We study distributed declarative workflow execution in an adversarial setting.In this setting, parties to an agreed-upon workflow do not trust each other to follow that workflow, or suspect the other party might misrepresent proceedings at a later time.We demonstrate how distributed declarative workflow execution can be implemented as smart contracts, guaranteeing (I) enforcement of workflow semantics, and (II) an incontrovertible record of workflow execution history.Crucially, we achieve both properties without relying on a trusted third party.The implementation is based on the Ethereum blockchain, inheriting the security properties (I) and (II) from the guarantees given by that chain.A recurring challenge for both the implementation and the analysis is the cost of operations on Ethereum: This cost must be minimised for honest parties, and an adversary must be prevented from inflicting extra cost on others.
Public key server is a simple yet effective way of key management in secure end-to-end communication. To ensure the trustworthiness of a public key server, transparent log systems such as CONIKS employ a tamper-evident data structure on the server and a gossiping protocol among clients in order to detect compromised servers. However, due to lack of incentive and vulnerability to malicious clients, a gossiping protocol is hard to implement in practice. Meanwhile, alternative solutions such as EthIKS are not scalable. This paper presents Trusternity, an auditing scheme relying on Ethereum blockchain that is easy to implement, scalable and inexpensive to operate.
Zhi Li, Layne Liu, Ali Vatankhah Barenji, Waiming Wang
This paper proposes a cloud-based manufacturing knowledge sharing system for injection mould redesign (IMR) based on blockchain technology. In our proposed system, private cloud is used to store the IMR knowledge, and blockchain provides standards and protocols for implementing the system as well as ensuring the security in a trustless environment. K-Nearest Neighbors is used for retrieving the blockchain-based document knowledge. The proposed system not only can facilitate injection mould redesign, but also provide a mechanism for knowledge owners to share their own assets securely.
Yinghui Zhang, Robert H. Deng, Jiangang Shu, Kan Yang ¡ 5 authors
As a very attractive computing paradigm, cloud computing makes it possible for resource-constrained users to enjoy cost-effective and flexible resources of diversity. Considering the untrustworthiness of cloud servers and the data privacy of users, it is necessary to encrypt the data before outsourcing it to the cloud. However, the form of encrypted storage also poses a series of problems, such as: How can users search over the outsourced data? How to realize user-side verifiability of search results to resist malicious cloud servers? How to enable server-side verifiability of outsourced data to check malicious data owners? How to achieve payment fairness between the user and the cloud without introducing any third party? Towards addressing these challenging issues, in this paper, we introduce TKSE, a trustworthy keyword search scheme over encrypted data without any third party, trusted or not. In TKSE, the encrypted data index based on digital signature allows a user to search over the outsourced encrypted data and check whether the search result returned by the cloud fulfills the pre-specified search requirements. In particular, for the first time, TKSE realizes server-side verifiability which protects honest cloud servers from being framed by malicious data owners in the data storage phase. Furthermore, blockchain technologies and hash functions are used to enable payment fairness of search fees without introducing any third party even if the user or the cloud is malicious. Our security analysis and performance evaluation indicate that TKSE is secure and efficient and it is suitable for cloud computing.
Throughout the history of mankind, trusted relationships have played a vital part in every \ntransaction humans have made. Those transactions belong to a spectrum that starts from \neveryday life decisions and acts, to a more complex, sensitive and wide area that even nations \nare involved. \nBefore the era of globalization of telecommunications that we live in, achieving trust was \nmore related to human relations. Even though that the meaning of trust is known to all, it is \nhard to find a definition that strictly describes it. \nTrust is multidimensional, multidisciplinary and multifaceted concept. Many definitions can \nbe found in literature and are related to notions as goodness, strength, reliability, integrity, \nability or character of a person or thing. A trust relationship involves two parties, a trustor \nand a trustee. The trustor is the person that holds confidence, belief on the reliability of \nanother person or thing which is the other party, the trustee. (Zheng & Valtteri Niemi, \nTowards User Driven Trust Modeling and Management, 2009) \nHow though trust is established in modern computer networks, where the notions of the \ntrustor and trustee are not represented by strictly humans, but from entities that might never \nhave had a relationship upon the trust can be build. \nIn this project we will study the achievement of trust in traditional kinds of networks such as \nad-hoc, mobile and wireless and we will examine the ability to elevate the trust level in a \ncomputer network using the under development and mostly promising blockchain network. \nThe network is going to be setup as a private blockchain network, where all the nodes that \nconsist it, will be pre-set from an administrative team. The computers that will participate will \nhave all the requirements in order to connect to the private network running as services on \nboot. \nThe application will run on each node and on starting the application the very first check will \nbe to start the node and connect to the network. Only if the network has been found and the \nnode is connected to it, the application proceeds with checking the presence of web3js and \nonly after successfully checking the communication of the web3js with the network, the user \nis prompt with the login page. \nThe authorization of the user is checked upon a smart contract on the blockchain network \nand after a successfully prompt from the smart contract, the credentials are checked, in our \ncase, on a fake backend where a JWT token is issued to the user in order to use the application \ndepending on the role that he has.
