Blockchain Papers

Rachid Guerraoui, Jingjing Wang

No abstract is available for this record.

Ashley S. McAbee, Murali Tummala, John McEachen

In this paper, the authors review documented problems in military intelligence that appear well suited for improvement via blockchain technology. We review guidance from the literature related to determining blockchain technology applicability and propose a decision aid tailored to military intelligence perspectives. We also propose applying batch queueing theory to enable initial feasibility studies and present analysis toward the first known case study of military intelligence incorporation of blockchain technology, a project reviewing blockchain applicability to an intelligence database that stores geographic locations of units of interest.

Ashish Rajendra Sai, Andrew Le Gear, Jim Buckley

Attaining consensus with no constraints on the consensus participation is a fundamental feature of decentralized blockchain solutions such as Bitcoin (Nakamoto, 2008) and Ethereum (Buterin et al., 2013). Unrestricted consensus participation removes the possibility of censorship and a potential single point of failure, but this design has led to a new concern: that of centralization. Centralization in decentralized blockchain refers to the concentration of a large portion of computing resources to a select few participants. In this paper, we identify the restriction on new participation as a critical contributor to the centralization of consensus power towards commercial and large-scale entities. We also examine the cause of the indirect restriction on participation and propose a metric to identify the degree of these indirect restrictions. This new metric may be used as a threat indicator to identify the centralization of decentralized blockchain caused by indirect participation restrictions.

Yackolley Amoussou-Guenou, Antonella Del Pozzo, Maria Potop-Butucaru, Sara Tucci-Pergiovanni

Committee-based blockchains are among the most popular alternatives of proof-of-work based blockchains, such as Bitcoin. They provide strong consistency (no fork) under classical assumptions, and avoid using energy-consuming mechanisms to add new blocks in the blockchain. For each block, these blockchains use a committee that executes Byzantine-fault tolerant distributed consensus to decide the next block they will add in the blockchain. Unlike Bitcoin, where there is only one creator per block, in committee-based blockchain any block is cooperatively created. In order to incentivize committee members to participate in the creation of new blocks, rewarding schemes have to be designed. In this paper, we study the fairness of rewarding in committee-based blockchains and we provide necessary and sufficient conditions on the system communication under which it is possible to have a fair reward mechanism.

Stefano Bistarelli, Claudio Pannacci, Francesco Santini

No abstract is available for this record.

Luis Cintron, Scott Graham, Douglas D. Hodson, Barry Mullins

No abstract is available for this record.

Tong Zhou, Xiaofeng Li, He Zhao

In today's digital information age, the conflict between the public's growing awareness of their own data protection and the data owners' inability to obtain data ownership has become increasingly prominent. The emergence of blockchain provides a new direction for data protection and data tokenization. Nonetheless, existing cryptocurrencies such as Bitcoin using Proof-of-Work are particularly energy intensive. On the other hand, classical protocols such as Byzantine agreement do not work efficiently in an open environment. Therefore, in this paper, we propose a permission-less blockchain with a novel double-DAG (directed acyclic graph) architecture called DLattice, where each account has its own Account-DAG and all accounts make up a greater Node-DAG structure. DLattice parallelizes the growth of each account's Account-DAG, each of which is not influenced by other accounts' irrelevant transactions. DLattice uses a new DPoS-BA-DAG(PANDA) protocol to reach consensus among users only when the forks are observed. Based on proposed DLattice, we introduce a process of data tokenization, including data assembling, data anchoring, and data authorization. We implement DLattice and evaluate its performance on 25 ECS virtual machines, simulating up to 500 nodes. The experimental results show that DLattice reaches a consensus in 10 seconds, achieves desired throughput, and incurs almost no penalty for scaling to more users.

Benedikt Kirpes, Micha Roon, Christopher Burgahn

The mobility sector experiences a fundamental shift to more connected, autonomous, shared and electric means of transportation. For an electric mobility system to function, an efficient and reliable electric vehicle charging network is required. The Open Charging Network, which is built and curated by the Share&Charge Foundation is a digital, open and decentralized infrastructure for operating and connecting assets of the e-mobility ecosystem like charge points and electric vehicles. In such a network validity and consistency of data are crucial. Since the underlying information system is designed based on distributed ledger technologies and distributed hash tables, also the validation of data for the respective key-value store should be implemented and executed in a distributed manner. In this paper, we contribute to the body of research by analyzing the current situation in distributed systems and presenting the design and development of a mechanism for a distributed data validation. We provide an outlook into the future implementation within the Open Charging Network, where the solution will be demonstrated in a suitable context. Further it will be evaluated regarding the primary requirement of data validity and secondary requirements such as availability, reliability and scalability.

