Blockchain Papers

Lucius Gregory Meredith

We give an interpretation of full classical linear logic, and linear proofs in terms of operations on the blockchain.

Ueli Maurer

No abstract is available for this record.

Oresta Karpenko

Abstract The article highlights major changes in systematic approach to family, establishment of institutions for child and family support, recognition of the priority of family-based care, decentralization of administration and financing of childcare institutions in Poland. The government tried to introduce a number of changes in legislation that would significantly improve the condition of the child. Childcare reforms in the 1990’s and at the beginning of the 21 st century aimed at modernizing local government and local organizations to provide appropriate childcare and social assistance to parents. The paradigm shift in social policy on child and family care determines the priority of family support aimed at creating comfortable conditions for the child. Nowadays the main objective of the family supportive policy of any country is to protect the child from the foster care model.

A.W. Jongbloed

In het Delta Lloyd magazine april 2015, p. 32, wordt aandacht besteed aan Martijn Wismeijer (43 jaar). Hij liet onlangs twee chips onder zijn huid implanteren, een voor bitcoins en een voor de honderden wachtwoorden die hij voor digitale toepassingen gebruikt. 1 Het is een feit dat we in het huidige ICT-tijdperk te maken krijgen met heel veel wachtwoorden die liefst zo weinig mogelijk identiek mogen zijn en het is duidelijk dat wie toegang krijgt tot die wachtwoorden ons leven behoorlijk kan ontwrichten. Maar is een chip voor bitcoins niet overbodig? Wat zijn bitcoins eigenlijk, wat is hun juridische status en zijn ze betaalmiddel?

류영아, 김필두

The purpose of this study is to analyze the right of autonomy, to investigate the perception of local autonomy, and to propose the key factors which desirable the local decentralization has. The research methods of this study are literature investigations, and central and local public servants surveys and citizens survey. We made an analysis framework focused on the preceding researches, and drew revitalization strategies of the local decentralization. As a result of empirical study, we found that local finance autonomy and local organization autonomy are the most important factors to revitalize the local decentralization. And as a result of depths interview, we found that there are perception differences between central and local public servant about the detailed contents of local finance autonomy, but all interviewees agree that the local finance autonomy should be enhanced.

류영아, 김필두

The purpose of this study is to analyze the right of autonomy, to investigate the perception of local autonomy, and to propose the key factors which desirable the local decentralization has. The research methods of this study are literature investigations, and central and local public servants surveys and citizens survey. We made an analysis framework focused on the preceding researches, and drew revitalization strategies of the local decentralization. As a result of empirical study, we found that local finance autonomy and local organization autonomy are the most important factors to revitalize the local decentralization. And as a result of depths interview, we found that there are perception differences between central and local public servant about the detailed contents of local finance autonomy, but all interviewees agree that the local finance autonomy should be enhanced.

