Nabeel Younis, Muhammad Anas Imtiaz, David Starobinski, Ari Trachtenberg
Efficient and reliable block propagation on the Bitcoin network is vital for ensuring the scalability of this peer-to-peer network. To this end, several schemes have been proposed over the last few years to speed up the block propagation, most notably the compact block protocol (BIP 152). Despite this, we show experimental evidence that nodes that have recently joined the network may need about ten days until this protocol becomes 90% effective. This problem is endemic for nodes that do not have persistent network connectivity. We propose to mitigate this ineffectiveness by maintaining mempool synchronization among Bitcoin nodes. For this purpose, we design and implement into Bitcoin a new prioritized data synchronization protocol, called FalafelSync. Our experiments show that FalafelSync helps intermittently connected nodes to maintain better consistency with more stable nodes, thereby showing promise for improving block propagation in the broader network. In the process, we have also developed an effective logging mechanism for bitcoin nodes we release for public use.
This Article examines the role of the global financial markets in promoting sustainability and the governance challenges arising from this phenomenon. A growing range of financial instruments and strategies catalyze the desire of investors and corporations to support environmentally and socially sustainable commercial activity. This Article focuses on green bonds, a form of debt financing whose proceeds are specifically dedicated to environmentally-friendly “green” projects, assets, and business activities. Having emerged in the past three years, green bonds are expected to play an integral role in responding to the existential threat and enormous costs posed by climate change. Largely missing from the still-nascent green bond market are government regulators. Instead, its governance is decentralized and primarily shaped by private governance regimes (such as investment standards, certification schemes, ratings, and third-party assessment), which compete or collaborate with each other for market adoption. In comparison to public regulation, private governance is often faster to implement and more responsive to the needs of market participants but may suffer from a lack of legitimacy, accountability, and consistency and be susceptible to greenwashing. To address these deficits, this Article identifies and analyzes governance gaps in the green bond market and outlines a public-private hybrid regulatory framework to optimize the interests of investors and stakeholders.
Modern blockchain systems are a fresh look at the paradigm of distributed computing, applied under assumptions of large-scale public networks. They can be used to store and share information without a trusted central party. There has been much effort to develop blockchain systems for a myriad of uses, ranging from cryptocurrencies to identity control, supply chain management, etc. None of this work has directly studied the fundamental database issues that arise when using blockchains as the underlying infrastructure to manage data. The key difference between using blockchains to store data and centrally controlled databases is that transactions are accepted to a blockchain via a consensus mechanism. Hence, once a user has issued a transaction, she cannot be certain if it will be accepted. Moreover, a yet unaccepted transaction cannot be retracted by the user, and may be appended to the blockchain in the future. This causes difficulties as the user may wish to reissue a transaction, if it was not accepted. Yet this data may then become appended twice to the blockchain. In this paper we present a database perspective on blockchains by introducing formal foundations for blockchains as a storage layer that underlies a database. The main issue that we tackle is uncertainty in transaction appending that is a result of the consensus mechanism. We study two flavors of transaction appending problems: (1) the complexity of determining whether it is possible for a denial constraint to be contradicted, given the state of the blockchain, pending transactions, and integrity constraints and (2) the complexity of generating transactions that are mutually (in)consistent with given subsets of pending transactions. Solving these problems is critical to ensure that users can issue transactions consistent with their intentions. Finally, we chart important directions for future work.
Jiayu Zhou, Fengyi Tang, He Zhu, Ning Nan · 5 authors
Recent advances in blockchain technologies have provided exciting opportunities for decentralized applications. Specifically, blockchain-based smart contracts enable credible transactions without authorized third parties. The attractive properties of smart contracts facilitate distributed data vending, allowing for proprietary data to be securely exchanged on a blockchain. Distributed data vending can transform domains such as healthcare by encouraging data distribution from owners and enabling large-scale data aggregation. However, one key challenge in distributed data vending is the trade-off dilemma between the effectiveness of data retrieval, and the leakage risk from indexing the data. In this paper, we propose a framework for distributed data vending through a combination of data embedding and similarity learning. We illustrate our framework through a practical scenario of distributing and aggregating electronic medical records on a blockchain. Extensive empirical results demonstrate the effectiveness of our framework.
