Online auction systems allow to achieve an optimal trading of digital goods and services in a competitive market. Existing blockchain-based auctions allow the bidders to take part in the process while maintaining the confidentiality of their bids in a decentralized, transparent, secure and auditable way. However, in a competitive market, parties would prefer not to disclose their interests to competitors, and to remain anonymous during auctions. In this paper, we firstly analyze the specific requirements for blockchain-based anonymous fair auctions. We propose a formal model tailored to study auction systems facilitating anonymity, and we put forward a generic protocol relying on existing cryptographic primitives, such as designated verifier ring signature, to achieve bid confidentiality and bidder anonymity. Finally, we prove it to be secure against the security model we defined.
Open access
Blockchain Technology Applications and Security
Internet Traffic Analysis and Secure E-voting
Advanced Steganography and Watermarking Techniques
Xi He, Ketai He, Shenwen Lin, Jinglin Yang · 5 authors
Abstract Single heuristic method and incomplete heuristic conditions were difficult to cluster a large number of addresses comprehensively and accurately. Therefore, this paper analysed the associations between Bitcoin transactions and addresses and used six heuristic conditions to cluster addresses and entities. We proposed an improved change address detection algorithm and compared it with the original change address algorithm to prove the effectiveness of the improved algorithm. By adding conditional constraints, the identified change address was more accurate, and the convergence speed of the algorithm was accelerated. Our work presented the pseudo‐anonymity mechanism of the Bitcoin system, which could be used by the law enforcement agencies to track and crack down illegal transactions.
Matthew Tsao, Kaidi Yang, Stephen Zoepf, Marco Pavone
The era of big data has brought with it a richer understanding of user behavior through massive datasets, which can help organizations optimize the quality of their services. In the context of transportation research, mobility data can provide municipal authorities (MAs) with insights on how to operate, regulate, or improve the transportation network. Mobility data, however, may contain sensitive information about end users and trade secrets of mobility providers (MPs). Due to this data privacy concern, MPs may be reluctant to contribute their datasets to MA. Using ideas from cryptography, we propose an interactive protocol between an MA and an MP, in which MA obtains insights from mobility data without MP having to reveal its trade secrets or sensitive data of its users. This is accomplished in two steps: 1) a commitment step and 2) a computation step. In the first step, Merkle commitments and aggregated traffic measurements are used to generate a cryptographic commitment. In the second step, MP extracts insights from the data and sends them to MA. Using the commitment and zero-knowledge proofs, MA can certify that the information received from MP is accurate, without needing to directly inspect the mobility data. We also present a differentially private version of the protocol that is suitable for the large query regime. The protocol is verifiable for both MA and MP in the sense that dishonesty from one party can be detected by the other. The protocol can be readily extended to the more general setting with multiple MPs via secure multiparty computation.
This PhD thesis focuses on lattice-based cryptography and how to apply it to build post-quantum online voting systems. It is the result of the research done by the author at Scytl in close collaboration with Dr. Paz Morillo, from the Department of Applied Mathematics at UPC and Ramiro Martínez, PhD student. As part of her work at the electronic voting company Scytl, the author has participated in the design of several electronic voting systems as well as in their implementation, by providing support to the development team. Nevertheless, all these systems use standard and well-known cryptographic primitives, i.e., not lattice-based primitives, to ensure that the security requirements are fulfilled. Due to this, one of the main challenges of this PhD has been to start researching on a field which was not familiar to the author and contribute to its state of the art. This has allowed the company to enter the post-quantum world by participating in a project which aims to implement a lattice-based online voting system. The thesis has the following contents: an introduction to the lattice theory by describing some of its basic concepts and the computational problems in which the security of lattice-based cryptosystems relies. In this first part it is also described in detail those cryptosystems that are used as building blocks of three new protocols proposed in the thesis: a lattice-based coercion-resistant cast-as-intended