Blockchain Papers

Alexander Mühle, Andreas Grüner, Tatiana Gayvoronskaya, Christoph Meinel

This paper provides an overview of the Self-Sovereign Identity (SSI) concept, focusing on four different components that we identified as essential to the architecture. Self-Sovereign Identity is enabled by the new development of blockchain technology. Through the trustless, decentralised database that is provided by a blockchain, classic Identity Management registration processes can be replaced. We start off by giving a simple overview of blockchain based SSI, introducing an architecture overview as well as relevant actors in such a system. We further distinguish two major approaches, namely the Identifier Registry Model and its extension the Claim Registry Model. Subsequently we discuss identifiers in such a system, presenting past research in the area and current approaches in SSI in the context of Zooko's Triangle. As the user of an SSI has to be linked with his digital identifier we also discuss authentication solutions. Most central to the concept of an SSI are the verifiable claims that are presented to relying parties. Resources in the field are only losely connected. We will provide a more coherent view of verifiable claims in regards to blockchain based SSI and clarify differences in the used terminology. Storage solutions for the verifiable claims, both on- and off-chain, are presented with their advantages and disadvantages.

Seyed Yahya Nikouei, Ronghua Xu, Deeraj Nagothu, Yu Chen · 6 authors

Information from surveillance video is essential for situational awareness (SAW). Nowadays, a prohibitively large amount of surveillance data is being generated continuously by ubiquitously distributed video sensors. It is very challenging to immediately identify the objects of interest or zoom in suspicious actions from thousands of video frames. Making the big data indexable is critical to tackle this problem. It is ideal to generate pattern indexes in a real-time, on-site manner on the video streaming instead of depending on the batch processing at the cloud centers. The modern edge-fog-cloud computing paradigm allows implementation of time sensitive tasks at the edge of the network. The on-site edge devices collect the information sensed in format of frames and extracts useful features. The near-site fog nodes conduct the contextualization and classification of the features. The remote cloud center is in charge of more data intensive and computing intensive tasks. However, exchanging the index information among devices in different layers raises security concerns where an adversary can capture or tamper with features to mislead the surveillance system. In this paper, a blockchain enabled scheme is proposed to protect the index data through an encrypted secure channel between the edge and fog nodes. It reduces the chance of attacks on the small edge and fog devices. The feasibility of the proposal is validated through intensive experimental analysis.

bhaskar bhaskar

The present paper attempts to look into the nuances of the direct funding of local government from a vantage point of fiscal federalism in India and also the dynamics of financial decentralization. The reports of finance commissions regarding the devolution of tax powers to local governments in order to make them financially autonomous has been looked into with a incisive constitutional mindset. The impact of centrally sponsored scheme in this regard has been looked into by the researcher in order to get the exposer of current federal implications of the same where the party politics and an attempt to create loyal vote bank is driving the pace of CSS which is affecting the fiscal federalism. The GST has also affected the tax structure of country in many aspects and in paper the impact of it on local government has been contemplated.

John Butcher

Abstract Externalised service provision is now an embedded feature of Australia's service delivery architecture. However, the lessons drawn from two decades of contracted service delivery suggest that “competition” is an imperfect platform for the delivery of public services, especially where issues of trust in government come into play. Could the concept of a “social license to operate” (SLO), which has been in use in the natural resources sector for over two decades, help to facilitate the conferral of greater trust, credibility and legitimacy upon governments, and externalised service providers in social policy spaces?

Albert Guan, Wen-Guey Tzeng

No abstract is available for this record.

Zhaojun Lu, Qian Wang, Gang Qu, Zhenglin Liu

The public key infrastructure (PKI) based authentication protocol provides the basic security services for vehicular ad-hoc networks (VANETs). However, trust and privacy are still open issues due to the unique characteristics of vehicles. It is crucial for VANETs to prevent internal vehicles from broadcasting forged messages while simultaneously protecting the privacy of each vehicle against tracking attacks. In this paper, we propose a blockchain-based anonymous reputation system (BARS) to break the linkability between real identities and public keys to preserve privacy. The certificate and revocation transparency is implemented efficiently using two blockchains. We design a trust model to improve the trustworthiness of messages relying on the reputation of the sender based on both direct historical interactions and indirect opinions about the sender. Experiments are conducted to evaluate BARS in terms of security and performance and the results show that BARS is able to establish distributed trust management, while protecting the privacy of vehicles.