Greg Anderson

Greg Anderson is an Associate Professor of History at Ohio State University, where he has taught since 2005. His teaching and research cover ancient Greece, critical theory, and historical thought. In his first book, The Athenian Experiment: Building an Imagined Political Community in Ancient Attica, 508–490 b.c. (University of Michigan Press, 2003), and a number of other pieces, he questions the use of modern categories such as “state,” “tyranny,” and “democracy” to characterize phenomena in ancient Greek experience. He is currently working on two book projects: a monograph, The Realness of Things Past: Ancient Greece and Ontological History, and a volume of essays on states in history titled State Formations: Histories and Cultures of Statehood, which he is co-editing with John Brooke and Julia Strauss. The Decree of Eukrates (337/6 b.c.). This decree authorizes Athenians to assassinate anyone who attempts to establish a tyranny in the polis of Athens and prescribes punishments for any would-be collaborators. The sculpted relief shows Demos (“the People of the Athenians”) being crowned by a personified Demokratia. As the image suggests, the Athenians conceptualized Demos as a unitary corporate person, not as an aggregate of autonomous individual persons. In contemporary thought and practice, this corporate self was a kind of primordial superorganism, one that existed prior to and apart from the particular flesh-and-blood Athenians who happened to embody it at any given time. As “the rule of Demos,” Athenian demokratia was thus not just institutionally different from modern individualist democracies. It was premised upon entirely different ontological foundations. Athens, Agora Museum I 6524. American School of Classical at Athens: Agora Excavations. Photo: C. Mauzy. Our discipline's grand historicist project, its commitment to producing a kind of cumulative biography of our species, imposes strict limits on the kinds of stories we can tell about the past. Most immediately, our histories must locate all of humanity's diverse lifeworlds within the bounds of a single universal “real world” of time, space, and experience. To do this, they must render experiences in all those past lifeworlds duly commensurable and mutually intelligible. And to do this, our histories must use certain commonly accepted models and categories, techniques and methods. The fundamental problem here is that all of these tools of our practice presuppose a knowledge of experience that is far from universal, as postcolonial theorists and historians such as Dipesh Chakrabarty have so well observed. In effect, these devices require us to “translate” the experiences of all past lifeworlds into the experiences of just one lifeworld, namely a post-Enlightenment “Europe,” the world of our own secular, capitalist modernity. In so doing, they actively limit our ability to represent the past's many non-secular, non-capitalist, non-modern “ways of being human.”1 To be sure, the discipline's cultural turn of the last thirty has us to the of non-modern our of past and the have us to the of our with the of and cultural history has us to that our non-modern in its it a knowledge of one that for a primordial and a and the one to represent that it is a historicist that us to the experiences of To the a by the a of and and in they by own on the of the as as one attempts to this to tell a in the by our discipline's and one the ability to the here by The one can do within the limits of our is to to the and of cultural to it as the of his who can be the the to a history of the one that to a the of the as it was by the the of to an of to a of it past. It that past into the past of namely our that the of past all those of the lifeworlds that by the the postcolonial of has for our as of historians have to as the of historical knowledge us to non-modern experiences by all into modern the of in is the To have on and a has to Our be to ontological which to be we can our of and non-modern we to the of To us all those that we have in we a that can of non-modern on its own ontological as a world in its own and to ontological experience. past of its own particular its own of the of its own particular of and and and and and so our historicist categories, and do not us to past experiences all the to the ontological they require us to non-modern lifeworlds as all within one and the within a single universal by of and a where and individualist The is a practice that the of non-modern past the to the of own experience. the of and that the of this historicist practice far they a these have and by of thought in a of from and critical to and on the of these we can in turn to an one that in an entirely not as an as a as an by the of thought and this of require us to an ontological turn in our It us to of past in its own our non-modern was in be an of was at the And we to this we duly histories that at and As a lifeworld, Athens can as a for the us to in an ontological turn in historical of at and a of ontological In to in and upon the world as a the of any given historical must that world as a must a knowledge of is of the and of which that world must a of the phenomena that the and of phenomena those we and and and and and the and of And they of in the all and upon the of such a and In other past and for and to its own particular its own of it to be the is to have in not just To this we have to the world of our own capitalist which on at ontological and is The and other upon which modern being is all presuppose a a world in which is to those phenomena that with our of and As our world has for it as and It is thus a world entirely of all the and and and and the other that have and all other historical for It is a world where is a world of and and all those from to the to and from the It is a world that has all those that and and It is a world this it of that modern is as it the of at it as of the and of as of and not as in own It thus all and the that to a of experience a that is from the of This of a of well to those who have to of as a of the of it have at all in non-modern where was in all of where have the who it of is a that in our modern a world that is secular, a world where have from into that they have the and the to of And this us to the commitment of our modern which is its who of the of within a of a of own have about upon the of his capitalist is upon an of The of experience is thus into two mutually an of knowledge and and to be from a of from a of and And with this of have world from not all non-modern have from of being by the of the and the by the of and from who the that in as from who it for that and in and all the modern ontological that be to non-modern be those we and other persons. we to the and last of the ontological that capitalist namely our our that all This ontological have the of where the the of the was “the of of the and thus the in his own person, as a of his own such that his all of the It have for that in the world of where and as the and of a single primordial And the of a individual be and the of who all as as of all the and of that have in the modern capitalist it as the primordial of the that all with a to a and upon our to and thus to of of and so as not as of our of who we as And we that being to individual the other we that individual in the first who our us to at any given the of a this of and any be to and the to it is by a since it to rule to other who rule for must be by such as and “the of on the of to on to a of must be from the of by of and other such And in our modern world it entirely that not the of that we the of our be from any In our world it to the to all of for the tools of historicist practice to the ontological of past experience. they us to modern upon all non-modern To the we can to Athens, a non-modern lifeworld, and the Athenian of that has us of the Athenians to be the of it the Athenians not of to tell was and was was in the stories they about and in all and it was far and our was premised upon just a and the two in the of Attica, not just The Athenians with and other polis was with “the and not just of and in the world of and space, who all of and the in Athens not for the of the in Athens was the of of and And and to and from and to and the Athenians to in on just so with and a of in Athens was not a of to It was all about those to and the of the polis as a The of Athenian being was the of In the of the was not of It was a a that was at and and To since the Athenians to be an who since the was to be a a of to by they as as a with they an Attica, they given to the first such as and who from As the first 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that they a the of the as a And they This of is they It to do with “democracy” as we the It was Demos to do to its own in its particular where upon with in the of from other In demokratia was the of and in and upon the world to the of the This be in it be in the in at on the Athenians to as one in the unitary of the polis so they in as and other as as of the of the As these Athenian and with for a of any it is demokratia in it is not demokratia to to Greek historians of that the Athenians to own all those just we we to use models and categories, tools that actively this non-modern to our own modern ontological tools first of to a modern of ontological us to that the of Athens, the of all to be in a of the the and the they us to that the Athenian and other a of “state,” an that was from a Athenian that these two mutually categories do not to phenomena in ancient experience. it is Athenian was entirely by by of Athenian we that the polis of Athens must have kind of of and the that us to these two as mutually in the first the of a from have entirely to the our us to that such as and must have an it to us that the Athenians not have such a was a world where as It that was an where to the of where individual was its own where by for for ancient to the of a modern an not that was not in It that its must have in In we the of Athens, our the of non-modern experience into modern such as and we these to be of the in have to the to not it is the tools of our practice that us to in the first by modern ontological upon the ancient As for the own the non-modern that our historicist tools have us this to a of to a of the world that we have all the and other phenomena that all and at the time, the of this ancient have in history to the of with all the other non-modern of the Athenian by us to Athenian of its in this our historicist tools of require us to As cultural as Athenian can be from the world they It that the Athenians premised upon the that the of not all of to the of the 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the of the the upon which all our one they have at and in that this particular of is a historical a of knowledge and the of modern capitalist have the of other modern and to be of thought and And postcolonial theorists have to the of categories and from and the to theorists have the of modern knowledge just as theorists of and the have to the of this historians and of have the of the by And have on the of any knowledge It be to of all these as of our as of the our modern experience as from they us with a critical of our world from a kind of they not that is world the they the we about the of us to it as that is and so that one can where a and an as all thus in the primordial and and the and the that of and in the first And they do this by us and the of a world be from the of the of those for that world is those to the that the two can in be In so doing, the of the us to past the ontological of our world and the and of its of they us to this on a kind of us to the in which as with of to 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the of experience. this turn to ontological history we of the of in and an ontological history of Athens have for the we It not the Athenian into entirely and of by its own and all it have to the polis as the Athenians it as a single of experience by two entirely the and the And it have to the of the of the polis in Athenian to one from to the these that the Athenians to be to use and of that they to the with they And the polis in this we its of as a it us to the we about the of in of the of to a of “the we have to that a of this was to be by different in Athens the and they all of and from and to and from and to and And we to the in Athens of all this we have to that the to the of and in was not in the by the Athenians in the and other such It the they at a of and the of into the of that the to and the of the polis as a this turn to ontological history require us to of any in The in a world where the of all and It in an where the was a and a kind of one that actively It in a where the for where the of by where as a rule for the Athenians have the of an such as and they have these to be all for to in the was not a a that be by of was the primordial upon which the of all Athenians since was a of the the and the of the the Athenian on its own in this us to for that the in the polis those the and the and the for such as and to the to the of the the time, this us to the many by to Athenian own to into Athenian not just the the of an to the of within that with the for and that Athenian to as in the first And it us to the of the as a to upon the by the of As the of the polis of these to a for its to use and to and the of Demos on a And with duly such was for Demos to its In this of the of and to the of the polis us to any use of the modern and in our of the Athenian as these we to that Athenian demokratia an the corporate self of Demos and its the of the and the of its it was for in Athens that and all of from of and to and to Demos which by the Athenians to any of with a a of In Athens, it have to from the upon which they all and which they all and the the polis and its to that the of a particular a and was as a to the of the polis as a And of it to it to the Athenians that all in the and be by not by was a in Athens a and the of its it was thus not a in the of experience any of and It was a within the of a and an a that that Athenian to be in different a particular of a particular and a of the Demos we to that Athenian demokratia to do with individualist and and to do with corporate by a of our with other modern categories, and And we such categories and to of the Athenian on its own we can that all those of of our own Athenian not of the polis to of our own individualist of in Demos in Athens have to any As the of Attica, as of in and as and of as and who and the of the Athenians as to the of Demos as that to that be not was the and demokratia as the Athenians the This the in of who the and Demos and of in the to Athenians in the to as and and for the and and to and the of the In other demokratia was entirely those who the to such as the of to the of Demos with Athens and its demokratia by these not by and Athenian demokratia was in a in corporate not an in the of as and to In an where for not for the of the was the of a in have any And as we have Athens have many of the and cultural to The was to the from the of other the of which is the Athenians in the of the the Athenian was the of this to lifeworlds at a certain Most an ontological turn require us to our with its of and all its of a unitary experience in a single It the that has the the and other to this practice of the ontological from which different have the past's many of and of and so And this is the that we have to for histories that at and it to be well this of the for our modern that the ontological of experience to the of lifeworlds that have