protocol, a post-quantum mix-net and a fully post-quantum proof of a shuffle. The former is the lattice version of an existing protocol and allows the voter to check that the vote cast contains the selected voting options. The second and third protocols are the result of the research on lattice-based mix-nets. Two constructions are proposed: the first one allows to demonstrate that a mix-node has permuted and re-encrypted a list of RLWE ciphertexts without modifying them, but it cannot be considered fully post-quantum since the binding property of the commitment scheme relies on classical computational problems. The second one is fully post-quantum since all the cryptographic schemes used for building it, i.e., commitment scheme and zero-knowledge proofs, are based on lattices. Last but not least, for this second proposal a security definition and a proof of security are also provided. Finally, the last part of the thesis consists of building a post-quantum online voting system using as building blocks the protocols already presented and existing lattice-based constructions. This system is considered secure under quantum attacks and provides long-term privacy. It also guarantees vote anonymity, vote authenticity, vote integrity, individual verifiability and receipt-freeness. The algorithms involved in each phase are described in detail as well as the interaction among the participants. An implementation of this system is not given as part of this thesis although a lattice-based online voting system based on that is already being implemented at the company. Aquest tesi es centra en la criptografia basada en reticles i com aplicar-la a la construcció de sistemes de votació electrònica post-quàntics. És el fruit de la recerca feta per l'autora de la tesi a Scytl en estreta col·laboració amb la Dra. Paz Morillo, del Departament de Matemàtica Aplicada de la UPC i en Ramiro Martínez, estudiant de doctorat. Com a part de la seva feina a l'empresa de vot electrònic Scytl, l'autora ha participat tant en el disseny de sistemes de votació electrònica com en la seva implementació, donant suport a l'equip de desenvolupament. No obstant, tots aquests sistemes utilitzen primitives criptogràfiques estàndard (primitives no basades en reticles) per assegurar que els requisits de seguretat es compleixen, i és per aquest motiu que un dels principals reptes d'aquest doctorat ha estat fer en recerca en un camp que no era familiar per l'autora, i contribuir-hi. Per altra banda, això ha permès a l'empresa endinsar-se en el món post-quàntic i participar en un projecte que té per objectiu implementar un sistema de vot electrònic basat en reticles. Aquest tesi consta dels següents continguts: una introducció a la teoria dels reticles on es descriuen alguns dels seus conceptes bàsics i els problemes computacionals dels quals depèn la seguretat dels criptosistemes basats en reticles. En aquesta primera part també es descriuen en detall aquells criptosistemes utilitzats en la construcció dels tres nous protocols presentats en aquesta tesi: un protocol basat en reticles resistent a la coacció i que ofereix verificabilitat “cast-as-intended”; una “mix-net post-quàntica” i una prova de coneixement nul totalment post-quàntica que permet demostrar que la barreja de vots s'ha realitzat correctament. El primer protocol és la versió basada en reticles d'un protocol ja existent i permet que el votant comprovi que el vot emès conté les opcions que havia seleccionat. El segon i el tercer protocol són el resultat de la recerca feta en el camp de les mix-nets basades en reticles. Es proposen dues construccions: la primera d'elles permet demostrar que un node de la mix-net ha barrejat i rexifrat una llista de xifrats RLWE sense modificar-los, però no es pot considerar totalment post-quàntica ja que la propietat de lligar de l'esquema de compromís utilitzat per construir la prova es basa en problemes computacionals clàssics. La segona construcció és totalment post-quàntica ja que tots els esquemes criptogràfics utilitzats en el seu disseny, és a dir, esquema de compromís i proves de coneixement nul, estan basats en reticles. Finalment, però no per això menys important, per aquesta segona proposta també es dóna una definició de seguretat i una prova de seguretat. L'última part de la tesi consisteix en construir un sistema de vot online post-quàntic, utilitzant com a components els protocols prèviament presentats i construccions ja existents basades en reticles. El sistema es considera segur en front atacs quàntics i ofereix privadesa a llarg plaç. També garanteix l'anonimat del vot, la seva autenticitat i integritat, verificabilitat individual i resistència a la coacció. Es descriuen en detall tant els algoritmes executats a cada fase com la interacció entre els seus participants. Com a part de la tesi no s'inclou cap implementació del sistema tot i que l'empresa està implementant un sistema de vot online basat en el que es presenta en aquesta tesi.
