Decentralisation is one of the promises introduced by blockchain technologies: fair and secure interaction amongst peers with no dominant positions, single points of failure or censorship. Decentralisation, however, appears difficult to be formally defined, possibly a continuum property of systems that can be more or less decentralised, or can tend to decentralisation in their lifetime. In this paper we focus on decentralisation in quorum-based approaches to open (permissionless) consensus as illustrated in influential protocols such as the Ripple and Stellar protocols. Drawing from game theory and computational complexity, we establish limiting results concerning the decentralisation vs. safety trade-off in Ripple and Stellar, and we propose a novel methodology to formalise and quantitatively analyse decentralisation in this type of blockchains.
Blockchains are becoming increasingly relevant in a variety of fields, such as finance, logistics, and real estate. The fundamental task of a blockchain system is to establish data consistency among distributed agents in an open network. Blockchain consensus protocols are central for performing this task. Since consensus protocols play such a crucial role in blockchain technology, several projects are underway that apply formal methods to these protocols. One such project is carried out by a team of the Formal Methods Group at IOHK. This project, in which the author is involved, aims at a formally verified implementation of the Ouroboros family of consensus protocols, the backbone of the Cardano blockchain. The first outcome of our project is the $\natural$-calculus (pronounced "natural calculus"), a general-purpose process calculus that serves as our implementation language. The $\natural$-calculus is a domain-specific language embedded in a functional host language using higher-order abstract syntax. This paper will be a ramble through the $\natural$-calculus. First we will look at its language and its operational semantics. The latter is unique in that it uses a stack of two labeled transition systems to treat phenomena like data transfer and the opening and closing of channel scope in a modular fashion. The presence of multiple transition systems calls for a generic treatment of derived concurrency concepts. We will see how such a treatment can be achieved by capturing notions like scope opening and silent transitions abstractly using axiomatically defined algebraic structures based on functors and monads.
While previous work has recognized the potential for open badges and blockchain to play a role in online courses, this potential has yet to be realized in a fully decentralized cMOOC. This paper describes the design objectives of an application that integrates open badges and blockchain with a cMOOC. The work described was undertaken during the offering on an online course, and thus development took place in an actual course context with interaction with course participants. The full workflow from course content to storage on the blockchain is described, and some concluding comments are offered on the results of this course, and the potential for future applications.
Atomic Crosschain Transaction technology allows composable programming across private Ethereum blockchains. It allows for inter-contract and inter-blockchain function calls that are both synchronous and atomic: if one part fails, the whole call graph of function calls is rolled back. Traditional Ethereum contract functions can limit which accounts can call them by specialised application program logic. This is important as it allows application developers to specify which callers can execute functions that update contract state. In this paper we introduce the strategy required to restrict which contracts on one blockchain can call a function in a contract that is deployed on another blockchain. We show that validating the Originating Blockchain Id (the blockchain the crosschain function call started on), From Blockchain Id, and From Account provides contracts with certainty that a function call came from a specific contract on a specific blockchain.
The proportion of information that is exclusively available online is continuously increasing. Unlike physical print media, online news outlets, magazines, or blogs are not immune to retrospective modification. Even significant editing of text in online news sources can easily go unnoticed. This poses a challenge to the preservation of digital cultural heritage. It is nearly impossible for regular readers to verify whether the textual content they encounter online has at one point been modified from its initial state, and at what time or to what extent the text was modified to its current version. In this paper, we propose a web-based platform that allows users to submit the URL for any web content they wish to track for changes. The system automatically creates a trusted timestamp stored in the blockchain of the cryptocurrency Bitcoin for the hash of the HTML content available at the user-specified URL. By using trusted timestamping to secure a âsnapshotâ of online information as it existed at a specific time, any subsequent changes made to the content can be identified.