Anna Wiśniewska

The aim of this article is to show the position of Bitcoin among virtual currencies. On the basis of the reports published by the European Central Bank and The Financial Action Task Force, as well as the available Internet and primary sources, there have been presented the types and the history of virtual currencies, the way in which Bitcoin functions and the methods of acquiring it. The article is based on the assumption that an in-depth knowledge of virtual currencies, their classification and their functioning will make it possible to regulate their legal status. It is necessary not only for tax purposes, but also in order to avoid the risk of using this payment method for terrorist or criminal purposes. The knowledge of the history of virtual currencies also makes it possible to foresee the problems that may hinder the functioning of Bitcoin and other virtual currencies. The growing popularity of virtual currencies and cryptocurrencies is linked with the increase of importance of non-cash payments on global scale. Thus, Bitcoin may be considered a next step in the evolution of digital money.

Cristianne Maria Famer Rocha, Silvia Helena De Bortoli Cassiani

In recent decades, health care networks in diff erent parts of the world have incorporated new forms of social organization that involve extensive use of technology to produce and disseminate information and are based on the autonomous, non-hierarchical and decentralized cooperation and collaboration of those within these networks. In Latin American countries, Nursing Networks were created in the 2000s on the initiative of professionals seeking to exchange knowledge and experiences. Over time this initiative gained ground with the support and leadership of the Regional Council for Nursing and Health Technicians of the Pan American Health Organization (PAHO) and, in 2007 and, in 2007, the 1 st International Nursing Network Conference was held in Toledo (Spain), during the 9 th Ibero-American Conference of the Latin American Association of Nursing Schools (ALADEFE). These networks operate as a communication strategy, stimulating cohesion and cooperation between nurses interested in developing nursing care, management, research, information and education with a view to supporting the advancement of the profession and help countries achieve universal health care coverage and access to health services. There are currently around 25 International Nursing Networks in the Americas, which together form Rede EnfAmericas and consist of more than 3000 nurses in Latin America. Information on each of these networks is available at: http://www.

