Blockchain Papers

Arushi Arora, Sumit Kr. Yadav

No abstract is available for this record.

Rudrajit Das, Aditya Golatkar, Suyash P. Awate

In this paper, we propose a new method to perform Sparse Kernel Principal Component Analysis (SKPCA) and also mathematically analyze the validity of SKPCA. We formulate SKPCA as a constrained optimization problem with elastic net regularization (Hastie et al.) in kernel feature space and solve it. We consider outlier detection (where KPCA is employed) as an application for SKPCA, using the RBF kernel. We test it on 5 real-world datasets and show that by using just 4% (or even less) of the principal components (PCs), where each PC has on average less than 12% non-zero elements in the worst case among all 5 datasets, we are able to nearly match and in 3 datasets even outperform KPCA. We also compare the performance of our method with a recently proposed method for SKPCA by Wang et al. and show that our method performs better in terms of both accuracy and sparsity. We also provide a novel probabilistic proof to justify the existence of sparse solutions for KPCA using the RBF kernel. To the best of our knowledge, this is the first attempt at theoretically analyzing the validity of SKPCA.

Mate Puljiz, Stjepan Begušić, Zvonko Kostanjčar

No abstract is available for this record.

Reza M. Parizi, Ali Dehghantanha, Kim‐Kwang Raymond Choo, Amritraj Singh

The emerging blockchain technology supports decentralized computing paradigm shift and is a rapidly approaching phenomenon. While blockchain is thought primarily as the basis of Bitcoin, its application has grown far beyond cryptocurrencies due to the introduction of smart contracts. Smart contracts are self-enforcing pieces of software, which reside and run over a hosting blockchain. Using blockchain-based smart contracts for secure and transparent management to govern interactions (authentication, connection, and transaction) in Internet-enabled environments, mostly IoT, is a niche area of research and practice. However, writing trustworthy and safe smart contracts can be tremendously challenging because of the complicated semantics of underlying domain-specific languages and its testability. There have been high-profile incidents that indicate blockchain smart contracts could contain various code-security vulnerabilities, instigating financial harms. When it involves security of smart contracts, developers embracing the ability to write the contracts should be capable of testing their code, for diagnosing security vulnerabilities, before deploying them to the immutable environments on blockchains. However, there are only a handful of security testing tools for smart contracts. This implies that the existing research on automatic smart contracts security testing is not adequate and remains in a very stage of infancy. With a specific goal to more readily realize the application of blockchain smart contracts in security and privacy, we should first understand their vulnerabilities before widespread implementation. Accordingly, the goal of this paper is to carry out a far-reaching experimental assessment of current static smart contracts security testing tools, for the most widely used blockchain, the Ethereum and its domain-specific programming language, Solidity to provide the first...

Yuanyuan Zhang, Stephen Chan, Jeffrey Chu, Saralees Nadarajah

No abstract is available for this record.

Marko Hölbl, Marko Kompara, Aida Kamišalić, Lili Nemec Zlatolas

Blockchain technology enables a decentralized and distributed environment with no need for a central authority. Transactions are simultaneously secure and trustworthy due to the use of cryptographic principles. In recent years, blockchain technology has become very trendy and penetrated different domains, mostly due to the popularity of cryptocurrencies. One field where blockchain technology has tremendous potential is healthcare, due to the need for a more patient-centric approach to healthcare systems and to connect disparate systems and increase the accuracy of electronic healthcare records (EHRs). In this systematic review, an analysis of state-of-the-art blockchain research in the field of healthcare is conducted. The aim is to reveal the potential applications of the technology and to highlight the challenges and possible directions of blockchain research in healthcare. First, background information is discussed, followed by a description of the exact methodology used in this paper. Next, an analysis of the results is given, which includes a bibliometric overview, an analysis of gathered data and its properties, and the results of a literature quality assessment. Lastly, there is a discussion of the results from the analysis. The findings indicate that blockchain technology research in healthcare is increasing and it is mostly used for data sharing, managing health records and access control. Other scenarios are very rare. Most research is aimed at presenting novel structural designs in the form of frameworks, architectures or models. Findings also show that technical details about the used blockchain elements are not given in most of the analyzed publications and that most research does not present any prototype implementation or implementation details. Often even with a prototype implementation, no details about blockchain elements are given.