Open access
Archaeological Research and Protection
Advanced Steganography and Watermarking Techniques
Many sectors, like finance, medicine, manufacturing, and education, use blockchain applications to profit from the unique bundle of characteristics of this technology. Blockchain technology (BT) promises benefits in trustability, collaboration, organization, identification, credibility, and transparency. In this paper, we conduct an analysis in which we show how open science can benefit from this technology and its properties. For this, we determined the requirements of an open science ecosystem and compared them with the characteristics of BT to prove that the technology suits as an infrastructure. We also review literature and promising blockchain-based projects for open science to describe the current research situation. To this end, we examine the projects in particular for their relevance and contribution to open science and categorize them afterwards according to their primary purpose. Several of them already provide functionalities that can have a positive impact on current research workflows. So, BT offers promising possibilities for its use in science, but why is it then not used on a large-scale in that area? To answer this question, we point out various shortcomings, challenges, unanswered questions, and research potentials that we found in the literature and identified during our analysis. These topics shall serve as starting points for future research to foster the BT for open science and beyond, especially in the long-term.
Open access
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Blockchain Technology Applications and Security
Innovative Microfluidic and Catalytic Techniques Innovation
A problem of developing the consensus protocols in public blockchain systems which spend a combination of energy and space resources is addressed. A technique is proposed that provides a flexibility for selection of the energy and space resources which should be spent by a player participating in the consensus procedure. The technique originates from the cryptographic time-memory-data trade-off approaches for cryptanalysis. The proposed technique avoids the limitations of Proof-of-Work (PoW) and Proof-of Space (PoS) which require spending of only energy and space, respectively. Also, it provides a flexibility for adjusting the resources spending to the system budget. The proposed consensus technique is based on a puzzle where the problem of inverting one-way function is solved employing a dedicated Time-Memory-Data Trade-Off (TMD-TO) paradigm. The algorithms of the consensus protocol are proposed which employ certain unconstrained and constrained TMD-TO based inversions. Security of the proposed technique is considered based on the probability that the honest pool of nodes generate a longer extension of the blockchain before its update, and a condition on the employed parameters in order to achieve desired security have been derived. Implementation complexity of the proposed consensus protocol is discussed and compared with the complexities when PoW and PoS are employed.
Abstract Recent studies show that 20.4% of the internet traffic originates from automated agents. To identify and block such ill-intentioned traffic, mechanisms that verify the humanness of the user are widely deployed, with CAPTCHAs being the most popular. Traditional CAPTCHAs require extra user effort (e.g., solving mathematical puzzles), which can severely downgrade the end-userâs experience, especially on mobile, and provide sporadic humanness verification of questionable accuracy. More recent solutions like Googleâs reCAPTCHA v3, leverage user data, thus raising significant privacy concerns. To address these issues, we present zkSENSE: the first zero-knowledge proof-based humanness attestation system for mobile devices. zkSENSE moves the human attestation to the edge: onto the userâs very own device, where humanness of the user is assessed in a privacy-preserving and seamless manner. zkSENSE achieves this by classifying motion sensor outputs of the mobile device, based on a model trained by using both publicly available sensor data and data collected from a small group of volunteers. To ensure the integrity of the process, the classification result is enclosed in a zero-knowledge proof of humanness that can be safely shared with a remote server. We implement zkSENSE as an Android service to demonstrate its effectiveness and practicality. In our evaluation, we show that zkSENSE successfully verifies the humanness of a user across a variety of attacking scenarios and demonstrate 92% accuracy. On a two years old Samsung S9, zkSENSEâs attestation takes around 3 seconds (when visual CAPTCHAs need 9.8 seconds) and consumes a negligible amount of battery.
Alex Groce, Josselin Feist, Gustavo Grieco, Michael Colburn
An important problem in smart contract security is understanding the likelihood and criticality of discovered, or potential, weaknesses in contracts. In this paper we provide a summary of Ethereum smart contract audits performed for 23 professional stakeholders, avoiding the common problem of reporting issues mostly prevalent in low-quality contracts. These audits were performed at a leading company in blockchain security, using both open-source and proprietary tools, as well as human code analysis performed by professional security engineers. We categorize 246 individual defects, making it possible to compare the severity and frequency of different vulnerability types, compare smart contract and non-smart contract flaws, and to estimate the efficacy of automated vulnerability detection approaches.