In this article, the author discusses several developments in the virtual currency sector (Ethereum, smart contracts, initial coin offerings), investigates potential applications of blockchain technology and summarizes some of the recently issued opinions of tax and regulatory bodies on virtual currency.
Financial innovation has entered a new era in which a digitalized system and cryptocurrency have been created. This paper examines the factors that influence the price movement of bitcoin. This is not a legal currency in Indonesia; the Indonesian government has not made any regulations legalizing bitcoin’s use, but it has also not issued any new laws to prohibit the trade in bitcoins and other digital currencies. The demand for, and price growth of, bitcoin are interesting matters to study, especially for Indonesians who still have questions about the progress of Bitcoin transactions and the factors that influent them. In Indonesia itself, without any protection from the government, the bitcoin price on December 14, 2017 had already reached more than IDR224.5 million, compare to IDR60 million in October 2017. Bitcoin is the first peer-to-peer currency, and was introduced by Satoshi Nakamoto in 2008. Since its inception, bitcoin has served more than 17 million users, including Indonesians. Bitcoin behaves in a different manner, compared to traditional currencies and the one that affects bitcoin’s price is its attractiveness for investors. The Vector Error Correction Model (VECM) is applied to analyze the short-term and long-term influences. VECM is used in this research because the data is stationary in the first difference and has a cointegration relationship. To make the interpretation clearer, the impulse response function and variance decomposition also are included in this research. The result indicates that the macroeconomic indicator, represented by the Dow Jones Industrial Average (DJIA), the demand for bitcoins and the gold price influence bitcoin’s price fluctuations in the short-run and long-run. Bitcoin’s supply does not influence its price fluctuation in the long-run but does influence it in the short-run. The implication of this research is bitcoin could compete as an alternative investment compared to the capital markets and gold.
Privacy and safety are the most needed features while accessing the data in the IoT. Due to the complicated decentralization and heterogeneous environment present in IoT, the security and privacy of the data becomes a challenging job for the developers. The current methods are not suitable for these scenarios where a decentralized and heterogeneous system exists. This paper provides a new method for access control in IoT based on the booming technology "Block Chain," which helps the user in accessing or controlling their data. The contribution consists of a description of the model used to show how a blockchain is used for creating access control methods. To implement the method, the blockchain is taken as the decentralized access manager. The proposed method is validated with respect to the previous related work. Finally, the limitations and future work of the paper are discussed. Access Control Systems are proved to provide access control to critical resources. The right to access the resources is defined by the access control policies that are executed during the access request time.
Maofan Yin, Dahlia Malkhi, Michael K. Reiter, Guy Golan Gueta · 5 authors
We present HotStuff, a leader-based Byzantine fault-tolerant replication protocol for the partially synchronous model. Once network communication becomes synchronous, HotStuff enables a correct leader to drive the protocol to consensus at the pace of actual (vs. maximum) network delay--a property called responsiveness--and with communication complexity that is linear in the number of replicas. To our knowledge, HotStuff is the first partially synchronous BFT replication protocol exhibiting these combined properties. HotStuff is built around a novel framework that forms a bridge between classical BFT foundations and blockchains. It allows the expression of other known protocols (DLS, PBFT, Tendermint, Casper), and ours, in a common framework. Our deployment of HotStuff over a network with over 100 replicas achieves throughput and latency comparable to that of BFT-SMaRt, while enjoying linear communication footprint during leader failover (vs. quadratic with BFT-SMaRt).
Recently, there has been a growing interest in using online technologies to design protocols for secure electronic voting. The main challenges include vote privacy and anonymity, ballot irrevocability and transparency throughout the vote counting process. The introduction of the blockchain as a basis for cryptocurrency protocols, provides for the exploitation of the immutability and transparency properties of these distributed ledgers. In this paper, we discuss possible uses of the blockchain technology to implement a secure and fair voting system. In particular, we introduce a secret share-based voting system on the blockchain, the so-called SHARVOT protocol. Our solution uses Shamir's Secret Sharing to enable on-chain, i.e. within the transactions script, votes submission and winning candidate determination. The protocol is also using a shuffling technique, Circle Shuffle, to de-link voters from their submissions.
