Blockchain technology has been highly praised for its immutability, attracting considerable attention in the academic and industrial community. However, since permanent storage in blockchains would result in copyright disputes and harmful information spreads, it is desired to equip blockchains with mutability nowadays for legal and moral duty restrictions. A redactable blockchain is a variation, which enables the editing of block objects without affecting other blocks in the blockchain. Most existing redactable blockchains can only support editing operations such as modification and deletion, rather than insertion. However, insertion is necessary for some scenarios, especially when patching codes are needed for smart contracts and mistaken deletions occur. In addition, we argue that the verifiability of blockchains is also significantly important, especially for the redactable ones, in which one block may have multiple versions. Hence, an efficient mechanism is required to invalidate history versions and incent distributed adoptions of editing operations. In this paper, we propose a verifiable and redactable blockchain with fully editing operations for the first time. One distinguishable property is the simultaneous achievement of fully editability of block objects and verifiability of blockchain state, with acceptable extra cost. Specifically, we construct the redactable blockchain based on a double trapdoor chameleon hash family, enabling computationally efficient and key-exposure resistant block editing. Additionally, we combine trapdoorless universal accumulators and the largest sequence number principle to make the blockchain state verifiable. Furthermore, we present a comprehensive analysis and extensive experiments to demonstrate the security and feasibility of the proposed redactable blockchain.
The immutability of blockchains is critical for cryptocurrencies, but an imperative need arises for the redaction of on-chain data due to privacy-protecting laws like GPDR. Recently, Ateniese et al. (EuroS&P 2017) proposed an elegant solution to this problem based on chameleon hash functions, followed by many subsequent works. While these works offered a solution to the permissioned blockchain, the approaches were not efficient enough for the permissionless setting, in terms of either security (which may cause inconsistent historical transactions) or performance (only up to a few hundred nodes). In this paper, we investigate this problem and present Wolverine, a redactable permissionless blockchain. First, we present a formal redactable blockchain model, carefully considering transaction consistency. Next, towards a practical scheme, we introduce the novel concept of non-interactive chameleon hash (NITCH). NITCHs dynamically distribute a trapdoor key among a group and each party in the group can compute its partial share without communicating with others. Anyone who possesses enough shares can then find a valid hash collision. To prevent the static group from being compromised after a sufficiently long time, we provide a generic transform from NITCHs to decentralized random beacons (DRBs) and design a committee evolution protocol based on DRBs that refresh the group after every fixed interval of time. Based on NITCH and the committee evolution protocol, we construct Wolverine which offers important features such as scalability, transaction consistency, and public accountability. Finally, we demonstrate the practicality of Wolverine by giving a proof-of-concept implementation based on Bitcoin in Golang.
Saminur Islam, Mohammad Jaminur Islam, Mahmud Hossain, Shahid Noor · 6 authors
Recently, Blockchain-based applications have become immensely popular because of limited reliance on a single entity, unlike a centralized system. However, reaching a consensus among blockchain networks is a challenging and vital aspect of blockchain-based applications. There are various types of blockchain networks for different kinds of application scenarios. Among all of them, the consensus algorithm is the most crucial part of reaching an agreement in the complex blockchain network. Over the years, researchers have focused on dealing with the challenges like distributed computing, storage, transaction speed, security, validity, interoperability, and many more. However, only some of them are appropriate for all domains. Therefore, this paper presents an extensive study of different types of consensus protocols used in existing blockchain solutions with the strength and limitations of each algorithm. We also provide an inherent comparison among different algorithms to understand consensus protocol selection better. Moreover, we investigate operational and interoperability issues in existing blockchain-based applications to understand challenges and provide recommendations for future developers.
Distributed filesystem architectures use commodity hardware to store data on a large scale with maximum consistency and availability. Blockchain makes it possible to store information that can never be tampered with and incentivizes a traditional decentralized storage system. This project aimed to implement a decentralized filesystem that leverages the blockchain to keep a record of all the transactions on it. A conventional filesystem viz. GFS [1] or HDFS [2] uses designated servers owned by their organization to store the data and are governed by a master service. This project aimed at removing a single point of failure and makes use of participating users’ machines to store data. The implemented file system uses a distributed hash table to evenly store data on multiple machines and efficiently look up, track, maintain, and persist the data. The data stored on the file system is made easily and readily accessible to a user ensuring its soundness. Finally using smart contracts enabled incentives and increased the integrity and reliability of storing data by recording all the transactions. The project functions autonomously by coordinating multiple participant machines in the network to store data and monetize unused storage space on the machines. It supports the basic functionalities of a filesystem which include storing, deletion, and reading a file as desired. The filesystem’s performance was tested with files of different sizes and a variable number of nodes. The current file system is able to store files as big as 100 MB within 12 seconds and 300 MB in less than 25 seconds. This is significantly faster than Storj [3] which nearly takes more than a minute for a similar operation. The tests also provided observations on the average gas consumed during transactions.