Pablo G. Bringas, Iker Pastor, Giuseppe Psaila

No abstract is available for this record.

Massimo Bartoletti, Letterio Galletta, Maurizio Murgia

The Ethereum platform supports the decentralized execution of smart contracts, i.e. computer programs that transfer digital assets between users. The most common language used to develop these contracts is Solidity, a Javascript-like language which compiles into EVM bytecode, the language actually executed by Ethereum nodes. While much research has addressed the formalisation of the semantics of EVM bytecode, relatively little attention has been devoted to that of Solidity. In this paper we propose a minimal calculus for Solidity contracts, which extends an imperative core with a single primitive to transfer currency and invoke contract procedures. We build upon this formalisation to give semantics to the Ethereum blockchain. We show our calculus expressive enough to reason about some typical quirks of Solidity, like e.g. re-entrancy.

Luong, Dang Hai

Centralized network solution have been around for a long time, despite having a considerable issue of trust, in which users need to rely on the implementation of the system. During unfortunate incidents such as centralized server hacking attacks, users' data can be stolen and distorted, as well as not available while requested. Blockchain is discovered and believed to be a distributed network solution which can mitigate the above issue.
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\nThis bachelor's thesis studies how blockchain network can be integrated into a social financial mobile application. The research is completed by developing a smart contract and connect it with the mobile application. The smart contract is written in the Solidity programming language and run on the Ethereum network.

Jusik Yun, Yunyeong Goh, Jong‐Moon Chung

Blockchains guarantee data integrity through consensus of distributed ledgers based on multiple validation nodes called miners. For this reason, any blockchain system can be critically disabled by a malicious attack from a majority of the nodes (e.g., 51% attack). These attacks are more likely to succeed as the number of nodes required for consensus is smaller. Recently, as blockchains are becoming too large (making them difficult to store, send, receive, and manage), sharding is being considered as a technology to help improve the transaction throughput and scalability of blockchains. Sharding distributes block validators to disjoint sets to process transactions in parallel. Therefore, the number of validators of each shard group is smaller, which makes shard-based blockchains more vulnerable to 51% attacks than blockchains that do not use sharding. To solve this problem, this paper proposes a trust-based shard distribution (TBSD) scheme that assigns potential malicious nodes in the network to different shards, preventing malicious nodes from gaining a dominating influence on the consensus of a single shard. TBSD uses a trust-based shard distribution scheme to prevent malicious miners from gathering in on one shard by integration of a trust management system and genetic algorithm (GA). First, the trust of all nodes is computed based on the previous consensus result. Then, a GA is used to compute the shard distribution set to prevent collusion of malicious miners. The performance evaluation shows that the proposed TBSD scheme results in a shard distribution with a higher level of fairness than existing schemes, which provides an improved level of protection against malicious attacks.

Vicent Cholvi, Antonio Fernández Anta, Chryssis Georgiou, Nicolas Nicolaou

This work provides a proper formalization for Distributed Ledger Objects (as first defined in [Antonio Fernández Anta et al., 2018]), when processes may be Byzantine. The formal definitions are accompanied by algorithms to implement Byzantine Distributed Ledgers by utilizing a Byzantine Atomic Broadcast service.

Mauro Conti, Ankit Gangwal, Michele Todero

A variety of solutions, e.g., Proof-of-Work (PoW), Proof-of-Stake (PoS), Proof-of-Burn (PoB), and Proof-of-Elapsed-Time (PoET), have been proposed to make consensus mechanism used by the blockchain technology more democratic, efficient, and scalable. However, these solutions have a number of limitations, e.g., PoW approach requires a huge amount of computational power, scales poorly, and wastes a lot of electrical energy. Recently, an innovative protocol called Algorand has been proposed to overcome these limitations. Algorand not only guarantees an overwhelming probability of linearity of the blockchain, but it also aims to solve the “blockchain trilemma” of decentralization, scalability, and security. In this paper, we present a security analysis of Algorand. To the best of our knowledge, it is the first security analysis as well as the first formal study on Algorand. We designed an attack scenario in which a group of malicious users tries to break the protocol, or at least limit it to a reduced partition of network users, by exploiting a security flaw in the messages validation process of the Byzantine Agreement (BA). Since the source code or an official simulator for Algorand was not available at the time of our study, we created a simulator (which is available on request) to implement the protocol and assess the feasibility of our attack scenario. Our attack requires the attacker to merely have the trivial capability of establishing multiple connections with targeted nodes, and it costs practically nothing to the attacker. Our results show that it is possible to slow down the message validation process on honest nodes - which eventually forces them to select default values on the consensus - leaving the targeted nodes behind in the chain as compared to the non-attacked nodes. Even though our results are subject to the real implementation of the protocol, the core concept of our attack remains valid.

