Sybil attack is one of the most serious security threats in distributed systems. This paper proposes an anti-sybil consensus algorithm, which can effectively defend against sybil attacks. This algorithm is an improved version of the PBFT algorithm. It introduces a reputation system, which assigns trust scores to nodes based on their behavior, and uses these trust scores to determine their voting weight in the consensus process. In order to evaluate the performance of the algorithm, the simulation is performed on a blockchain network with different number of nodes and sybil attackers. The results show that the algorithm can effectively defend against sybil attacks. Compared with the existing methods, the anti-sybil consensus algorithm in this paper has several advantages. First, it is lightweight and easy to implement, which makes it suitable for resource-constrained devices. Second, the performance of the improved algorithm has not significantly decreased. In short, the anti-sybil consensus algorithm proposed in this paper provides a practical solution for protecting distributed systems from sybil attacks.
Data synchronization in decentralized storage systems is essential to guarantee sufficient redundancy to prevent data loss. We present SNIPS, the first succinct proof of storage algorithm for synchronizing storage peers. A peer constructs a proof for its stored chunks and sends it to verifier peers. A verifier queries the proof to identify and subsequently requests missing chunks. The proof is succinct, supports membership queries, and requires only a few bits per chunk. We evaluated our SNIPS algorithm on a cluster of 1000 peers running Ethereum Swarm. Our results show that SNIPS reduces the amount of synchronization data by three orders of magnitude compared to the state-of-the-art. Additionally, creating and verifying a proof is linear with the number of chunks and typically requires only tens of microseconds per chunk. These qualities are vital for our use case, as we envision running SNIPS frequently to maintain sufficient redundancy consistently.
Abstract This project aims to produce a cryptocurrency blockchain application. An online application can be accessed via this Blockchain Application System. Everyone with a net connection is able to access it throughout the Internet. This programme will assist the user in sending and receiving Ethereum over the blockchain network. A blockchain is a distributed, trustworthy data repository. Public-key cryptography and the Nobel idea are combined to make it work. The legitimate owner of the resource being traded signs each transaction on the blockchain. New currencies (resources) are created and given to an owner. Simply embed the new owner's public key in the transaction and sign it with the owner's private key to get ready for subsequent transactions that deliver those coins to other people. In this manner, a verifiable chain of transactions is established, with each new transaction linking to the previous transaction with the previous owner and having a new owner.
Open access
Blockchain Technology Applications and Security
Peer-to-Peer Network Technologies
Advanced Steganography and Watermarking Techniques
Currently, digital certificate systems based on blockchain have been extensively developed and adopted. However, most of them do not take into account the certificate quality. To evaluate the credibility of certificates issued by educational institutions, we propose a novel blockchain-based system with credit self-adjustment (BC-CS). In BC-CS, employers can provide feedback according to the performances of their employees (i.e., students) holding different certificates. Based on the feedback, BC-CS automatically adjusts the certificate credits by using our proposed credit self-adjustment algorithm. To verify the feasibility of our proposed system, a decentralized application prototype has been developed on an Ethereum network. Experimental results demonstrate that the proposed system can fully support multi-step accreditation and automatic adjustment for certificate credit.
A non-fungible token (NFT) is a data unit stored on the blockchain. Nowadays, more and more investors and collectors (NFT traders), who participate in transactions of NFTs, have an urgent need to assess the performance of NFTs. However, there are two challenges for NFT traders when analyzing the performance of NFT. First, the current rarity models have flaws and are sometimes not convincing. In addition, NFT performance is dependent on multiple factors, such as images (high-dimensional data), history transactions (network), and market evolution (time series). It is difficult to take comprehensive consideration and analyze NFT performance efficiently. To address these challenges, we propose NFTVis, a visual analysis system that facilitates assessing individual NFT performance. A new NFT rarity model is proposed to quantify NFTs with images. Four well-coordinated views are designed to represent the various factors affecting the performance of the NFT. Finally, we evaluate the usefulness and effectiveness of our system using two case studies and user studies.
We introduce semitopology, a generalisation of point-set topology that removes the restriction that intersections of open sets need necessarily be open. The intuition is that points represent participants in a decentralised system, and open sets represent collections of participants that collectively have the authority to collaborate to update their local state; we call this an actionable coalition. Examples of actionable coalition include: majority stakes in proof-of-stake blockchains; communicating peers in peer-to-peer networks; and even pedestrians working together to not bump into one another in the street. Where actionable coalitions exist, they have in common that: collaborations are local (updating the states of the participants in the coalition, but not immediately those of the whole system); collaborations are voluntary (up to and including breaking rules); participants may be heterogeneous in their computing power or in their goals (not all pedestrians want to go to the same place); participants can choose with whom to collaborate; and they are not assumed subject to permission or synchronisation by a central authority. We develop a topology-flavoured mathematics that goes some way to explaining how and why these complex decentralised systems can exhibit order, and gives us new ways to understand existing practical implementations.