Gerry Braun, Stan Hazelroth

Transitioning to clean, climate-friendly and smarter electricity systems means bringing innovative, capital-intensive, and increasingly decentralized power sector infrastructure on stream. National, state, and local policy should recognize and address the implications for finance , particularly the need for investments that capture and optimize local economic benefits.

Young-Aa Ryoo, Pildoo Kim

No abstract is available for this record.

Victor Ranieri Bomfim Sampaio de Araújo, Márcia Reis Machado Machado

Bitcoins are in use today to do transitions. There are companies that accept Bitcoins as payment whem supply goods and services. However there isn’t currency status. It’s made of mathematics equations that its transactions are validated through encryption, hash function, p2p network and proof-of-work. Like a currency that just exists in the virtual form it needs the user’s confidence for have a valour. Although the large growth since your creation, in 2008, and be considered for many a big evolution, in the informatic and business fields, some entities and researchers say the Bitcoins are a ponzi scheme. This research aims to describe the transitions that envolve cripto-currency and the suitable accounting treatment in Brazil, based on the current standards. For this was done a general analysis that shows the best classifications as Contingent Asset, because their uncertainty value and their uncertainty existence too. The second section of the analysis was done hypothetical situations. The first was the mining situation, then the receive bitcoins as payment and finished with the company had bought that. Because it’s a Contingent Asset was generated a conflict on the two last situations. But for that was suggested an account on the current asset that represent the expectative to generate future cash flows when liquidate the Bitcoins without excluding the disclosure in the notes as Contingent Asset. Lastly was concluded that the risks associated with property losses and the association with illicit activity, beyond that there are so many indications that is a ponzi scheme and even it isn’t, there are not perspective for their operation.

Myungsun Kim, Bolam Kang

본 논문에서는 미리 알려진 임의의 다항식과 암호화된 다항식의 곱셈을 수행한 후, 해당 곱셈이 정당하게 수행되었음을 보이기 위해 증명자 (Prover)와 검증자 (Verifier)간의 다항식 상등성 영지식증명 (Zero-knowledge Proof) 프로토콜을 일반화할 수 있는 방법을 다룬다. 이를 위하여 다항식의 상등성을 증명하는 일반화된 프로토콜을 제시하고 랜덤오라클 (Random Oracle) 모델에서 안전성을 증명한다. 이러한 기법은 안전한 집합연산 기법을 포함하여 다항식에 기반한 다자간 연산기법 (Secure Multi-party Computation)에 적용될 수 있다. In this paper, we are interested in a generalization of zero-knowledge interactive protocols between prover and verifier, especially to show that the product of an encrypted polynomial and a random polynomial, but published by a secure commitment scheme was correctly computed by the prover. To this end, we provide a generalized protocol for proving that the resulting polynomial is correctly computed by an encrypted polynomial and another committed polynomial. Further we show that the protocol is also secure in the random oracle model. We expect that our generalized protocol can play a role of building blocks in implementing secure multi-party computation including private set operations.

Shiret Elezi

Local Government finance is of immense importance for a state and for the government functions of rendering services to the citizens. Local finances reflect the fiscal independence of municipalities and the financial capacity to carry out its responsibilities under the legal provisions of the central government. It is therefore very important to monitor the development of local finance in transition countries and in transferring experiences from countries with higher fiscal decentralization to countries which are pre-accesion candidates to EU. Countries with higher fiscal decentralization are more acceptable bycountries that are recently new members of the European Union under similar region. In this study, a parallel overview of the local finances of new member country in the EU, Slovenia and pre-accesion candidate country to the EU i.e. Macedonia, was taken

Benoît Libert

This habilitation thesis deals with cryptographic primitives that preserve the algebraic structure of underlying objects (messages, keys, etc) and their applications to the design of non-interactive zero-knowledge proofs and privacy-enhancing cryptographic primitives.In 2008, Groth and Sahai showed how to make these proof systems relatively efficient in abelian groups endowed with a bilinear map. These techniques, however, require to work with lower-level primitives where handled objects all live in a cyclic abelian group. Among other things, we need to sign messages without destroying their algebraic structure (in particular, without hashing them first) so as to be able to efficiently prove properties about hidden signed messages. The first part of this thesis describes a structure-preserving signature scheme which was the first efficient realization under previously studied algorithmic assumptions. These tools are also utilized in the design of a novel revocation mechanism for group signatures, which allow users to anonymously sign messages on behalf of a population they belong to. The second part of this thesis considers structure-preserving signatures endowed with homomorphic properties. We show how to use them in the design of non-malleable cryptographic primitives. Using linearly homomorphic structurepreserving signatures, we notably obtain non-malleable commitments to group elements and non-interactive zero-knowledge proofs, as well as public-key encryption schemes that resist chosen-ciphertext attacks.