Alexandra Covaci, Simone Madeo, Patrick Motylinski, Stéphane Vincent
Blockchain-driven technologies are considered disruptive because of the availability of dis-intermediated, censorship-resistant and tamper-proof digital platforms of distributed trust. Among these technologies, smart contract platforms have the potential to take over functions usually done by intermediaries like banks, escrow or legal services. In this paper, we introduce a novel protocol aiming to execute smart contracts as part of a blockchain transaction validation. We enable extensions in the execution of smart contracts while guaranteeing their privacy, correctness and verifiability. Man-in-the-middle attacks are prevented, since no communication between participants is requested, and contract validations do not imply the re-execution of the code by all the nodes in the network. However, proofs of correct execution are stored on the blockchain and can be verified by multiple parties. Our solution is based on programming tools which optimize the time execution and the required memory while preserving the embedded functionality.
This paper introduces the underlying mechanics and interface for PhoeniχCoin (PHX), an Ethereum ERC223-compliant cryptocurrency. The supply of PHX tokens is tied directly to the Ethereum balance of the smart contract underpinning the ‘EthPhoenix’ decentralised application, and mined using a novel, generalisable technique we refer to as proof-of-volatility.
Open access
Cryptographic Implementations and Security
Security and Verification in Computing
Physical Unclonable Functions (PUFs) and Hardware Security
Blockchain technology has evolved from being an immutable ledger of transactions for cryptocurrencies to a programmable interactive environment for building distributed reliable applications. Although the blockchain technology has been used to address various challenges, to our knowledge none of the previous work focused on using Blockchain to develop a secure and immutable scientific data provenance management framework that automatically verifies the provenance records. In this work, we leverage Blockchain as a platform to facilitate trustworthy data provenance collection, verification, and management. The developed system utilizes smart contracts and open provenance model (OPM) to record immutable data trails. We show that our proposed framework can securely capture and validate provenance data that prevents any malicious modification to the captured data as long as the majority of the participants are honest.
Blockchain Technology Applications and Security
Scientific Computing and Data Management
Innovative Microfluidic and Catalytic Techniques Innovation
Σκοπός της παρούσας διπλωματικής εργασίας είναι η εξέταση της τεχνολογίας που κρύβεται πίσω από τα κρυπτονομίσματα. Η τεχνολογία αυτή είναι το Blockchain και συγκεκριμένα το Blockchain Ethereum, το οποίο είναι μια δημόσια αποκεντρωμένη και κατανεμημένη πλατφόρμα που επιτρέπει σε οποιονδήποτε να δημιουργεί και να χρησιμοποιεί αποκεντρωμένες εφαρμογές που λειτουργούν με αυτή την τεχνολογία. Η καινοτομία της τεχνολογίας Blockchain δίνει λύση στο ζήτημα που αφορά την συγχρονισμένη καταγραφή δεδομένων σε ένα κατανεμημένο δίκτυο από ανεξάρτητους και άγνωστους μεταξύ τους κόμβους (υπολογιστές), συμφωνώντας ότι τα δεδομένα που αποθηκεύονται κάθε φορά είναι ακριβώς τα ίδια. Όλοι οι υπολογιστές που συμμετέχουν σε ένα δίκτυο Blockchain έχουν ακριβώς τα ίδια δεδομένα χωρίς να μπορούν να τα αλλάξουν ή να τα παραμετροποιήσουν, ενώ η ασφάλεια αυτών των δεδομένων επιτυγχάνεται μέσω της κρυπτογραφίας. \nΧρησιμοποιώντας λοιπόν την τεχνολογία Ethereum Blockchain, επιχειρήθηκε η δημιουργία μιας αποκεντρωμένης κατανεμημένης εφαρμογής σε συνεργασία με την εταιρία Intelen Inc. Συγκεκριμένα, έγινε χρήση της τεχνολογίας Blockchain για να επιτευχθεί επικοινωνία μεταξύ έξυπνων οικιακών μπαταριών χωρίς να απαιτείται η παρέμβαση οποιασδήποτε κεντρικής αρχής. Με άλλα λόγια δημιουργήθηκε σχετική εφαρμογή όπου οι έξυπνες μπαταρίες είναι σε θέση να χρησιμοποιήσουν το προσωπικό τους ηλεκτρονικό πορτοφόλι για να ανταλλάζουν κρυπτονομίσματα και πληροφορίες χωρίς την παρέμβαση από τρίτα άτομα.