For Nakamoto's longest-chain consensus protocol, whose proof-of-work (PoW) and proof-of-stake (PoS) variants power major blockchains such as Bitcoin and Cardano, we revisit the classic problem of the security--performance tradeoff: Given a network of nodes with finite communication- and computation-resources, against what fraction of adversary power is Nakamoto consensus (NC) secure for a given block production rate? State-of-the-art analyses of NC fail to answer this question, because their bounded-delay model does not capture the rate limits to nodes' processing of blocks, which cause congestion when blocks are released in quick succession. We develop a new analysis technique to prove a refined security--performance tradeoff for PoW NC in a bounded-capacity model. In this model, we show that, in contrast to the classic bounded-delay model, Nakamoto's private attack is no longer the worst attack, and a new attack we call the teasing strategy, that exploits congestion, is strictly worse. In PoS, equivocating blocks can exacerbate congestion, making traditional PoS NC insecure except at very low block production rates. To counter such equivocation spamming, we present a variant of PoS NC we call Blanking NC (BlaNC), which achieves the same resilience as PoW NC.
With the fast growth of the Internet ofThings, location-based services are becoming more important for quality-relevantapplications. Quality-relevant applications often require to be auditable inorder to ensure quality of products and services. However, positioning systemstypically only provide position claims that are not secured and can be forgedor manipulated. This work proposes an auditable positioning system to tacklethis issue. The proposed system performs a proof of location to assert that thetracked asset tag was at the claimed position and immutably stores thisinformation on a distributed ledger. Additionally, an adaptive storage rate wasproposed to save disk storage on the distributed ledgers. A testbed based onBluetooth's Angle of Arrival positioning was implemented for the evaluation ofthe auditable positioning system. The evaluation shows that auditablepositioning is secure, feasible for low-power devices, and that adaptivestorage rates can significantly reduce disk usage and improve scalability.
Currently, Gasper, the implemented consensus protocol of Ethereum, takes between 64 and 95 slots to finalize blocks. Because of that, a significant portion of the chain is susceptible to reorgs. The possibility to capture MEV (Maximum Extractable Value) through such reorgs can then disincentivize honestly following the protocol, breaking the desired correspondence of honest and rational behavior. Moreover, the relatively long time to finality forces users to choose between economic security and faster transaction confirmation. This motivates the study of the so-called single slot finality protocols: consensus protocols that finalize a block in each slot and, more importantly, that finalize the block proposed at a given slot within such slot. In this work we propose a simple, non-blackbox protocol that combines a synchronous dynamically available protocol with a partially synchronous finality gadget, resulting in a consensus protocol that can finalize one block per slot, paving the way to single slot finality within Ethereum. Importantly, the protocol we present can finalize the block proposed in a slot, within such slot.
Guzmán Llambías, Bruno Bradach, Juan J. Nogueira, Laura González · 5 authors
Blockchain is a distributed ledger technology (DLT) to manage data in a decentralised way. During the last years, interoperability has become one of the main challenges within blockchain research as blockchains increasingly require integration between each other. Indeed, blockchains work by design in silos of information as interoperability is not a native feature. The main efforts in the field are focused on blockchains, such as Bitcoin and Ethereum. However, interoperability in DLT remains as an almost untouched area of work as they introduce additional requirements focusing on privacy and identity. Although there are some interoperability solutions for DLT, they are either high-level design proposals not providing concrete implementations or focus on interoperability issues between business applications and blockchain platforms. In this paper we propose a gateway-based platform-to-platform interoperability solution for DLT, which comprises a detailed solution design and a reference implementation. The proposal was assessed through the development of a social security case scenario and the evaluation through two interoperability frameworks. A reference implementation was built using two DLT: Hyperledger Fabric and Corda. The experimental results shows that it is possible to achieve technical interoperability between two heterogeneous DLT platforms using a gateway-based interoperability solution, relaxing decentralisation, data privacy, identity and authorisation management properties.