Eman Daraghmi, YousefâAwwad Daraghmi, ShyanâMing Yuan
Although blockchain technology was first introduced through Bitcoin, extending its usage to non-financial applications, such as managing academic records, is a new mission for recent research to balance the needs for increasing data privacy and the regular interaction among students and universities. In this paper, a design for a blockchain-based system, namely UniChain, for managing Electronic Academic Records (EARs) is proposed. UniChain is designed to improve the current management systems as it provides interoperable, secure, and effective access to EARs by students, universities, and other third parties, while keeping the studentsâ privacy. UniChain employs timed-based smart contracts for governing transactions and controlling access to EARs. It adopts advanced encryption techniques for providing further security. This work proposes a new incentive mechanism that leverages the degree of universities regarding their efforts on maintaining academic records and creating new blocks. Extensive experiments were conducted to evaluate the UniChain performance, and the results indicate the efficiency of the proposal in handling a large dataset at low latency.
Alex Groce, Josselin Feist, Gustavo Grieco, Michael D. Colburn
An important problem in smart contract security is understanding the\nlikelihood and criticality of discovered, or potential, weaknesses in\ncontracts. In this paper we provide a summary of Ethereum smart contract audits\nperformed for 23 professional stakeholders, avoiding the common problem of\nreporting issues mostly prevalent in low-quality contracts. These audits were\nperformed at a leading company in blockchain security, using both open-source\nand proprietary tools, as well as human code analysis performed by professional\nsecurity engineers. We categorize 246 individual defects, making it possible to\ncompare the severity and frequency of different vulnerability types, compare\nsmart contract and non-smart contract flaws, and to estimate the efficacy of\nautomated vulnerability detection approaches.\n
Recent studies show that 20.4% of the internet traffic originates from automated agents. To identify and block such ill-intentioned traffic, mechanisms that verify the humanness of the user are widely deployed across the internet. CAPTCHA is the most popular among such mechanisms. Original CAPTCHAs require extra user effort (e.g., solving mathematical or image-based puzzles), which severely harms user's experience, especially on mobile, and provide only sporadic verification of their humanness. More recent solutions like Google's reCAPTCHA v3 leverage attestation data (e.g., user behavioral data, device fingerprints) shared with a remote server, thus raising significant privacy concerns. To address all of the above, we present ZKSENSE: the first zero knowledge proof-based humanness attestation system designed for mobile devices. Contrary to state-of-the-art systems, ZKSENSE assesses humanness continuously on the background in a privacy preserving way. ZKSENSE achieves that by classifying the motion sensor outputs of the mobile device based on a model trained by using both publicly available sensor data and data collected from a small group of volunteers. The classification result is enclosed in a zero knowledge proof of humanness that can be safely shared with an attestation service such as Privacy Pass. We implement ZKSENSE as an Android service to demonstrate its effectiveness and practicability. In our evaluation, we show that ZKSENSE verifies the humanness of the users asynchronously, on the background, without degrading their experience or jeopardizing user privacy, while it achieves 91% accuracy across a variety of attack scenarios. On a two years old Samsung S9, each attestation takes around 3 seconds in total (when visual CAPTCHAs need 9.8 seconds) and consumes a negligible amount of battery.
