In this computer world, digital transformation is a thoughtful and unavoidable one. The impact of this digital transformation is reflected both in government and private sectors. Amongst these, financial and business sectors must face a lot of challenges to undergo this transformation. In financial sector, transaction between two parties has become a part of their life. A transaction normally happens with the help of few centralized authorities. In the centralized system, all the transaction needs to be verified and signed by a centralized authority. But there are many issues exist in executing this methodology. Among them two important issues concerned with financial sector are, large storage space required for processing and cost of committing a transaction. Blockchain, a blooming technology has overcome this drawback by changing the execution model. Blockchain makes use of distributed ledger and crypto currencies, thus converting the centralized processing into a distributed processing system. Here, all the ledgers needed for the transaction are maintained as distributed database. Block chain also minimizes the process by executing all the rules with the help of software. The software that acts as the execution unit of the blockchain is known as smart contract. Smart contracts facilitate the implementation of user-defined operations of uninformed complexity which are not probably plain cryptocurrency protocols. It facilitates user to realize the constraints, instructions, and policies of the domain applications. To explore the feature of the smart contracts, it should be properly designed and coded. Smart contracts work in the application layer of the blockchain. All the rules for the applications can be realized using smart contract. Data for the verification can also be obtained from external sources. i.e., usually, the data for the contract execution is supplied through the transactions. But it can also be obtained from external sources. Each smart contract in the blockchain is assigned a unique address of size 20 bytes. To run a contract, the transaction must be sent to the contract&s;s address. The smart contract performs the necessary operation and when all the protocols are satisfied, the smart contract by itself executes the transaction. This transaction will be run by different miners whose output will be validated and the block of the miner who wins it will be added to the chain. Smart contracts run on Ethereum virtual machine and solidity is the programming language used for writing smart contracts. Ethereum smart contracts need gas to run. When the required gas is not found, then the requested transactions cannot be executed. In this chapter, the detailed explanation of the smart contract along with its architecture is discussed. Also, designing of the smart contract using the programming language solidity is discussed.
Munavwar Shaikh, Charles Shibu, Enrico Angeles, Deepa Pavithran
Data storage in IoT systems describe how data is pushed from the sensor and where it will be stored. In Bitcoin, there is a limit to the number of transactions that can be stored in the block, similarly in Ethereum it is limited by the gas limit in block. An IoT infrastructure have several applications that includes a sensor collecting data from physical environment. Storing a large amount data in a blockchain faces several challenges due to the distributed nature of the blockchain, high transaction processing time, and reduced scalability. Hence it is crucial to identify what data should be stored and how to store it in a secure way. In this paper, we provide how data is being stored in various blockchain based IoT applications and provides data storage compliance in treating IoT data in a blockchain environment.
With the tremendous growth of IoT application, providing security to IoT systems has become more critical. In this paper, a technique is presented to ensure the safety of Internet of Things (IoT) devices. This technique ensures hardware and software security of IoT devices. Blockchain technology is used for software security and hardware logics are used for hardware security. For enabling a Blockchain, Ethereum Network is used for secure peer-to-peer transmission. A prototype model is also used using two IoT nodes to demonstrate the security logic.
Jae-Yun Kim, Jun-Mo Lee, Yeon-Jae Koo, Sang-Hyeon Park · 5 authors
Ethereum is a popular account-based blockchain whose number of accounts and transactions has skyrocketed, causing its data explosion. As a result, ordinary clients using PCs or smartphones cannot easily bootstrap as a full node, but rely on other full nodes to verify transactions, thus being exposed to security risks. The most serious overhead is caused by synchronizing the state of all accounts in the block's state trie, which takes several tens of gigabytes. Observing that more than 95% of the accounts are dormant, we propose a novel state optimization technique, named Ethanos. Ethanos downsizes the state trie by periodically emptying it, and then re-build it only with the active accounts used in the period's transactions. Ethanos runs transactions using the accounts available in the current period's state trie as well as those available at the end of the previous period's state trie. For an account in neither of the tries, the account first restores itself by transmitting a restore transaction. One important result of this state management is that a node can now bootstrap only with the latest period's state trie, yet can fully verify all transactions thereafter. We evaluated Ethanos with real Ethereum transactions for 300,000 blocks from the 7.0 million block, with a one-week period of emptying the state trie. Our result shows that Ethanos can sharply reduce the state trie, with only a tiny fraction of the restore transactions. More importantly, unlike the Ethereum state trie which continues to grow as time goes on, the Ethanos state trie size at the end of each period is bounded by a few hundred MB, when there are more than one million, one-week-active accounts.
