One of the main issues in digital forensics is the management of evidences. From the time of evidence collection until the time of their exploitation in a legal court, evidences may be accessed by multiple parties involved in the investigation that take temporary their ownership. This process, called Chain of Custody (CoC), must ensure that evidences are not altered during the investigation, despite multiple entities owned them, in order to be admissible in a legal court. Currently digital evidences CoC is managed entirely manually with entities involved in the chain required to fill in documents accompanying the evidence. In this paper, we propose a Blockchain-based Chain of Custody (B-CoC) to dematerialize the CoC process guaranteeing auditable integrity of the collected evidences and traceability of owners. We developed a prototype of B-CoC based on Ethereum and we evaluated its performance.
Most languages are given an informal semantics until they are implemented, so the formal semantics comes later. Consequently, there are usually inconsistencies among the informal semantics, the implementation, and the formal semantics. IELE is an LLVM-like language for the blockchain that was specified formally and its implementation, a virtual machine, generated from the formal specification. Moreover, its design was based on problems observed formalizing the semantics of the Ethereum Virtual Machine (EVM) and from formally specifying and verifying EVM programs (also called “smart contracts”), so even the design decisions made for IELE are based on formal specifications. A compiler from Solidity, the predominant high-level language for smart contracts, to IELE has also been implemented, so Ethereum contracts can now also be executed on IELE. The virtual machine automatically generated from the semantics of IELE is shown to be competitive in terms of performance with the state of the art and hence can stand as the de facto implementation of the language in a production setting. Indeed, IOHK, a major blockchain company, is currently experimenting with the IELE VM in order to deploy it as its computational layer in a few months. This makes IELE the first practical language that is designed and implemented as a formal specification. It took only 10 man-months to develop IELE, which demonstrates that the programming language semantics field has reached a level of maturity that makes it appealing over the traditional, adhoc approach even for pragmatic reasons.
Arati Baliga, I Subhod, Pandurang Kamat, Siddhartha Chatterjee
Quorum is a permissioned blockchain platform built from the Ethereum codebase with adaptations to make it a permissioned consortium platform. It is one of the key contenders in the permissioned ledger space. Quorum supports confidentiality and privacy of smart contracts and transactions, and crash and Byzantine fault tolerant consensus algorithms. In this paper, we characterize the performance features of Quorum. We study the throughput and latency characteristics of Quorum with different workloads and consensus algorithms that it supports. Through a suite of micro-benchmarks, we explore how certain transaction and smart contract parameters can affect transaction latencies.
Blockchain is an emerging technology that gained a lot of attention in the last years. Many different consensus protocols have been proposed to improve both the scalability and the resilience of existing blockchain. However, all these solutions have been defined for rather static settings. We propose a modular approach for analysing and comparing different consensus protocols used in blockchain under churn.
This paper presents LinBFT, a novel Byzantine fault tolerance (BFT) protocol for blockchain systems that achieves amortized O(n) communication volume per block under reasonable conditions (where n is the number of participants), while satisfying determinist guarantees on safety and liveness. This significantly improves previous results, which either incurs quadratic communication complexity, or only satisfies safety in a probabilistic sense. LinBFT is based on the popular PBFT protocol, and cuts down its $O(n^4)$ complexity with three tricks, each by $O(n)$: linear view change, threshold signatures, and verifiable random functions. All three are known, i.e., the solutions are right in front of our eyes, and yet LinBFT is the first $O(n)$ solution with deterministic security guarantees. Further, LinBFT also addresses issues that are specific to permission-less, public blockchain systems, such as anonymous participants without a public-key infrastructure, proof-of-stake with slashing, rotating leader, and a dynamic participant set. In addition, LinBFT contains no proof-of-work module, reaches consensus for every block, and tolerates changing honesty of the participants for different blocks.
Jun Duan, Alexei Karve, Vugranam C. Sreedhar, Sai Zeng
Business interest in blockchain technology is increasing due the potential for change that it offers. Large scale adoption in enterprise IT environments brings about a need for service management and DevOps processes for blockchain deployments. Nodes in the network may fail or be taken down for maintenance requiring visibility across hybrid, traditional, cloud enabled and cloud native deployments. Service management is necessary to ease deployment woes for those looking to install code within their own data centers on-premises or on dedicated cloud servers and further to handle the life cycle of the deployments that includes security patches, critical updates, upgrades, change management and restarting services. In this paper, we provide a mechanism to optimally perform such operations with no disruption to the consensus and transactions for such emerging blockchain applications.