Hanna Hałaburda, Miklós Sárváry

In this chapter, we discuss economic aspects of cryptocurrencies. 4.1. The double spending problem 4.2. How does Bitcoin work? Brief overview 4.3. Not the first one – predecessors of Bitcoin 4.4. Problems with Bitcoin (new challenges) 4.5. Competition against other crypto-currencies 4.6. Non-currency use of blockchain technology 4.7. Trading cryptocurrencies 4.8. How do crypto-currencies’s attributes compare to earlier money? For Chapter 1 (Introduction), see https://ssrn.com/abstract=3135021. For Chapter 2 (Means of Exchange: Ever-present Competition), see https://ssrn.com/abstract=3135028. For Chapter 3 (Platform-based Currencies), see https://ssrn.com/abstract=3135030. For Chapter 5 (Conclusions), see https://ssrn.com/abstract=3135057.

Vincent Van Mieghem, Johan Pouwelse

This paper describes the process of remaining anonymous online and its concurrent operational security that has to be performed. It focusses particularly on remaining anonymous while purchasing online goods, resulting in anonymously bought items. Different aspects of the operational security process as well as anonymously funding with cryptocurrencies are described. Eventually it is shown how to anonymously purchase items and services from the hidden web, as well as the delivery. It is shown that, while becoming increasingly difficult, it is still possible to make anonymous purchases. Our presented work combines existing best-practices and deliberately avoids untested novel approaches when possible.

Tjaša Bjedov

This PhD thesis falls within the fields of public finance and public choice. It studies the following issues: ideological polarization, decentralization and conflict. It consists of three chapters can be read independently. In the first chapter the focus is on the importance of ideological polarization between but also within political parties on the level and composition of cantonal public spending. The analysis is on Swiss cantonal parliaments and is based on the use and econometric treatment of a very rich database. We made two contributions to the literature on the impact of political fragmentation on public spending. First, we showed that ideological dispersion within political parties is associated with higher public spending while the dispersion between political parties is associated with less public spending. This finding implies that the mode of organization and discipline within political parties are both important. This result is particularly interesting given that previous literature has completely abstracted from ideological dispersion within political parties. Lastly, we showed that ideological dispersion between and within political parties is mainly relevant for current expenditures. The second chapter focuses on the conflict of objectives that may exist between economic agents in a two-stage game with asymmetric payoffs. The literature showed that coordination failures are frequent in one-stage games and that communication can help individuals coordinate with the use of take turn strategies that allow for a reduction in the payoffs’ inequality in the long run. Our contribution was to study whether communication has the same capacity in a two-stage game where the subgame perfect Nash equilibrium requires both players to make opposite choices at both stages of the game and accept unequal payoffs. Our results show that coordination failures occur half of the time and that 18% of the pairs use the take turn strategy. Communication significantly increases coordination on the subgame perfect Nash equilibrium because it increases the ability of subjects to initiate a take turn strategy and to maintain it. Thus, communication allows subjects to establish a long-term strategy that increases efficiency and reduces payments differences, induced by the asymmetry in payoffs, by exchanging their relative positions in a fair way. Our results show that communication can solve coordination conflicts, even in more complex situations than in one-stage games usually studied until now. The last chapter focuses on a particular type of conflict: political secessions. Specifically, it addresses the link between secessions, decentralization and group identity. We aim at determining, by means of a laboratory experiment, if decentralizing the provision of public goods reduces the likelihood of secession. We emphasize the importance of local identity. Our experimental design, obviously, do not reproduce all the trade-offs that separatist movements face in the real world. It allows, however, capturing at least two key forces that drive these movements: the proximity to public goods that reduces the phenomena of free-riding and brings public goods closer to citizens’ preferences and the importance of local identities. Our results indicate that the Decentralization treatment increases contributions to local public goods and decreases the likelihood of secessions also when identity is made more salient. If fact, reinforcing local group identity increases the likelihood of secession only when local group members are cooperators.

George Danezis, Sarah Meiklejohn

Current cryptocurrencies, starting with Bitcoin, build a decentralized blockchain-based transaction ledger, maintained through proofs-of-work that also serve to generate a monetary supply. Such decentralization has benefits, such as independence from national political control, but also significant limitations in terms of computational costs and scalability. We introduce RSCoin, a cryptocurrency framework in which central banks maintain complete control over the monetary supply, but rely on a distributed set of authorities, or mintettes, to prevent double-spending. While monetary policy is centralized, RSCoin still provides strong transparency and auditability guarantees. We demonstrate, both theoretically and experimentally, the benefits of a modest degree of centralization, such as the elimination of wasteful hashing and a scalable system for avoiding doublespending attacks.

Ekaterina Mikhailovna Taran, Irina Pavlovna Salmanova, Elena Viktorovna Dokukina, Margarita Arkadevna Menshikova · 5 authors

The article highlights the issues of emergence and existence of cryptocurrency. Exploring online space, you canselect the most popular existing electronic currency which is bitcoin (Bitcoin). The article analyzed the pros andcons and the legality of these