Internet of Things (IoT) is a relatively new concept in computer science that connects devices with constrained resources to insecure internet through different technologies. IoT's fundamental components, including the wireless sensor networks and the internet, have an unsecured foundation that leads to DoS attacks, namely, sinkhole, blackhole, and grey hole attacks. To maintain the integrity and security of the IoT networks, many researchers implemented distributed ledgers in IoT environments. In this paper, we designed a hybrid framework between blockchain and IoT devices; the aim is to secure data transmission in IoT networks using blockchain technology to defend against DoS attacks. Our framework is called HFSDT-IoT. The method proposed in this paper consists of two phases to maintain security in the IoT. In the first phase, both a list of attackers and a safe list based on the Ethereum Proof-of-Stake (PoS) protocol is used, which complemented by utilizing the proposed IDSs Intrusion Detection System to discover malicious things. In the second phase, to decrease the obstacles in facilitating communication between blockchains, the inter-blockchain communication model creates a network of multiple blockchains with secp256k1 encryption used for heterogeneous blockchains. The experimental results of simulated scenarios show the HFSDT-IoT strategy can achieve better results when DoS attacks were launched compared to other blockchain-based methods, namely Bubble of Trust and Credibility Verification Method.
Without the requirement of trusted third parties (TTPs), Blockchain builds an environment where mutual trust among valid members is established. Nevertheless, the associated transparency property caused a hazard to real-world applications because every on-chain information is exposed to the public. That implies those applications involving sensitive data or personal information, which require security and privacy protection, are not suitable to be implemented in Blockchain, directly. Fully homomorphic encryption (FHE) schemes have been treated as one of the end-to-end solutions to data security and privacy protection problems. In this article, we examine the possibility (or cost) of embedding the ideal lattice-based FHE into the Ethereum Blockchain for building up a new trustworthy framework with security and privacy protection capability. Due to the limitations of current Blockchain, the execution of FHE is conducted off-chain; at the same time, on-chain members can call FHE-based functions to directly compute the ciphertext domain operations after their Smart Contracts have been deployed to the Blockchain. To illustrate and benchmark the examining results of our framework, an FHE and Blockchain-based Vickrey auction system is also developed, in which the online bidding prices are kept in secret. Simultaneously, the determination of the winner and the transferring of payments are conducted autonomously by Smart Contracts.
Bishakh Chandra Ghosh, Tanay Bhartia, Sourav Kanti Addya, Sandip Chakraborty
With the increasing adoption of private blockchain platforms, consortia operating in various sectors such as trade, finance, logistics, etc., are becoming common. Despite having the benefits of a completely decentralized architecture which supports transparency and distributed control, existing private blockchains limit the data, assets, and processes within its closed boundary, which restricts secure and verifiable service provisioning to the end-consumers. Thus, platforms such as e-commerce with multiple sellers or cloud federation with a collection of cloud service providers cannot be decentralized with the existing blockchain platforms. This paper proposes a decentralized gateway architecture interfacing private blockchain with end-users by leveraging the unique combination of public and private blockchain platforms through interoperation. Through the use case of decentralized cloud federations, we have demonstrated the viability of the solution. Our testbed implementation with Ethereum and Hyperledger Fabric, with three service providers, shows that such consortium can operate within an acceptable response latency while scaling up to 64 parallel requests per second for cloud infrastructure provisioning. Further analysis over the Mininet emulation platform indicates that the platform can scale well with minimal impact over the latency as the number of participating service providers increases.
