Blockchain Papers

Gabrielle De Micheli, Pierrick Gaudry, Cécile Pierrot

No abstract is available for this record.

Pingcheng Ruan, Tien Tuan Anh Dinh, Qian Lin, Meihui Zhang · 6 authors

No abstract is available for this record.

Cathrine Paulsen

Hyperledger Fabric is a permissioned enterprise blockchain allowing organizations to collaborate and automate processes via smart contracts. However, these contracts could contain security vulnerabilities leading to unexpected behavior or other negative consequences. Therefore, this study takes a closer look at three reported smart contract vulnerabilities in Fabric: rich queries, pseudorandom number generators, and global variables. Smart contracts containing these vulnerabilities were deployed on a test network, and the vulnerable contract features were exploited and explained. The study provides an estimation of each vulnerability's impact severity, and possible countermeasures to lower it were explored and evaluated. This study found that the proposed countermeasures can at least mitigate the impact severity of all three vulnerabilities.<br/>Additionally, the study provides an overview of compatible analysis tools. The available tools were found to be lacking, however, as most of them do not exist outside of research papers. Overall, static code analysis tools were found to be effective at detecting all three vulnerabilities.

Petr Kuznetsov, Yvonne-Anne Pignolet, Pavel Ponomarev, Andrei Tonkikh

Most modern asset transfer systems use consensus to maintain a totally ordered chain of transactions. It was recently shown that consensus is not always necessary for implementing asset transfer. More efficient, asynchronous solutions can be built using reliable broadcast instead of consensus. This approach has been originally used in the closed (permissioned) setting. In this paper, we extend it to the open (permissionless) environment. We present {Pastro}, a permissionless and asynchronous asset-transfer implementation, in which quorum systems, traditionally used in reliable broadcast, are replaced with a weighted Proof-of-Stake mechanism. {Pastro} tolerates a dynamic adversary that is able to adaptively corrupt participants based on the assets owned by them.

David Chaum, Christian Grothoff, Thomas Moser

With the emergence of Bitcoin and recently proposed stablecoins from BigTechs, such as Diem (formerly Libra), central banks face growing competition from private actors offering their own digital alternative to physical cash. We do not address the normative question whether a central bank should issue a central bank digital currency (CBDC) or not. Instead, we contribute to the current research debate by showing how a central bank could do so, if desired. We propose a token-based system without distributed ledger technology and show how earlier-deployed, software-only electronic cash can be improved upon to preserve transaction privacy, meet regulatory requirements in a compelling way, and offer a level of quantum-resistant protection against systemic privacy risk. Neither monetary policy nor financial stability would be materially affected because a CBDC with this design would replicate physical cash rather than bank deposits.

Hyoungsung Kim, Jaehyuk Jang, Sangjun Park, Heung-No Lee

The error-correction code proof-of-work (ECCPoW) algorithm is based on a low-density parity-check (LDPC) code. ECCPoW can impede the advent of mining application-specific integrated circuits (ASICs) with its time-varying puzzle generation capability. Previous research studies on the ECCPoW algorithm have presented its theory and implementation on Bitcoin. In this study, we have not only designed ECCPoW for Ethereum, called ETH-ECC, but have also implemented, simulated, and validated it. In the implementation, we have explained how the ECCPoW algorithm has been integrated into Ethereum 1.0 as a new consensus algorithm. Furthermore, we have devised and implemented a new method for controlling the difficulty level in ETH-ECC. In the simulation, we have tested the performance of ETH-ECC using a large number of node tests and demonstrated that the ECCPoW Ethereum works well with automatic difficulty-level change capability in real-world experimental settings. In addition, we discuss how stable the block generation time (BGT) of ETH-ECC is. Specifically, one key issue we intend to investigate is the finiteness of the mean of ETH-ECC BGT. Owing to a time-varying cryptographic puzzle generation system in the ECCPoW algorithm, the BGT in the algorithm may lead to a long-tailed distribution. Thus, simulation tests have been performed to determine whether the BGT distribution is heavy-tailed and has a finite mean. If the distribution is heavy-tailed, transaction confirmation cannot be guaranteed. In the validation, we have presented statistical analysis results based on the two-sample Anderson–Darling test and discussed how the BGT distribution satisfies the necessary to be considered an exponential distribution. Our implementation is available for download at https://github.com/cryptoecc/ETH-ECC.