Jul 1, 2018·2018 IEEE International Conference on Internet of Things (iThings) and IEEE Green Computing and Communications (GreenCom) and IEEE Cyber, Physical and Social Computing (CPSCom) and IEEE Smart Data (SmartData)
As an alternative to the energy greedy proof-of-work, new blockchains constrain the set of participants whose selection is debatable. These blockchains typically allow a fixed consortium of machines to decide upon new transaction blocks. In this paper, we introduce the community blockchain that bridges the gap between these public blockchains and constrained blockchains. The idea is to allow potentially all participants to decide upon “some” block while restricting the set of participants deciding upon “one” block. We also propose an implementation called ComChain that builds upon the Red Belly Blockchain, the fastest blockchain we are aware of. It runs a consensus among the existing community to elect a new community. This reconfiguration speeds up as the number of removed nodes increases.
Jul 1, 2018·2018 IEEE International Conference on Internet of Things (iThings) and IEEE Green Computing and Communications (GreenCom) and IEEE Cyber, Physical and Social Computing (CPSCom) and IEEE Smart Data (SmartData)
Aleksey Charapko, Ailidani Ailijiang, Murat Demirbaş
The distributed consensus problem has been extensively studied in the last four decades as an important problem in distributed systems. Recent advances in decentralized consensus and blockchain technology, however, arose from a disparate model and gave rise to disjoint knowledge-base and techniques than those in the classical consensus research. In this paper we make a case for bridging these two seemingly disparate approaches in order to help transfer the lessons learned from the classical distributed consensus world to the blockchain world and vice versa. To this end, we draw parallels between blockchain consensus and a classical consensus protocol, Paxos. We also survey prominent approaches to improving the throughput and providing instant irreversibility to blockchain consensus and show analogies to the techniques from classical consensus protocols. Finally, inspired by the central role formal methods played in the success of classical consensus research, we suggest more extensive use of formal methods in modeling the blockchains and smartcontracts.
Jul 1, 2018·2018 IEEE International Conference on Internet of Things (iThings) and IEEE Green Computing and Communications (GreenCom) and IEEE Cyber, Physical and Social Computing (CPSCom) and IEEE Smart Data (SmartData)
Saulo dos Santos, Daniyal Khowaja, Muskan Vinayak, Ruppa K. Thulasiram · 5 authors
Cryptocurrencies especially bitcoin has received a lot of attention in the past year. The popularity has increased the volume of transactions in an unprecedented way. The time to complete a simple pairwise transaction from one virtual wallet to other takes time in proof-of-work where transactions are added into the Blockchain. At the same time, validating a pairwise transaction is very significant in this new technology as a payment option. Through this study, we propose a heuristic approach for validating pairwise transactions on cryptocurrencies. Our heuristic simulate all entities sending and receiving transactions among themselves. We use SHA256 algorithm to enhance our solution for pairwise transactions, creating a local Blockchain of transactions that has been used in the development of various Blockchain systems. For our experiments, we ran simulations in-file and in-memory with 2 million transactions in 290.39 and 5.34 seconds respectively. Our peak transactions per second was 6.887 using a file persistence version and 374.255 with in-memory version. Based on our experiments we conclude that is possible to improve the number of transactions processed per second increasing the size of the block as well as avoiding access to the file during the simulation. We also present some of our results implementing our algorithm in a parallel environment and hence show better performance.