Muhammad Saad, Aminollah Khormali, Aziz Mohaisen

In-browser cryptojacking involves hijacking the CPU power of a website's visitor to perform CPU-intensive cryptocurrency mining, and has been on the rise, with 8500% growth during 2017. While some websites advocate cryptojacking as a replacement for online advertisement, web attackers exploit it to generate revenue by embedding malicious cryptojacking code in highly ranked websites. Motivated by the rise of cryptojacking and the lack of any prior systematic work, we set out to analyze malicious cryptojacking statically and dynamically, and examine the economical basis of cryptojacking as an alternative to advertisement. For our static analysis, we perform content-, currency-, and code-based analyses. Through the content-based analysis, we unveil that cryptojacking is a wide-spread threat targeting a variety of website types. Through a currency-based analysis we highlight affinities between mining platforms and currencies: the majority of cryptojacking websites use Coinhive to mine Monero. Through code-based analysis, we highlight unique code complexity features of cryptojacking scripts, and use them to detect cryptojacking code among benign and other malicious JavaScript code, with an accuracy of 96.4%. Through dynamic analysis, we highlight the impact of cryptojacking on system resources, such as CPU and battery consumption (in battery-powered devices); we use the latter to build an analytical model that examines the feasibility of cryptojacking as an alternative to online advertisement, and show a huge negative profit/loss gap, suggesting that the model is impractical. By surveying existing countermeasures and their limitations, we conclude with long-term countermeasures using insights from our analysis.

Virbahu Nandishwar Jain, Devesh Mishra, DAZ SI

No abstract is available for this record.

Vijaya Ramachandran, Thomas Rehermann

Block chain, or distributed ledger
\n technology, has the potential to address many problems in
\n emerging markets. In this note the authors consider whether
\n block chain can be used to mitigate the problem of
\n de-risking by financial institutions, which affects
\n receivers of remittances, businesses that need correspondent
\n banking relationships, and charities working in conflict
\n countries. Block chain is an evolving technology, and
\n understanding its scope and limitations will be critical to
\n employing it to address these and related issues.

Sanjay Prasad, Ravi Shankar, Rachita Gupta, Sreejit Roy

Purpose Over last few years, a major innovation known as blockchain technology has emerged as potentially one of the most disruptive technology of recent times. The purpose of this paper is to identify and analyze various critical success factors (CSFs) that can facilitate success of blockchain-based cloud services. Further, this paper aims to analyze and understand mutual interactions among these CSFs. Design/methodology/approach In this paper, 19 CSFs have been identified through literature review and expert opinions. The hierarchical framework developed using total interpretive structural modeling has revealed the inter-dependencies among these CSFs. The methodology employed in this study provides a mechanism to conduct an exploratory study by identifying the factors and analyzing their interactions through the development of a hierarchical framework. This research further categorizes CSFs into multiple clusters based on their driving power and dependence power. Findings This paper has identified 19 CSFs, namely, user engagement, industry collaboration, rich ecosystem, blockchain technology standardization, regulatory clarity, cost efficiency, energy efficiency (wasted resources), handling blockchain bloat, miner incentives, business case alignment to blockchain capability, sidechains development, blockchain talent pool availability, leadership readiness for a decentralized consensus based technology, technology investment and maturity, trust on blockchain networks, integration with other cloud services, robust and mature smart contracts platform, blockchain security and user control on data (privacy). Further, driver and dependent variables have been identified. Research limitations/implications Future research can discover and detail the sub-factors behind the 19 CSFs identified in this paper. Additionally, more work can be done to extend the current structural model for blockchain-based services to a more functional form. Practical implications It provides a comprehensive list of CSFs that are relevant for development of blockchain-based cloud services. This will help industry leaders to strategically focus on the main drivers that will ensure that businesses get maximum benefit of this disruptive technology. Originality/value This study makes a significant contribution in the literature of blockchain-based cloud services, which captures the perspective of different stakeholders. This study is one of the first (if not the first) systematic research on adoption of blockchain-based services. It creates the foundation to carry out further research in this area.