Waleed W. Smari, Antonio Montero Navarro, William K. McQuay

During the past two decades, we have seen rising interest in computer-supported collaboration and, with the advent of the Web 2.0 and semantic technologies, increased importance for collaborative work. Worldwide, people expect unlimited access to information within and across cultures. Social networking continues to expand and impact collaboration approaches at the personal and enterprise levels. As a result, the computer-supported collaboration research community has turned its attention to the study of human social behavior from records such as blogs, wikis, social media, and social networking sites 1. The desire for mobile and pervasive connectivity is pushing expansion of an ever growing wired and wireless high speed backbone that globally combines computing, sensing, and communication technologies. Annually, new classes of mobile devices are added to the traditional desktop, laptop, tablet, and smartphones. However, computer-based collaboration encompasses complex hardware and software issues that have been in the focus of the research community for a long time 2. In 1981, Johnson-Lenz coined the term groupware as ‘intentional group processes plus software to support them’ 3. By 1988, the term computer-supported cooperative work was defined as ‘a scientific discipline guiding the design and development of groupware in a meticulous and appropriate way’ 4. Computer-supported cooperative work (CSCW) is a multidisciplinary discipline that encompasses technical, human, and social factors that can vary its implementations depending on the context, culture, organization, and country that apply it 5. As collaborative/cooperative applications evolved, important challenges also arose for developers 6. As a result, significant on-going research works address topics such as collaboration systems infrastructure, human systems, collaboration work and processes, and unique domain-specific issues. The field of infrastructure is one of the most active areas in computer-supported collaboration, with research focused on underlying technologies such as cloud computing, big data, service-oriented architectures, smart networks, and grids. Advanced infrastructure technologies offer a vision of resources (networks, computational servers, storage, search engines, collaboration tools and applications, etc.) as a service, with greater ease to collaborate while lowering cost. The Internet of Things (IoT) captures the growing importance of sensor swarms and collaborative devices that are often attached to one's smartphone or tablet. At the same time, there are new complementary challenges for privacy and security as we attempt to understand how to handle trust in complex systems and how to measure trustworthiness in human-to-human, human-to-machine, and machine-to-machine collaborations. The field of human systems focuses on the human component in collaboration such as coordination and cooperation mechanisms, cultural and psychological aspects, natural languages, human-machine interaction and interfaces, human centric aspects of trust and trustworthiness, cognitive engineering, and user-centered design. The field of collaboration work and processes focuses on aspects that traditionally relate to management and business but gradually have been considered by the software engineering area, such as virtual and remote project coordination, distributed team management, workflows, coordination, distributed and virtual organizations, and distributed design and development. Finally, the domains where computer-based collaboration can be applied continue to grow and are almost endless. Social media, knowledge management, e-learning, financial systems, simulation environments, decision making, design and engineering, logistics, e-business, telemedicine, public health, and emergency and disaster response are some examples of these domains. The annual International Conference on Collaboration Technologies and Systems, held since 1999, comes in the mid of these exciting developments. The conference has also produced special journal issues in recent years and this is one of them. This special issue contains eleven papers representing recent advances in the areas of the infrastructure, operation, evaluation, and application of collaboration systems. These papers were carefully selected from the 2012 International Conference on Collaboration Technologies and Systems (CTS 2012), which was held at the Westin Westminster Hotel, Denver, Colorado, USA, on 21–25 May, 2012 7 and the 2013 International Conference on Collaboration Technologies and Systems (CTS 2013), which was held at the Sheraton San Diego Hotel & Marina, San Diego, California, USA, on 20–24 May, 2013 8. Selected papers from the conference were invited for extended submission based on the conference technical program committee and the track organizers recommendations. In addition and in order to provide a wider overview of the current research in collaboration related topics, an open Call for Papers was publicly announced and distributed. In response, additional papers were received with a total of eighteen papers submitted for consideration. The complete set of submissions went through three rigorous review cycles, with three to six reviews per paper per cycle. Upon the conclusion of the review process, the eleven submissions that received the highest review ratings were accepted for publication in this special issue. The papers published in this special issue can be classified under three groups: collaborative system design methodologies, security and trust, and collaborative applications. The selected papers in each of these groups are briefly introduced in this section. There are six manuscripts that fall under this category, which covers a wide range of issues, approaches, and solutions. Drabble 9 presents an overview of the Cassandra Analysis and Planning System (CAPS) collaborative design tool kit, which provides designers with the capabilities to identify the direct effects of their own decisions and their indirect effects on the designs of others. The CAPS provides capabilities for reasoning with both quantitative and qualitative constraints and employs two dependency reasoning engines—one handles quantitative values and the other controls qualitative ones. CAPS supports a dynamic design process which identifies the most important design decisions, alerts the impacted designers, and supports a mitigation process to deal with any issues. The paper describes the CAPS architecture and an initial evaluation against a large collaborative task involving the design of a helicopter's electrical, hydraulic, structural, and mechanical systems. Tanaka et al. 10 study the effects real-time avatars had on distant communications when the avatars served as a substitute for videos in distributed environments. The paper discusses two experiments involving videos, photos, or avatars to supplement voice communications. In the first experiment, the subjects watched a conversation partner's video, avatar, photo, or nothing when speaking to the distant partner. The trials were made separately to observe the effects of motion and appearance on the frequency of pauses and speed of speaking. In the second experiment, the researchers compared avatar chat and a tele-operated robot conferencing to find how a physical embodiment influenced the degree of smoothness of speech. Traditionally, in distributed collaborative systems, video connections have been considered unimportant to effective distant communication. Dorn and Taylor 11 investigate the adaptability of the collaboration structure based on an analysis framework consisting of aspects such as behavior, asynchrony, state, and execution. They discuss seven distinctively different collaboration patterns in terms of those aspects. These collaboration patterns and resulting insights into their inherent adaptability may guide design decisions and trade-off analyses for the development of collaborative environments. The collaboration pattern construct is an extension of design pattern concepts and mechanisms from the software architecture domain. The success of software architecture description languages 20 led the authors to investigate a modeling approach for collaboration topologies and the development of a human Architecture Description Language (hADL) for specifying adaptation authority or flexibility conditions. In Davoust et al. 12, the authors define, classify, and characterize distributed wikis. They have identified three classes of distributed wiki systems, each using a different collaboration model and distribution scheme: highly available wikis, decentralized social wikis, and federated wikis. They have classified existing distributed wikis according to these classes and detail their underlying complexities and social and technical motivations. Davoust et al. 13 address the challenge that existing wiki systems, such as Wikipedia, depend