Jul 1, 2018·2018 IEEE International Conference on Internet of Things (iThings) and IEEE Green Computing and Communications (GreenCom) and IEEE Cyber, Physical and Social Computing (CPSCom) and IEEE Smart Data (SmartData)
Giovanni Di Stasi, Stefano Avallone, Roberto Canonico, Giorgio Ventre
Bitcoin is a new digital currency created with the aim of being decentralized, peer-to-peer, censorship-resistant, borderless, scarce, fast and cheap to use. Since Bitcoin main way of operating is based on broadcast communications, e.g. all transactions of the currency reach all network peers, how to achieve scalability is one of the most important concerns for it to achieve wide usage. One of the proposals to improve its scalability takes the form of the Lightning Network (LN) which consists of an overlay network on top of the base Bitcoin layer. Such an overlay allows to perform a new kind of off-blockchain transactions, i.e. transactions not broadcast to the entire network, that, differently from previous off-blockchain solutions, do not require to put trust in any third entity. Important open problems of the LN are i) defining how payments should be routed and ii) establishing which fee policies intermediate nodes should apply for forwarding payments. The contributions of this work are twofold: we first propose a new, more general, way for nodes to apply fees for forwarding payments which allows to keep the network balanced and improve its performance in the long term. Secondly, we propose a new multipath routing payment scheme, based on the atomic multipath payment method, which is able to significantly reduce the fees paid by users, while being fast and also able to keep the network balanced.
Jul 1, 2018·2018 IEEE International Conference on Internet of Things (iThings) and IEEE Green Computing and Communications (GreenCom) and IEEE Cyber, Physical and Social Computing (CPSCom) and IEEE Smart Data (SmartData)
Emmanuelle Anceaume, Antoine Guellier, Romaric Ludinard
The presence of forks in permissionless blockchains is a recurrent issue. So far this has been handled either a posteriori, through local arbitration rules (e.g., “keep the branch which has required the most computational power”)which are applied once a fork is present in the blockchain, or a priori, via a Byzantine resilient agreement protocol periodically invoked by a committee of well identified and online nodes. In the former case, local arbitration rules guarantee that if they are correctly applied by a majority of users, then with high probability forks are progressively resolved, while in the latter case, the sequence of Byzantine resilient agreements decide on the unique sequence of blocks to be appended to the blockchain. The question we may legitimately ask is the following one: To prevent the period of uncertainty inherent to optimistic-based solutions, are we doomed to rely on the decisions made by a unique committee whose members are already actively involved in the creation of blocks? We negatively answer this question by presenting a solution that combines the best features of optimistic and pessimistic approaches: we leverage the presence of Unspent Transaction Output (UTXO)owners and “the public-key as identities” principle to make UTXO owners (i.e. users)self-organize in small Byzantine resilient committees “around” each new object (i.e., blocks and transactions)to decide on their validity. Validated objects are conflict-free, which guarantees the absence of blockchain forks and allows for fast-payment transactions facility. This is achieved without fearing Sybil attacks and selfish mining attacks. We are not aware of any solutions enjoying such features.
There is surge of interest to the blockchain technology not only in the scientific community but in the business community as well. Proof of Work (PoW) and Byzantine Fault Tolerant (BFT) are the two main classes of consensus protocols that are used in the blockchain consensus layer. PoW is highly scalable but very slow with about 7 (transactions/second) performance. BFT based protocols are highly efficient but their scalability are limited to only tens of nodes. One of the main reasons for the BFT limitation is the quadratic $O(n^2)$ communication complexity of BFT based protocols for $n$ nodes that requires $n \times n$ broadcasting. In this paper, we present the {\em Musch} protocol which is BFT based and provides communication complexity $O(f n + n)$ for $f$ failures and $n$ nodes, where $f < n/3$, without compromising the latency. Hence, the performance adjusts to $f$ such that for constant $f$ the communication complexity is linear. Musch achieves this by introducing the notion of exponentially increasing windows of nodes to which complains are reported, instead of broadcasting to all the nodes. To our knowledge, this is the first BFT-based blockchain protocol which efficiently addresses simultaneously the issues of communication complexity and latency under the presence of failures.
Blockchain technology is the underlying infrastructure and support technology to build trust of Bitcoin. It is not only an emerging technology that relies on pure mathematical method to create trust relationship in a distributed environment but also an innovative combination of hash algorithm, asymmetric cryptography, time stamp, consensus mechanism and many other technologies, with characteristics of decentralization, trustlessness, collective maintenance, reliable database, openness, security and untamperability, anonymity, verifiability and traceability, programmable and so on. This paper mainly introduces the technical characteristics and models of block chain, summarizes the development status and branch classification of Blockchain and outlines the future application of Blockchain technology.
