Blockchain Papers

Chao Wu, Liyi Zhou, Chulin Xie, Yuhang Zheng · 5 authors

No abstract is available for this record.

Nataša Živić, Christoph Ruland, Jochen Sassmannshausen

Distributed Ledger Technologies (DLT) are seen as data bases of the future, which reduce the cost of trust and revolutionize transactions between individuals, companies and governments. They are considered as one of the main drivers of future applications, especially in field of Machine to Machine (M2) communications which are one of the basic technologies for Internet of Things (IoT). Therefore, Distributed Ledger Technologies with their inherent property to provide security, privacy and decentralized operation are engine for todays and future reliable, autonomous and trusted IoT platforms. For this reason, IoT using DLT can be considered as “Internet of Trusted Things”. This paper considers tree basic DLT technologies according to their architecture: blockchain, tangle and hashgraph. Their characteristics are compared considering number of criteria, with the aim to find a proper architecture for a specific M2M application.

Muneeb Ul Hassan, Mubashir Husain Rehmani, Jinjun Chen

Modern smart homes are being equipped with certain renewable energy resources that can produce their own electric energy. From time to time, these smart homes or microgrids are also capable of supplying energy to other houses, buildings, or energy grid in the time of available self-produced renewable energy. Therefore, researches have been carried out to develop optimal trading strategies, and many recent technologies are also being used in combination with microgrids. One such technology is blockchain, which works over decentralized distributed ledger. In this paper, we develop a blockchain based approach for microgrid energy auction. To make this auction more secure and private, we use differential privacy technique, which ensures that no adversary will be able to infer private information of any participant with confidence. Furthermore, to reduce computational complexity at every trading node, we use consortium blockchain, in which selected nodes are given authority to add a new block in the blockchain. Finally, we develop differentially private Energy Auction for bLockchain-based microgrid systems (DEAL). We compare DEAL with Vickrey-Clarke-Groves (VCG) auction scenario and experimental results demonstrates that DEAL outperforms VCG mechanism by maximizing sellers' revenue along with maintaining overall network benefit and social welfare.

Jorge Bernal Bernabé, José Luis Cánovas, José L. Hernández-Ramos, Rafael Torres Moreno · 5 authors

Blockchains offer a decentralized, immutable and verifiable ledger that can record transactions of digital assets, provoking a radical change in several innovative scenarios, such as smart cities, eHealth or eGovernment. However, blockchains are subject to different scalability, security and potential privacy issues, such as transaction linkability, crypto-keys management (e.g. recovery), on-chain data privacy, or compliance with privacy regulations (e.g. GDPR). To deal with these challenges, novel privacy-preserving solutions for blockchain based on crypto-privacy techniques are emerging to empower users with mechanisms to become anonymous and take control of their personal data during their digital transactions of any kind in the ledger, following a Self-Sovereign Identity (SSI) model. In this sense, this paper performs a systematic review of the current state of the art on privacy-preserving research solutions and mechanisms in blockchain, as well as the main associated privacy challenges in this promising and disrupting technology. The survey covers privacy techniques in public and permissionless blockchains, e.g. Bitcoin and Ethereum, as well as privacy-preserving research proposals and solutions in permissioned and private blockchains. Diverse blockchain scenarios are analyzed, encompassing, eGovernment, eHealth, cryptocurrencies, Smart cities, and Cooperative ITS.

Jestine Paul, Quanqing Xu, Shao Fei, Bharadwaj Veeravalli · 5 authors

No abstract is available for this record.

Aafaf Ouaddah

No abstract is available for this record.

Ziqing Guo, Hua Zhang, Xin Zhang, Zhengping Jin · 5 authors

With the rapid development of the Internet of things (IoT), more and more IoT\ndevices are connected and communicate frequently. In this background, the\ntraditional centralized security architecture of IoT will be limited in terms\nof data storage space, data reliability, scalability, operating costs and\nliability judgment. In this paper, we propose an new key information storage\nframework based on a small distributed database generated by blockchain\ntechnology and cloud storage. Specifically, all encrypted key communication\ndata will be upload to public could server for enough storage, but the\nabstracts of these data (called "communication logs") will be recorded in "IoT\nledger" (i.e., an distributed database) that maintained by all IoT devices\naccording to the blockchain generation approach, which could solve the problem\nof data reliability, scalability and liability judgment. Besides, in order to\nefficiently search communication logs and not reveal any sensitive information\nof communication data, we design the secure search scheme for our "IoT ledger",\nwhich exploits the Asymmetric Scalar-product Preserving Encryption (ASPE)\napproach to guarantee the data security, and exploits the 2-layers index which\nis tailor-made for blockchain database to improve the search efficiency.\nSecurity analysis and experiments on synthetic dataset show that our schemes\nare secure and efficient.\n

