Matteo Varvello, Iñigo Querejeta Azurmendi, Antonio Nappa, Panagiotis N. Papadopoulos · 6 authors
Distributed Virtual Private Networks (dVPNs) are new VPN solutions aiming to solve the trust-privacy concern of a VPN's central authority by leveraging a distributed architecture. In this paper, we first review the existing dVPN ecosystem and debate on its privacy requirements. Then, we present VPN0, a dVPN with strong privacy guarantees and minimal performance impact on its users. VPN0 guarantees that a dVPN node only carries traffic it has "whitelisted", without revealing its whitelist or knowing the traffic it tunnels. This is achieved via three main innovations. First, an attestation mechanism which leverages TLS to certify a user visit to a specific domain. Second, a zero knowledge proof to certify that some incoming traffic is authorized, e.g., falls in a node's whitelist, without disclosing the target domain. Third, a dynamic chain of VPN tunnels to both increase privacy and guarantee service continuation while traffic certification is in place. The paper demonstrates VPN0 functioning when integrated with several production systems, namely BitTorrent DHT and ProtonVPN.
Developing smart contract decentralised application based systems typically involves writing code for various platforms, from the smart contract code residing on the underlying distributed ledger technology implementation to back end oracles and front end websites or mobile apps. In addition to the different technologies used for the different parts, the programmer is also burdened with implementing communication channels between the various parts. In this paper we propose a unified programming model allowing for developers to build such systems through a single code artifact, using a macroprogramming approach.
Beom Suk Lee, Jae Song, Sung Jun Moon, In Hwan Park · 5 authors
We consider blockchain architectures for P2P energy trading of surpluses and demands between prosumers and consumers in the neighborhood without any intermediaries. We identify key elements comprising the P2P energy trading platform based on blockchain. The software architecture of our energy trading platform is provided with example codes. We build smart contracts on Ethereum for determination of trading price as well as matching between prosumers and consumers in such a way to balance the surpluses and the demands. At the start of each trading period, the prosumers and consumers send their respective amounts of surplus or demand. And the smart contract for price determination automatically evaluates the price in a predetermined way to balance surplus and demand within the neighborhood. Another smart contract performs matching between prosumers and consumers using this price. Authenticated and private messaging called `whisper' is employed for prosumers and DSO(Distributed System Operator)s to notify injection of surplus energy to the DSO and verify the ownership of the injected energy. Each participant interacts with Ethereum virtual machine through web server built with Node.js, Web3.js and Geth. We build a small experimental setup with 4 Raspberry-Pis in a private Ethereum network to provide proof-of-concept for our blockchain based P2P trading architecture between neighbors.
Blockchain technology is being used in many areas, during last few years. Furthermore, different application opportunities are still been investigated. Blockchain relies on and permits to implement the concept of Decentralized Application (DApps). This makes the applications more transparent, distributed and flexible. The complexity of blockchain and its integration problems require expertise that differs from traditional application development approaches. Within this context, this paper presents our experience in building a DApp with one of the most popular blockchain based platforms called Ethereum.
A blockchain is a database of sequential events that is maintained by a distributed group of nodes. A key consensus problem in blockchains is that of determining the next block (data element) in the sequence. Many blockchains address this by electing a new node to propose each new block. The new block is (typically) appended to the tip of the proposer's local blockchain, and subsequently broadcast to the rest of the network. Without network delay (or adversarial behavior), this procedure would give a perfect chain, since each proposer would have the same view of the blockchain. A major challenge in practice is forking. Due to network delays, a proposer may not yet have the most recent block, and may, therefore, create a side chain that branches from the middle of the main chain. Forking reduces throughput, since only one a single main chain can survive, and all other blocks are discarded. We propose a new P2P protocol for blockchains called Barracuda, in which each proposer, prior to proposing a block, polls $\ell$ other nodes for their local blocktree information. Under a stochastic network model, we prove that this lightweight primitive improves throughput as if the entire network were a factor of $\ell$ faster. We provide guidelines on how to implement Barracuda in practice, guaranteeing robustness against several real-world factors.
