Biblio

User privacy is an attractive and valuable task to the success of blockchain systems. However, user privacy protection's performance and data capacity have not been well studied in existing access control models of blockchain systems because of traceability and openness of the P2P network. This paper focuses on investigating performance and data capacity from a blockchain infrastructure perspective, which adds secondary encryption to shield confidential information in a non-invasive way. First, we propose an efficient asymmetric encryption scheme by combining homomorphic encryption and state-of-the-art multi-signature key aggregation to preserve privacy. Second, we use smart contracts and CA infrastructure to achieve attribute-based access control. Then, we use the non-interactive zero-knowledge proof scheme to achieve secondary confidentiality explicitly. Finally, experiments show our scheme succeeds better performance in data capacity and system than other schemes. This scheme improves availability and robust scalability, solves the problem of multi-signature key distribution and the unlinkability of transactions. Our scheme has established a sound security cross-chain system and privacy confidentiality mechanism and that has more excellent performance and higher system computing ability than other schemes.

Nowadays, network information security is of great concern, and the measurement of the trustworthiness of terminal devices is of great significance to the security of the entire network. The measurement method of terminal device security trust still has the problems of high complexity, lack of universality. In this paper, the device fingerprint library of device access network terminal devices is first established through the device fingerprint mixed collection method; Secondly, the software and hardware features of the device fingerprint are used to increase the uniqueness of the device identification, and the multi- dimensional standard metric is used to measure the trustworthiness of the terminal device; Finally, Block chain technology is used to store the fingerprint and standard model of network access terminal equipment on the chain. To improve the security level of network access devices, a device access method considering the trust of terminal devices from multiple perspectives is implemented.

IoT has been an efficient technology for interconnecting different physical objects with the internet. Several cyber-attacks have resulted in compromise in security. Blockchain distributed ledger provide immutability that can answer IoT security concerns. The paper aims at highlighting the challenges & problems currently associated with IoT implementation in real world and how these problems can be minimized by implementing Blockchain based solutions and smart contracts. Blockchain helps in creation of new highly robust IoT known as Blockchain of Things(BCoT). We will also examine presently employed projects working with integrating Blockchain & IoT together for creating desired solutions. We will also try to understand challenges & roadblocks preventing the further implementation of both technologies merger.

CP-ABE (Ciphertext-policy attribute based encryption) is considered as a secure access control for data sharing. However, the SK(secret key) in most CP-ABE scheme is generated by Centralized authority(CA). It could lead to the high cost of building trust and single point of failure. Because of the characters of blockchain, some schemes based on blockchain have been proposed to prevent the disclosure and protect privacy of users' attribute. Thus, a new CP-ABE identity-attribute management(IAM) data sharing scheme is proposed based on blockchain, i.e. IAM-BDSS, to guarantee privacy through the hidden policy and attribute. Meanwhile, we define a transaction structure to ensure the auditability of parameter transmission on blockchain system. The experimental results and security analysis show that our IAM-BDSS is effective and feasible.

With the rapid development of blockchain technology, it provides a new technical solution for secure storage of data and trusted computing. However, in the actual application of data traceability, blockchain technology has an obvious disadvantage: the large amount of data stored in the blockchain system will lead to a long response time for users to query data. Higher query delay severely restricts the development of block chain technology in the traceability system. In order to solve this problem, we propose an efficient, secure and low storage overhead blockchain query scheme. Specifically, we design an index structure independent of Merkle tree to support efficient intra-block query, and create new fields in the block header to optimize inter-block query. Compared with several existing schemes, our scheme ensures the security of data. Finally, we simulate and evaluate our proposed scheme. The results show that the proposed scheme has better execution efficiency while reducing additional overhead.

Blockchain is a relatively new technology, a distributed database used for sharing between nodes of computer networks. A blockchain stores all information in automated digital format as a database. Blockchain innovation ensures the accuracy and security of the data record and generates trust without the need for a trusted third party. The objectives of this paper are to determine the security risk of the blockchain systems, analyze the vulnerabilities exploited on the blockchain, and identify recent security challenges that the blockchain faces. This review paper presents some of the previous studies of the security threats that blockchain faces and reviews the security enhancement solutions for blockchain vulnerabilities. There are some studies on blockchain security issues, but there is no systematic examination of the problem, despite the blockchain system’s security threats. An observational research methodology was used in this research. Through this methodology, many research related to blockchain threats and vulnerabilities obtained. The outcomes of this research are to Identify the most important security threats faced by the blockchain and consideration of security recently vulnerabilities. Processes and methods for dealing with security concerns are examined. Intelligent corporate security academic challenges and limitations are covered throughout this review. The goal of this review is to serve as a platform as well as a reference point for future work on blockchain-based security.