on a centralized authority and cannot easily accommodate multiple points of view. The authors present P2Pedia, a social peer-to-peer wiki system, where users have their own local repository and can collaborate by creating, discovering, editing, and sharing pages with their peers but without synchronizing them. Multiple versions of each page can thus coexist on each repository and across the network, which allows for multiple points of view. Browsing or searching the wiki can yield multiple page versions. The authors describe an experimental study where the system was deployed for academic writing exercises, and the results are analyzed to demonstrate this collaboration approach. Missikoff et al. 14 present an end-to-end framework based on an open, collaborative approach for developing and maintaining business domain ontologies. While modern virtual enterprises require the definition of a common, agreed to, and shared conceptual basis that is captured in a reference ontology, no single methodology has been recognized as the primary solution for building ontologies. The authors propose a method for building domain ontologies, which is capable of integrating in one single software framework the features of cooperative participation, shared agreement, multilevels of formalism, and reuse of knowledge. The authors' methodology is characterized by a social participation approach that allows a community of practice, including knowledge engineers, domain experts, and ontology stakeholders to cooperate to produce conceptual models and reach consensus on their suitability while providing formal encoding into a computational ontology. Security and privacy issues in collaboration environments continue to be a major concern. We have three manuscripts that address some of the contemporary concerns. In Aldini et al. 15, the authors have proposed a collaborative framework for checking Android applications for malware by generating probabilistic behavior contracts. Repackaged Android applications are based on genuine applications, but they can include some hidden malwares to access private data or user credit information. The proposed framework performs analysis of the app's behavior at run-time from a contract that is built dynamically from monitoring real world usage. The contract specifies the set of legal actions that can be performed by an application. In the proposed framework, application contracts are generated dynamically by a central server that merges execution traces that are collected and shared continuously by collaborative users executing the application. Because the contract is built by monitoring real user behaviors, it is possible to detect misbehaviors that may not be noticed through static analysis alone. Kong et al. 16 present a technique for indoor location of mobile devices using Bluetooth wireless signal strength. The proposed method treats locations as fuzzy sets and fuzzifies the signal strength to define set membership. Membership values are then fused from multiple sources using a rules engine to deduce location values. The principal benefits of this technique include that it requires little or no calibration, can be used with widely available commercial devices, and places more attention on location information such as a room and floor of a building rather than coordinates. In Tang et al. 17, the authors address the need for extensions to the role-based access control model as cloud service providers expand user activities for cross-tenant interaction. Currently, most cloud service providers isolate user activities and data within a single tenant boundary. It is anticipated that this situation will evolve to foster cross-tenant collaboration supported by Authorization as a Service (AaaS). At present, there is no widely accepted model for cross-tenant authorization. The authors have built on an existing informal multi-tenancy authorization system (MTAS) 21, formalized the MTAS model, and proposed extensions for finer-grained cross-tenant trust. They have demonstrated the utility and feasibility of MTAS by means of an example policy specification, developed a prototype system, and conducted experiments on the prototype. The design and development of collaboration applications are important to respond to society's needs and solutions. In this special issue, there are two papers that apply. Lang and Fink 18 address rival machine scheduling of one or more homogeneous machines by autonomous agents. Machine scheduling by itself is computationally complex, and the presence of autonomous agents makes the problem more difficult. Autonomous agents pursue their own goals, act noncooperatively, and might not be willing to reveal information due to privacy concerns. To overcome the conflict of interests and prevent strategic interactions, the authors present a negotiation protocol to facilitate the coordination of noncooperative agents. Pani et al. 19 present the design and evaluation of a patient-centric collaborative tele-rehabilitation framework aimed at supporting a multidisciplinary team in the follow-up of domiciliary patients. The proposed framework builds on the experience of a clinical trial that exploited a novel tele-rehabilitation device not originally intended to support collaborative scenarios. The authors argue that collaborative technology in healthcare represents an important way to improve the quality of the care services and at a reduced cost. The authors conducted semi-structured interviews with a panel of experts to evaluate the proposed approach. Based on the papers submitted to and accepted in this special issue, we can draw some interesting conclusions. Computer-supported collaboration is in the mainstream interest of the research community. It is utilized in the everyday way of work of individuals, communities, and organizations. This usage is identifying subtle problems that have to be solved by researchers and practitioners in academia and industry. Technological, procedural, human, and domain-dependent issues have to be addressed by works such as those presented in this special issue. However, because computer-supported collaboration is being used in vastly different domains, the problems that this use identify are of very diverse nature. As we have seen, the papers published in this special issue address collaborative design, real time avatars, collaboration patterns, distributed wikis, business ontologies, malware detection, location of mobile devices, access control, autonomous agents, and tele-health. We anticipate this trend to continue as these systems and technologies get more pervasive and experience wider usage in numerous sectors and application domains. In some cases, the issues addressed by computer-supported collaboration fall within the focus of interest of other well-established areas of computer science and engineering such as operating systems, software engineering, information systems, or telecommunications,. In other cases, they are more related to organizational and business, sociology, psychology, anthropology, or human factors. If computer-supported collaboration is to be a discipline on its own, the key issues that describe it have to be identified. It is commonly accepted that computer-supported collaboration is not just a narrow and deep computing discipline but, on the contrary, is a broad and multidisciplinary field that cuts across many computing and noncomputing areas. In our opinion, the definition of the discipline of computer-supported collaboration has to be one of the hot topics of the research community in the short term. Thus, the development of the computer-supported collaboration body of knowledge could help to define this discipline. We hope that works like this special issue promote the interest for this discipline and its research topics. The guest editors of this special issue would like to express their deep gratitude to all authors, external reviewers, and Geoffrey Fox for their efforts in making this special issue possible. Moreover, they wish to thank all of the external reviewers who contributed at different levels to this special issue: Marie-Hélène Abel, Gail-Joon Ahn, Mortaza S. Barg, Louise Barkhuus, Sanat K. Bista, Christos Bouras, Mario Cannataro, Kyle Chard, Giuliana Dettori, Schahram Dustdar, Ana María Fernández-Pampillón, Maria Grazia Fugini, Ronald Hartung, Andrea J. Hester, Douglas Hodson, Claudia Ignat, James Joshi, Malik Ahmad Kamran, Kyoung-Yun Kim, Gregorij Kurillo, Tanu Malik, Cristina Manresa, Laurent Moccozet, Pascal Molli, James Myers, Grzegorz J. Nalepa, Mads Nygaard, Francesco Palmieri, Daniel Perry, T.K. Prasad, Wolfgang Prinz, Paolo Renna, Vassil Roussev, Filippo A. Salustri, Liliana P. Santacruz, Antonio Sarasa, José Luis Sierra, Hala Skaf-Molli, Irena Spasic, Anna Squicciarini, Kyle Stewart, Julianne Stiller, Jeffrey Stuckman, Hassan Takabi, Giordano Tamburrelli, Srikumar Venugopal, Bin Wang, Liu Yang, Chee Shin Yeo, Dimitrios Zissis, and Urko Zurutuza.