Dmitrij Lagutin, Francesco Bellesini, Tommaso Bragatto, Alessio Cavadenti · 13 authors

The lack of interoperability among IoT platforms has led to a fragmented environment, where the users and society as a whole suffer from lock-ins, lack of privacy, and reduced functionality. This paper presents SOFIE, a solution for federating the existing IoT platforms in an open and secure manner using Distributed Ledger Technologies (DLTs) and without requiring modifications to the IoT platforms, and describes how SOFIE is used to enable two complex real life pilots: food supply chain tracking from field to fork and electricity distribution grid balancing with guided electrical vehicle (EV) charging. SOFIE's main contribution is to provide interoperability between IoT systems while also enabling new functionality and business models.

Yao-Tsung Yang, Li‐Der Chou, Chia-Wei Tseng, Fan‐Hsun Tseng · 5 authors

Sharing traffic information on the vehicular network can help in the implementation of intelligent traffic management, such as car accident warnings, road construction notices, and driver route changes to reduce traffic congestion earlier. In the future, in the case of autonomous driving, traffic information will be exchanged more frequently and more immediately. Once the exposed traffic incident is incorrect, the driving route will be misleading, and the driving response may be in danger. The blockchain ensures the correctness of data and tampers resistance in the consensus mechanism, which can solve such similar problems. This paper proposes a proof-of-event consensus concept applicable to vehicular networks rather than proof-of-work or proof-of-authority approaches. The traffic data are collected through the roadside units, and the passing vehicles will verify the correctness when receiving the event notification. In addition, a two-phase transaction on blockchain is introduced to send warning messages in appropriate regions and time periods. The simulation results show that the proposed mechanism can effectively feedback the correctness of traffic events and provide traceable events with trust verification.

Fridtjof Nystrøm

A blockchain is a distributed ledger comprised of practically unchange- able, digital recorded data in packages called blocks. Each block in the chain contains data and is cryptographically hashed. The blocks of hashed data draw upon the previous block in the chain, ensuring all data in the overall blockchain is untampered. Blockchain and Distributed Ledger ad- vantages are related to enhanced transparency in business applications and between the involved parties compared to using ordinary databases. Since the blockchain is cryptographically protected, it can be shared, al- lowing anyone to check the correctness of a transaction. Previously, this technology was mostly used for enabling public, decent- ralized digital currencies, known as cryptocurrencies, such as BitCoin and LiteCoin. In the latest years, however, additional use-cases have been de- signed, including non-money asset tokenization, digital identity and sup- ply chain management. Together with the rise of new use-cases, distrib- uted ledger technology frameworks emerged to assist and simplify the development process of such use-cases. These frameworks accelerate the development process at the cost of resource overhead. In this thesis, we use Hyperledger Fabric, a distributed ledger technology framework maintained by the Linux Foundation, to design, develop and analyze the performance of a use-case granted by DNV-GL. We explore the network resource cost of a transaction and model the network traffic flow. In addition, we measure and present the performance of this system and demonstrate why such a performance display alone is misleading.

Daniel Burkhardt, Patrick Frey, Heiner Lasi

The Internet of Things (IoT) describes the fusion of the physical and digital world which enables assets on the edge to send data to a platform where it gets analyzed. Defined actions are then triggered to influence cross-functional edge activities. Furthermore, on the platform tier functionalities and relations need to be identified and implemented to realize assets operating autonomously and ubiquitously. The exploration of this paper results in the identification of autonomous characteristics and shows functional components to implement autonomous assets on the edge. Distributed Ledger Technology (DLT) and its fusion with Machine Learning (ML) as an area of Artificial Intelligence (AI) provides an integral part to realize the described outline. Thus, the recognition of DLT’s and ML’s usage in the IoT and the evaluation of the relevance as well as the synergies build the main focus of this paper.

Yibin Xu, Yangyu Huang

Distributed Ledger Technology (DLT) is promising to become the foundation of many decentralised systems. However, the unbalanced and unregulated network layout contributes to the inefficiency of DLT especially in the Internet of Things (IoT) environments, where nodes connect to only a limited number of peers. The data communication speed globally is unbalanced and does not live up to the constraints of efficient real-time distributed systems. In this paper, we introduce a new communication protocol, which enables nodes to calculate the tradeoff between connecting/disconnecting a peer in a completely decentralised manner. The network layout globally is continuously re-balancing and optimising along with nodes adjusting their peers. This communication protocol weakened the inequality of the communication network. The experiment suggests this communication protocol is stable and efficient.