Next-generation blockchain ecosystem will be fuelled by a large variety of blockchain systems. These systems increasingly demand proper cross-chain cooperation to provide richer functionalities and enhanced capabilities in the future landscape. How to enable such `interoperability' - effective communication and efficient data transfer across multiple blockchain systems is thus critical and facing many unprecedented theoretical and practical challenges. In this paper, we first clarify the definition of interoperability based on the cross disciplinary nature. Second, a roadmap of challenges needed to be addressed for interoperability has been laid out. Third, we articulate novel architectural approaches to fill in the gap by enforcing the interoperability from different blockchain layers.
A developing field of interest for the distributed systems and applied cryptography communities is that of smart contracts: self-executing financial instruments that synchronize their state, often through a blockchain. One such smart contract system that has seen widespread practical adoption is Ethereum, which has grown to a market capacity of 100 billion USD and clears an excess of 500,000 daily transactions. Unfortunately, the rise of these technologies has been marred by a series of costly bugs and exploits. Increasingly, the Ethereum community has turned to formal methods and rigorous program analysis tools. This trend holds great promise due to the relative simplicity of smart contracts and bounded-time deterministic execution inherent to the Ethereum Virtual Machine (EVM). Here we present KEVM, an executable formal specification of the EVM's bytecode stack-based language built with the K Framework, designed to serve as a solid foundation for further formal analyses. We empirically evaluate the correctness and performance of KEVM using the official Ethereum test suite. To demonstrate the usability, several extensions of the semantics are presented. and two different-language implementations of the ERC20 Standard Token are verified against the ERC20 specification. These results are encouraging for the executable semantics approach to language prototyping and specification.
Rachid El Bansarkhani, Matthias Geihs, Johannes Buchmann
Blockchain technology has arisen as a promising protocol to replace centralized and less efficient systems. In fact, for the first time, it is possible to achieve decentralized consensus without the need for trusted authorities, resulting in more efficient processes and saving both money and time.
Jul 1, 2018·2018 IEEE International Conference on Internet of Things (iThings) and IEEE Green Computing and Communications (GreenCom) and IEEE Cyber, Physical and Social Computing (CPSCom) and IEEE Smart Data (SmartData)
Distributed Ledger Technology (DLT) allows multiple organizations to share transaction data while protecting data integrity without the need for a central authority. However, there is a strong need to protect the privacy of transactions from parties that are not stakeholders of each transaction. Since DLT is a technology for sharing replicas of the same ledger data across multiple parties, protecting confidentiality and data privacy is essentially difficult. In this paper, we first define the properties of integrity and privacy requirements and discuss the requirements in typical use cases. Finally, we review how the requirements are addressed in existing implementations.
Luo Kan, Wei Yu, Amjad Hafiz Muhammad, Siyuan Wang · 6 authors
Blockchain is a new technology for data sharing between untrusted peers. However, it does not work well with massive transactions. Besides, there are high barriers between heterogeneous blockchain systems. In this paper, we proposed an innovative component-based framework for exchanging information across arbitrary blockchain system called interactive multiple blockchain architecture. In our architecture, a dynamic network of multi-chain is created for inter-blockchain communication. We propose the inter-blockchain connection model for routing management and messages transferring. Additionally, our proposed protocols provide transactions with atomicity and consistency in crossing-chain scene. In the end, our experiment results based on a network of private multiple blockchain systems show that the throughput is increased by a number of chains parallel running.