Off-chain transaction networks can mitigate the scalability issues of today's trustless electronic cash systems such as Bitcoin. However, these peer-to-peer networks also introduce a new attack surface which is not well-understood today. This paper identifies and analyzes, a novel Denial-of-Service attack which is based on route hijacking, i.e., which exploits the way transactions are routed and executed along the created channels of the network. This attack is conceptually interesting as even a limited attacker that manipulates the topology through the creation of new channels can navigate tradeoffs related to the way it attacks the network. Furthermore, the attack also highlights a fundamental design tradeoff for the defender (who determines its own routes): to become less predictable and hence secure, a rational node has to pay higher fees to nodes that forward its payments. We find that the three most common implementations for payment channels in Bitcoin (lnd, C-lightning, Eclair) approach routing differently. We begin by surveying the current state of the Lightning network and explore the routes chosen by these implementations. We find that in the current network nearly 60\% of all routes pass through only five nodes, while 80\% go through only 10 nodes. Thus, a relatively small number of colluding nodes can deny service to a large fraction of the network. We then turn to study an external attacker who creates links to the network and draws more routes through its nodes by asking for lower fees. We find that just five new links are enough to draw the majority (65\% - 75\%) of the traffic regardless of the implementation being used. The cost of creating these links is very low. We discuss the differences between implementations and eventually derive our own suggested routing policy, which is based on a novel combination of existing approaches.
James Kempf, Sambit Nayak, Remi Robert, Jim Feng · 9 authors
In this paper, we describe a virtual services marketplace, called Nubo, designed to connect buyers of virtual services (or tenants) with providers of those services on a cloud computing platform. The marketplace is implemented as a collection of distributed microservices along with a marketplace portal that runs as a Web application. The heart of Nubo is the Saranyu tenant and service management microservice. Saranyu is a decentralized application (dApp) built on top of the J.P. Morgan Quorum blockchain. Tenant and service accounts are represented as static (nonnegotiable) smart contracts written in the Solidity language. Quorum provides a tamper evident and tamper resistant distributed ledger, whereby multiple cloud and service providers can co-operate to provide service resources to tenants in a trustworthy fashion. Services offer resources consisting of a collection of attributes describing what the tenant can consume, and tenants subscribe to service resources through the Nubo Marketplace portal. The Service Manager microservice provides multitenant support for containerized services built for deployment and orchestration using Docker that were originally not designed to be managed through Saranyu. We discuss our design goals for Nubo, describe the overall architecture, discuss some details on how Saranyu uses the blockchain and smart contracts, and provide comprehensive performance and scalability data measured on the Saranyu REST API. The results indicate Saranyu is competitive with published results for comparable operations on the Havana release of OpenStack Keystone, but Saranyu provides a much richer collection of tenant and service management functionality than Keystone.
Iago Sestrem Ochôa, Rafael Alexandre Piemontez, Lucas M. C. e Martins, Valderi Reis Quietinho Leithardt · 5 authors
Blockchain technology has aroused the interest of researchers as it ensures security and privacy in decentralized applications. One of the platforms currently used for the development of new blockchain-based solutions is the Ethereum network. This article presents an experimental analysis of the scalability of this network to identify its cost and performance for several contracts in a simulated private Ethereum network. The results obtained demonstrate that storage operations for large amounts of data can prevent the use of blockchain due to the high cost of gas charged for this type of operation. The experiments also pointed out that processing operations which do not store information have a small cost of gas.
The method of evaluating the effectiveness of the economic parameters for the implementation at industrial enterprises of “Peer-to-Peer Distributed Storage and Processing of Protected Information in Corporate Networks,” designed primarily to protect distributed computing and isolate private networks without limiting the possibilities of useful interaction in the framework of the technologies Industry 5.0 and Super Smart Society is proposed. Within the framework of these concepts, there is a gradual integration of production, logistics, sales, and information systems into a global information exchange system. The proposed system provides for effective counteraction to the threats using cryptography, protection against unauthorized access using biometrics, and an innovative protocol for information interaction and control of topology based on distributed ledger technologies, it optimizes the use of computing power and provides tools for distributed computing without changing the logic of existing software.
In the highly connected age of information and data, the push for the development of ‘clean data’ has necessitated sustainability strategies for data centers. Green innovations are increasingly implemented to reduce the formidable power consumption of inefficient computing processes while heat reuse solutions repurpose the large volumes of server waste heat, decreasing facility footprint. This project examined the efficiency optimization potential of co-located power generation and greenhouse waste heat reuse for cryptocurrency data center platforms in Alberta. The proposed 45 MW data center capitalized on favorable climatic conditions to reduce energy requirements, improving facility efficiency and decreasing theoretical PUE values from 2.13 to 1.51. Resultant waste heat sufficiently supplied year-round heating to an 8.34-acre greenhouse suitable for commercial cannabis growth. The total annual avoided emissions for this proposed system were calculated at 70,000 tonnes of CO2, illustrating the potential of integrated economizer cyles and waste heat reuse in Alberta.