Virtual power plants are among the promising ways that variable generation and flexible demand may be optimally balanced in the future. The virtual power plant is an important branch of the energy internet, and it plays an important role in the aggregation of distributed power generation resources and the establishment of virtual power resource transactions. However, in the existing virtual power plant model, the following problems are becoming increasingly prominent, such as safeguard, credit rating system, privacy protection, benefit distribution. Firstly, the operation and transaction mechanism of the virtual power plant was introduced. Then, the blockchain technology is introduced into the virtual power plant transaction to make it more conducive to the information transparent, stable dispatch system, data security, and storage security. Finally, the operation and transaction system based on blockchain technology for the virtual power plant was design.

Blockchain smart contracts are prevalent nowadays as numerous applications are developed based on this feature. Though smart contracts are important and widely used, they contain certain vulnerabilities. This paper discusses various security issues that arise in smart contract applications. They are categorized in the smart contract platform, the applications that integrate with the Blockchain, and the vulnerabilities in smart contract code. A detailed study of smart contract-specific vulnerabilities and the defense against those vulnerabilities are presented in this article. Because of certain limitations of platforms or programming language used to write smart contract, there are possibilities of attacks on smart contracts. Hence different security measures or precautions to be taken while writing the smart contract code is discussed in this article. This will prevent the potential attacks happening on Blockchain distributed applications.

The term cryptocurrency refers to a digital currency based on cryptographic concepts that have become popular in recent years. Bitcoin is a decentralized cryptocurrency that uses the distributed append-only public database known as blockchain to record every transaction. The incentive-compatible Proof-of-Work (PoW)-centered decentralized consensus procedure, which is upheld by the network's nodes known as miners, is essential to the safety of bitcoin. Interest in Bitcoin appears to be growing as the market continues to rise. Bitcoins and Blockchains have identical fundamental ideas, which are briefly discussed in this paper. Various studies discuss blockchain as a revolutionary innovation that has various applications, spanning from bitcoins to smart contracts, and also about it being a solution to many issues. Furthermore, many papers are reviewed here that not only look at Bitcoin’s fundamental underpinning technologies, such as Mixing and the Bitcoin Wallets but also at the flaws in it.

In recent years, blockchain technology has become one of the key technical innovation fields in the world. From the simple Bitcoin that can only be transferred at first to the blockchain application ecology that is now blooming, blockchain is gradually building a credible internet of value. However, with the continuous development and application of blockchain, even the blockchain based on cryptography is facing a series of network security problems and has caused great property losses to participants. Therefore, studying blockchain security and accelerating standardization of blockchain security have become the top priority to ensure the orderly and healthy development of blockchain technology. This paper briefly introduces the scope of blockchain security from the perspective of network security, sorts out some existing standards related to blockchain security, and gives some suggestions to promote the development and application of blockchain security standardization.

As permissioned blockchain becomes a common foundation of blockchain-based applications for current organizations, related stakeholders need a means to assess the security risks of the applications. Therefore, this study proposes a security risk management framework for permissioned blockchain applications. The framework divides itself into different implementation stacks and provides guidelines to control the security risks of permissioned blockchain applications. According to the best of our knowledge, this study is the first research that provides a means to evaluate the security risks of permissioned blockchain applications from a holistic point of view. If users can trust the applications that adopted this framework, this study can hopefully contribute to the adoption of permissioned blockchain technologies.

Blockchain technology is a decentralized ledger of all transactions across peer to peer network. Being decentralized in nature, a blockchain is highly secure as no single user can alter or remove an entry in the blockchain. The security of office premises and data is a very major concern for any organization. This paper majorly focuses on its application of blockchain technology in security surveillance. This paper proposes a blockchain based multi level network model for security surveillance system. The proposed system architecture is composed of different blockchain based systems connected to a multi level decentralized blockchain system to insure authentication, secure storage, Integrity and accountability.