Christian Bräm, Marco Eilers, Péter Müller, Robin Sierra · 5 authors
Smart contracts are programs that execute inside blockchains such as Ethereum to manipulate digital assets. Since bugs in smart contracts may lead to substantial financial losses, there is considerable interest in formally proving their correctness. However, the specification and verification of smart contracts faces challenges that do not arise in other application domains. Smart contracts frequently interact with unverified, potentially adversarial outside code, which substantially weakens the assumptions that formal analyses can (soundly) make. Moreover, the core functionality of smart contracts is to manipulate and transfer resources; describing this functionality concisely requires dedicated specification support. Current reasoning techniques do not fully address these challenges, being restricted in their scope or expressiveness (in particular, in the presence of re-entrant calls), and offering limited means of expressing the resource transfers a contract performs.
In this paper, we present a novel specification methodology tailored to the domain of smart contracts. Our specification constructs and associated reasoning technique are the first to enable: (1) sound and precise reasoning in the presence of unverified code and arbitrary re-entrancy, (2) modular reasoning about collaborating smart contracts, and (3) domain-specific specifications based on resources and resource transfers, which allow expressing a contract's behavior in intuitive and concise ways and exclude typical errors by default. We have implemented our approach in 2vyper, an SMT-based automated verification tool for Ethereum smart contracts written in the Vyper language, and demonstrated its effectiveness in succinctly capturing and verifying strong correctness guarantees for real-world contracts.
Christian Bräm, Marco Eilers, Péter Müller, Robin Sierra · 5 authors
Smart contracts are programs that execute inside blockchains such as Ethereum to manipulate digital assets. Since bugs in smart contracts may lead to substantial financial losses, there is considerable interest in formally proving their correctness. However, the specification and verification of smart contracts faces challenges that do not arise in other application domains. Smart contracts frequently interact with unverified, potentially adversarial outside code, which substantially weakens the assumptions that formal analyses can (soundly) make. Moreover, the core functionality of smart contracts is to manipulate and transfer resources; describing this functionality concisely requires dedicated specification support. Current reasoning techniques do not fully address these challenges, being restricted in their scope or expressiveness (in particular, in the presence of re-entrant calls), and offering limited means of expressing the resource transfers a contract performs. In this paper, we present a novel specification methodology tailored to the domain of smart contracts. Our specification constructs and associated reasoning technique are the first to enable: (1) sound and precise reasoning in the presence of unverified code and arbitrary re-entrancy, (2) modular reasoning about collaborating smart contracts, and (3) domain-specific specifications based on resources and resource transfers, which allow expressing a contract's behavior in intuitive and concise ways and exclude typical errors by default. We have implemented our approach in 2vyper, an SMT-based automated verification tool for Ethereum smart contracts written in the Vyper language, and demonstrated its effectiveness in succinctly capturing and verifying strong correctness guarantees for real-world contracts.
The article reviews the essence of blockchain – the technology of new generation, raised from the computer and internet development. The article also analyses several aspects in legal regulation of one of the most famous cryptocurrencies: Ethereum by using the blockchain technology. Except for that, the article describes steps of computer and internet development and the involvement of blockchain in these steps, as a revolutionary invention. The article analyses the essence of blockchain technology, the steps of its development and also, coming from its high confidentiality, the possibilities of its legal regulation by the states. In this regard, several countries are represented as an example (Great Britain, Vietnam, Canada). Except for blockchain, the article reviews essence and specification of Ethereum, as the cryptocurrency, as well as smart contract, analyses the area of smart contract development and the indispensability of its legal regulation, because they have an ability to detach simple consumer agreements in one of the directions of digital economy – electronic commerce, in the nearest future. In addition to this, the binary nature Ethereum is also analyzed, in particular it can be a method of payment, as well as have a form of a legally binding deal – contract with the high self-fulfillment mechanism and securing parties confidentiality standards.
We propose a novel framework for off-chain execution and verification of computationally-intensive smart contracts. Our framework is the first solution that avoids duplication of computing effort across multiple contractors, does not require trusted execution environments, supports computations that do not have deterministic results, and supports general-purpose computations written in a high-level language. Our experiments reveal that some intensive applications may require as much as 141 million gas, approximately 71x more than the current block gas limit for computation in Ethereum today, and can be avoided by utilizing the proposed framework.