Mohammed Amine Bouras, Boming Xia, Adnan Omer Abuassba, Huansheng Ning · 5 authors
Access control is a critical aspect for improving the privacy and security of IoT systems. A consortium is a public or private association or a group of two or more institutes, businesses, and companies that collaborate to achieve common goals or form a resource pool to enable the sharing economy aspect. However, most access control methods are based on centralized solutions, which may lead to problems like data leakage and single-point failure. Blockchain technology has its intrinsic feature of distribution, which can be used to tackle the centralized problem of traditional access control schemes. Nevertheless, blockchain itself comes with certain limitations like the lack of scalability and poor performance. To bridge the gap of these problems, here we present a decentralized capability-based access control architecture designed for IoT consortium networks named IoT-CCAC. A blockchain-based database is utilized in our solution for better performance since it exhibits favorable features of both blockchain and conventional databases. The performance of IoT-CCAC is evaluated to demonstrate the superiority of our proposed architecture. IoT-CCAC is a secure, salable, effective solution that meets the enterprise and business's needs and adaptable for different IoT interoperability scenarios.
Chiara Spadafora, Riccardo Longo, Massimiliano Sala
We propose a decentralized e-voting protocol that is coercion-resistant and vote-selling resistant, while being also completely transparent and not receipt-free. We achieve decentralization using blockchain technology. Because of the properties such as transparency, decentralization, and non-repudiation, blockchain is a fundamental technology of great interest in its own right, and it also has large potential when integrated into many other areas. We prove the security of the protocol under the standard DDH assumption on the underlying prime-order cyclic group (e.g. the group of points of an elliptic curve), as well as under standard assumptions on blockchain robustness.
Bitcoin came into existence as a peer-to-peer payment system for use on online transactions. This achievement was the result of a shared vision about the future relationship between governments’ control and citizenry, and the collaborative work of the many who contributed to the development of the cryptographic field. This innovation and its underlying technology, the blockchain, have been at the root of a change of paradigm, as the joint use of blockchain and artificial intelligence (AI) seed the next technological revolution. However, as it is often the case, these revolutionary inventions have also been met with skepticism in the financial sector and society at large. Using the case of Bitcoin and the blockchain, this paper analyzes the intersection between the philosophy and technology underlying these innovations, and the outlook of a sector of society who fears these developments while others try to profit. In this chapter, we first look at the history of Bitcoin together with that of those behind it. We then review the mixed reception it obtained after coming to the market. We assess the innovations’ properties and confront these with the needs of a society eager to obtain further clarity and enjoy more transparency in matters of relevance to their participation in democratic processes.
Voting is one of the most fundamental aspects of democracy. Over the past few decades, voting methods around the world have expanded from traditional paper ballot systems to electronic voting (e-voting), in which votes are written directly to computer memory. Like any computer system, voting machines are susceptible to technical vulnerabilities that open up opportunities for hackers to tamper with votes, causing the use of electronic voting technology to raise concerns about ballot security. We describe how electronic voting can be supported by blockchain technology to ensure voter secrecy, vote correctness, and equal voting rights. In this paper, we present a system using two separate blockchains, each with separate transactions and consensus algorithms. We describe a prototype implementation that validates our ideas by executing several proof-of-concept simulations of a range of voting scenarios.
R Manikandaprabhu, Mohamed Ashwak M., Mohamed Ashwak P, K Jegan · 5 authors
An electoral system or voting system is a set of rules that determine how elections and referendums are conducted and how their results are determined. Election is a very important event in a modern democracy but large sections of society around the world do not trust their election system which is major concern for the democracy. Distributed ledger technology is an exciting technological advancement in the information technology world. Blockchain Technologies offer an infinite range of applications benefiting from sharing economies. In this paper the proposed system is to store the ballot information as a block node for each and every voter and transfer the voters vote hash over the internet to all other nodes. The proposed system is cost-efficient when compared to the traditional electronic voting machines.