The global Electronic Health Record (EHR) market is growing dramatically and expected to reach \$39.7 billions by 2022. To safe-guard security and privacy of EHR, access control is an essential mechanism for managing EHR data. This paper proposes a hybrid architecture to facilitate access control of EHR data by using both blockchain and edge node. Within the architecture, a blockchain-based controller manages identity and access control policies and serves as a tamper-proof log of access events. In addition, off-chain edge nodes store the EHR data and apply policies specified in Abbreviated Language For Authorization (ALFA) to enforce attribute-based access control on EHR data in collaboration with the blockchain-based access control logs. We evaluate the proposed hybrid architecture by utilizing Hyperledger Composer Fabric blockchain to measure the performance of executing smart contracts and ACL policies in terms of transaction processing time and response time against unauthorized data retrieval.

Energy is the material basis for human society to survive and has a very important strategic position in the national economy. With the advancement of Internet technology and the extensive use of clean energy, the energy industry has demonstrated a new development trend. Based on blockchain technology, this paper analyzes energy data security and multi-source synergy mechanism, processes and classifies a large amount of energy data in energy system, and builds a blockchain-based energy data supervision and transaction model. A summary tree of energy data is proposed; a consensus mechanism based on multi-source collaboration is proposed to ensure efficient negotiation; and finally, blockchain is verified in the energy scenario. This provides reference for the application of blockchain technology in the energy industry.

Due to their specific features, blockchains have become popular in recent years. Blockchains are layered systems where security is a critical factor for their success. The main focus of this work is to systematize knowledge about security and privacy issues of blockchains. To this end, we propose a security reference architecture based on models that demonstrate the stacked hierarchy of various threats as well as threat-risk assessment using ISO/IEC 15408. In contrast to the previous surveys [23], [88], [11], we focus on the categorization of security vulnerabilities based on their origins and using the proposed architecture we present existing prevention and mitigation techniques. The scope of our work mainly covers aspects related to the nature of blockchains, while we mention operational security issues and countermeasures only tangentially.

In this paper, we propose the traceability of assets in a permissioned blockchain connected with a permissionless blockchain. We make traceability of assets in the permissioned blockchain be defined and be expressed as a hidden Markov model. There exists no dishonest increase and decrease of assets in this model. The condition is called balance. As we encrypt this model with fully homomorphic encryption and apply the zero knowledge proof of plaintext knowledge, we show that the trace-ability and balance of the permissioned blockchain are able to be proved in zero knowledge to the permissionless blockchain with concealing the asset allocation of the permissioned blockchain.

A cooperative network defense is one approach to fend off large-scale Distributed Denial-of-Service (DDoS) attacks. In this regard, the Blockchain Signaling System (BloSS) is a multi-domain, blockchain-based, cooperative DDoS defense system, where each Autonomous System (AS) is taking part in the defense alliance. Each AS can exchange attack information about ongoing attacks via the Ethereum blockchain. However, the currently operational implementation of BloSS is not interactive or visualized, but the DDoS mitigation is automated. In realworld defense systems, a human cybersecurity analyst decides whether a DDoS threat should be mitigated or not. Thus, this work presents the design of a security management dashboard for BloSS, designed for interactive use by cyber security analysts.

As a decentralized ledger technology, blockchain is considered to be a potential solution for applications with highly concentrated management mechanism. However, most of the existing blockchain networks are employed with the hash-puzzle-solving consensus protocol, known as proof-of-work. The competition of solving the puzzle introduces high latency, which directly leads to a long transaction-processing time. One solution of this dilemma is to establish a blockchain network with shards. In this paper, we focus on the blockchain network with shards and adopt the security-deposit based consensus protocol, studying the problem of how to balance the security incentive and the economic incentive. Also, the inherent features of the blockchain, i.e., anonymity and decentralization, introduce the information asymmetric issue between the beacon chain and the participants. The contract theory is utilized to formulate the problem between them. As such, the optimal rewards related to the different types of validators can be obtained, as well as the reasonable deposits accordingly. Compared with the fixed deposits, the flexible deposits can provide enough economic incentive for the participants without losing the security incentives. Besides, the simulation results demonstrate that the contract theory approach is capable of maximizing the beacon chain's utility and satisfying the incentive compatibility and individual rationality of the participants.