In recent years we have witnessed a dramatic increase in the applications of blockchain and smart contracts in a variety of contexts, including supply-chain, decentralized finance, and international money transfers. However, a critical stumbling block to their further adoption is smart contract security (or more precisely, the lack thereof). Smart contracts, once deployed on a blockchain, are immutable. Hence, unlike traditional software systems, smart contracts are particularly vulnerable to latent security issues. It is therefore imperative that security analysis tools be developed that help improve smart contract security if they are to have continued adoption and impact. A particularly widespread class of security vulnerabilities that afflicts Ethereum smart contracts is the gas-based denial of service (DoS). Briefly, these vulnerabilities generally present in contracts containing unbounded loops. \n \nTo address the described problem, we present Gas Gauge, a tool aimed at detecting gas-based DoS vulnerabilities in Ethereum smart contracts. Gas Gauge consists of three major components: the Detection Phase, Identification Phase, and Correction Phase. First, we describe a highly accurate static analysis approach that finds all the loops in a smart contract (the Detection Phase). Then, a set of inputs that causes the contract to run out of gas is generated using a fuzzing approach. The last component uses static analysis and run-time verification to predict the maximum loop bounds consistent with allowable gas usage automatically. This component uses a binary search approach and an independent parallel processing design to speed up the process. Each part of the tool can be used separately for different purposes or all together to detect, identify and help repair the contracts vulnerable to out-of-gas behaviors. \n \nGas Gauge was tested on 2,000 real-world solidity smart contracts. The results were compared to seven state-of-the-art tools, and it was empirically demonstrated that Gas Gauge is highly effective and useful.
Mahboob Ullah, Maria Shaikh, Imran Abbas Jadoon, Muhammad Azizullah Khan · 5 authors
Purpose of the Study: In this research, the association between the COVID-19 pandemic and cryptocurrencies' price volatility has been examined.
 Methodology: To check the contagion effects of the COVID-19 pandemic on the price volatility of cryptocurrencies: BITCOIN, LITECOIN, XRP(RIPPLE), and ETHEREUM, the prices of all four are deployed from 10th August 2016 to 10th August 2020. The exponential generalized autoregressive conditional heteroscedastic (EGARCH) model is used to check the leverage effect exists or not. Stata 16 has been used to execute all the tests.
 Main Findings: The study's findings indicated that the leverage effect on the price volatility is present for LITECOIN, XRP(RIPPLE), and ETHEREUM but not for BITCOIN.
 Applications of the study: This study is significant for investors to develop strategies for investments and secure the transactions and control the creation of additional currency units. Also, it gives insight to the policy and decision-makers to articulate proper guidelines to overcome or minimize the effect of COVID-19 on cryptocurrency.
 Novelty/Originality of this Study: The motive for taking the crypto market into account is that the crypto market is one of the emerging markets and has started to have significance worldwide, linking with financial markets and economic growth. The leverage effect of COVID-19 is considered in this study as the epidemic has affected the supply and demand of goods due to lockdowns, blockages, and disruptions in delivery chains that lead to undiminished economic growth.
In this paper, two of the main Blockchain development platforms, Ethereum and EOS.IO are compared. The objective is to help developers select the most appropriate platform as the back-end Blockchain for their apps. A decentralized application was implemented on each of the platforms triggering basic operations and timing them. The simulations were performed on Microsoft's Azure cloud, running up to 150 Blockchain nodes while recording the user response time, the CPU utilization, and the totally used memory in Mbytes. The results in this study show that although recognized as a major competitor to Ethereum, EOS.IO fails to outperform the Ethereum platform in this experiment, recording a very high response time in comparison to Ethereum.
The purpose of this paper is to select the best GARCH-type model for modelling the volatility of Bitcoin, Bitcoin Cash, Litecoin, Dogecoin and Ethereum. GARCH (1,1), IGARCH(1,1), EGARCH(1,1), TGARCH(1,1) and CGARCH(1,1) are used on the cryptocurrencies closing day return. We select the model with the highest Maximum Likelihood and run an OLS regression on the conditional volatility to measure the day-of-the-week effect. The findings show that EGARCH(1,1) model best suits Bitcoin, Litecoin, Dogecoin and Ethereum data and that the GARCH(1,1) model suits best Bitcoin data. The results show a significant presence of day-of-the-week effects on the conditional volatility of some days for Bitcoin, Bitcoin Cash and Ethereum. Wednesday has a significant negative effect on Bitcoin conditional volatility. Friday, Saturday and Sunday are found to be significant and positive on Bitcoin Cash conditional volatility. Finally, Saturday is found to be significant and positive on Ethereum conditional volatility.