Michiel Van Beirendonck, Louis-Charles Trudeau, Pascal Giard, Alexios Balatsoukas‐Stimming

Lyra2REv2 is a hashing algorithm that consists of a chain of individual hashing algorithms and it is used as a proof-of-work function in several cryptocurrencies that aim to be ASIC-resistant. The most crucial hashing algorithm in the Lyra2REv2 chain is a specific instance of the general Lyra2 algorithm. In this work we present the first FPGA implementation of the aforementioned instance of Lyra2 and we explain how several properties of the algorithm can be exploited in order to optimize the design.

Michiel Van Beirendonck, Pascal Giard, Alexios Balatsoukas‐Stimming

No abstract is available for this record.

Xiaoyao Qian

One of the most important components in a public blockchain like Bitcoin and Ethereum is the authenticated data structure that keeps track of all block data, transactions, and the world state (account balance, smart contract states, etc.) Thanks to authenticated data structures, lightweight nodes only need to store authentication information and can delegate queries to those nodes with a full replica of data and the authenticated data structure. The lightweight nodes can trust the query results after verifying against the authentication information. It is also critical to have enough nodes in the network that are equipped with the authenticated data structure to ensure scalability and availability, which is especially important for public blockchains. Therefore, every public blockchain highly encourages users to download the authenticated data structure as the first step.\n\nFetching all elements from the entire authenticated data structure is a novel query type that has not gathered attention in the past. We describe this new emerging query type in the three-party authenticated data structure (ADS). We improve the design and implementation of the authenticated data structure so that the new query type is well-supported. We specifically apply the improvements to the Ethereum blockchain network. With our proposed ADS system in Ethereum, we improve Ethereum state synchronization performance by 216 times.

B. Moustapha

In this paper, we revisit the fundamental question of Bitcoins security against selfish-mine attack introduced by I. Eyal and E. G. Sirer in We study the state machine of Bitcoin's network under the influence of one pool miner adopting the selfish mine strategy while the rest of the community following the standard protocol. We prove that the process following by the states of Bitcoin's system is a irreducible, positive-recurrent, aperiodic, and discrete Markov chain. We give an invariant (stationary) distribution for this Markov chain and deduce easily the rate of convergence towards the stationary equilibrium situation.

Francesco Bortolussi, Zeger Hoogeboom, Frank W. Takes

Cryptocurrencies such as Bitcoin and Ethereum have recently gained a lot of popularity, not only as a digital form of currency but also as an investment vehicle. Online marketplaces and exchanges allow users across the world to convert between dozens of different cryptocurrencies and regular currencies such as euros or dollars. Due to the novelty of this concept, the volatility of these markets and the differences in maturity and usage of particular marketplaces, currency pairs may appear at multiple marketplaces but at different trading prices. This paper proposes a novel algorithmic approach to take advantage of these mispricings and capitalize upon the pricing differences that exist between exchanges and currency pairs. To do so, we model each combination of a currency and a market as one node in a graph. A directed link between two nodes indicates that a conversion between these two currency/market pairs is possible. The weight of the link relates to the exchange rate of executing this particular currency exchange. To leverage the mispricings, we seek for cycles in the graph such that upon multiplying the weights of the links in the cycle, a value greater than 1 is found and thus a profit can be made. Our goal is to do this efficiently, without exhaustively enumerating all possible cycles in the graph. Therefore, we convert our data and address the problem in terms of finding minimum weight triangles in graphs with integer weights, for which efficient algorithms can be utilized. We experiment with parameter settings (heuristics) related to the conversion of exchange rate data into integer weight values. We show that our approach improves upon a reasonable baseline algorithm in terms of computation time. Furthermore, using a real-world dataset, we demonstrate how the obtained minimal weight cycles indeed unveil a number of currency exchange cycles that result in a net profit.