Morteza Alizadeh, Karl Andersson, Olov Schelén

Blockchain technology has enabled the keeping of a decentralized, tamper-proof, immutable, and ordered ledger of transactional events. Efforts to leverage such a ledger may be challenging when data storage requirements exceed most blockchain protocols' current capacities. Storing large amounts of decentralized data while maintaining system efficiency is the challenge that we target. This paper proposes using the IPFS distributed hash table (DHT) technology to store information immutably and in a decentralized manner to mitigate the high cost of storage. A storage system involving blockchain and other storage systems in concert should be based on immutable data and allow removal of data from malicious users in the DHT. Efficiency is improved by decreasing the overall processing time in the blockchain with the help of DHT technology and introducing an agreement service that communicate with the blockchain via a RESTful API. We demonstrate the applicability of the proposed method and conclude that the combination of IPFS and blockchain provides efficient cryptographic storage, immutable history and overall better efficiency in a decentralized manner.

Titu-Marius I. Băjenescu

Facebook will soon launch the world's first digital payment currency: Libra. Libra's mission is to foster the development of a simple global currency and financial infrastructure that serves billions of people. This document presents the project, based on a new decentralized blockchain, a cryptomonnaie low volatility and a smart contract platform. The combination of these elements aims to create a new opportunity for innovative and responsible financial services. Libra will be sustained through a small charge per transaction on the blockchain. Many of these charges will be transferred to vendors who can then absorb the costs themselves or relay them to users. Collaboration and innovation with the financial sector (especially with of regulators and experts from various sectors) is the only way to ensure that this new system is based on a durable, secure and reliable framework. This can also lead to a real step towards a low-cost, more accessible and more connected global financial system. Washington and Brussels are calling for far-reaching regulation of Facebook. Responsible citizens have the courage to deal with the ideas of dissidents in social networks, and they have the ability to do so rationally and critically.

Florian Adamsky, Daniel Kaiser, Michael Steglich, Thomas Engel

Distributed Hash Table (DHT) protocols, such as Kademlia, provide a decentralized key-value lookup which is nowadays integrated into a wide variety of applications, such as Ethereum, InterPlanetary File System (IPFS), and BitTorrent. However, many security issues in DHT protocols have not been solved yet. DHT networks are typically evaluated using mathematical models or simulations, often abstracting away from artefacts that can be relevant for security and/or performance. Experiments capturing these artefacts are typically run with too few nodes.

Divija Swetha Gadiraju, V. Lalitha, Vaneet Aggarwal

Blockchain is a distributed ledger with wide applications. Due to the\nincreasing storage requirement for blockchains, the computation can be afforded\nby only a few miners. Sharding has been proposed to scale blockchains so that\nstorage and transaction efficiency of the blockchain improves at the cost of\nsecurity guarantee. This paper aims to consider a new protocol,\nSecure-Repair-Blockchain (SRB), which aims to decrease the storage cost at the\nminers. In addition, SRB also decreases the bootstrapping cost, which allows\nfor new miners to easily join a sharded blockchain. In order to reduce storage,\ncoding-theoretic techniques are used in SRB. In order to decrease the amount of\ndata that is transferred to the new node joining a shard, the concept of exact\nrepair secure regenerating codes is used. The proposed blockchain protocol\nachieves lower storage than those that do not use coding, and achieves lower\nbootstrapping cost as compared to the different baselines.\n

Sangjun Park, Haeung Choi, Heung-No Lee

The protocol for cryptocurrencies can be divided into three parts, namely consensus, wallet, and networking overlay. The aim of the consensus part is to bring trustless rational peer-to-peer nodes to an agreement to the current status of the blockchain. The status must be updated through valid transactions. A proof-of-work (PoW) based consensus mechanism has been proven to be secure and robust owing to its simple rule and has served as a firm foundation for cryptocurrencies such as Bitcoin and Ethereum. Specialized mining devices have emerged, as rational miners aim to maximize profit, and caused two problems: i) the re-centralization of a mining market and ii) the huge energy spending in mining. In this paper, we aim to propose a new PoW called Error-Correction Codes PoW (ECCPoW) where the error-correction codes and their decoder can be utilized for PoW. In ECCPoW, puzzles can be intentionally generated to vary from block to block, leading to a time-variant puzzle generation mechanism. This mechanism is useful in repressing the emergence of the specialized mining devices. It can serve as a solution to the two problems of recentralization and energy spending.