Nikos Fotiou, Iakovos Pittaras, Vasilios A. Siris, George C. Polyzos · 5 authors
Service providers usually require detailed statistics in order to improve their services. On the other hand, privacy concerns are intensifying and sensitive data is protected by legislation, such as GDPR (General Data Protection Regulation). In this paper, we present the design, implementation, and evaluation of a marketplace that allows “data consumers” to buy information from “data providers”, which can then be used for generating meaningful statistics. Additionally, our system enables “system operators” that can select which data providers are allowed to provide data, based on filtering criteria specified by the data consumer. We leverage local differential privacy to protect the data provider's privacy against data consumers, as well as against system operators, and we build a blockchain-based solution for ensuring fair exchange, and immutable data logs. Our design targets use cases that involve hundreds or even thousands of data providers. We prove the feasibility of our approach through a proof-of concept implementation of a measurement sharing application for smart-grid systems.
Yojna Arora, Mr. Vivek Birla, Mr. Rajat Gupta, Mr. Samarth Tiku
Voting is a constitutional part of governmental systems which gives the people of the nation the liberty to express their opinions. The contemporary system constitutes Electronic Voting Machines (EVM) that is a pile-up of data natively and centralized, making it implausible. Since the data is amassed locally over the EVM(s) prior to the election's cessation, it could be hacked. Furthermore, there have been events of "polling booth hijacking" in some regions during the elections. Ethereum blockchain technology addresses concerns regarding integrity, security, and accessibility of current voting systems. Expanding e-voting into Ethereum based blockchain technology is one potential application of the emerging blockchain technology. This paper presents a decentralized, incognito, and limpid e-voting system named "DILE". It will escalate accessibility as the users could cast their votes without paying a visit to the polling booths. DILE makes practical and effective use of Ethereum's blockchain technology and smart contracts for its implementation.
Open access
Internet Traffic Analysis and Secure E-voting
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
Abstract In recent years, blockchain-based systems have emerged powerfully and led to the development of several new and improved applications in terms of increased security, trust, accountability and reliability. One important trust-based application is electronic voting system which still lacks in providing good throughput while also reducing the costs in voting given the deployment of state-of-the-art technologies. So, there is a need to imply an efficient consensus protocol to impart cost-efficiency as well as better performance of a blockchain-based electronic voting system. This paper focuses on boosting up the cost-efficiency in the voting process, while also being auditable, thus, strengthening the trust of voters on the government and lessening the overall costs incurred in voting. In this paper, Proof-of-Stake-Voting is used as consensus protocol which is observed to give a throughput of 4-5K transactions per second. Then its performance is compared with the other existing consensus protocols such as Proof-of-Work and Proof-of-Authority in terms of gas consumption, gas cost, and throughput. It has been shown through the results that there is a significant difference in the total gas cost, with Proof-of-Stake-Voting protocol consuming 3.1 x 10 −7 Ethers (ETH), as compared to the Proof-of-Work, taking 5.42536 x 10 −4 ETH and Proof-of-Authority protocols taking 2.49759 x 10 −4 ETH.
Open access
Blockchain Technology Applications and Security
Internet Traffic Analysis and Secure E-voting
Advanced Steganography and Watermarking Techniques
Matthias Grundmann, Hedwig Amberg, Hannes Hartenstein
Bitcoin is based on a P2P network that is used to propagate transactions and blocks. While the P2P network design intends to hide the topology of the P2P network, information about the topology is required to understand the network from a scientific point of view. Thus, there is a natural tension between the 'desire' for unobservability on the one hand, and for observability on the other hand. On a middle ground, one would at least be interested on some statistical features of the Bitcoin network like the number of peers that participate in the propagation of transactions and blocks. This number is composed of the number of reachable peers that accept incoming connections and unreachable peers that do not accept incoming connections. While the number of reachable peers can be measured, it is inherently difficult to determine the number of unreachable peers. Thus, the number of unreachable peers can only be estimated based on some indicators. In this paper, we first define our understanding of unreachable peers and then propose the PAL (Passive Announcement Listening) method which gives an estimate of the number of unreachable peers by observing ADDR messages that announce active IP addresses in the network. The PAL method allows for detecting unreachable peers that indicate that they provide services useful to the P2P network. In conjunction with previous methods, the PAL method can help to get a better estimate of the number of unreachable peers. We use the PAL method to analyze data from a long-term measurement of the Bitcoin P2P network that gives insights into the development of the number of unreachable peers over five years from 2015 to 2020. Results show that about 31,000 unreachable peers providing useful services were active per day at the end of the year 2020. An empirical validation indicates that the approach finds about 50 % of unreachable peers that provide useful services.