Mic Bowman, Andrea Miele, Michael Steiner, Bruno Vavala

We present Private Data Objects (PDOs), a technology that enables mutually untrusted parties to run smart contracts over private data. PDOs result from the integration of a distributed ledger and Intel Secure Guard Extensions (SGX). In particular, contracts run off-ledger in secure enclaves using Intel SGX, which preserves data confidentiality, execution integrity and enforces data access policies (as opposed to raw data access). A distributed ledger verifies and records transactions produced by PDOs, in order to provide a single authoritative instance of such objects. This allows contracting parties to retrieve and check data related to contract and enclave instances, as well as to serialize and commit contract state updates. The design and the development of PDOs is an ongoing research effort, and open source code is available and hosted by Hyperledger Labs [5, 7].

Song-Kyoo Kim

This paper deals with the design of the secure blockchain network framework to prevent damages from an attacker. The decentralized network design called the Blockchain Governance Game is a new hybrid theoretical model and it provides the stochastic game framework to find best strategies towards preparation for preventing a network malfunction by an attacker. Analytically tractable results are obtained by using the fluctuation theory and the mixed strategy game theory. These results enable to predict the moment for operations and deliver the optimal portion of backup nodes to protect the blockchain network. This research helps for whom considers the initial coin offering or launching new blockchain based services with enhancing the security features.

Victor Dostov, Pavel Shust, A. A. Khorkova

Digital currency became a relevant topic lately, with the central banks contemplating the idea of issuing their own virtual currencies. Central banks may issue their virtual currencies to simplify interbank cross-border settlements and make them cheaper. In order to achieve this, both commercial and central banks recognize these virtual currencies as means of payments. In these projects blockchain could be used to store information about the digital currencies, instead of fiat money. We have identified the risks associated with the virtual currencies issued by the central banks: conversion and volatility risks. We have looked at different approaches to the distributed ledger, principles for decentralized virtual currencies, possibility of these technologies being used by the central banks, various risks and their mitigation strategies. We also formulated the technological and legal principles that may guide the issuance of the digital currency by the central banks. And reviewed the practicability of issuing virtual currencies by the central banks, based on exogenous and endogenous factors.

Shinji Kakinaka, Ken Umeno

The recent emergence of cryptocurrencies such as Bitcoin and Ethereum has posed possible alternatives to global payments as well as financial assets around the globe, making investors and financial regulators aware of the importance of modeling them correctly. The Lvy's stable distribution is one of the attractive distributions that well describes the fat tails and scaling phenomena in economic systems. In this paper, we show that the behaviors of price fluctuations in emerging cryptocurrency markets can be characterized by a non-Gaussian Lvy's stable distribution with ' 1:4 under certain conditions on time intervals ranging roughly from 30 min to 4 h. Our arguments are developed under quantitative valuation defined as a distance function using the Parseval's relation in addition to the theoretical background of the General Central Limit Theorem (GCLT). We also discuss the model-fitting for returns by employing the method based on likelihood ratios. Even though the cubic power-law model is a better fitting model than the Lvy's stable model in the tail part of returns, the Lvy's stable model outperforms the fit for the entire and wider range of returns. Our approach can be extended for further analysis of statistical properties and contribute to developing proper applications for financial modeling.