Derek Leung, Adam Suhl, Yossi Gilad, Nickolai Zeldovich

Decentralized cryptocurrencies rely on participants to keep track of the state of the system in order to verify new transactions. As the number of users and transactions grows, this requirement becomes a significant burden, requiring users to download, verify, and store a large amount of data to participate.

Ali Shahaab, B. Lidgey, Chaminda Hewage, Imtiaz Khan

Advancement of consensus protocols in recent years has enabled distributed ledger technologies (DLTs) to find its application and value in sectors beyond cryptocurrencies. Here we reviewed 66 known consensus protocols and classified them into philosophical and architectural categories, also providing a visual representation. As a case study, we focus on the public sector and highlighted potential protocols. We have also listed these protocols against basic features and sector preference in a tabular format to facilitate selection. We argue that no protocol is a silver bullet, therefore should be selected carefully, considering the sector requirements and environment.

Marianna Belotti, Nikola Bozic, Guy Pujolle, Stefano Secci

Blockchain is a technology making the shared registry concept from distributed systems a reality for a number of application domains, from the cryptocurrency one to potentially any industrial system requiring decentralized, robust, trusted, and automated decision making in a multi-stakeholder situation. Nevertheless, the actual advantages in using blockchain instead of any other traditional solution (such as centralized databases) are not completely understood to date, or at least there is a strong need for a vademecum guiding designers toward the right decision about when to adopt blockchain or not, which kind of blockchain better meets use-case requirements, and how to use it. In this paper, we aim at providing the community with such a vademecum, while giving a general presentation of blockchain that goes beyond its usage in Bitcoin and surveying a selection of the vast literature that emerged in the last few years. We draw the key requirements and their evolution when passing from permissionless to permissioned blockchains, presenting the differences between proposed and experimented consensus mechanisms, and describing existing blockchain platforms.

Michael D. Spain, Sean Foley, Vincent Gramoli

In this paper, we present the most extensive evaluation of blockchain system to date. To achieve scalability across servers in more than 10 countries located on 4 different continents, we drastically revisited Byzantine fault tolerant blockchains and verification of signatures. The resulting blockchain, called the Red Belly Blockchain (RBBC), commits more than a hundred thousand transactions issued by permissionless nodes. These transactions are grouped into blocks within few seconds through a partially synchronous consensus run by permissioned nodes. It prevents double spending by guaranteeing that a unique block is decided at any given index of the chain in a deterministic way by all participants. We compared the performance of RBBC against traditional Byzantine fault tolerant alternatives and more recent randomized solutions. In the same geo-distributed environment with low-end machines, we noticed two interesting comparisons: (i) the RBBC throughput scales to hundreds of machines whereas the classic 3-step leader-based BFT state machine used by consortium blockchains cannot scale to 40 identically configured nodes; (ii) RBBC guarantees transaction finality in 3 seconds and experiences a third of the latency that randomized-based solutions like HoneyBadgerBFT can offer. This empirical evaluation demonstrates that blockchain scalability can be achieved without sacrificing security.

Antonio Fernández Anta, Chryssis Georgiou, Nicolas Nicolaou

The various applications using Distributed Ledger Technologies (DLT) or blockchains, have led to the introduction of a new `marketplace' where multiple types of digital assets may be exchanged. As each blockchain is designed to support specific types of assets and transactions, and no blockchain will prevail, the need to perform interblockchain transactions is already pressing. In this work we examine the fundamental problem of interoperable and interconnected blockchains. In particular, we begin by introducing the Multi-Distributed Ledger Objects (MDLO), which is the result of aggregating multiple Distributed Ledger Objects -- DLO (a DLO is a formalization of the blockchain) and that supports append and get operations of records (e.g., transactions) in them from multiple clients concurrently. Next, we define the AtomicAppends problem, which emerges when the exchange of digital assets between multiple clients may involve appending records in more than one DLO. Specifically, AtomicAppend requires that either all records will be appended on the involved DLOs or none. We examine the solvability of this problem assuming rational and risk-averse clients that may fail by crashing, and under different client utility and append models, timing models, and client failure scenarios. We show that for some cases the existence of an intermediary is necessary for the problem solution. We propose the implementation of such intermediary over a specialized blockchain, we term Smart DLO (SDLO), and we show how this can be used to solve the AtomicAppends problem even in an asynchronous, client competitive environment, where all the clients may crash.