We initiate the study of non-interactive zero-knowledge (NIZK) arguments for languages in QMA. Our first main result is the following: if Learning With Errors (LWE) is hard for quantum computers, then any language in QMA has an NIZK argument with preprocessing. The preprocessing in our argument system consists of (i) the generation of a CRS and (ii) a single (instance-independent) quantum message from verifier to prover. The instance-dependent phase of our argument system involves only a single classical message from prover to verifier. Importantly, verification in our protocol is entirely classical, and the verifier needs not have quantum memory; its only quantum actions are in the preprocessing phase. Our second contribution is to extend the notion of a classical proof of knowledge to the quantum setting. We introduce the notions of arguments and proofs of quantum knowledge (AoQK/PoQK), and we show that our non-interactive argument system satisfies the definition of an AoQK. In particular, we explicitly construct an extractor which can recover a quantum witness from any prover which is successful in our protocol. Finally, we show that any language in QMA has an (interactive) proof of quantum knowledge.
We provide several advances to the understanding of the class of Quantum Merlin-Arthur proof systems (QMA), the quantum analogue of NP. Our central contribution is proving a longstanding conjecture that the Consistency of Local Density Matrices (CLDM) problem is QMA-hard under Karp reductions. The input of CLDM consists of local reduced density matrices on sets of at most k qubits, and the problem asks if there is an n-qubit global quantum state that is locally consistent with all of the k-qubit local density matrices. The containment of this problem in QMA and the QMA-hardness under Turing reductions were proved by Liu [APPROX-RANDOM 2006]. Liu also conjectured that CLDM is QMA-hard under Karp reductions, which is desirable for applications, and we finally prove this conjecture. We establish this result using the techniques of simulatable codes of Grilo, Slofstra, and Yuen [FOCS 2019], simplifying their proofs and tailoring them to the context of OMA. In order to develop applications of CLDM, we propose a framework that we call locally simulatable proofs for QMA: this provides QMA proofs that can be efficiently verified by probing only k qubits and, furthermore, the reduced density matrix of any k-qubit subsystem of a good witness can be computed in polynomial time, independently of the witness. Within this framework, we show several advances in zero-knowledge in the quantum setting. We show for the first time a commit-and-open computational zero-knowledge proof system for all of QMA, as a quantum analogue of a âsigmaâ protocol. We then define a Proof of Quantum Knowledge, which guarantees that a prover is effectively in possession of a quantum witness in an interactive proof, and show that our zero-knowledge proof system satisfies this definition. Finally, we show that our proof system can be used to establish that QMA has a quantum non-interactive zero-knowledge proof system in the secret parameter setting.11The full version of this work can be found in https://arxiv.org/abs/1911.07782.
Through the Internet of Industrial Things, significant investments in the industry are expected. In this new environment, machine-to-machine communication showed immediate potential. However, most communication implementations require a trusted intermediary. The introduction of smart contracts can enable communication without the need for a trusted intermediary. To provide security and decentralization in industrial communication processes, smart contract-based middleware is proposed. This proposal is evaluated for impacts against the stringent communication requirements required by industrial applications. Experimental results show that while this approach offers greater security and decentralization than traditional proposals, blockchain-based smart contracts cannot yet be applied to industrial systems due to blocking time.
We provide several advances to the understanding of the class of Quantum Merlin-Arthur proof systems (QMA), the quantum analogue of NP. First, we answer a longstanding open question by showing that the Consistency of Local Density Matrices problem is QMA-complete under Karp reductions. We also show for the first time a commit-and-open computational zero-knowledge proof system for all of QMA as a quantum analogue of a sigma protocol. We then define a Proof of Quantum Knowledge, which guarantees that a prover is effectively in possession of a quantum witness in an interactive proof, and show that our zero-knowledge proof system satisfies this definition. Finally, we show that our proof system can be used to establish that QMA has a quantum non-interactive zero-knowledge proof system in the secret parameters setting.
Our main technique consists in developing locally simulatable proofs for all of QMA: this is an encoding of a QMA witness such that it can be efficiently verified by probing only five qubits and, furthermore, the reduced density matrix of any five-qubit subsystem can be computed in polynomial time and is independent of the witness. This construction follows the techniques of Grilo, Slofstra, and Yuen [FOCS 2019].