For more than a decade, Bitcoin has gained as much adoption as it has received criticism. Fundamentally, Bitcoin is under fire for the high carbon footprint that results from the energy-intensive proof-of-work (PoW) consensus algorithm. There is a trend however for Bitcoin mining to adopt a trajectory toward achieving carbon-negative status, notably due to the adoption of methane-based mining and mining-based flexible load response (FLR) to complement variable renewable energy (VRE) generation. Miners and electricity sellers may increase their profitability not only by taking advantage of excess energy, but also by selling green tokens to buyers interested in greening their portfolios. Nevertheless, a proper ''green Bitcoin'' accounting system requires a standard framework for the accreditation of sustainable bitcoin holdings. The proper way to build such a framework remains contested. In this paper, we survey the different sustainable Bitcoin accounting systems. Analyzing the various alternatives, we suggest a path forward.
Bitcoin uses an unspent transaction output (UTXO) model for coin circulation, which is similar to the banknotes. The transaction history is publicly available and allows to trace cryptocurrency flows. Different users merge transactions into a single bigger one to tangle flows. The merged transaction is called a shared send mixer (SSM). One can try to find the original subtransactions–solve an untangling problem. Based on the number of untanglings and their size, one extracts additional information about coin circulation. Theoretical analysis of the untangling problem is known from the literature. The paper aims to collect statistics of the SSM usage by transaction type for Bitcoin blockchain. We propose an algorithm to solve the problem, prove its correctness, and provide a source code. We applied the algorithm to the Bitcoin historical data. 15% transactions are SSM, and 90% of them allow unique untangling. The future work is an algorithm application to other UTXO systems and the results adaptation to an address grouping.
Open access
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
Pour un internet des objets sécurisé et respectueux de la vie privée basé sur le contrôle d'usage et les registres distribués Les objets connectés représentent l'une des principales cibles de la cybercriminalité. Les raisons en sont multiples : d'abord, pour limiter le coût de la sécurité, les fabricants peuvent vendre des produits vulnérables avec des failles de sécurité. Deuxièmement, de nombreux objets connectés sont soumis à des contraintes de performance et ne disposent pas de la puissance nécessaire pour exécuter des logiciels de sécurité. Enfin, l'hétérogénéité des applications, du matériel et des logiciels élargit la surface d'attaque.Pour parer à ces menaces, l'Internet des Objets (IoT) a besoin de technologies de sécurité et de préservation de la vie privée sur mesure.En ce qui concerne la protection de la vie privée, le contrôle d'usage donne aux utilisateurs la possibilité de spécifier comment leurs données peuvent être utilisées et par qui. Le contrôle d'usage étend le contrôle d'accès classique en introduisant des obligations, c'est-à-dire des actions à effectuer pour obtenir l'accès, et des conditions qui sont liées à l'état du système, comme la charge du réseau ou le temps.Cette thèse vise à apporter des réponses aux défis de l'internet des objets en termes de performance, de sécurité et de respect de la vie privée. Pour cela, les registres distribués (DLT) constituent, de par leur caractère décentralisé, une solution prometteuse aux contraintes de l'internet des objets, en particulier pour les micro-transactions. Cela se traduit par trois contributions:1. un ensemble de technologies pour des transactions sans frais préservant la vie privée, conçu pour passer à l'échelle;2. une méthode d'intégration du contrôle d'usage et des registres distribués pour permettre une protection efficace des données des utilisateurs;3. un modèle étendu pour le contrôle d'usage dans les systèmes distribués, afin d'y ajouter le contrôle de flux décentralisé et les aspects liés à l'internet des objets.Une preuve de concept de l'intégration (2) a été mise en place pour démontrer la faisabilité et effectuer des tests de performance. Elle s'appuie sur IOTA, un registre distribué qui utilise un graphe orienté acyclique pour son graphe de transactions au lieu d'une blockchain. Les résultats des tests de performance sur un réseau privé montrent une diminution d'environ 90% du temps nécessaire pour effectuer des transactions et pour évaluer des politiques de contrôle d'usage, dans le cas où ce dernier est intégré au réseau.
Tayyaba Noreen, Qiufen Xia, Muhammad Zeeshan Haider
In the past decade, blockchain has emerged as a promising solution for building secure distributed ledgers and has attracted significant attention. However, current blockchain systems suffer from limited throughput, poor scalability, and high latency. Due to limitations in consensus mechanisms, especially in managing node identities, blockchain is often considered unsuitable for applications such as the Internet of Things (IoT). This paper proposes the Advanced DAG-based Ranking (ADR) protocol to enhance blockchain scalability and throughput. ADR employs a directed acyclic graph (DAG) structure where nodes are positioned based on their rankings. Unlike traditional chains, ADR allows honest nodes to write blocks and verify transactions using a DAG-based topology. The protocol follows a three-step approach to secure the network against double-spending and enhance performance. First, it verifies nodes using their public and private keys before granting entry. Second, it builds an advanced DAG ledger enabling block production and transaction validation. Third, a ranking algorithm filters out malicious nodes, ranks the remaining nodes based on performance, and arranges them topologically. This process increases throughput and ensures robust scalability. We evaluated ADR on Amazon EC2 clusters with over 100 nodes, including scenarios with injected malicious nodes. Simulation results demonstrate that ADR significantly improves transaction throughput and network liveness compared to existing DAG-based blockchains such as IOTA and ByteBall, making it well-suited for IoT applications.