Mark Holub, Jackie Johnson

No abstract is available for this record.

Madhusudan Singh, Shiho Kim

No abstract is available for this record.

Till Neudecker, Hannes Hartenstein

Permissionless blockchains reach decentralized consensus without requiring pre-established identities or trusted third parties, thus enabling applications such as cryptocurrencies and smart contracts. Consensus is agreed on data that is generated by the application and transmitted by the system's (peer-to-peer) network layer. While many attacks on the network layer were discussed so far, there is no systematic approach that brings together known attacks, the requirements, and the design space of the network layer. In this paper, we survey attacks on the network layer of permissionless blockchains, and derive five requirements: 1) performance; 2) low cost of participation; 3) anonymity; 4) DoS resistance; and 5) topology hiding. Furthermore, we survey the design space of the network layer and qualitatively show the effect of each design decisions on the fulfillment of the requirements. Finally, we pick two aspects of the design space, in-band peer discovery and relay delay, and demonstrate possible directions of future research by quantitatively analyzing and optimizing simplified scenarios. We show that while most design decisions imply certain tradeoffs, there is a lack of models that analyze and formalize these tradeoffs. Such models could aid the design of the network layer of permissionless blockchains. One reason for the lack of models is the deliberately limited observability of deployed blockchains. We emphasize that simulation based approaches cope with these limitations and are suited for the analysis of the network layer of permissionless blockchains.

Parwat Singh Anjana, Sweta Kumari, Sathya Peri, Sachin Rathor · 5 authors

Blockchain platforms such as Ethereum and several others execute complex transactions in blocks through user-defined scripts known as smart contracts. Normally, a block of the chain consists of multiple transactions of smart contracts which are added by a miner. To append a correct block into the blockchain, miners execute these transactions of smart contracts sequentially. Later the validators serially re-execute the smart contract transactions of the block. If the validators agree with the final state of the block as recorded by the miner, then the block is said to be validated. It is then added to the blockchain using a consensus protocol. In Ethereum and other blockchains that support cryptocurrencies, a miner gets an incentive every time such a valid block successfully added to the blockchain. In most of the current day blockchains the miners and validators execute the smart contract transactions serially. In the current era of multi-core processors, by employing the serial execution of the transactions, the miners and validators fail to utilize the cores properly and as a result, have poor throughput. By adding concurrency to smart contracts execution, we can achieve better efficiency and higher throughput. In this paper, we develop an efficient framework to execute the smart contract transactions concurrently using optimistic Software Transactional Memory systems (STMs). Miners execute smart contract transactions concurrently using multi-threading to generate the final state of blockchain. STM is used to take care of synchronization issues among the transactions and ensure atomicity. Now when the validators also execute the transactions (as a part of validation) concurrently using multi-threading, then the validators may get a different final state depending on the order of execution of conflicting transactions. To avoid this, the miners also generate a block graph of the transactions during the concurrent execution and store it in the block. This graph captures the conflict relations among the transactions and is generated concurrently as the transactions are executed by different threads. The miner proposes a block which consists of set of transactions, block graph, hash of the previous block, and final state of each shared data-objects. Later, the validators re-execute the same smart contract transactions concurrently and deterministically with the help of block graph given by the miner to verify the final state. If the validation is successful then proposed block appended into the blockchain and miner gets incentive otherwise discard the proposed block. We execute the smart contract transactions concurrently using Basic Time stamp Ordering (BTO) and Multi-Version Time stamp Ordering (MVTO) protocols as optimistic STMs. BTO and MVTO miner achieves 3.6x and 3.7x average speedups over serial miner respectively. Along with, BTO and MVTO validator outperform average 40.8x and 47.1x than serial validator respectively.