Blockchain is seen as a promising technology to provide reliable and secure services due to its decentralized characteristic. However, because of the limited throughput, current blockchain platforms can not meet the transaction demand in practical use. Though researchers proposed many new solutions, they suffered either decentralization or security issues. In this paper, using Directed Acyclic Graph (DAG) structure, we improve the linear structure of traditional blockchain protocol. In the new structure, blocks are organized in levels and width, which will generate into a compacted DAG structure (CoDAG). To make CoDAG more efficient and secure, we design algorithms and protocols to place the new-generated blocks appropriately. Compared with traditional blockchain protocols, CoDAG improves the security and transaction verification time, and enjoys the consistency and liveness properties of blockchain. Taking adversary parties into consideration, two possible attack strategies are presented in this paper, and we further prove that CoDAG is a secure and robust protocol to resist them. The experimental results show that CoDAG can achieve 394 transactions per second, which is 56 times of Bitcoin's throughput and 26 times of Ethereum's.

Proof-of-Work (PoW) is a popular protocol used in Blockchain systems to resolve double-spending problems. However, if an attacker has access to calculation hash power greater than half of the total hash power, this attacker can create a double-spending attack or 51% attack. The cost of creating a 51% attack is surprisingly low if hash power is abundantly available. That posts a great threat to lots of PoW blockchains. We propose a technique to combine history weighted information of miners with the total calculation difficulty to alleviate the 51% attack problem. Analysis indicates that with the new technique, the cost of a traditional attack is increased by two orders of magnitude.

In this paper we consider the threat surface and security of air gapped wallet schemes for permissioned blockchains as preparation for a Markov based mathematical model, and quantify the risk associated with private key leakage. We identify existing threats to the wallet scheme and existing work done to both attack and secure the scheme. We provide an overview the proposed model and outline justification for our methods. We follow with next steps in our remaining work and the overarching goals and motivation for our methods.

Witnessing the increasingly pervasive deployment of security video surveillance systems(VSS), more and more individuals have become concerned with the issues of privacy violations. While the majority of the public have a favorable view of surveillance in terms of crime deterrence, individuals do not accept the invasive monitoring of their private life. To date, however, there is not a lightweight and secure privacy-preserving solution for video surveillance systems. The recent success of blockchain (BC) technologies and their applications in the Internet of Things (IoT) shed a light on this challenging issue. In this paper, we propose a Lightweight, Blockchain-based Privacy protection (Lib-Pri) scheme for surveillance cameras at the edge. It enables the VSS to perform surveillance without compromising the privacy of people captured in the videos. The Lib-Pri system transforms the deployed VSS into a system that functions as a federated blockchain network capable of carrying out integrity checking, blurring keys management, feature sharing, and video access sanctioning. The policy-based enforcement of privacy measures is carried out at the edge devices for real-time video analytics without cluttering the network.

Blockchain is a powerful and distributed platform for transactions which require a unified, resilient, transparent and consensus-based record keeping system. It has been applied to scenarios like smart city, supply chain, medical data storing and sharing, and etc. Many works have been done on improving the performance and security of such systems. However, there is a lack of the mechanism of identity binding when a human being is involved in corresponding physical world, i.e., if one is involved in an activity, his/her identity in the real world should be correctly reflected in the blockchain system. To mitigate this gap, we propose BlockID, a novel framework for people identity management that leverages biometric authentication and trusted computing technology. We also develop a prototype to demonstrate its feasibility in practice.

In a consensus algorithm based on Proof-of-Work, miners are motivated by crypto rewards. Furthermore, security is guaranteed because a cost of a 50% attack chance is higher than the potential rewards. However, because of the sudden price jump of cryptocurrencies and cheap prices of mining machines like ASICs, the cost and profit were on equilibrium for Bitcoin in 2017. In this situation, attackers are motivated by the balance between hash power and profits. In this paper, we describe that there is relevance between mining power on the network and price of tokens that can be taken securely on a blockchain. Users who exchange tokens on the PoW blockchain should monitor mining power and exchange tokens cheaper than the attack cost so that profit and cost of the attacker are not in equilibrium.

Blockchain technology has been increasingly used for decentralizing cloud-based Internet of Things (IoT) architectures to address some limitations faced by centralized systems. While many existing efforts are successful in leveraging blockchain for decentralization with multiple servers (full nodes) to handle faulty nodes, an important issue has arisen that external clients (also called lightweight clients) have to rely on a relay node to communicate with the full nodes in the blockchain. Compromization of such relay nodes may result in a security breach and even a blockage of IoT sensors from the network. We propose censorship resistant decentralized IoT management systems, which include a "diffusion" function to deliver all messages from sensors to all full nodes and an augmented consensus protocol to check data loss, replicate processing outcome, and facilitate opportunistic outcome delivery. We also leverage the cryptographic tool of aggregate signature to reduce the complexity of communication and signature verification.