Jordan Bear

In the first age of artificial illumination, when gaslight seeped into homes and street lighting dispelled the perilous night, darkness seemed to vanish. Most elusive of all was a darkness so complete that it could serve as an epistemic vacuum, a degree zero in which both philosophical and scientific experimentation could flourish. In a more benighted era, Hume had fumbled around in search of a sufficiently severe designation for this place: ‘entire darkness’, ‘deepest darkness’, and ‘absolute darkness’ all take their turns in the spotlight.1 This was the domain for Hume’s speculations about blind men and their perceptions and, ultimately, about the nature of knowledge and understanding. The disenchanted evening of the nineteenth century made this absolute darkness hard to fathom, even as commentators asserted its necessity as the backdrop for the most profound ways of knowing.2 In studying the optical visibility of electrical phenomena, Humphry Davy noted that a vacuum tube cooled below zero degrees made the light so faint as to require almost ‘absolute darkness’ to be perceptible.3 Such utter blackness was familiar terrain for Davy, for he had once sought to dispel, rather than to cultivate, it. His innovative wire gauze safety lamp helped illuminate the gloom of the northern coal mines, supplanting competitors’ less-calibrated torches, which tended to explode on contact with the methane permeating the pits. Producing the darkness could be more difficult than banishing it. It is easy to imagine how essential this absolute darkness would have been to the researches of another unorthodox chemist, Sir William Crookes, for his aim was the measurement of light itself. To achieve this, he invented what is now called the Crookes Radiometer, a glass bulb containing vanes mounted on a spindle. The more intense the light to which the apparatus is exposed, the faster the spindle rotates. Crookes’s prolific career included a number of investigative forays into the darkness, not least when he presided over séances as the president of the Society for Psychical Research.4 But earlier in his career, Crookes had dedicated himself to visual manifestations of a different sort. With his former classmate John Spiller, Crookes published in 1854 his ‘Further Researches on the Methods of Preserving the Sensitiveness of Collodion Plates’, the culmination of several innovative years of photographic experimentation. He closed his article by spelling out a chief desideratum in retaining photosensitivity: ‘One of the most important things to be attended to is the necessity of preserving the plates where they are perfectly free from any light. It will be evident to all, that anything short of absolute darkness, when the sensitive surface is exposed to its action for day after day, and perhaps week after week, must be fatal to its subsequent cleanliness’.5 An effort to reproduce experiments in the luminosity of magnets, which had been undertaken in complete darkness by the vitalist chemist Carl Reichenbach, led one investigator to decry the impracticality of the arrangement. The faint light emitted by magnets, Reichenbach averred, could be sensed only by eyes that had already been plunged into total darkness for several hours. ‘This in itself makes the experiment difficult’, a successor wrote, ‘as absolute darkness is not easily obtained, nor are there many observers willing to be confined in it for many hours at a time’.6 The fundamental challenge was not to be solved simply by making a room completely light-tight and convincing observers to spend the better part of a day waiting in sepulchral surroundings. For the more elementary impediment was the body of the human observer herself, and the unsuitability of total darkness to her sensorium. Even in this darkness, Reichenbach’s replicator lamented, ‘the eye retains luminous impressions for many hours’.7 The darkness would be pierced by the persistent luminescence of earlier stimuli, whose intensity might even be heightened against the backdrop of the laboratory’s nullity. Absolute darkness was an aspiration, a void where, as in the omnipresent vacuums of nineteenth-century science, phenomena would appear unsullied by the conditions of being observed. Only in such a complete abyss could light serve as vehicle for and symbol of pure knowledge. Yet what becomes clear in the age of flash is how fantastical both total darkness and unadulterated knowledge were. As Horkheimer and Adorno would assert, the illumination of the darkness that was the Enlightenment project comes at a high price.8 It offers a rational universality that rejects other sources of truth, furnishing a ‘false clarity [which] is only another name for myth’.9 Such was the burden of flash photography, whose startling incandescence announced the camera’s presence, and in doing so changed the phenomena it set out to record. Early in her book Flash! Photography, Writing, and Surprising Illumination, Kate Flint offers a dazzling reading of Mary Shelley’s Frankenstein, a cautionary tale for those who, in the name of science, are tempted to meddle with primal forces. The crucial scene commences in darkness, by the shores of Lake Geneva, when a lightning storm suddenly and fleetingly lights up the setting, making the lake appear ‘like a vast sheet of fire’.10 And then, to the horror of synthetic biologist Victor Frankenstein, ‘a flash of lightning illuminated the object and discovered its shape plainly to me: its gigantic stature, and the deformity of its aspect, more hideous than belongs to humanity’.11 In this moment a most reliable Enlightenment motif reveals a hideous terror which could only be the product of the darkest strain of Romanticism. This