Shiming Liu, Daniel Roy, Sophie Hennequin

International audience

François Verdier, Primavera De Filippi, Frédéric Mallet, Philippe Collet · 12 authors

Innovative services induced by blockchain technologies have social, economical, legal and technical impacts. For this reason, the project smart Internet of Things (IoT) for mobility has adopted a transdisciplinary scientific approach to investigate how blockchain technology would enhance confidence in IoT based services. More precisely, it focuses on services whose systems are decentralized, mainly based on the adoption of the execution of Smart Contracts (intelligent contracts), the whole being really adaptable to the rising generation of IoT. The study targets the social impacts of smart contracts’ adoption within IoT. Its aim is to design a smart contract based on a well understanding of its social acceptance and its legal context and prerogatives. In this paper, it is presented the context, the social study, the use cases targeted and finally first analysis

Parwat Singh Anjana, Sweta Kumari, Sathya Peri, Sachin Rathor · 5 authors

It is commonly believed that blockchain is a revolutionary technology for doing business on the Internet. Blockchain is a decentralized, distributed database or ledger of records. It ensures that the records are tamper-proof but publicly readable. Blockchain platforms such as Ethereum [3] and several others execute complex transactions in blocks through user-defined scripts known as smart contracts. Normally, a block of the chain consists of multiple transactions of smart contracts which are added by a miner. To append a correct block into the blockchain, miners execute these transactions of smart contracts sequentially. Later the validators serially re-execute the smart contract transactions of the block. If the validators agree with final state of the blocks as recorded by the miner, then the block is said to be valid and added to the blockchain using a consensus protocol.

Parwat Singh Anjana, Sweta Kumari, Sathya Peri, Sachin Rathor · 5 authors

No abstract is available for this record.

Zhenzhen Jiao, Rui Tian, Dezhong Shang, Hui Ding

Blockchain has received great attention in recent years and motivated innovations in different scenarios. However, many vital issues which affect its performance are still open. For example, it is widely convinced that high level of security and scalability and full decentralization are still impossible to achieve simultaneously. In this paper, we propose Bicomp, a bilayer scalable Nakamoto consensus protocol, which is an approach based on high security and pure decentralized Nakamoto consensus, and with a significant improvement on scalability. In Bicomp, two kinds of blocks are generated, i.e., microblocks for concurrent transaction packaging in network, and macroblocks for leadership competition and chain formation. A leader is elected at beginning of each round by using a macroblock header from proof-of-work. An elected leader then receives and packages multiple microblocks mined by different nodes into one macroblock during its tenure, which results in a bilayer block structure. Such design limits a leader's power and encourages as many nodes as possible to participate in the process of packaging transactions, which promotes the sharding nature of the system. Furthermore, several mechanisms are carefully designed to reduce transaction overlapping and further limit a leader's power, among which a novel transaction diversity based metric is proposed as the second level criteria besides the longest-chain-first principle on selecting a legitimate chain when fork happens. Security issues and potential attacks to Bicomp are extensively discussed and experiments for evaluation are performed. From the experimental results based on 50 nodes all over the world, Bicomp achieves significant improvement on scalability than that of Bitcoin and Ethereum, while the security and decentralization merits are still preserved.

George Danezis, Dave Hrycyszyn

Blockmania is a byzantine consensus protocol. Nodes emit blocks forming a directed acyclic graph (block DAG) that is subsequently interpreted by each node separately to ensure consensus with safety, liveness and finality. The resulting system has communication complexity $O(N^2)$ even in the worse case, and very low constant factors --- as compared to $O(N^4)$ for PBFT; it is leaderless; and network operations do not depend on the composition of the quorum or node stake. This makes Blockmania very efficient (leading to over 400K transactions per second on a wide area network), and ideal for dynamic membership and flexible and non-interrupted proof-of-stake protocols. A X-Blockmania variant, has $O(N)$ communication cost but also higher latency $O(\log N)$.