Electing democratic representatives via voting has been a common mechanism since the 17th century. However, these mechanisms raise concerns about fairness, privacy, vote concealment, fair calculations of tally, and proxies voting on their behalf for the voters. Ballot voting, and in recent times, electronic voting via electronic voting machines (EVMs) improves fairness by relying on centralized trust. Homomorphic encryption-based voting protocols also assure fairness but cannot scale to large scale elections such as presidential elections. In this paper, we leverage the blockchain technology of distributing trust to propose a smart contract-based protocol, namely, \proto. There are many existing protocols for voting using smart contracts. We observe that these either are not scalable or leak the vote tally during the voting stage, i.e., do not provide vote concealment. In contrast, we show that FASTEN preserves voter's privacy ensures vote concealment, immutability, and avoids double voting. We prove that the probability of privacy breaches is negligibly small. Further, our cost analysis of executing FASTEN over Ethereum is comparable to most of the existing cost of elections.
In the current work we discuss the notion of gateways as a means for interoperability across different blockchain systems. We discuss two key principles for the design of gateway nodes and scalable gateway protocols, namely (i) the opaque ledgers principle as the analogue of the autonomous systems principle in IP datagram routing, and (ii) the externalization of value principle as the analogue of the end-to-end principle in the Internet architecture. We illustrate the need for a standard gateway protocol by describing a unidirectional asset movement protocol between two peer gateways, under the strict condition of both blockchains being private/permissioned with their ledgers inaccessible to external entities. Several aspects of gateways and the gateway protocol is discussed, including gateway identities, gateway certificates and certificate hierarchies, passive locking transactions by gateways, and the potential use of delegated hash-locks to expand the functionality of gateways.
Cryptocurrencies redefined how money can be stored and transferred among users. However, independent of the amount being sent, public blockchain-based cryptocurrencies suffer from high transaction waiting times and fees. These drawbacks hinder the wide use of cryptocurrencies by masses. To address these challenges, payment channel network concept is touted as the most viable solution to be used for micro-payments. The idea is exchanging the ownership of money by keeping the state of the accounts locally. The users inform the blockchain rarely, which decreases the load on the blockchain. Specifically, payment channel networks can provide transaction approvals in seconds by charging a nominal fee proportional to the payment amount. Such attraction on payment channel networks inspired many recent studies which focus on how to design them and allocate channels such that the transactions will be secure and efficient. However, as payment channel networks are emerging and reaching large number of users, privacy issues are becoming more relevant that raise concerns about exposing not only individual habits but also businesses' revenues. In this paper, we first propose a categorization of the existing payment networks formed on top of blockchain-backed cryptocurrencies. After discussing several emerging attacks on user/business privacy in these payment channel networks, we qualitatively evaluate them based on a number of privacy metrics that relate to our case. Based on the discussions on the strengths and weaknesses of the approaches, we offer possible directions for research for the future of privacy based payment channel networks.