Blockchain-based decentralized applications (DApp) draw more attention with the increasing development and wide application of blockchain technologies. A wealth of funds are invested into the crowd-funding of various types of DApp. As reported in August 2022, there are more than 5,000 DApps with more than 1.67 million daily Unique Active Wallets (users). However, the definition, architectures, and classifications of the DApps are still not cleared up till now. This survey aims to provide a comprehensive overview of DApps for further research. First, the definitions and typical architectures of DApps are presented. Then we collect 3,118 popular DApps and categorize them into different types, and summarize their typical advantages and challenges. Finally, we provide an overview of the recent research problems of DApps from the perspectives of economics, security, and performance and then figure out promising research opportunities in the future.
The accomplishment of blockchain has increased the focus on the various applications for simplifying the confidentiality and transaction sanctuary using the decentralized architecture via consensus mechanisms between different internet of things (IoT) nodes in daily increasing societal areas. The growth of blockchain lasted to grow and used to do compare technologies. The major shortcomings of blockchain is the lack of scalability in modern application settings. Holochain technology vends itself as a “thinking” exterior to blocks, and it is a peer-to-peer disseminated ledger technology. It works contrarily compared to the blockchain, and it offers an exclusive value in the existing market. IoT devices are continuously used in distributed environments, in various smart applications. The peer-to-peer IoT networks, connected to smart agricultural systems are exposed to the security issues. Specifically, the personal data of agricultural land records need protection against unauthorized access and eradicate corruption in land transactions. The Blockchain offers a possible solution based on distributed ledger, but it has scalability issues due to high storage and processing requirements with growing network size. Also data is not locally stored in a Blockchain. This paper studies the conventions of holochain technology, its architecture and challenges, and critical mechanisms of holochain applications. We also analyze the numerous models utilized for the implementation of protected transactions. We discuss an agent centric framework with distributed hash table for secured applications.
Blockchains are a new approach to creating distributed networks that were first introduced in 2008. It allows the formation of peer-to-peer networks based on consensus, forming chains from accepted blocks without requiring a central authority or centralized controller. A prominent application of this technology is its use in decentralized storage systems. Individuals in decentralized storage networks rent unused hardware storage space to other individuals. A decentralized network utilizing end-to-end encryption eliminates the risk of data loss associated with centralized data control by enabling clients to transmit their files securely. The storage providers must prove that they have kept unaltered files in this network for this time. Many studies have been conducted in this specific domain, most targeting storage capacity and efficiency, but a security, integrity and privacy loophole need to be addressed. This paper presents an overview of blockchain-based storage systems and how they work, followed by a comparison with cloud-based storage networks and a survey of various decentralized storage networks like SIA, File coin, and Storj available on the market. Next, we discuss the advantages and disadvantages of blockchain-based storage. In our final discussion, we examine the security problems of decentralized storage networks and explore potential solutions and research directions for the future.
This paper presents an architectural overview and detailed design of the Krypton network, the first decentralized search engine built on Web3 principles. Krypton leverages blockchain technology, token-driven incentives, and privacy-focused features to revolutionize internet search. The proposed solution incorporates distributed storage, decentralized web crawling and indexing, a consensus mechanism, open-source search algorithms, and a privacy-focused search experience. Krypton introduces the novel concept of Proof of Learning, a machine learning protocol embedded in the search engine to facilitate the discovery of decentralized platforms and enable direct peer-to-peer networking. The system also employs decentralized cloud technologies (validators in the PoS blockchain) to promote enhanced decentralization and encryption, paving the way for a more secure and equitable internet.
Blockchain, or Web3 technology has the potential to disrupt the everyday use of the Internet. The polarised discussion around blockchain technology is notoriously difficult to navigate between the opposing narratives of blockchain evangelists and skeptics. This article focuses on blockchain domain names, a rapidly growing trend using blockchain technology that is currently non-interoperable with the Domain Name System (DNS) and therefore, out of scope of traditional Internet governance. Alternative DNS roots are not new and have previously not become popular due to the lack of supporting browsers. On one view, blockchain domain names are nothing more than another alternative root, insignificant and undeserving of attention. Other narratives regard them as offering an exciting prospect of a decentralised and novel way for managing online naming and addressing. This study explores the burgeoning growth, assesses the challenges of blockchain domain names and provides five recommendations to address them. Although many in traditional Internet communities may be hostile or ignore the blockchain alternative for naming and addressing, we argue that a pragmatic response should be adopted. Even if it is not clear that blockchain domain names solve any problems not currently solved by the DNS, the increase in registrations continues to rise and diverse Internet communities must keep ahead of the trends to understand them and integrate policy implications. Furthermore, the technologies will continue to advance and due to the decentralised nature of the blockchain, developments or changes can be more rapidly implemented than within the DNS.