Johannes Göbel, Paul Keeler, A. E. Krzesinski, Peter Taylor

In the context of the `selfish-mine' strategy proposed by Eyal and Sirer, we study the effect of propagation delay on the evolution of the Bitcoin blockchain. First, we use a simplified Markov model that tracks the contrasting states of belief about the blockchain of a small pool of miners and the `rest of the community' to establish that the use of block-hiding strategies, such as selfish-mine, causes the rate of production of orphan blocks to increase. Then we use a spatial Poisson process model to study values of Eyal and Sirer's parameter $γ$, which denotes the proportion of the honest community that mine on a previously-secret block released by the pool in response to the mining of a block by the honest community. Finally, we use discrete-event simulation to study the behaviour of a network of Bitcoin miners, a proportion of which is colluding in using the selfish-mine strategy, under the assumption that there is a propagation delay in the communication of information between miners.

Nathaniel Popper

"A New York Times technology and business reporter charts the dramatic rise of Bitcoin and the fascinating personalities who are striving to create a new global money for the Internet age.Digital Gold is New York Times reporter Nathaniel Popper's brilliant and engrossing history of Bitcoin, the landmark digital money and financial technology that has spawned a global social movement.The notion of a new currency, maintained by the computers of users around the world, has been the butt of many jokes, but that has not stopped it from growing into a technology worth billions of dollars, supported by the hordes of followers who have come to view it as the most important new idea since the creation of the Internet. Believers from Beijing to Buenos Aires see the potential for a financial system free from banks and governments. More than just a tech industry fad, Bitcoin has threatened to decentralize some of society's most basic institutions.An unusual tale of group invention, Digital Gold charts the rise of the Bitcoin technology through the eyes of the movement's colorful central characters, including a British anarchist, an Argentinian millionaire, a Chinese entrepreneur, Tyler and Cameron Winklevoss, and Bitcoin's elusive creator, Satoshi Nakamoto. Already, Bitcoin has led to untold riches for some, and prison terms for others.Digital Gold includes 16 pages of black-and-white photos"...

Sebastián Acosta, Carlos Montalto

In this paper we consider the mathematical model of thermo- and photo-acoustic tomography for the recovery of the initial condition of a wave field from knowledge of its boundary values. Unlike the free-space setting, we consider the wave problem in a region enclosed by a surface where an impedance boundary condition is imposed. This condition models the presence of physical boundaries such as interfaces or acoustic mirrors which reflect some of the wave energy back into the enclosed domain. By recognizing that the inverse problem is equivalent to a statement of boundary observability, we use control operators to prove the unique and stable recovery of the initial wave profile from knowledge of boundary measurements. Since our proof is constructive, we explicitly derive a solvable equation for the unknown initial condition. This equation can be solved numerically using the conjugate gradient method. We also propose an alternative approach based on the stabilization of waves. This leads to an exponentially and uniformly convergent Neumann series reconstruction when the impedance coefficient is not identically zero. In both cases, if well-known geometrical conditions are satisfied, our approaches are naturally suited for variable wave speed and for measurements on a subset of the boundary.