Weiqi Dai, Jun Deng, Qinyuan Wang, Changze Cui ¡ 6 authors
Due to the increasing total value of the digital currency, the security of encryption wallet is becoming more and more important. The hardware-based wallet is safe, but it is inconvenient because users need to carry an additional physical device, the software-based wallet is convenient, but the safety cannot be guaranteed. All these wallets need to synchronize the blockchain, while most current mobile devices do not have the capability to store all blocks. To solve these problems, mobile devices can use simplified payment verification (SPV). Nevertheless, in existing methods, there is no good way to protect the verification process of the transaction. In this paper, we design a secure blockchain lightweight wallet based on Trustzone to protect SPV. It is more portable compared with the hardware wallet, and safer than the software wallet. Through the isolation, it can also protect the private key and the wallet's address from being stolen by the attackers no matter whether the Rich OS is malicious or not. Meanwhile, it can protect the verification process by verifying transactions in the secure execution environment (SEE), and keep the local block headers unreadable directly from the Rich OS through encryption. We deploy it on the RASPBERRY PI 3 MODEL B development board. The result of the experiment shows that it has little impact on the system.
Yanqi Zhao, Yannan Li, Qilin Mu, Bo Yang ¡ 5 authors
The cyber physical system (CPS) has gained considerable success in large-scale distributed integration environment. In such systems, the sensor devices collect data which would be disseminated via reliable manner to all interested co-operant entities from the physical world. However, highly unreliable environment of CPS, for example, a number of limitations of existing network middle wares, makes secure and reliable data distribution services a challenge issue. In this paper, we propose a new architecture called secure pub-sub (SPS) without middle ware, i.e., blockchain-based fair payment with reputation. In SPS, publishers publish a topic on the blockchain and subscribers specify an interest message by making a deposit to subscribing the topic. Then, if the interest message matches the topic, the publisher transmits the encrypted content of the topic to the blockchain such that the subscribers can decrypt the ciphertext to obtain the content, and mark the publisher as its reputation. Finally, the publisher receives the payment from the subscriber. The new proposal provides confidentiality and reliability of data, anonymity of subscribers and payment fairness between the publishers and subscribers. Different from the traditional pub-sub services, no trusted third party is involved in our system due to employing blockchain technique. The security of the proposed SPS is analyzed as well. The implementation of the protocol on Ethereum of smart contract demonstrates the validity of SPS.
With the widespread of E-commerce, the need of a trusted system to ensure the delivery of traded items is crucial. Current proof of delivery (PoD) systems lacks transparency, traceability, and credibility. These systems are mostly centralized and rely on trusted third parties (TTPs) to complete the delivery between sellers and buyers. TTPs can be costly, a single point of failure, and subject to hacking, privacy evasion, and compromise. The blockchain is an immutable, trusted, and decentralized ledger with logs and events that can be used for transparency, traceability, and tracking. In this paper, we present a solution and a general framework using the popular permissionless Ethereum blockchain to create a trusted, decentralized PoD system that ensures accountability, auditability, and integrity. The solution uses Ethereum smart contracts to prove the delivery of a shipped item between a seller and a buyer irrespective of the number of intermediate transporters needed. In our proposed solution, all participating entities are incentivized to act honestly by using a double deposit collateral. Automated payment in ether is an integral part of a solution to ensure that every entity gets its intended share of ether upon successful delivery. An arbitration mechanism is also incorporated if a dispute arises during the shipping process. In this paper, we show how we implemented, verified, and tested the proper functionality of our PoD solution. We also provide security analysis and give estimates of the cost consumption in ether gas. We made the full code of the Ethereum smart contracts publicly available at Github.