Julian Nagele, Maria A. Schett

In the blockchain-based, distributed computing platform Ethereum, programs called smart contracts are compiled to bytecode and executed on the Ethereum Virtual Machine (EVM). Executing EVM bytecode is subject to monetary fees---a clear optimization target. Our aim is to superoptimize EVM bytecode by encoding the operational semantics of EVM instructions as SMT formulas and leveraging a constraint solver to automatically find cheaper bytecode. We implement this approach in our EVM Bytecode SuperOptimizer ebso and perform two large scale evaluations on real-world data sets.

Shreyas Gandlur

Over the past few years, massive cyberattacks have dominated the public imagination. Most
\nAmericans have been directly affected by data breaches and an overwhelming majority believe
\nthat they are no longer in control of their data. At the same time, there are important applications in
\nwhich the aggregation of private data is unavoidable. Not surprisingly, there has been considerable
\ninterest in developing protocols for secure multi-party computation (MPC), i.e., N parties providing
\nprivate inputs to jointly compute some function f. Recent developments in MPC have led to leaps
\nin efficiency and MPC is quickly becoming a practical approach for privacy-centric distributed
\napplications. As MPC applications become deployed, guaranteeing the security of these protocols,
\neven when interacting with other applications, is essential. The standard approach to showing
\nsecurity of MPC protocols under arbitrary composition is through the universal composability (UC)
\nframework. There has been much prior work on this topic; however, most previous work either
\nmakes synchronicity assumptions or does not guarantee output delivery in the presence of even
\none fault. For practical MPC applications, though, dealing with asynchronicity and robustness is
\nessential. In this thesis, we describe two new keywords, eventually and leak, that aid in defining
\nprotocols in the asynchronous world and define wrappers that implement these within the UC
\nframework. We then use this novel wrapper to give a UC-realization of a reliable broadcast primitive, by means of Bracha’s classic protocol. Finally, we define and prove a realization of what we call the
\nsmart contract model of MPC, which serves as a UC-idealization of asynchronous, robust MPC.

Jonathan Lee, Kirill Nikitin, Srinath Setty

This paper introduces a new approach to reduce end-to-end costs in large-scale replicated systems built under a Byzantine fault model. Specifically, our approach transforms a given replicated state machine (RSM) to another RSM where nodes incur lower costs by delegating state machine execution: an untrusted prover produces succinct cryptographic proofs of correct state transitions along with state changes, which nodes in the transformed RSM verify and apply respectively.To realize our approach, we build Piperine, a system that makes the proof machinery profitable in the context of RSMs. Specifically, Piperine reduces the costs of both proving and verifying the correctness of state machine execution while retaining liveness-a distinctive requirement in the context of RSMs. Our experimental evaluation demonstrates that, for a payment service, employing Piperine is more profitable than naive reexecution of transactions as long as there are > 104nodes. When we apply Piperine to ERC-20 transactions in Ethereum (a real-world RSM with up to 105nodes), it reduces per-transaction costs by 5.4× and network costs by 2.7×.

Manoharan Ramachandran, Niaz Chowdhury, Allan Third, John Domingue · 6 authors

Over-centralisation of data leads to tampering and sharing user information without the consent of the owners. This problem has been studied extensively in recent times providing separate solutions involving distributed storage, Blockchain technology and Solid Pods. Individually these solutions are not sufficient to build realistic applications in a decentralised environment; however, a combination of them can effectively provide more powerful and useful use-cases. In this paper, we propose the methods of combining Solid Pods and distributed ledgers in introducing complete decentralisation of data with total user-control, keeping the integrity of the stored information intact through Blockchain-based verification. We demonstrated multiple configurations of our solutions, offering several new use-cases in various sectors. These configurations introduce new dimensions on the Web and mobile applications’ data storage that developers can benefit from building Distributed Applications (DApps) in a complete decentralised environment.