The main objective of this paper is to provide a Blockchain based framework for conducting and evaluating academic tests in a peer-to-peer manner with auto-generation of certificates upon successful completion of the examination. We illustrate how a self-sustained education ecosystem can be developed on top of a blockchain for a fair evaluation without the need of a central trusted entity for obtaining certificates or degrees that prove one's dexterity over a subject. In order to make the test as transparent as possible, we store the hash-digest of every question asked and every question answered, directly on the blockchain. This facilitates the tracing of how exactly a candidate received the score that he/she received, adding more credibility to the obtained certificate.
Value in algorithmic currencies resides literally in the information content of the calculations; but given the constraints of consensus (security drivers) and the necessity for network effects (economic drivers), the definition of value extends to the multilayered structure of the network itself --that is, to the information content of the topology of the nodes in the blockchain network, and, on the complexity of the economic activity in the peripheral networks of the web, mesh-IoT networks, and so on. In this phase change between the information flows of the native network that serves as the substrate to the blockchain, and that of the real-world data, is where a new "fragility vector" emerges. Our research question is whether factors related to market structure and design, transaction and timing cost, price formation and price discovery, information and disclosure, and market maker and investor behavior, are quantifiable to the degree that can be used to price risk in digital asset markets. The results obtained show that while in the popular discourse blockchains are considered robust and cryptocurrencies anti-fragile, the cryptocurrency markets are in fact fragile. This research is pertinent to the regulatory function of governments, that are actively seeking to advance the state of knowledge regarding systemic risk, to develop policies for crypto markets, and for investors, who are in need of expanding their understanding of market behavior beyond explicit price signals and technical analysis.
Shivika Narang, Praphul Chandra, Shweta Jain, Y. Narahari
The blockchain concept forms the backbone of a new wave technology that promises to be deployed extensively in a wide variety of industrial and societal applications. In this article, we present the scientific foundations and technical strengths of this technology. Our emphasis is on blockchains that go beyond the original application to digital currencies such as bitcoin. We focus on the blockchain data structure and its characteristics; distributed consensus and mining; and different types of blockchain architectures. We conclude with a section on applications in industrial and societal settings, elaborating upon a few applications such as land registry ledger, tamper-proof academic transcripts, crowdfunding, and a supply chain B2B platform. We discuss what we believe are the important challenges in deploying the blockchain technology successfully in real-world settings.
Due to their rapid growth and deployment, Internet of things (IoT) devices have become a central aspect of our daily lives. However, they tend to have many vulnerabilities which can be exploited by an attacker. Unsupervised techniques, such as anomaly detection, can help us secure the IoT devices. However, an anomaly detection model must be trained for a long time in order to capture all benign behaviors. This approach is vulnerable to adversarial attacks since all observations are assumed to be benign while training the anomaly detection model. In this paper, we propose CIoTA, a lightweight framework that utilizes the blockchain concept to perform distributed and collaborative anomaly detection for devices with limited resources. CIoTA uses blockchain to incrementally update a trusted anomaly detection model via self-attestation and consensus among IoT devices. We evaluate CIoTA on our own distributed IoT simulation platform, which consists of 48 Raspberry Pis, to demonstrate CIoTA's ability to enhance the security of each device and the security of the network as a whole.