Blockchain networks and similar cryptoeconomic networks are systems, specifically complex systems. They are adaptive networks with multiscale spatio-temporal dynamics. Individual actions may be incentivized towards a collective goal with âpurpose-drivenâ tokens. Blockchain networks, for example, are equipped cryptoeconomic mechanisms that allow the decentralized network to simultaneously maintain a universal state layer, support peer-to-peer settlement, and incentivize collective action. These networks represent an institutional infrastructure upon which socioeconomic collaboration is facilitated â in the absence of intermediaries or traditional organizations. They provide a mission-critical and safety-critical regulatory infrastructure for autonomous agents in untrusted economic networks. Their tokens provide a rich, real-time data set reflecting all economic activities in their systems. Advances in network science and data science can thus be leveraged to design and analyze these economic systems in a manner consistent with the best practices of modern systems engineering. Research that reflects all aspects of these socioeconomic networks needs (i) a complex systems approach, (ii) interdisciplinary research, and (iii) a combination of economic and engineering methods, here referred to as âeconomic systems engineering,â for the regulation and control of these socioeconomic systems. This manuscript provides a conceptual framework synthesizing the research space and proceeds to outline specific research questions and methodologies for future research in this field, applying an inductive approach based on interdisciplinary literature review and relative contextualization of the works cited.
The purpose of the research is to investigate the implementation of blockchains (BCs) and smart contracts (SCs) in smart tourism. BCs and SCs in the context of tourism are underexplored. Data were collected and analysed from relevant secondary sources in extensive desktop research between January and August 2018. The results highlight some implemented examples of BCs and SCs in tourism and few that are still in probation phase. The findings are interesting for tourism policy-makers, professionals, academics and tourism suppliers who are interested in real value added of BCs and SCs in tourism.
In this report, the University Medical Center Groningen (UMCG) has written down lessons learned on how blockchain technology can have an impact on the healthcare domain. By looking at two use-cases, the hospital challenged several teams, participating in an open innovation program and blockchain hackathon, to find a solution that showed the added value of the technology for patient care and scientific research. Besides this practical perspective, the report also considers literature discussing the current state of blockchain technology in regard to developments in the healthcare domain (touching on patient empowerment, data management, regulations, and interoperability between healthcare systems).
Andrea Gaggioli, Shayan Eskandari, Pietro Cipresso, Edoardo Lozza
Blockchain is widely regarded as a breakthrough innovation that may have a profound impact on the economy and society, of a magnitude comparable to the effects of the introduction of the Internet itself. In essence, a blockchain is a decentralized peer-to-peer network with no central authority figure, which adds information to the distributed database by collectively validating the accuracy of data. Since each node of the network participates in the review and confirmation of the new information before being accepted, the need for a trustworthy intermediary is eliminated. However, as trust plays an essential role in affecting decisions when transacting with one another, it is important to understand which implications the decentralized nature of blockchain may have on individuals' sense of trust. In this contribution, we argue that the adoption of blockchain is not only a technological, but foremostly a psychological challenge, which crucially depends on the possibility of creating a trust management approach that matches the underlying distributed communication system. We first describe the decentralization technologies and possibilities they hold for the near future. Next, we discuss the psycho-social implications of the introduction of decentralized processes of trust, examining some potential scenarios, and outline a research agenda.