Pingcheng Ruan, Dumitrel Loghin, Quang-Trung Ta, Meihui Zhang · 6 authors

Smart contracts have enabled blockchain systems to evolve from simple cryptocurrency platforms, such as Bitcoin, to general transactional systems, such as Ethereum. Catering for emerging business requirements, a new architecture called execute-order-validate has been proposed in Hyperledger Fabric to support parallel transactions and improve the blockchain's throughput. However, this new architecture might render many invalid transactions when serializing them. This problem is further exaggerated as the block formation rate is inherently limited due to other factors beside data processing, such as cryptography and consensus. In this work, we propose a novel method to enhance the execute-order-validate architecture, by reducing invalid transactions to improve the throughput of blockchains. Our method is inspired by state-of-the-art optimistic concurrency control techniques in modern database systems. In contrast to existing blockchains that adopt database's preventive approaches which might abort serializable transactions, our method is theoretically more fine-grained. Specifically, unserializable transactions are aborted before ordering and the remaining transactions are guaranteed to be serializable. For evaluation, we implement our method in two blockchains respectively, FabricSharp on top of Hyperledger Fabric, and FastFabricSharp on top of FastFabric. We compare the performance of FabricSharp with vanilla Fabric and three related systems, two of which are respectively implemented with one standard and one state-of-the-art concurrency control techniques from databases. The results demonstrate that FabricSharp achieves 25% higher throughput compared to the other systems in nearly all experimental scenarios. Moreover, the FastFabricSharp's improvement over FastFabric is up to 66%.

Aviv Yaish, Aviv Zohar

Cryptocurrencies that are based on Proof-of-Work (PoW) often rely on special purpose hardware to perform so-called mining operations that secure the system, with miners receiving freshly minted tokens as a reward for their work. A notable example of such a cryptocurrency is Bitcoin, which is primarily mined using application specific integrated circuit (ASIC) based machines. Due to the supposed profitability of cryptocurrency mining, such hardware has been in great demand in recent years, in-spite of high associated costs like electricity. In this work, we show that because mining rewards are given in the mined cryptocurrency, while expenses are usually paid in some fiat currency such as the United States Dollar (USD), cryptocurrency mining is in fact a bundle of financial options. When exercised, each option converts electricity to tokens. We provide a method of pricing mining hardware based on this insight, and prove that any other price creates arbitrage. Our method shows that contrary to the popular belief that mining hardware is worth less if the cryptocurrency is highly volatile, the opposite effect is true: volatility increases value. Thus, if a coin's volatility decreases, some miners may leave, affecting security. We compare the prices produced by our method to prices obtained from popular tools currently used by miners and show that the latter only consider the expected returns from mining, while neglecting to account for the inherent risk in mining, which is due to the high exchange-rate volatility of cryptocurrencies. Finally, we show that the returns made from mining can be imitated by trading in bonds and coins, and create such imitating investment portfolios. Historically, realized revenues of these portfolios have outperformed mining, showing that indeed hardware is mispriced.

Pengxiang Ning, Boqin Qin

Recent years have witnessed a boom in blockchain systems written in Rust to utilize its efficiency and safety. Unfortunately, deadlock bugs have become one of the ubiquitous banes to these systems due to the heavy use of locks for parallelism and the misunderstanding of the lock mechanism in Rust. This paper analyzed the common lock-related pitfalls in blockchain systems written in Rust and proposed Stuck-me-not, the first MIR-based static deadlock detector, for the most common deadlock type: double-lock. We have discovered 29 previously unknown double-lock bugs in 11 popular blockchain-related projects. We believe our work can greatly improve the concurrency security of the current blockchain ecosystem.

