, which we classify by their application domain. We measure the evolution in time of the usage of each protocol, the distribution of OP_RETURN transactions by application domain, and their space consumption.