Abstract Election is an important event in all countries. Conventional voting suffers many issues, such as cost of time and efforts needed for tallying and counting results, cost in papers, arrangements and all that it takes for a voting process to be achieved. Many countries such as Australia, Belgium, Brazil, Canada, Estonia, France, Germany, India, Italy, Namibia, the Netherlands, Norway, Peru, Switzerland, the UK, Venezuela and the Philippines considered online e-voting systems, but the traditional e-voting systems suffer a lack of trust, it is not known if a vote is counted correctly, tampered or not. The voter has no guarantee that his/her vote is considered as they voted in elections, it’s a lack of transparency. A solution is e-voting systems based on blockchain (sometimes referred as Distributed Ledger Technology (DLT)) has now turned to be promising for what properties it offer, such as, privacy, security, transparency, accuracy, decentralization in which no central control exist, and most of all, creates an immutable system, where citizens are allowed to vote from their location by using digital devices (smart phones, computers, electronic voting machines). Also, due to the COVID-19 pandemic, many technology applications are heading towards systems with all these properties, at the same time, maintaining social distancing. This review introduced many different ideas for implementing e-voting systems based on Blockchain and how the users (voters and candidates) interact with the system showing the voting process from the first step of registration to authentication till showing the final results. At the end of this review we will illustrate a table that contain all mechanisms used in the papers involved that covers the most important requirements needed for every e-voting system based on blockchain or Distributed Ledger Technology (DLT).
Open access
Internet Traffic Analysis and Secure E-voting
Blockchain Technology Applications and Security
Advanced Steganography and Watermarking Techniques
As the next-generation network architecture, software-defined networking (SDN) has great potential. But how to forward data packets safely is a big challenge today. In SDN, packets are transferred according to flow rules which are made and delivered by the controller. Once flow rules are modified, the packets might be redirected or dropped. According to related research, we believe that the key to forward data flows safely is keeping the consistency of flow rules. However, existing solutions place little emphasis on the safety of flow rules. After summarizing the shortcomings of the existing solutions, we propose FRChain to ensure the security of SDN data forwarding. FRChain is a novel scheme that uses blockchain to secure flow rules in SDN and to detect compromised nodes in the network when the proportion of malicious nodes is less than one-third. The scheme places the flow strategies into blockchain in form of transactions. Once an unmatched flow rule is detected, the system will issue the problem by initiating a vote and possible attacks will be deduced based on the results. To simulate the scheme, we utilize BigchainDB, which has good performance in data processing, to handle transactions. The experimental results show that the scheme is feasible, and the additional overhead for network performance and system performance is less than similar solutions. Overall, FRChain can detect suspicious behaviors and deduce malicious nodes to keep the consistency of flow rules in SDN.
Cryptocurrencies have enhanced financial transactions, but being decentralized, they pose numerous security threats to their users, warranting new anomaly detection systems for fraud prevention.The present research focuses on the machine learning (ML) techniques used in detecting suspicious activities in cryptocurrency networks, focusing on their contribution to AML and CFT compliance.The paper also compares supervised and unsupervised learning techniques and their merits and demerits.The supervised learning techniques, including Decision Trees, SVMs, and Neural Networks, are presented for their accuracy and flexibility, and, on the other hand, the unsupervised learning approaches, including Clustering, Isolation Forests, and Autoencoders are considered for their potential to discover new fraud patterns even if the training data is not labeled.An analysis of the use of explainability tools such as LIME and SHAP in artificial intelligence systems is also carried out to improve how users understand the results given to them by the AI models.These models have their real-life application illustrated by case studies, which prove helpful in identifying anomalies in Bitcoin and Ethereum transactions.New research directions suggest improvements in machine learning methods, the connection of the results with analysis tools based on blockchain, and cooperation with relevant authorities to improve the identification of threats and conformity with established guidelines.The potential of applying the idea of this work in traditional finance and cybersecurity is discussed, highlighting the possibility of applying ML in multiple fields to enhance security and compliance.The study then informs the significance of continued research and collaboration among disciplines to combat the emerging issues of financial fraud and cybercrimes related to cryptocurrencies.