Yu‐Jia Chen, Li‐Chun Wang, Shu Wang

This paper proposes a blockchain-based data checking scheme to protect data integrity in Internet of Things (IoT). Traditional data integrity schemes such as symmetric key approaches and public key infrastructure (PKI) suffer from the single-point of failure and network congestion due to the centralized architecture. Motivated by the distributed data authentication in blockchain, we propose to adopt blockchain to ensure the data integrity in IoT networks. However, the existing blockchain scheme cannot be directly applied to IoT nodes with limited computing and network resources. Hence, we develop a stochastic blockchain scheme to limit the number of cooperative nodes and distribute the load to IoT edge nodes. In our scheme, the IoT data are broadcast by randomly selected cooperative nodes, thereby introducing uncertainty to the attacker and improving the system security level. Finally, we propose a lightweight mining process to make only the IoT edge nodes compete for block generation and share the block with other nodes. If our scheme is used in the case of having 9,000 legitimate nodes and 1,000 compromised nodes, only three cooperative nodes can achieve the probability of successful defense over 99 percent.

Xixun Yu, Zheng Yan, Rui Zhang

No abstract is available for this record.

Mengmeng Yang, Tianqing Zhu, Kaitai Liang, Wanlei Zhou · 5 authors

No abstract is available for this record.

Yonggen Gu, Jiashen Chen, Xiaohong Wu

With the gradual promotion, crowdsourcing has become an efficient way to solve problems that are very complicated for computers and simple for human crowd intelligence in recent years. Traditional crowdsourcing is based on a central system where requesters post tasks on a crowdsourcing central server or platform, however, this centralized model currently faces various challenges such as prohibitive cost, single point of failure, and vulnerability to malicious attacks. To this end, this paper proposes a smart contract-based decentralized online crowdsourcing mechanism, which includes task assignment rules and reward payment rules, etc. The mechanism has the characteristics like decentralization, unalterable, truthfulness and so on. In addition, the corresponding smart contract is designed, so that the mechanism can really run and process the actual data, and the effectiveness is shown by experiments. In this way, the entire crowdsourcing process no longer requires the participation of trusted third-party agencies, information and privacy security is guaranteed, and the cost is lower.

Cheng Xu, Ce Zhang, Jianliang Xu

Blockchains have recently been under the spotlight due to the boom of cryptocurrencies and decentralized applications. There is an increasing demand for querying the data stored in a blockchain database. To ensure query integrity, the user can maintain the entire blockchain database and query the data locally. However, this approach is not economic, if not infeasible, because of the blockchain's huge data size and considerable maintenance costs. In this paper, we take the first step toward investigating the problem of verifiable query processing over blockchain databases. We propose a novel framework, called vChain, that alleviates the storage and computing costs of the user and employs verifiable queries to guarantee the results' integrity. To support verifiable Boolean range queries, we propose an accumulator-based authenticated data structure that enables dynamic aggregation over arbitrary query attributes. Two new indexes are further developed to aggregate intra-block and inter-block data records for efficient query verification. We also propose an inverted prefix tree structure to accelerate the processing of a large number of subscription queries simultaneously. Security analysis and empirical study validate the robustness and practicality of the proposed techniques.

Liehuang Zhu, Baokun Zheng, Meng Shen, Shui Yu · 8 authors

With the more and more extensive application of blockchain, blockchain security has been widely concerned by the society and deeply studied by scholars. Moreover, the security of blockchain data directly affects the security of various applications of blockchain. In this survey, we perform a comprehensive classification and summary of the security of blockchain data. First, we present classification of blockchain data attacks. Subsequently, we present the attacks and defenses of blockchain data in terms of privacy, availability, integrity and controllability. Data privacy attacks present data leakage or data obtained by attackers through analysis. Data availability attacks present abnormal or incorrect access to blockchain data. Data integrity attacks present blockchain data being tampered. Data controllability attacks present blockchain data accidentally manipulated by smart contract vulnerability. Finally, we present several important open research directions to identify follow-up studies in this area.

Sophocles Theodorou, Nicolas Sklavos

No abstract is available for this record.