Crypto tokens are digital assets, similar to the coins of a cryptocurrency, except that they do not have their own blockchain or distributed ledger. Rather, they are built on top of an existing one. Areas of application include their use as means of investment, as a local currency in a decentralized application, as well as means for building an ecosystem or a community. Depending on the purpose, it is common to categorize tokens into payment tokens, security tokens and utility tokens. The distinction is of interest since in most jurisdictions, security tokens are more heavily regulated than other tokens. In this paper, we present a heuristic approach towards automatic detection of security tokens from blockchain data. To this end, we first discuss several methods for the (semi-) automatic identification of token contracts. Then we attempt to identify the token type. For our analysis, we examine both the deployed bytecode and the calls to token contracts that we extract from transaction data of the Ethereum main chain up to block 9500000, mined on Feb 17, 2020.
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
Ethereum is a promising but revolutionary blockchain approach to support rich computational services enabled by Turing-complete instructions, also known as smart contract. Using smart contract as "back-end", any party can publish its Decentralized Applications (DApps) available to all Internet users. In other words, blockchain and smart contract enable evolving existing Internet services and applications to decentralised versions. With the developments of versatile Internet applications, the QoS requirements can be very different. For example, new-age applications such as AR/VR can be quite sensitive to even millisecond delays. End-to-end transaction latency in blockchain is a critical factor that affects the performance of DApps. It is the time duration from sending out a transaction (from the client) to having the transaction recorded on the chain. In this paper, we experimentally evaluate the end-to-end latency in Ethereum and discuss the factors that may affect latency on the Ethereum main-net. It has a particular focus on the gas price because it is a key parameter controlled by users. The experiment results demonstrate some counter intuitive finding, e.g. increasing gas price does not reduce the Ethereum end-to-end latency significantly for a certain range of gas prices.
Lin Zhao, Sourav Sen Gupta, Arijit Khan, Robby Luo
With over 42 billion USD market capitalization (October 2020), Ethereum is the largest public blockchain that supports smart contracts. Recent works have modeled transactions, tokens, and other interactions in the Ethereum blockchain as static graphs to provide new observations and insights by conducting relevant graph analysis. Surprisingly, there is much less study on the evolution and temporal properties of these networks. In this paper, we investigate the evolutionary nature of Ethereum interaction networks from a temporal graphs perspective. We study the growth rate and model of four Ethereum blockchain networks, active lifespan and update rate of high-degree vertices. We detect anomalies based on temporal changes in global network properties, and forecast the survival of network communities in succeeding months leveraging on the relevant graph features and machine learning models.
The amalgamation of different generations of mobile cellular networks around the globe has resulted in diverse data speed experiences for end users. At present there are no defined mechanisms in place for a subscriber of one mobile network operator (MNO) to use the services of a WiFi provider. Cellular and Data Service providers also have no standardized procedures to securely interact with each other, and to allow their subscribers to use third party services on a pay-as-you-go basis. This paper proposes a blockchain-based offloading framework that allows a subscriber of a mobile operator to temporarily use another MNO or WiFi provider's higher speed network. Smart contracts allow diverse entities such as MNOs, Brokers and WiFi Providers to automatically execute mutual agreements to enable the utilization of third party infrastructure in a secure and controlled manner. To test the proposed framework, the offloading of a subscriber from 3G/4G/4G-LTE/5G networks to a fixed broadband WiFi network was carried out and the results analyzed. The offloading framework was implemented using the ns-3 network simulator, and the Ethereum blockchain smart contract features were used for the settlement of invoices.