Bilgisayar ve internet teknolojilerindeki gelişmeler, hayatımızın her alanında etkisini gösterdiği gibi ekonomi boyutunda da etkileri yadsınamaz. Ekonomi alanındaki yeni ekonomik reform mahiyetinde kabul gören bu yenilikler FinTek (Finans ve Teknoloji) kapsamı içerisinde yer almaktadır. FinTech inovasyonu ile ekonomide ademi merkeziyetçi bir akım başlatan Bitcoin, şu an dünya ekonomisinde önemli bir yere sahiptir. Bitcoin ile hayatımıza giren Blockchain (Blokzincir) teknolojisinin ise yakın gelecekte hayatımızın vazgeçilmez bir parçası haline geleceği öngörülmektedir. Tüm bu gelişmeler ışığında günümüzün popüler teknolojilerinden olan yapay zeka yöntemlerinden yararlanılarak, kitle haberleşme aracı olarak tanımlanan gazetelerde yer alan, insan ve toplumu ilgilendiren ve toplumun en önemli ihtiyaçlarından olan haberlerin, geleceğin para birimi olarak görülen Bitcoin üzerindeki etkileri ortaya konmak istenmiştir. Bu bağlamda 5 ulusal finans gazetesi belirlenip, Bitcoin’in ilk halka arz yılından itibaren yayınlanan haberleri olumlu ve olumsuz yorum içeriklerine göre sayısallaştırarak, Bitcoin altyapı teknolojisi olan blokzinciri verileri ile ikinci en popüler kripto para olan Ethereum’un ABD dolar karşılığı alınarak, yapay sinir ağları teknikleri ile oluşturulan ağ içerisinde ilişkilendirilmiştir. Çalışma sonucunda %99’luk tahminsel başarı içeren yapay sinir ağında, finansal gazetelerin yayınlamış olduğu Bitcoin içerikli haberlerin, Bitcoin fiyat tahminine güçlü bir etkisinin olmadığı sonucuna varılmıştır. Bunulan birlikte seçilen finansal gazetelerden The Wall Street gazetesinin diğer finansal gazetelere oranla Bitcoin fiyat tahminde nispeten etkisinin olduğu saptanmıştır.
Wide Area Protection System (WAPS) undertakes the important task of maintaining system reliability and stability when the power system is subject to abnormal or predetermined unstable conditions. The existing WAPS adopts a centralized mechanism to record and audit communication messages, which faces the risk of excessive authority and tampering with communication records and audit logs, thus making it impossible to achieve true transparency and fairness. Due to the involvement of multiple parties and equipment maintained by different manufacturers in the communication of WAPS, there are difficulties in tracing the cause of the accident and determining the at-fault party following misoperations and miss trips. To address this issue, we propose a semi-centralized blockchain system with multi-chain for auditing communications of WAPS. We first propose a semi-centralized system architecture according to the system architecture and management requirements of WAPS. Then, we utilize the blockchain network as a self-recording channel to achieve tamper-proof and non-repudiation verification interaction. We also design a multi-chain structure and classification node mechanism to meet the communication auditing requirements of multiple WAPS. We have designed a new block structure that conforms to the communication protocol of WAPS. To reduce the storage burden caused by the ever-expanding blockchain ledger, we propose a deletable blockchain scheme while maintaining the integrity and security of blockchain. Analysis and experiments show that the proposed blockchain system can support the secure, transparent, tamper-proof and traceable communication recording and auditing of WAPS along with high performance.
Electronic voting systems have several necessarily requirements, such as anonymity that others cannot link voters with votes, the fairness that votes should not be leaked before the tally, and the accuracy that eligible voters' votes should be counted correctly. There have been proposed various methods to realize the requirements. Some of them require anonymous communication paths as necessary elements to satisfy the anonymity requirement for a practical electronic voting system. Cruz et al. proposed an electronic voting system that does not need anonymous communication paths, using Bitcoin, a cryptographic currency, as a distributed database. However, Bitcoin is a system in which all data are disclosed, and anyone can check what exchanges a person of a certain ID (Bitcoin address) has done. It is possible to reveal which voter made what vote, and hence(anonymity is not satisfied. In this paper, we propose a method to solve the above problem by using Bitcoin mixing. We propose an electronic voting system using Zerocoin, a variant of Bitcoin, as a database, in which zero knowledge proof is used instead of blind signature for mixing.