Today, the new knowledge, works, data and archives are growing day by day and circulating rapidly. At the same time, people's demands for knowledge and information are increasingly diversified, showing such characteristics as personalization, internationalization, cross-time-space and intelligent integration. Traditional libraries, whether paper or digital, cannot adapt to them. In this paper, we propose a framework for establishing virtual digital library based on P2P and blockchain, called Peer Book Search and Library, or PBSL for short. In PBSL: Firstly, books and all kinds of materials are stored digitally on, peers, i.e., personal computers and other digital devices distributed around the world. Secondly, the search, distribution and transmission of various digital resources are based on DHT, peer search, peer transfer and other P2P technologies. Thirdly, blockchain technology is used in digital copyright protection, trade, propagation link maintenance, reading charge and so on. By integrating all above aspects creatively and systematically in software, a PBSL library will completely overcome the disadvantages of the existing library system, and become a brand new as well as subversive way for knowledge production, distribution, acquisition and consumption.
As the monetary value of cryptocurrency increases, the security measures for cryptocurrency becomes more important. A limitation of the existing cryptocurrency exchanges is their vulnerability to threats of hacking due to their centralized manner of management. In order to overcome such limitation, blockchain technology is increasingly adopted. The blockchain technology enables decentralization and Peer-to-Peer(P2P) transactions, in which blocks of information are linked in chain topology, and each node participating in the blockchain shares a distributed ledger. In this paper, we propose and implement a mobile electronic wallet that can safely store, send and receive cryptocurrencies. The proposed mobile cryptocurrency wallet connects to the network only when the wallet actively is used. Wallet owner manages his or her private key offline, which is advantageous in terms of security. JavaScript based wallet apps were implemented to respectively run on Android and iOS mobile phones. I demonstrate the process of transferring Ethereum cryptocurrency from an account to another account through Ropsten, a test net for Ethereum. Hardware wallets, such as Ledger Nano S, provide a slightly higher level of security, yet have the disadvantages of added burden of carrying additional physical devices and high costs (about 80$).
Distributed ledgers based on blockchain, such as Bitcoin and Ethereum, are known and used worldwide now. But the existing distributed ledgers are too slow for commercial requirements when compared with centralized systems like Visa. To tackle this issue, many strategies have been put forward, including GHOST, Bitcoin-NG, Sharding, State channel, Plasma, etc. But few of them is focused on the P2P layer, while the P2P layer plays a crucial role as a distributed ledger needs to be updated via block propagation process. We propose an alternative protocol named Ari, which is a P2P optimization for blockchain systems. Ari protocol makes the block propagation graph an intercrossing net rather than a unidirectional tree, thus leading to a great reduction on latency as well as a great expansion on throughput, and the security as well as scalability is still guaranteed.
IOTA opened recently a new line of research in distributed ledgers area by targeting algorithms that ensure a high throughput for the transactions generated in IoT systems. Transactions are continuously appended to an acyclic structure called tangle and each new transaction selects as parents two existing transactions (called tips) that it approves. G-IOTA, a very recent improvement of IOTA, targets to protect tips left behind offering hence a good confidence level. However, this improvement had a cost: the use of an additional tip selection mechanism which may be critical in IoT systems since it needs additional energy consumption. In this paper we propose a new metamorphic algorithm for tip selection that offers the best guaranties of both IOTA and G-IOTA. Our contribution is two fold. First, we propose a parameterized algorithm, E-IOTA, for tip selection which targets to reduce the number of random walks executed in previous versions (IOTA and G-IOTA) while maintaining the same security guaranties as IOTA and the same confidence level and fairness with respect to tips selection as G-IOTA. Then we propose a formal analysis of the security guaranties offered by E-IOTA against various attacks mentioned in the original IOTA proposal (e.g. large weight attack, parasite chain attack and splitting attack). Interestingly, to the best of our knowledge this is the first formal analysis of the security guaranties of IOTA and its derivatives.
Permissioned blockchain protocols generally use voting based algorithms to reach consensus. Scaling such protocols is hard because of their high message complexity and thus, have a limited number of applications. Use cases like banking and healthcare blockchain require a scalable distributed protocol to maintain the consistency of the ledger and ensure its safety. This paper presents Colosseum, a scalable consensus protocol designed for permissioned blockchain systems. It is a knockout tournament based protocol over a structured ring network to reach consensus on the next set of block proposers. Participants compete in the rounds of a novel two-player game in each tournament to become eligible to propose block. Colosseum introduces Proof-of-Win as the certificate for the result of matches to have an efficient and easy way to propose trusted blocks and verify them.