A treasury system is a community-controlled and decentralized collaborative decision-making mechanism for sustainable funding of blockchain development and maintenance. During each treasury period, project proposals are submitted, discussed, and voted for; top-ranked projects are funded from the treasury. The Dash governance system is a real-world example of such kind of systems. In this work, we, for the first time, provide a rigorous study of the treasury system. We modelled, designed, and implemented a provably secure treasury system that is compatible with most existing blockchain infrastructures, such as Bitcoin, Ethereum, etc. More specifically, the proposed treasury system supports liquid democracy/delegative voting for better collaborative intelligence. Namely, the stake holders can either vote directly on the proposed projects or delegate their votes to experts. Its core component is a distributed universally composable secure end-to-end verifiable voting protocol. The integrity of the treasury voting decisions is guaranteed even when all the voting committee members are corrupted. To further improve efficiency, we proposed the world's first honest verifier zero-knowledge proof for unit vector encryption with logarithmic size communication. This partial result may be of independent interest to other cryptographic protocols. A pilot system is implemented in Scala over the Scorex 2.0 framework, and its benchmark results indicate that the proposed system can support tens of thousands of treasury participants with high efficiency.
KuoâHui Yeh, Chunhua Su, Jia-Li Hou, Wayne Chiu ¡ 5 authors
Recently, the popularity and universality of smart-devices has led to rapid advancement in the development of applications for mobile commerce around the world. Novel mobile payment schemes, such as Apple pay, Android pay, and Samsung pay are becoming an increasingly popular ways to conduct online transactions, no matter what type of smart devices are used. Due to the attendant growth in the importance of security, significant attention has been devoted to the challenge of designing and implementing a robust mobile payment scheme for securing online transactions. In this paper, we demonstrate a robust mobile payment scheme based on sturdy certificateless signatures with bilinear pairing. We elegantly refine the proposed mobile payment scheme to make it suitable for computation-constrained mobile devices. The practicability of the proposed mobile payment scheme is then certified via a rigorous security analysis and thorough performance evaluation using the Raspberry PI as the implementation platform for our proposed scheme. Furthermore, we implement a transaction repository with the aid of smart contract technology. The simulation results, based on Ethereum, demonstrate the feasibility of employing the smart contract technology to secure mobile payments.
Blockchain is a new distributed and decentralized technology, and gradually attracts worldwide attention, but it is vulnerable to quantum attacks that would solve elliptic curve digital logarithm problem, which is mainly used for transaction authentication in blockchain. The key needed for authentication comes from the wallet. To ensure that the size of the wallet is fixed and easy to manage, deterministic wallets are required to be used. But if existing anti-quantum signature schemes, such as lattice-based signature are used directly in blockchain to solve the problem, it would have made the wallet bloat. In this paper, we present a novel anti-quantum transaction authentication scheme in the blockchain. In order to construct lightweight nondeterministic wallets, the key point is that public and private keys are generated from a set of master public and private key(Seed Key). We leverage on Bonsai Trees technology and propose a new authentication method which can extend a lattice space to multiple lattice spaces accompanied by the corresponding key. Every signature of a transaction uses a lattice space so as to ensure the randomness and the security of the master private key. And we give the complete security proof and analysis. This paper provides the theoretical support for the application of blockchain in the post quantum age.
Bruno Tavares, Filipe Figueiredo Correia, AndrÊ Restivo, João Pascoal Faria ¡ 5 authors
The applications of the blockchain technology are still being discov-ered. When a new potential disruptive technology emerges, there is a tendency to try to solve every problem with that technology. However, it is still necessary to determine what approach is the best for each type of application. To find how distributed ledgers solve existing problems, this study looks for blockchain frameworks in the academic world. Identifying the existing frameworks can demonstrate where the interest in the technology exists and where it can be miss-ing. This study encountered several blockchain frameworks in development. However, there are few references to operational needs, testing, and deploy of the technology. With the widespread use of the technology, either integrating with pre-existing solutions, replacing legacy systems, or new implementations, the need for testing, deploying, exploration, and maintenance is expected to in-tensify.