Budankailu Kumar Subudhi, Faruk Catal, Nikolay Tcholtchev, Kin Tsun Chiu · 7 authors
VoIP-based emergency communication is a promising approach to improving the safety of citizens worldwide. The transition required in this scope includes substituting the legacy PSTN/SS7 based emergency call system by Next Generation IP based components for call establishment and control. Thereby, SIP is used as a session control protocol and RTP as the means to transfer emergency data between the caller and the corresponding Public Safety Access Point (PSAP). The emergency data is not only restricted to voice communication but can cover a rich variety of data, which can be acquired by different means (including the end-user devices) and transmitted over IP. This includes video, geopositioning data, voice, Real-Time Text, and sensor data in line with emerging IoT architectures and approaches. A vital aspect in this scope is given by the performance of the underlying network, including its capability to establish calls in emergencies and to transfer the data required for serving the situation. Therefore, in this paper, we evaluate the computational performance of the most recent VoIP emergency system implementation, which was developed by the H2020-EMYNOS project as a realisation of the EENA NG112 Long Term Definition (LTD) vision. We perform a series of trials and evaluate the performance of the EMYNOS system in a multi-party lab environment established during the project. We evaluate the time needed to perform basic emergency call operations over IP, whilst in parallel generating Internet type of background traffic. Correspondingly, we worked out a methodology and implemented it in our testbed, both of which are presented in the current paper. The obtained numerical results lead to the conclusion that SIP-based emergency services stand a good chance to replace legacy systems when it comes to their performance. Additionally, we also provide a perspective on how the blockchain technology could potentially be put to use to enhance the quality of the next-generation emergency services. We propose the utilisation of blockchain technology for tracking emergency calls and enabling efficient recognition of fraud calls, which is a critical aspect for PSAP providers concerning the potential denial of service attacks. In this context, we provide evaluations and numerical results based on a private Ethereum based blockchain playground running at the premises of Fraunhofer FOKUS.
Audi Ramadhan, Chandra Indira Septiarani, Faisal Dias, Deden Yoga Pratama
Aplikasi trading cryptocurrency merupakan sebuah aplikasi yang relatif baru yang ditandai dengan munculnya banyak cryptocurrency seperti Bitcoin, Ethereum dan lain sebagainya. Oleh sebab itu, analisis penerimaan teknologi pada aplikasi tersebut sangat penting untuk dikaji lebih dalam. Penelitian ini bertujuan untuk menganalisis dan mengukur penerimaan aplikasi trading cryptocurrency yaitu Indodax Trading Platform dengan menggunakan Technology Acceptance Model (TAM) yang diintegrasikan dengan faktor resiko dan kepercayaan. Penelitian ini merupakan penelitian kuantitatif asosiatif dengan menggunakan kuesioner untuk mendapatkan data primer. Sampel yang digunakan pada penelitian ini sebesar 134 dengan menggunakan teknil analisis Semi Equation Model â Partial Least Square (SEM-PLS). Hasil dari penelitian ini yaitu adanya pengaruh dari perceived usefulness dan trust terhadap penggunaan aplikasi trading cryptocurrency. Sedangkan resiko dan perceived ease of use tidak berpengaruh terhadap penggunaan aplikasi trading cryptocurrency.
Tim K. Mackey, Neal Shah, Ken Miyachi, James E. Short · 5 authors
Scientific research activity is reaching a staggering growth rate, introducing new and compounding existing challenges regarding the quality of peer-review, rise of predatory journals, and larger issues involving academic integrity and fraud stemming from the increased pressure to publish. Blockchain, a distributed ledger technology, is well-suited to address some of the challenges specific to scientific publishing. Companies including ARTiFACTS, Pluto, Orvium, and ScienceMatters-EUREKA, along with academic researchers, are exploring blockchain-based solutions to facilitate research data provenance and workflows, optimize the peer-review process, introduce better incentives, and even create new research journals and platforms utilizing blockchain. Building upon a review of these efforts, we propose a governance framework for scientific publishing based on a consortium blockchain model to create a more efficient means of navigating the publishing process. At the center of this framework is a model that adopts shared governance and validated inclusion via a Democratic Autonomous Organization (DAO). A DAO is an entity wherein the organizational rules are implemented and executed via smart contracts. The DAO will be comprised of participants of validated individuals and organizations who are publishers, editors, peer-reviewers, and citizen scientists to manage and oversee the framework. The framework also maps specifically to the publication workflow of submitting, handling, peer-review, and final editorial decision-making for scientific manuscripts. The goal of this framework is to increase transparency of scientific publishing, create a âpedigreeâ of a manuscriptâs research life cycle, and democratize the publication process while maintaining the accepted workflow common to scientific publishing by journals.