Owing to Satoshi Nakamoto's brilliant idea, a P2P public ledger is shown to be implementable in anonymous network. Any Internet user can then join the anonymous network and contribute to the P2P public ledger by providing their computing power or proof-of-work. The proof-of-work is a clever implementation of one-CPU-one-vote by anonymous participants, and it protects the Bitcoin ledger from illegal modification. To compensate the nodes for their work, a cryptocurrency called Bitcoin is issued and given to nodes. However, the very nature of anonymity of the ledger and the cryptocurrency prevent the technology from being used in fiat money economy. Cryptocurrencies are not traceable even if they are used for money laundering or tax evasion, and the value of cryptocurrencies is not stable but fluctuates wildly. In this white paper, we introduce Gruut, a P2P ledger to implement a universal financial platform for fiat money. For this purpose, we introduce a new consensus algorithm called `proof-of-population,' which is one instance of `proof of public collaboration.' It can be used for multiple purposes; as a P2P ledger for banks, as a powerful tool for payment, including micropayment, and as a tool for any type of financial transactions. Even better, it distributes the profit obtained from transaction fee, currently dominated by a third party, to peers that cannot be centralized. Energy requirements of Gruut are so low that it is possible to run our software on a smartphone or on a personal computer without a graphic card.
The Enterprise Ethereum Client Specification by the Enterprise Ethereum Alliance defines the requirements which Ethereum Clients offering private smart contract capabilities should comply with. This specification though ground breaking, misses some important blockchain requirements and does not fully consider the requirements of Ethereum Clients offering Private Sidechain capabilities. This paper presents the case for Private Sidechains and defines requirements to be complied with to deliver this technology. The capabilities of three blockchain clients have been analysed based on the requirements: Quorum, Parity, and Hyperledger Fabric. Quorum and Hyperledger Fabric operate as private consortium blockchains where as Parity delivers private transaction capabilities on top of Ethereum MainNet. These differing approaches has led to different strengths and weaknesses which has resulted in each client not complying with one or more key requirement. In particular, none of the reviewed blockchain clients support the ability to determine bootstrap information to establish on-demand blockchains and none of the clients support secure management and pinning from Ethereum MainNet. This paper presents Ethereum Private Sidechains and a range of technologies which allow it to deliver on complex sidechain requirements. Ethereum Registration Authorities are presented, which allow entities which have not previously interacted to securely obtain information to bootstrap a sidechain, and a Management and Pinning strategy is described which allows the state of a sidechain to be securely pinned to Ethereum MainNet without compromising privacy.
Popularly known for powering cryptocurrencies such as Bitcoin and Ethereum, blockchains is seen as a disruptive technology capable of impacting a wide variety of domains, ranging from finance to governance, by offering superior security, reliability, and transparency in a decentralized manner. In this tutorial presentation, we first study the original Bitcoin design, as well as Ethereum and Hyperledger, and reflect on their design from an academic perspective. We provide an overview of potential applications and associated research challenges, as well as a survey of ongoing research projects. We mention opportunities blockchain creates for event-based systems. Finally, we conclude with a walkthrough showing the process of developing a decentralized application (ĐSApp), using a popular Smart Contract language (Solidity) for the blockchain platform of Ethereum.
Chuka Oham, Raja Jurdak, Salil S. Kanhere, Ali Dorri · 5 authors
In this paper, we propose a partitioned BlockChain based Framework for Auto-insurance Claims and Adjudication (B-FICA) for CAVs that tracks both sensor data and entity interactions with two-sided verification. B-FICA uses permissioned BC with two partitions to share information on a need to know basis. It also uses multi-signed transactions for proof of execution of instructions, for reliability and auditability and also uses a dynamic lightweight consensus and validation protocol to prevent evidence alteration. Qualitative evaluation shows that B-FICA is resilient to several security attacks from potential liable entities. Finally, simulations show that compared to the state of the art, B-FI CA reduces processing time and its delay overhead is negligible for practical scenarios and at marginal security cost.
We propose definitions and implementations of "S-money" - virtual tokens designed for high value fast transactions on networks with relativistic or other trusted signalling constraints, defined by inputs that in general are made at many network points, some or all of which may be space-like separated. We argue that one significant way of characterising types of money in space-time is via the "summoning" tasks they can solve: that is, how flexibly the money can be propagated to a desired space-time point in response to relevant information received at various space-time points. We show that S-money is more flexible than standard quantum or classical money in the sense that it can solve deterministic summoning tasks that they cannot. It requires the issuer and user to have networks of agents with classical data storage and communication, but no long term quantum state storage, and is feasible with current technology. User privacy can be incorporated by secure bit commitment and zero knowledge proof protocols. The level of privacy feasible in given scenarios depends on efficiency and composable security questions that remain to be systematically addressed.