Lots of privacy and security issues in the current cloud-based data markets will be eliminated by taking advantage of blockchain-based decentralized storage services, which can provide a new paradigm for safe data outsourcing and correct remote search. However, existing data markets are also questioned on their inflexible and opaque pricing, where the value of data ownership and the cost of query search are mixed. Thus, a better pricing model is necessarily needed in an emerging decentralized data market. In this paper, we envision an Ethereum-based data market, in which the pricing model for each query includes two parties: owner (paid for his data ownership) and miner (rewarded by query search). We study a new cooperative search scheme through a proxy to reduce cost on the client (user) side. Suppose each user query is charged based on the number of keywords in the query. The cost reduction is based on combining multiple queries into a group subject to the constraint that the resulting combined query is not significantly larger than any of its original query in terms of the number of keywords. The total price is based on total number of keywords in all groups. As the optimal grouping depends on the pricing of both owner and miner, we build a small testbed to analyze how price setting will affect grouping results. Since it is a cooperative model with shared resources, we also study various incentive properties on the client side, thereby yielding a cost sharing mechanism to split joint cost in a truth-revealing and fair manner.
Blockchains can now be used to distribute digital assets independent of specific organizations. One way to handle digital assets on a blockchain is through tokens. Tokens define chunks of data on a blockchain, allowing it to be distributed like virtual currency. However, storing all data related to digital assets in a token is difficult. Data is currently managed separately because storing a large amount of data in a blockchain can cause the ledger to grow large. When the management of data depends on a particular organization, the stability of the token's value depends on that particular organization. In this paper, we propose an organization-independent management method that combines a distributed content-addressable file system with a blockchain. Our proposed method places the data associated with the token and the access information to the token into the distributed content-addressable file system. As a result, the token associated with the data has the sharing control of the data stored in the distributed content-addressable file system, and a configuration independent of the specific contract is realized.
This article aims at introducing a new configurable and multipurpose electronic voting service based on the blockchain infrastructure. The objective is to design an architecture to automatically translate service configuration defined by the end user into a cloud-based deployable bundle, automating business logic definition, blockchain configuration, and cloud service provider selection. The article presents the preliminary results of the system and a SOA-based services definition implemented with smart contracts.
Tezos is an innovative blockchain that improves on several aspects compared to more established blockchains. It offers an original proof-of-stake consensus algorithm and can be used as a decentralized smart contract platform. It has the capacity to amend its own economic protocol through a voting mechanism and focuses on formal methods to improve safety.
Chain growth in a permissionless blockchain-based ledger is mostly defined by the characteristics of the distribution network and the chosen consensus protocol. In this paper, we investigate the performance of block propagation in a Bitcoin-like peer-to-peer distribution network, and highlight the impact of the Nakamoto consensus protocol on the dynamics of blockchain growth. We use a simulated network with nodes located in different geographic regions, each with its own propagation characteristics; the values of network parameters are chosen to match available data for the Bitcoin peer-to-peer network. We show that the latency of block propagation is mainly affected by the mean round-trip time; that forks occur more often when mean round-trip time is longer, and that the ratio of the number of nodes opting for one or the other of competing blocks as the main chain tip can occur in almost any ratio; finally, that the mean time to resolve a fork is approximately equal to block inter-arrival time.
As a promising method to enable fast and scalable Bitcoin transactions, Bitcoin Lightning Network (LN) has experienced rapid development since the end of 2017. LN utilizes the so-called "payment channels" to provide fast off-chain transactions, thereby offloading on-chain burden and enabling instant payments. With many new protocols proposed to improve the performance of LN, little is known about the current state of the network such as its topology, channel characteristics and application performance. In this paper, we conduct a systematic measurement on LN based on the data collected over a period of fifteen months. This measurement allows us to draw a network graph to study the payment routing success rate and the level of decentralization. We also analyze payment channels regarding their functions. Our work provides an in-depth understanding of network mechanisms and helps to explore future implications of LN.
Muhammad Saad, Victor Cook, Lan N. Nguyen, My T. Thai · 5 authors
Bitcoin is the leading example of a blockchain application that facilitates peer-to-peer transactions without the need for a trusted intermediary. This paper considers possible attacks related to the decentralized network architecture of Bitcoin. We perform a data driven study of Bitcoin and present possible attacks based on spatial and temporal characteristics of its network. Towards that, we revisit the prior work, dedicated to the study of centralization of Bitcoin nodes over the Internet, through a fine-grained analysis of network distribution, and highlight the increasing centralization of the Bitcoin network over time. As a result, we show that Bitcoin is vulnerable to spatial, temporal, spatio-temporal, and logical partitioning attacks with an increased attack feasibility due to network dynamics. We verify our observations by simulating attack scenarios and the implications of each attack on the Bitcoin . We conclude with suggested countermeasures.