Soosan Naderi Mighan, Jelena Mišić, Vojislav B. Mišić
In this paper, we provide a comprehensive analytical model for transaction distribution time in Ethereum derived from the analytical model of gossip data delivery protocol. We introduce three classes of priority for transactions which corresponds to the current Ethereum fee scheme and investigate the impact of transaction priority on response and delivery times using a Jackson network and priority queuing system. Our results show that the delivery times depend on priority and that their distribution is slightly hyper-exponential. We also note anomalous scenarios where lowest priority transactions receive faster service than medium priority ones.
Before the advent of alternative blockchains such as Ethereum, the future of decentralization was all in the hands of Bitcoin. Together with Nakamoto itself, early developers were trying to leverage Bitcoin potential to decentralize traditionally centralized applications. However, being Bitcoin a decentralized machine, available non-trustless oracles were considered unsuitable. Therefore, strategies had to be elaborated to solve the so-called oracle problem in the newborn scenario. By interviewing early developers and crawling early forums and repositories, this paper aims to retrace and reconstruct the chain of events and contributions that gave birth to oracles on Bitcoin. The evolution of early trust models and approaches to solving the oracle problem is also outlined. Analyzing technical and social barriers to building oracles on Bitcoin, the transition to Ethereum will also be discussed.
With the progress of the internet from web 2.0 to web 3.0, the increased use of decentralized applications has emerged. Popularized by BlockChain but not limited to decentralized finance, decentralized applications have vast applications with regards to security, storage, and delivery of content over the web. In this paper we outlines the development of a web application prototype using JavaScript programming language, JavaScript based libraries such as BugOut and PeerJS, and the WebRTC (Web Real Time Communication) framework. We have also discuss the brief comparisons between the existing centralized applications and our proposed model. An essential component of this prototype is outlined via the use of P2P networking, which is the backbone of decentralization.
The Synchronic Web is a highly scalable notary infrastructure that provides tamper-evident data provenance for historical web data. In this document, we describe the applicability of this infrastructure for web archiving across three envisioned stages of adoption. We codify the core mechanism enabling the value proposition: a procedure for splitting and merging cryptographic information fluidly across blockchain-backed ledgers. Finally, we present preliminary performance results that indicate the feasibility of our approach for modern web archiving scales.
Abstract: This paper suggests a decentralised web hosting solution based on Web3 Storage and the Interplanetary File System (IPFS). The IPFS platform is used to host websites and store data. To guarantee that the source codes of the websites and users’ data are preserved over the long term, all storage miner nodes on the IPFS network provide the pinning service. Websites must use an encryption technique for data storage that protects user privacy. The suggested model integrates the Web3 Storage and IPFS networks to create a platform that offers decentralised site hosting. The suggested platform guarantees the privacy, availability, and integrity.
Distributed Ledger Technology (DLT) allows the maintenance of a continuously growing ledger in a peer-to-peer network. Nodes participating in the network require significant computational power and memory to download and verify the ledger. To solve this problem, light clients were developed to verify the integrity of the ledger by downloading only a subset of the ledger, but they are vulnerable to malicious influence. The thesis presents Aurora, a set of three stochastic algorithms that add trustlessness to DLT networks by analyzing the network structure and discovering sets that contain honest nodes that can be used for future interactions. The solution allows a new node to join the network and initiate ledger download with an honest node, or to check the presence of a transaction without downloading the entire ledger or a subset of the ledger. The work provides a comprehensive overview of DLT, pseudocode for the solution, and an evaluation procedure using open-source DLT simulation tools. Furthermore, the solution was integrated into Trinity, a Python-based DLT client for the Ethereum network, and was evaluated on the Ethereum production network, consuming approximately 0.31 MB of RAM and 1 MB of storage at runtime. The proposed solution outperforms other state-of-the-art solutions and can be deployed on resource-constrained devices. It incentivizes users to interact with the ledger in a trustless manner. Overview of scientific contribution: 1. A new probabilistic honest set creation algorithm 2. A new probabilistic transaction history synchronization algorithm 3. A new probabilistic transaction presence checking algorithm 4. A new evaluation procedure in a resource constrained environment
Bitcoin builds upon an unstructured peer-to-peer overlay network to disseminate transactions and blocks. Broadcast in such a network is slow and brings inconsistencies, i. e., peers have different views of the system state. Due to the delayed block propagation and the competition of mining, forking, i. e., the blockchain temporarily diverges into two or more branches, occurs, which wastes computation power and causes security issues. This paper proposes an autonomous and distributed topology optimization mechanism to reduce block propagation delay and hence reduce the occurrence of blockchain forks. In the proposed mechanism, a node can autonomously update his neighbor set using the information provided by his current neighbors, since each neighbor will recommend a peer from his own neighbor set, i. e., a neighbor’s neighbor, to this node. Each recommendation is based on a peer’s propagation ability, which is characterized as a criteria function obtained through a combination of empirical analysis and machine learning. We further propose some metrics to evaluate a Bitcoin network topology. Experiment results reflect the effectiveness of the proposed mechanism and indicate the correlation between block propagation time and fork rate. Thus, we analyze the relation between block propagation time and fork rate by applying an epidemic model to capture the block propagation process. We prove that a Bitcoin network topology with a relatively small network delay variance among all nodes produces a lower fork rate than another topology if its average block propagation time to 84% of the entire network is shorter.