Tsung-Ting Kuo, Rodney A. Gabriel, Lucila Ohno‐Machado

OBJECTIVE: Decentralized privacy-preserving predictive modeling enables multiple institutions to learn a more generalizable model on healthcare or genomic data by sharing the partially trained models instead of patient-level data, while avoiding risks such as single point of control. State-of-the-art blockchain-based methods remove the "server" role but can be less accurate than models that rely on a server. Therefore, we aim at developing a general model sharing framework to preserve predictive correctness, mitigate the risks of a centralized architecture, and compute the models in a fair way. MATERIALS AND METHODS: We propose a framework that includes both server and "client" roles to preserve correctness. We adopt a blockchain network to obtain the benefits of decentralization, by alternating the roles for each site to ensure computational fairness. Also, we developed GloreChain (Grid Binary LOgistic REgression on Permissioned BlockChain) as a concrete example, and compared it to a centralized algorithm on 3 healthcare or genomic datasets to evaluate predictive correctness, number of learning iterations and execution time. RESULTS: GloreChain performs exactly the same as the centralized method in terms of correctness and number of iterations. It inherits the advantages of blockchain, at the cost of increased time to reach a consensus model. DISCUSSION: Our framework is general or flexible and can also address intrinsic challenges of blockchain networks. Further investigations will focus on higher-dimensional datasets, additional use cases, privacy-preserving quality concerns, and ethical, legal, and social implications. CONCLUSIONS: Our framework provides a promising potential for institutions to learn a predictive model based on healthcare or genomic data in a privacy-preserving and decentralized way.

Mei Yu, Jie Zhang, Jianrong Wang, Jie Gao · 8 authors

Now, the security and privacy-preserving of Internet of Things are receiving more attention. This article proposes a new method of Internet of Things security and privacy preserving by combining differentiated nodes, precision clustering, RSA, multi-signature, and blockchain. To calculate the node rank value in Internet of Things, the number of nodes’ links is taken as the weight of nodes based on PageRank. This method increases the node rank values’ difference between nodes. Accurate clustering determines the initial central nodes of k-means based on the differentiated node rank values, which effectively differentiates the active and inactive nodes in Internet of Things and achieve different levels of protection. To ensure data’s reusability, we adopt the multi-signature. And considering node’s incoming nodes have certain decision on whether data can be transmitted, we filter out two nodes with the highest node rank value from active node’s incoming nodes to do 2/3 multi-signature which saves resources. We encrypt and sign the transmitted data with RSA, helping receivers to verify data. Data are transmitted safely through the blockchain. Successful validation indicates successful transmission. Experiments show that the proposed method can effectively distinguish between active and inactive nodes, which increases the difficulty of attackers’ attack and effectively protects the security and privacy of Internet of Things nodes and data.

Xiaoshuai Zhang, Stefan Poslad, Zixiang Ma

In this paper, we propose an access control solution for exchanging Blockchain-based Electronic Medical Records (EMRs) called BBACS (Block-based Access Control Scheme) that includes an access model and an access scheme. Unlike the existing Blockchain-oriented access schemes for EMRs, our access model can omit the agent layer (gateway) in order to authorise users' access with block level granularity, whilst maintaining compatibility with the underlying Blockchain data structure. Furthermore, the authorisation, encryption, and decryption algorithms presented in BBACS dispense with the need to use a public key infrastructure (PKI) and hence cut down the cost of network construction and improve the computational performance. We validated the efficiency (time cost) of local computation and data transmission (over Wi-Fi) for BBACS using a simulation of BBACS against another Blockchain-oriented access control scheme for EMRs called HDG as our baseline. To the best of our knowledge, BBACS is the first Blockchain-oriented access control solution without the need for an agent (or gateway) design, supporting granular authorisation (block level), that has been proposed for secure EMRs management in eHealth.

Wenda Tang, Xuan Zhao, Wajid Rafique, Wanchun Dou

With the development of mobile computing technology, there has higher demand for computation resource in mobile applications than before. Fog computing has emerged as a promising infrastructure to provide elastic resources at the proximity of mobile users. Mobile users can offload some computations from the mobile devices to the nearby Fog servers so as to release the workloads of mobile devices, and therefore improve mobile users' quality of experience. However, mobile users may mistakenly offload their computations to the nearby Fog servers which have been injected by some attackers, and therefore induce some privacy and security issues. As most of mobile devices have natural mobility feature, it is very necessary to check the veracity of a Fog server in a very short time before doing computation offloading. In view of this challenge, we bring blockchain technique into Fog environment so as to verify each Fog server's authenticity and propose a blockchain-based offloading approach in this paper. Concretely, the proposed approach constantly maintains a set of candidate authorized Fog servers by leveraging blockchain technology, and the offloading decision could be made in a real-time fashion. Extensive experimental results have demonstrated our method's feasibility and efficiency.

Aurelie Bayle, Mirko Koscina, David Manset, Octavio Pérez Kempner

In this work we propose a new blockchain model that ensure the GDPR compliance by handling references to the sensitive data and using metadata instead of manipulate private data directly within the blockchain. We accomplish this by defining a modular architecture that relies on strong cryptographic assumptions that provide the means to guarantee that the right to be forgotten is being well enforced.