lightning, Flint brilliantly suggests, ‘mocks the association of illumination with scientific advance and the Enlightenment, and transforms it instead into an instrument that reveals the horrific distortions of human presumption, whilst at the same time it offers a practical demonstration of nature’s independent forces’.12 This episode encapsulates the central paradox of sudden illumination: that what it makes visible most powerfully is the darkness itself. It transforms the world from a void into a luminously rich landscape, if only for an instant. But the darkness to which its dissipation rapidly returns us is a changed one, no longer one of nothingness, but rather one of negation.13 The darkness that has reclaimed the world from the ephemeral flash now actively conceals. This would become a powerful epistemic and aesthetic distinction. * On the edge of a different lake, nearly a century later, a startled lynx confronted the camera’s lens (Figure 1). The creature seems to have been interrupted, perhaps whilst taking a drink from the crisp water in which we see its reflection. The lynx, too, is a seer, its name derived from Greek for ‘light’ or ‘bright’, its eyes noted for their capacity to see in the dark. But the very same properties that furnish lynx with their night vision also make them more visible, for they have retroreflectors, thin layers of tissue behind the retina that bounce available light back to photoreceptors. The lens belonged to George Shiras, a pioneering wildlife photographer, whose ingenious camera traps made it possible to capture animals in their nocturnal environs. Yet this is a most unnatural nature, for, as Flint rightly points out, the ‘illusory peace [is] one that has in fact just been shattered by the sudden burst of artificial light that took the image’.14 The interruption implied by the position of the lynx at the shore underlines the patent artificiality of the entire tableau. Had the photograph somehow been executed under cover of darkness, it would depict the lynx lapping at the water, absorbed fully in the relief of its thirst. Yet, as the product of flash photography, we see only a representation of the encounter catalysed by the apparatus itself. Like the lynx’s peculiar luminosity, flash photography must negotiate a light that is both an advantage and a threat. The invasiveness of flash, and the way in which it disrupts the putatively ‘natural’ activities that we imagine are cloaked in darkness, is technologically specific. But in this heightened, visible artificiality, flash photography only makes plain the constructedness with which less pyrotechnical photography also operates. George Shiras, “Lynx, Loon Lake, Ontario, Canada,” 1902. © National Geographic Creative Archive. ** Even when flash photography was the result of great ingenuity, it could nevertheless disappoint the figurative illumination to which it aspired. It was fully capable of producing visual representations that were antithetical to the regulating ideals of rational inquiry, which indeed invited controversial acts of interpretation. The stakes of this polysemy became evident when, in 1885, in a limestone quarry at Chancelade, in the Dordogne, the support structure collapsed, trapping several labourers in impenetrable darkness. Efforts to reach the imprisoned men were heroic, but much frenzied drilling and digging came to naught. There could have been little hope of a rescue, several days having passed with nary a sign of life. The need to know what had transpired was at least as strong as the urge to rescue the labourers. ‘How was it to be seen what had occurred’, one correspondent wondered, ‘how was it to be made certain that the men were dead, and that all hopes of rescue must be abandoned’?15 Desperate for any means of contact with the captives, and eager to appease the miners’ distraught kin, the local authorities sent for a Parisian photographer, Langlois. Upon arriving at the scene, Langlois assessed that the most promising route into the mine was via the narrow hole that the rescuers had managed to bore into the rock immediately above the area where the labourers toiled. He then fashioned a camera encased within a small cylinder, allowing it to be lowered down the cramped passageway and to unfold into position once it reached a sufficiently spacious cavity (Figure 2). The sparse natural light that penetrated all the way to the bottom was inadequate to produce a photograph, so Langlois cleverly decided to construct an atmosphere of complete darkness. He transformed the entire mine into a darkened chamber, erecting a lightless shed atop the opening. This darkness could then be illuminated by a battery of small incandescent lights, which were attached by a cord to a generator. The entire apparatus was then hoisted back up into the shanty, where the negative was developed. Woodcut illustration of Langlois’s camera. From La Nature, 14 (1886), 148–9. These photographs were truly shots in the dark, for Langlois could not anticipate what scene the camera would record, nor could he calibrate some of the most basic controls before exposing the negative. Nevertheless, he managed to capture some arresting photographs of the subterranean tragedy. The images seemed to provide what the authorities had desired: proof of the fate of the unfortunates. The most striking of these appeared to show ‘the corpse of a young miner whose face stands out in relief against the side of the gallery’16 (Figure 3). This photograph was reprinted widely in the international press, where editors tended to note tastefully but briefly the poignancy of the scene before declaring the triumph of the new photographic innovation. The correspondent for La Nature concluded that ‘this method of photographing inaccessible subterranean galleries ought to have numerous applications in the future’.17 One account spoke with a certainty about the outcome: ‘a number of negatives were taken and the effect of the disaster shown, even to the faces of two corpses. It was thus known that the men were dead, and that effort to succor them would be useless’.18 But the matter was not put to rest so easily. Langlois’s photograph of the interior of the Chancelade mine, supposedly showing the head of a deceased young labourer. Some weeks after news of the gruesome discovery at the bottom of the quarry, two miners were able to contort themselves through a channel amidst the rubble, entering the intact gallery of the mine. They were shocked by what they saw, and by what was missing: they obviously expected the most frightful spectacle, to see the bones of their comrades or at least the remains of the one who, it was said, had been photographed by Mr. Langlois. They roam the gallery under the impression of the terror caused by the discoveries which await them; fortunately, it is not so; they find the gallery intact . . . not the least trace of a corpse.19 Soon, another search party was organized by the local superintendent of mines, which confirmed that there were no corpses to be found in the area that had been photographed. The editor of La Nature, the polymathic aeronaut and meteorologist Gaston Tissandier, contacted Langlois with these new findings. The photographer responded somewhat defensively, seeming to interpret Tissandier’s inquiry as an accusation of tampering: I brought you the proofs of the photographs I obtained using my device, operating at the bottom of the Chancelade wellbore. Here are all the pictures . . . you can make sure that they are absolutely correct and that no editing has been done to any of them. I have never committed an unfair act. I assure you, on my honour that my photos are not retouched, I wish them to be available to all who wish to examine them, and to all the experts.20 Langlois nevertheless re-examined his photograph, wondering to himself ‘where can this profile come from’? After looking at the print with the aid of a magnifying glass, he understood his own error: I must confess that I hardly found there the certain aspect of a human head. That is only a fortuitous appearance. With the help of imagination, we thought we saw a human head in this singular silhouette. Our interpretation was repeated, amplified, and the newspapers spoke of the corpses of Chancelade revealed by the photograph. I was wrong to believe myself in this revelation.21 Tissandier concedes the credulity of his own journal in accepting the erroneous interpretation. On closer inspection, the image ‘gives neither the relief nor the modeling of a head; a simple profile is cut out in intense white on a black background’.22 He wonders whether ‘some white, well-lit stones have, by chance, produced this appearance, in the manner of flints, which sometimes look like a human head?’23 The ‘head’ of the corpse is, thus, purely an artefact of the imaging process, of the incandescent light glinting off the glassy surface of the quartz in the mine. Here, the particular properties of the flash have created the basis for this false ‘revelation’. Without the flash, in the darkness, the ‘truth’ of the scene would have remained intact, if invisible. This was a local example of the general dilemma of flash photography. Its users were left to choose between images inevitably encumbered by the markedly contrived circumstances of their making, or to do without even these compromised illuminations. It is not happenstance that such a dilemma would confront viewers especially forcefully at this moment. As Flint argues here, in her assessment of the specifically Victorian milieu of innovative flash photography, this newfound incandescence inflected a debate that was already taking shape by the late 1880s. While flash undoubtedly made possible the production of photographs of greater clarity and richer detail than were previously possible, its most dramatic impact may well have been aesthetic: first as a formal gesture and, subsequently, as the cornerstone an entire aesthetic ideology. The Pictorial photographers, who were at this time seeking to legitimate their medium by exploring its most vividly non-referential dimensions, enlisted flash in this way. This desire, Flint notes, ‘led to experimentation with creative effects achieved by letting off the flash at an angle, bouncing off a wall or screen’.24 It consisted, in other words, of achieving results not unlike those serendipitously produced by Langlois deep beneath the earth at Chancelade, only doing so by design and not by accident. Flash, then, was emerging as a criterion by which two quite different conceptions of photography – conveniently if superficially designated artistic and documentary – might help to distinguish themselves from one another. Flint writes eloquently of the work of Jacob Riis, in whose carefully composed scenes of social disorder these two conceptions of photography often cohabit. Of Riis’s photographs Flint notes that in addition to ‘making visible the material details of dwelling and workplace, the flash did something else besides: it could create great pools of contrastive and visually impenetrable darkness at the sides of images (Flint, p. 276). The intersection of the darkness and the light, the place where one ends and the other begins, is where the flash photograph reveals its aspirations and its limitations. The history of flash, so lucidly by Flint in this book and is a route into the of several of and into a Victorian intersection of the and aesthetic of visual of was by the