Recent attention to Bitcoin and other cryptocurrencies has opened investors and the public to the realm of digital currency. Greater exposure around the world has led to a frenzy of entry into the market and a test into the long-term feasibility of Bitcoin being able to remain a functioning peer-to-peer (P2P), decentralized currency. Its main structure is supported by the Proof-of-Work (PoW) protocol in which users can elect to participate in determining transaction approval and ensuring an honest blockchain. This system relies on elected users to expend computational power and energy to solve puzzles to prove the accuracy of the networkâs transactions and create new blocks.\nEach cryptocurrency uses their own method to ensure blockchain accuracy, and this paper will focus on how a Proof-of-Stake (PoS) protocol is a superior algorithm to PoW by assigning mining ability equal to oneâs stake within a coin, rather than her energy consumption, among other factors. We will discuss Bitcoinâs PoW as a baseline for our eventual analysis of PoS in terms of advantages and performance metrics. The main factors that can be compared between the two protocols is how each system can prevent itself against a variety of attacks from adversarial users within the network, as well as long-term sustainability.\nFinally, we will use the Cardano (ADA) cryptocurrency by IOHK as a case study for understanding how their Ouroboros Praos PoS protocol works. Our goal is to show how long-term adoption of PoS framework is more realistic from an energy perspective than PoW.
Identity-based cryptosystems mean that public keys can be directly derived from user identifiers, such as telephone numbers, email addresses, and social insurance number, and so on. So they can simplify key management procedures of certificate-based public key infrastructures and can be used to realize authentication in blockchain. Linearly homomorphic signature schemes allow to perform linear computations on authenticated data. And the correctness of the computation can be publicly verified. Although a series of homomorphic signature schemes have been designed recently, there are few homomorphic signature schemes designed in identity-based cryptography. In this paper, we construct a new ID-based linear homomorphic signature scheme, which avoids the shortcomings of the use of public-key certificates. The scheme is proved secure against existential forgery on adaptively chosen message and ID attack under the random oracle model. The ID-based linearly homomorphic signature schemes can be applied in e-business and cloud computing. Finally, we show how to apply it to realize authentication in blockchain.
Nowadays, blockchain has become one of the most cutting-edge technologies, which has been widely concerned and researched. However, the quantum computing attack seriously threatens the security of blockchain, and related research is still less. Targeting at this issue, in this paper, we present the definition of post-quantum blockchain (PQB) and propose a secure cryptocurrency scheme based on PQB, which can resist quantum computing attacks. First, we propose a signature scheme based on lattice problem. We use lattice basis delegation algorithm to generate secret keys with selecting a random value, and sign message by preimage sampling algorithm. In addition, we design the first-signature and last-signature in our scheme, which are defined as double-signature. It is used to reduce the correlation between the message and the signature. Second, by combining the proposed signature scheme with blockchain, we construct the PQB and propose this cryptocurrency scheme. Its security can be reduced to the lattice short integer solution (SIS) problem. At last, through our analysis, the proposed cryptocurrency scheme is able to resist the quantum computing attack and its signature satisfies correctness and one-more unforgeability under the lattice SIS assumption. Furthermore, compared with previous signature schemes, the sizes of signature and secret keys are relatively shorter than that of others, which can decrease the computational complexity. These make our cryptocurrency scheme more secure and efficient.
Tiago M. FernĂĄndezâCaramĂŠs, Paula FragaâLamas
The paradigm of Internet of Things (IoT) is paving the way for a world, where many of our daily objects will be interconnected and will interact with their environment in order to collect information and automate certain tasks. Such a vision requires, among other things, seamless authentication, data privacy, security, robustness against attacks, easy deployment, and self-maintenance. Such features can be brought by blockchain, a technology born with a cryptocurrency called Bitcoin. In this paper, a thorough review on how to adapt blockchain to the specific needs of IoT in order to develop Blockchain-based IoT (BIoT) applications is presented. After describing the basics of blockchain, the most relevant BIoT applications are described with the objective of emphasizing how blockchain can impact traditional cloud-centered IoT applications. Then, the current challenges and possible optimizations are detailed regarding many aspects that affect the design, development, and deployment of a BIoT application. Finally, some recommendations are enumerated with the aim of guiding future BIoT researchers and developers on some of the issues that will have to be tackled before deploying the next generation of BIoT applications.