Ronghua Xu, Xuheng Lin, Qi Dong, Yu Chen

The emergence of big data and Artificial Intelligence (AI) technology is reshaping the world. While the technological revolution improves the quality of our life, new concerns are triggered. The superhuman capability enables AI to outperform human workers in many data- and/or computing-intensive tasks. Also, digital superpowers are showing arrogance towards individuals, which erodes the trust foundation of the society. In this position paper, we suggest to construct trustworthy and safe communities based on a BLockchain-Enabled Social credits System (BLESS) that rewards the residents who commit in socially beneficial activities. Human being's true value lies in serving other people. The BLESS system is considered as an efficient approach to promote the value and dignity in efforts focused on enhancing our communities and regulating business and private behaviors. The BLESS system leverages the decentralized architecture of the blockchain network, which not only allows grassroots individuals to participate rating process of a social credit system (SCS), but also provides tamper proof of transaction data in the trustless network environment. The anonymity in blockchain records also protects individuals from being targeted in the fight against powerful enterprises. Smart contract enabled authentication and authorization strategy prevents any unauthorized entity from accessing the credit system. The BLESS scheme is promising to offer a secure, transparent and decentralized SCS.

Samuel Green

Blockchain is a simple yet powerful innovation – a new record keeping mechanism that replaces centralized ledgers and double entry bookkeeping. The technology first arose as a backbone to cryptocurrencies such as bitcoin, but has quickly garnered attention for its other applications, such as those in the areas of government record keeping, supply chain tracking, land title management, and, as will be explored throughout this paper, agri-food markets. Blockchain’s potential applications to agri-food markets are wide ranging, and hinge on the technology’s ability to track a physical commodity throughout an entire supply chain and provide easy access to this information for multiple parties. The technology thus enables improvements in food safety programs, by allowing the provenance of a product to be discovered within seconds, tracing the source of a foodborne illness back to its source before it becomes a widespread issue. It will also give credibility to - and increase participation in - environmental certification programs due to its ability to reduce paperwork and simplify the auditing process. Finally, the technology has the potential to change the way farmers market their products, reducing counterparty risk and empowering smallholder farmers in the process. [vi] The technology holds immense promise for the Agri-food sector, and several start-up firms and even governments have initiated pilot programs and studies to further understand its many applications. These pilots are often in their early stages of implementation, but offer insights into the potential and limitations of the technology. This paper explores the potential applications of blockchain to the agri-food market, with a specific focus on food safety, environmental certifications, and commodity marketing. It finds that the technology holds immense potential, but that a number of obstacles must be overcome before this potential is reached. Chief among these obstacles is further integration of real-world links to the blockchain, be it RFID or NFC chips, or changes to precision agriculture equipment and other on-farm machinery. If these obstacles are overcome, however, blockchain could have profound impacts on international agri-food markets. Well thought out government policy and regulation will need to accompany the technological advancements being made in the sector. As such, regulators and legislators alike should maintain a loose regulatory framework that allows new and innovative applications of the technology to flourish. This can be achieved through regulatory sandboxes and an iterative, cautious approach to policy making. Finally, there are areas, such as food safety and environmental monitoring, where the government should become more involved in research and development, either through applied research funding or government run initiatives. Blockchain technology, if accompanied by sensible government policy, stands to improve the way food is sourced, tracked, and sold. The recommendations put forth in this paper serve as guidelines for unleashing the technology’s potential.

Michael Schiff

Denken wir an Geld, haben wir instinktiv Geldscheine und Munzen vor Augen. Dabei ist im Euroraum die Geldmenge, die auf den Bankkonten liegt und uber die wir mit dem Griff zur Giro- oder Kreditkart...

Jose Berengueres

Traditionally, the Net Present Value method has been used to compare diverging investment strategies. However, valuating crypto-projects with fiat-based currency is confusing due to extreme coin appreciation rates as compared to fiat interest rates. Here, we provide a net present value method based on using crypto-coin as the underlying asset. Using this method, we compare buy-and-hold versus mine-and-hold; we also provide a sensitivity analysis of profitability.