Tianxin Hu, Jing Zhou

A multiplicity of spatial plans in a planning system can have different ways of co-existing under different institutional organizations. Having a highly centralized government like China, the phenomenon of a multitude of national-level plans dominating at the same time has its own unique characteristics. Much literature emphasizes only the lacking of coordination between governmental institutes. However, this research finds that the current constitution of the Chinese planning system profoundly reflects the relations between central and local governments. This paper first examines the characteristics of the Chinese political system, briefly reviewing the iterative process of "centralization-decentralization-selective centralization", showing the rise and fall of spatial planning as an administrative tool of local governments. Especially since the 1990s, the central government has raised revenue from the local level, which leads to local governments depending more on selling land for quick money. But as the urban expansion accelerates, the state asserts its control on local development by the National Mainfunction Plan and National Land-use Plan, which seriously impedes the coordination of spatial plans at different levels. Therefore, this study argues that spatial planning reform in China requires not only generating integrated information platforms and technical standards, but more importantly, establishing new relations between central and local government. In the end, some suggestions are made on central authorities reducing the constraints of a planning censorship system and rebalancing the responsibility and the public finance of local government on planning matters.

Taisiia Bondaruk, О. S. Bondaruk, Oksana Vinnytska

Administrative reforms in Ukraine focused on decentralization of governance system, change in the administrative and territorial system by consolidating communities and redistribution of authorities and financing sources at local governance level are expected to be implemented in keeping with European standards. The need to achieve positive dynamics of the economic system in Ukraine raises the importance of studies covering the array of problems related with the operation of local budgets, including European practices of local budget formation in the conditions of decentralization and their applicability for Ukraine. The purpose of the article is to investigate foreign practices of budget decentralization and their implementation perspectives in Ukraine.
 The essence of budget decentralization is highlighted; main indicators measuring budget decentralization and financial autonomy of local self-governance bodies are shown. As three models of local self-governance financing are distinguished by main criteria of financial decentralization (Scandinavian, Latin, and Hannover), peculiarities of the local budget formation in three countries belonging to the above models are analyzed: Finland (Scandinavian model), Spain (Latin model), and Poland (Hannover model). Results of the study show that while in countries of Scandinavian and Latin model taxation of consumption and residents’ incomes prevails, with fiscal importance of taxation of real estate, in countries of Hannover model taxation of consumption has minor significance.