Distributed ledger technologies (DLTs) are receiving much attention. As discussion focuses on the potential applications of DLTs, Blockchain-as-a-Service (BaaS) offerings are emerging to provide the underlying supporting infrastructure. BaaS entails a provider supplying and managing aspects of a DLT infrastructure to facilitate and bring efficiencies regarding the development, experimentation, deployment, and the ongoing management of DLT applications. However, much of the interest in DLTs stems from their potential to decentralise, disintermediate, and enable âtrustlessâ interactions. At first sight, BaaS â being offered by a provider â appears to run counter to this. In practice, whether BaaS raises substantive trust concerns depends on the nature of the offering, the applicationâs specifics, and the participantsâ goals and risk appetite. This paper elaborates the nature of BaaS offerings, exploring the role of the provider as part of a wider infrastructure, and related issues of trust.
Blockchain ledgers and the Cloud are a perfect match. On the one hand, there is an inherent requirement for multiple separate authentication nodes to validate every Blockchain transaction with each node requiring substantial encryption calculation capability. On the other hand, massive economies of scale can bring down the cost per transaction, and provide service continuity. Additionally, the Cloud provides a perfect incubator for proof-of-concept projects. This paper considers the future implications of Blockchain, as the concept of disintermediated trustless ledgers stimulates the imagination of computer scientists and innovators. The Cloudâs role in implementing this new paradigm is also highlighted, as a new decentralized P2P-Cloud model. Finally, this paper discusses how Blockchain may be integrated into the university level computer science and information technology curriculum.
Recently, cryptocurrencies and bitcoin have become the main topics in the financial industry. A cryptocurrency is a digital or virtual currency that uses cryptography for security. A cryptocurrency is difficult to counterfeit because of this security feature. A defining feature of a cryptocurrency, and arguably its most endearing allure, is its organic nature; it is not issued by any central authority, rendering it theoretically immune to government interference or manipulation. Cryptocurrencies have their benefits and drawbacks. The paper elaborates different aspects of cryptocurrencies, starting with their early development, challenges and risks, opportunities, advantages and disadvantages, and their future. In addition, the paper covered issues related to the practical and technical function of cryptocurrencies. It was concluded that is not easy to predict the future of cryptocurrencies, since there is a lot to be done especially in the field of formal regulations. However, the banks and other financial institutions should see and consider cryptocurrencies as an alternative for the financial transactions in the future. Key words: cryptocurrencies, development, advantages disadvantages, financial transactions
Siwan Noh, Youngho Park, Chur Sur, Sang Uk Shin ¡ 5 authors
privacy. An exposure of personal medical records causes damage to the finance, etc. Sometimes, it could put patient's life in danger. To achieve secure data sharing between institutions, many studies use cloud storage to store medical records. However, many studies suppose that cloud service providers were trustworthy. These systems required a key establishment with the cloud service providers and all the access logs are governed by cloud service providers. Patients should ask cloud service providers to check these access logs. However, it can be forged by cloud service providers during the request process. In this paper, we propose blockchain based medical records management system for secure data sharing. In order to share securely, we use proxy re-encryption scheme. Also, we use blockchain technology to audit access logs without modification.
Summary In a data sharing group, each user can upload, modify, and access group files and a user is required to generate a new signature for the modified file after modification. There is a situation that two or more users modify the same file at almost the same time, which should be avoided as it gives rise to a signature conflict. However, the existing schemes do not take it into consideration. In this paper, we proposed a new mechanism SeShare for data storing based on blockchain to realize signature uniqueness, which solves the problem of generating signatures for the same file meanwhile by different group users. Specifically, we record every signature of a file in a blockchain in chronological order, and only one user is allowed to add new signature at the end of the blockchain when modification conflicts occur. On the other hand, to provide a secure data sharing service, SeShare introduces an efficient public auditing scheme for file integrity verification when a group user leaves the group. We also prove the security of the proposed scheme and evaluate the performance at the end of this paper. Our experimental results demonstrate the efficiency of public auditing for user leaving.