This paper presents SAILFISH, a scalable system for automatically finding state-inconsistency bugs in smart contracts. To make the analysis tractable, we introduce a hybrid approach that includes (i) a light-weight exploration phase that dramatically reduces the number of instructions to analyze, and (ii) a precise refinement phase based on symbolic evaluation guided by our novel value-summary analysis, which generates extra constraints to over-approximate the side effects of whole-program execution, thereby ensuring the precision of the symbolic evaluation. We developed a prototype of SAILFISH and evaluated its ability to detect two state-inconsistency flaws, viz., reentrancy and transaction order dependence (TOD) in Ethereum smart contracts. Further, we present detection rules for other kinds of smart contract flaws that SAILFISH can be extended to detect. Our experiments demonstrate the efficiency of our hybrid approach as well as the benefit of the value summary analysis. In particular, we show that S SAILFISH outperforms five state-of-the-art smart contract analyzers (SECURITY, MYTHRIL, OYENTE, SEREUM and VANDAL ) in terms of performance, and precision. In total, SAILFISH discovered 47 previously unknown vulnerable smart contracts out of 89,853 smart contracts from ETHERSCAN .
Samuel H. Christie, Amit K. Chopra, Munindar P. Singh
Current blockchain approaches for business contracts are based on smart contracts, namely, software programs placed on a blockchain that are automatically executed to realize a contract. However, smart contracts lack flexibility and interfere with the autonomy of the parties concerned. We propose Hercule, an approach for declaratively specifying blockchain applications in a manner that reflects business contracts. Hercule represents a contract via regulatory norms that capture the involved parties' expectations of one another. It computes the states of norms (hence, of contracts) from events in the blockchain. Hercule's novelty and significance lie in that it operationalizes declarative contracts over semistructured databases, the underlying representation for practical blockchain such as Hyperledger Fabric and Ethereum. Specifically, it exploits the map-reduce capabilities of such stores to compute norm states. We demonstrate that our implementation over Hyperledger Fabric can process thousands of events per second, sufficient for many applications.
Presently modern technology makes a significant contribution to the transition from traditional healthcare to smart healthcare systems. Mobile health (mHealth) uses advances in wearable sensors, telecommunications and the Internet of Things (IoT) to propose a new healthcare concept centered on the patient. Patients' real-time remote continuous health monitoring, remote diagnosis, treatment, and therapy is possible in an mHealth system. However, major limitations include the transparency, security, and privacy of health data. One possible solution to this is the use of blockchain technologies, which have found numerous applications in the healthcare domain mainly due to theirs features such as decentralization (no central authority is needed), immutability, traceability, and transparency. We propose an mHealth system that uses a private blockchain based on the Ethereum platform, where wearable sensors can communicate with a smart device (a smartphone or smart tablet) that uses a peer-to-peer hypermedia protocol, the InterPlanetary File System (IPFS), for the distributed storage of health-related data. Smart contracts are used to create data queries, to access patient data by healthcare providers, to record diagnostic, treatment, and therapy, and to send alerts to patients and medical professionals.
Selfish mining, as a serious threat to blockchain, has been attracting attentions from academic and industry. Stochastic modeling has been explored to quantitatively investigate selfish mining in imperfect blockchain networks. However, prior modeling-based analysis approaches have some of the following issues: (1) only focus on Bitcoin or Ethereum, or (2) ignore extended forks and just consider natural forks, or (3) only compute the mining revenue without assessing the performance and security of the blockchain system when the system suffers from selfish mining. In this paper, we aim to address these issues. We build a Markov chain to make quantitative analysis of selfish mining in imperfect Bitcoin and Ethereum networks with natural and extended forks. Formulas are derived to calculate the mining revenue for the selfish pool (comprising selfish miners) and honest miners, respectively. Moreover, we derive the formulas of performance metrics (namely, transactions per second and stale block ratio) and the formula of security metric (namely, the probability of double-spending success) of the system. These quantitative results can help understand the impact of selfish mining on imperfect blockchain networks and then help the detection of selfish mining.
Blockchain like Bitcoin and Ethereum suffer from scalability issues. Sharding is one of the most promising and leading solutions to scale blockchain. The basic idea behind sharding is to divide the blockchain network into multiple committees, where each processing a separate set of transactions, rather than the entire network processes all transactions. In this paper, we propose a probabilistic approach to analyze the security of sharding-based blockchain protocols. Based on this approach, we investigate the threat of Sybil attacks in these protocols. The key contribution of our paper is a tractable probabilistic approach to accurately compute the failure probability that at least one committee fails and ultimately compute the probability of a successful attack. To show the effectiveness of our approach, we conduct a numerical and comparative analysis of the proposed approach with existing approaches.