Lucian Trestioreanu, Wazen M. Shbair, Flaviene Scheidt de Cristo, Radu State
With the growing adoption of Distributed Ledger Technologies and the subsequent scaling of these networks, there is an inherent need for efficient and resilient communication used by the underlying consensus and replication mechanisms. While resilient and efficient communication is one of the main pillars of an efficient blockchain network as a whole, the Distributed Ledger Technology is still relatively new and the task of scaling these networks has come with its own challenges towards ensuring these goals. New content distribution concepts like Information Centric Networking, of which Named Data Networking is a worthy example, create new possibilities towards achieving this goal, through in-network caching or built-in native multicasting, for example. We present and evaluate XRP-NDN Overlay, a solution for increasing the communication efficiency for consensus-validation based blockchains like the XRP Ledger. We experiment by sending the XRP Ledger consensus messages over different Named Data Networking communication models and prove that our chosen model lowers the number of messages at node level to minimum necessary, while maintaining or improving blockchain performance by leveraging the possibilities offered by an overlay such as specific communication mechanisms.
This paper describes the author’s additions to Minecraft and Bitcoin. The topic of the paper is an implementation of modification into the popular game Minecraft, which demonstrates basic user concepts of cryptocurrency Bitcoin in a simple and free of charge manner.
Git has been the de-facto version control system for the Software Development industry. Although Git is distributed, developers’ tools for collaboration, such as GitHub, are centralized entities owned by large corporations such as Microsoft. The centralization creates trust and privacy issues for software development companies (preserving their intellectual property), along with a significant" single point of failure" issue. In addition, such centralized systems are susceptible to Sybil and distributed denial of service (DDoS) attacks due to the presence of malicious individuals. Blockchain technology has many key characteristics (such as decentralization, transparency, immutability, and audibility), solving these centralization issues. However, the requirement of having a storage system to store the user’s repositories over the blockchain creates a scalability issue (in terms of storage). Most importantly, it makes data (code) privacy more severe due to its open nature. In this paper, we propose a privacy-preserving decentralized alternative solution and framework named "DCGit" powered by Web3 technologies such as the Ethereum Blockchain and InterPlanetary File System (IPFS) to provide security and scalability yet user-friendly collaboration for software development.
Blockchain and other distributed ledger technologies have enabled peer-to-peer networks to maintain ledgers with an immutable history and guaranteed computation, all carried out without the need of trusted parties. In practice, few applications of blockchain are closed i.e. do not interact with the world outside the blockchain, and various techniques have been proposed and used to handle such interaction. One problem is that it is widely accepted that, due to the decentralised nature of blockchain networks and constraints to ensure trust and determinism, such communication can only flow into the blockchain, and that blockchain systems cannot initiate and execute calls to external systems or services. In this paper we show that this misconception is preconceived by building on our previously presented solution to demonstrate that such calls can be directly initiated from the blockchain itself in a feasible and efficient manner.
This paper presents a framework to manage the content whereabouts in the network consisting of heterogeneous resources by distributed ledger technology. Referring to our previously proposed Piggyback Network, which is an infrastructure-sharing-based large-volume digital content distribution/dissemination platform for the B5G society, we propose a partially ordered directed acyclic graph-based distributed ledger (DAG-DL) as a node-hosted transaction recording method. Through the computer simulations on the propagation delay of transactions over the network, we demonstrate that the proposed DAG-DL can record the past transactions with high censorship resistance, while a conventional blockchain cannot, even over an extremely large number of multiplex pathways and multi-hop relays in a distributed way.
The network formation process in the Bitcoin protocol is designed to hide the global network structure: while most of the nodes of the network can be easily discovered, the existence of an edge between two nodes is only known by the two endpoints. In [Becchetti et al., SODA2020] the authors propose a dynamic random graph model inspired by the network formation process in the Bitcoin protocol and they prove that the evolution of the graph quickly terminates and that the resulting graph is an expander, with high probability.