Mark Braverman, Klim Efremenko, Ran Gelles, Michael A. Yitayew

We consider fault-tolerant boolean formulas in which the output of a faulty gate is short-circuited to one of the gate's inputs. A recent result by Kalai et al. (FOCS 2012) converts any boolean formula into a resilient formula of polynomial size that works correctly if less than a fraction $1/6$ of the gates (on every input-to-output path) are faulty. We improve the result of Kalai et al., and show how to efficiently fortify any boolean formula against a fraction $1/5$ of short-circuit gates per path, with only a polynomial blowup in size. We additionally show that it is impossible to obtain formulas with higher resilience and sub-exponential growth in size. Towards our results, we consider interactive coding schemes when noiseless feedback is present; these produce resilient boolean formulas via a Karchmer-Wigderson relation. We develop a coding scheme that resists up to a fraction $1/5$ of corrupted transmissions in each direction of the interactive channel. We further show that such a level of noise is maximal for coding schemes with sub-exponential blowup in communication. Our coding scheme takes a surprising inspiration from Blockchain technology.

Ethan Buchman, Jae Kwon, Zarko Milosevic

The paper presents Tendermint, a new protocol for ordering events in a distributed network under adversarial conditions. More commonly known as Byzantine Fault Tolerant (BFT) consensus or atomic broadcast, the problem has attracted significant attention in recent years due to the widespread success of blockchain-based digital currencies, such as Bitcoin and Ethereum, which successfully solved the problem in a public setting without a central authority. Tendermint modernizes classic academic work on the subject and simplifies the design of the BFT algorithm by relying on a peer-to-peer gossip protocol among nodes.

Muhammad Nouman, Kareem Ullah, Muhammad Azam

A blockchain is a decentralized, distributed peer-to-peer network that allows one node to communicate with other nodes. When using blockchain technology in education, data or records can be stored permanently without fear of hacking du e to the secure hashing algorithms in blockchain techn

R. Bala, R. Manoharan

The Distributed nature of Bitcoin introduces security issues that necessitate security-specific enhancements in Bitcoin protocol. Therefore, proposing a method of incorporating criteria check and verification process for miners to participate in the mining process and join the mining pool respective

Freitas de Souza, Luciano, Tonkikh, Andrei, Tucci-Piergiovanni, Sara, Sirdey, Renaud · 7 authors

Blockchain is an emerging technology that gained a lot of attention in the last years. Many different consensus protocols have been proposed to improve both the scalability and the resilience of existing blockchain. However, all these solutions have been defined for rather static settings. We propose a modular approach for analysing and comparing different consensus protocols used in blockchain under churn.

Ronghua Xu, Yu Chen, Erik Blasch, Genshe Chen

While Internet of Things (IoT) technology has been widely recognized as an essential part of Smart Cities, it also brings new challenges in terms of privacy and security. Access control (AC) is among the top security concerns, which is critical in resource and information protection over IoT devices. Traditional access control approaches, like Access Control Lists (ACL), Role-based Access Control (RBAC) and Attribute-based Access Control (ABAC), are not able to provide a scalable, manageable and efficient mechanism to meet the requirements of IoT systems. Another weakness in today’s AC is the centralized authorization server, which can cause a performance bottleneck or be the single point of failure. Inspired by the smart contract on top of a blockchain protocol, this paper proposes BlendCAC, which is a decentralized, federated capability-based AC mechanism to enable effective protection for devices, services and information in large-scale IoT systems. A federated capability-based delegation model (FCDM) is introduced to support hierarchical and multi-hop delegation. The mechanism for delegate authorization and revocation is explored. A robust identity-based capability token management strategy is proposed, which takes advantage of the smart contract for registration, propagation, and revocation of the access authorization. A proof-of-concept prototype has been implemented on both resources-constrained devices (i.e., Raspberry PI nodes) and more powerful computing devices (i.e., laptops) and tested on a local private blockchain network. The experimental results demonstrate the feasibility of the BlendCAC to offer a decentralized, scalable, lightweight and fine-grained AC solution for IoT systems.