Canhuang Dai, Xingyu Xiao, Yuzhen Ding, Liang Xiao · 6 authors

The security issue is one of the greatest challenges in vehicular ad hoc networks (VANETs) attracting a great deal of attention. Malicious onboard units (OBUs) can attack other OBUs with various manners to obtain illegal gains, such as jamming, eavesdropping spoofing and so on. To reduce the potential attackers in the network, we propose an indirect reciprocity security framework with a scalar reputation assigned to each OBU to evaluate their dangerous level to the VANET. A blockchain technique that uses consensus mechanism and encryption algorithms to protect information from being tampered is applied for the transmitter to record the behaviors of other OBUs. We also propose a reinforcement learning based action selection strategy for an OBU in the VANET to choose a reliable relay OBU or determine whether to follow the request of a source OBU or not. A hotbooting technique is applied for the OBUs with prior knowledge to accelerate the learning speed. Simulation results show that the proposed action selection strategy can efficiently increase the packet delivery ratio, the reputation and the utility of the each OBU.

Chun‐I Fan, Yi‐Fan Tseng, Hui-Po Su, Ruei‐Hau Hsu · 5 authors

As the rising popularity of Bitcoin, people tend to use Bitcoin wallets to managing the keys for spending or receiving funds. Instead of generating pairs of keys randomly which are hard to be stored, hierarchical deterministic (HD) wallets derive all the keys from a single seed, thus storing that seed is sufficient to recover keys. In an HD wallet, it allows users to generate child public keys from parent public keys without knowledge of any private key. A suitable case for this feature is that an auditor is permitted to derive all the public keys for auditing, However, this impressive feature makes HD wallets suffered from so-called privilege escalation attacks that the leakage of any one of child private key along with its parent public key will cause the exposure of the other child private keys. To confront with this severe problem, we propose a novel HD wallet scheme that gives out a signature with trapdoor hash functions instead of directly giving anyone private keys for signing. Since it conceals private keys from any child nodes, it can prevent from privilege escalation attacks. Nevertheless, the proposed scheme also provides unlinkability between two public keys in order to achieve anonymity of user identity and high scalability to the derivations of keys. Thus, the proposed scheme achieves user anonymity, public key derivation and high scalability.

Vidhya Ramani, Tanesh Kumar, An Bracken, Madhusanka Liyanage · 5 authors

The healthcare industry is constantly reforming and adopting new shapes with respect to the technological evolutions and transitions. One of the crucial requirements in the current smart healthcare systems is the protection of patients sensitive data against the potential adversaries. Therefore, it is vital to have secure data access mechanisms that can ensure only authorized entities can access the patients medical information. Hence, this paper considers blockchain technology as a distributed approach protect the data in healthcare systems. This research proposes a blockchain based secure and efficient data accessibility mechanism for the patient and the doctor in a given healthcare system. Proposed system able to protect the privacy of the patients as well. The security analysis of our scheme shows that it can resist to well-known attacks along with maintaining the integrity of the system. Moreover, an Ethereum based implementation has used to verify the feasibility of our proposed system.

Chao Li, Balaji Palanisamy

In the age of Big Data, enabling task scheduling while protecting users' privacy is critical for various decentralized applications in blockchain-based smart contract platforms. Such a privacy-preserving task scheduler requires the task input data to be secretly maintained until a prescribed task execution time and be automatically recorded into the blockchain to enabling the execution of the task at the execution time, even if the user goes offline. While straight-forward centralized approaches provide a basic solution to the problem, unfortunately they are limited to a single point of trust and involve a single point of control. This paper presents decentralized techniques for supporting privacy-preserving task scheduling using smart contracts in Ethereum blockchain networks. We design a privacy-preserving task scheduling protocol that is managed by a manager smart contract. The protocol requires a user to schedule a task by deploying a proxy smart contract maintaining the non-sensitive information of the task while creating decentralized secret trust and selecting trustees from the network to maintain the sensitive information of the task. With security techniques including secret sharing and layered encryption as well as security deposit paid by trustees as economic deterrence, the protocol can protect the sensitive information against possible attacks including some trustees destroying the sensitive information (drop attack) or secretly releasing the sensitive information before the execution time (release-ahead attack). We demonstrate the attack-resilience of the proposed protocol through rigorous analysis.Our implementation and experimental evaluation on the Ethereum official test network demonstrate the low monetary cost and the low time overhead associated with the proposed approach.

Xiaoyang Zhu, Youakim Badr

The Internet of Things aims at connecting everything, ranging from individuals, organizations, and companies to things in the physical and virtual world. The digital identity has always been considered as the keystone for all online services and the foundation for building security mechanisms such as authentication and authorization. However, the current literature still lacks a comprehensive study on the digital identity management for the Internet of Things (IoT). In this paper, we firstly identify the requirements of building identity management systems for IoT, which comprises scalability, interoperability, mobility, security and privacy. Then, we trace the identity problem back to the origin in philosophy, analyze the Internet digital identity management solutions in the context of IoT and investigate recent surging blockchain sovereign identity solutions. Finally, we point out the promising future research trends in building IoT identity management systems and elaborate challenges of building a complete identity management system for the IoT, including access control, privacy preserving, trust and performance respectively.