Peng Zhao, Hongbing Cheng, Yicheng Fang, Xiaoqing Wang

The exponential growth of storage space in blockchain network has become a serious problem to hinder the distribution of blockchain and the expansion of blockchain nodes. In this paper. We propose a security strategy for distributed storage blockchains, which can delete part of blockchains so that nodes only store part of a blockchain. We design a kind of semi-full node between full node and light node according to the requirement of the strategy, besides describe the process of deleting block and synchronizing block, and the running logic of the semi-full node. Finally, we perform comprehensive experiments of the truncated MCMC random algorithm. The results show that in the case of multi-node, the truncated block will not affect the block chain network. Compared with the traditional block design, our storage strategies can reduce storage requirements under most of situation, thus enable blockchains to be deployed on mobile or smaller storage computers.

Steven Craig Bilow

Most people first encounter blockchain technology by way of cryptocurrencies like Bitcoin. Bitcoin came into existence during the start of the 2008 financial crisis and was first disclosed in October 2008.1Because of the timing and some clear indicators embedded into the first (genesis) block of Bitcoin, we know that a primary reason for developing cryptocurrency was a distrust of large institutions that control the world’s fiat currencies. However, what does currency have to do with media technology?

Omar Gray

No abstract is available for this record.

Kelly Snook, Tarik Barri, Monica Bolles, Petter Ericson · 10 authors

Kepler Concordia, a new scientific and musical instrument enabling players to explore the solar system and other data within immersive extended-reality (XR) platforms, is being designed by a diverse team of musicians, artists, scientists and engineers using audio-first principles. The core instrument modules will be launched in 2019 for the 400th anniversary of Johannes Kepler's Harmonies of the World, in which he laid out a framework for the harmony of geometric form as well as the three laws of planetary motion. Kepler's own experimental process can be understood as audio-first because he employed his understanding of Western Classical music theory to investigate and discover the heliocentric, elliptical behaviour of planetary orbits. Indeed, principles of harmonic motion govern much of our physical world and show up at all scales in mathematics and physics. Few physical systems, however, offer such rich harmonic complexity and beauty as our own solar system. Concordia is a musical instrument that is modular, extensible and designed to allow players to generate and explore transparent sonifications of planetary movements rooted in the musical and mathematical concepts of Johannes Kepler as well as researchers who have extended Kepler's work, such as Hartmut Warm. Its primary function is to emphasise the auditory experience by encouraging musical explorations using sonification of geometric and relational information of scientifically accurate planetary ephemeris and astrodynamics. Concordia highlights harmonic relationships of the solar system through interactive sonic immersion. This article explains how we prioritise data sonification and then add visualisations and gamification to create a new type of experience and creative distributed-ledger powered ecosystem. Kepler Concordia facilitates the perception of music while presenting the celestial harmonies through multiple senses, with an emphasis on hearing, so that, as Kepler wrote, ‘the mind can seize upon the patterns’.

Massimo Bartoletti, Maurizio Murgia, Roberto Zunino

BitML is a process calculus to express smart contracts that can be run on Bitcoin. One of its current limitations is that, once a contract has been stipulated, the participants cannot renegotiate its terms: this prevents expressing common financial contracts, where funds have to be added by participants at run-time. In this paper, we extend BitML with a new primitive for contract renegotiation. At the same time, the new primitive can be used to write recursive contracts, which was not possible in the original BitML. We show that, despite the increased expressiveness, it is still possible to execute BitML on standard Bitcoin, preserving the security guarantees of BitML.

Huawei Huang, Jianru Lin, Baichuan Zheng, Zibin Zheng · 5 authors

Constructing globally distributed file systems (DFS) has received great attention. Traditional Peer-to-Peer (P2P) distributed file systems have inevitable drawbacks such as instability, lacking auditing and incentive mechanisms. Thus, Inter-Planetary File System (IPFS) and Swarm, as the representative DFSs which integrate with blockchain technologies, are proposed and becoming a new generation of distributed file systems. Although the blockchain-based DFSs successfully provide adequate incentives and security guarantees by exploiting the advantages of blockchain, a series of challenges, such as scalability and privacy issues, are also constraining the development of the new generation of DFSs. Mainly focusing on IPFS and Swarm, this paper conducts an overview of the rationale, layered structure and cutting-edge studies of the blockchain-based DFSs. Furthermore, we also identify their challenges, open issues and future directions. We anticipate that this survey can shed new light on the subsequent studies related to blockchain-based distributed file systems.