Blockchain Papers

Huan Meng

Bitcoin is a digital currency which is based on P2P network and open source software. It is avirtual currency without any control by any centralized organization. New Bitcoins are issuedby lots of specified algorithms. The whole Bitcoin network utilizes the distributed database toverify and record all the transactions through the nodes in the P2P network in which thedouble spending is prevented. No person or organization is able to control Bitcoin based on adecentralized P2P network and algorithm. The cryptographic functions of Bitcoin are designedto allow only the real Bitcoin owner to pay and transfer, and ensure the anonymity andmarketability.The purpose of this thesis is to analyze the security architecture and services for the Bitcoin system and describe of all the features and infrastructures of the whole Bitcoin network. A whole establishment demo including wallet client, mining server with GUI and mining client is implemented. Further improvement will be suggested and recommended for the system

Emmanuelle Anceaume, Gilles Guette, Paul Lajoie-Mazenc, Thomas Sirvent · 5 authors

No abstract is available for this record.

Radim Tobolka

No abstract is available for this record.

Gebara M.F., L. Muccillo, May P., Claudia Suzanne Marie Nathalie Vitel · 6 authors

Key lessons<br><ul><li>While the constitutional rights (e.g. property rights) of indigenous peoples (IP) are strong in Brazil and may help to overcome their vulnerability, they are rarely enforceable and do not offer sufficient safeguards.</li><li>Informed consultation and a structured free, prior and informed consent (FPIC) process that considers cultural issues are fundamental to ensuring acceptance and consent by IP.</li><li>Local environmental funds can be a tool for increasing autonomy and decentralization while sharing benefits with IP and financing long-term and specific demands that can change over time.</li><li>Safeguard strategies implemented by the Amazon Fund to avoid conflicts of interest may result in restrictions on the participation of IP, having implications related to the legitimacy of decision-making in the distribution of benefits.</li><li>The absence of timely financial flows to meet IP needs may be a considerable risk since it can encourage environmentally damaging activities.</li><li>Relying on the voluntary market may be risky for IP initiatives because of market instability and possible lack of funding.</li></ul>

Gregory M Karch

Bitcoin is the world's first decentralized digital currency. According to Lawrence Lessig, cryptography is "the most important technological breakthrough in the last one thousand years" and will be transformative. Bitcoin, capitalizing on cryptography, is a revolutionary digital currency protocol--a software system capable of tracking financial transactions without the need for a third party intermediary. The Bitcoin software is a "community-driven open source project released under an MIT license.” This paper begins by briefly reviewing the mechanics of Bitcoin in Section I. Section II then surveys the rapidly expanding uses of Bitcoin, as well as the emerging application of Bitcoin. Since all new technologies face risk and downside, Section III will address a few of the risks and the highly publicized dark side of Bitcoin. Finally, Section IV will break down how the various governments have initially assessed this new technology and discuss policy implications going forward, as well as touch on the parameters for a twenty-first century regulatory framework by addressing emerging legal and policy issues. As the implementation of Bitcoin and other digital currencies continues, public policy makers should be encouraged to step back and assess the impact of the nascent technology prior to implementing regulatory schemes based upon pre-existing laws based upon outdated assumptions. The multiple applications of the emerging technology suggests policymakers take an innovative approach and adopt public policies and legal frameworks that accommodate the entire scope of its application. The new public policy formulates a regulatory scheme based upon a holistic understanding of the full range of characteristics of Bitcoin and digital currencies. Policymakers, starting with U.S. Congress and state legislatures, should develop public policies that recognize Bitcoin and digital currencies as possessing all of the following characteristics: currencies, payment systems, commodities, properties, investments, systems of commerce, and even systems of contracts. As this dynamic Smartmoney emerges, so emerges the requirement for a new innovative approach to laws and regulations: smart government.

Antti Puupponen, Ari Paloviita

This article is based on a case study that examines climate change adaptation of food supply chain inthree Finnish inland provinces Central Finland, Pirkanmaa and South Savo. The focus of the study was onfood processing enterprises and their adaptation strategies. For the study, 14 thematic interviews wereconducted and the research data was analysed using qualitative content analysis. The persons interviewedwere food entrepreneurs, managers of food enterprises and representatives of trade organizations andexpert organizations. The main research questions addressed in the article are: what kind of threat doesclimate change pose to food enterprises? What kind of adaptation aspects can be identified in the foodchain with respect to food supply chain management? According to the results, adaptation to climate changecan be characterized as reactive or autonomous strategy based on localization and decentralization offood supply chain as well as on regional food systems. We conclude that value-based strategic partnershipsin the food chain could enhance the regions’ adaptive capacity and resilience. Further research onregional impacts of climate change on the supply chain is required to provide decision-makers with morecomprehensive guidance.

Nico Döttling, Daniel Kraschewski, Jörn Müller‐Quade, Tobias Nilges

Universally composable secure computation was assumed to require trusted setups, until it was realized that parties exchanging (untrusted) tamper-proof hardware tokens allow an alternative approach (Katz; EUROCRYPT 2007). This discovery initialized a line of research dealing with two different types of tokens. Using only a single stateful token, one can implement general statistically secure two-party computation (Dottling, Kraschewski, Muller-Quade; TCC 2011); though all security is lost if an adversarial token receiver manages to physically reset and rerun the token. Stateless tokens, which are secure by definition against any such resetting-attacks, however, do provably not suffice for statistically secure computation in general (Goyal, Ishai, Mahmoody, Sahai; CRYPTO 2010). We investigate the natural question of what is possible if an adversary can reset a token at most a bounded number of times (e.g., because each resetting attempt imposes a significant risk to trigger a self-destruction mechanism of the token). Somewhat surprisingly, our results come close to the known positive results with respect to non-resettable stateful tokens. In particular, we construct polynomially many instances of statistically secure and universally composable oblivious transfer, using only a constant number of tokens. Our techniques have some abstract similarities to previous solutions, which we grasp by defining a new security property for protocols that use oracle access. Additionally, we apply our techniques to zero-knowledge proofs and obtain a protocol that achieves the same properties as bounded-query zero-knowledge PCPs (Kilian, Petrank, Tardos; STOC 1997), even if a malicious prover may issue stateful PCP oracles.

Mohsen Toorani

J-PAKE is a Password-Authenticated Key Exchange protocol, proposed in 2008 and presented again in 2010 and 2011. It does not require any public key infrastructure but uses zero-knowledge proofs. J-PAKE has been submitted as a candidate for the IEEE P1363.2 standard for password-based public key cryptography, and included in OpenSSL and OpenSSH. Since December 2010, J-PAKE has been used in Mozilla Firefox web browser. In this paper, we show that J-PAKE is vulnerable to password compromise impersonation attack, replay attack, and unknown key-share attack. We also propose some improvements for thwarting replay and unknown key-share attacks.

Sara Hillman

On New Year’s Eve of 1933 a train carrying a single passenger crossed the border into Switzerland. The passenger was the German-Jewish poet, philosopher, and literary critic Margarete Susman (1872-1966). Reflecting on the reasons for her departure, Susman later recalled: “When I left … my true Heimat I did so above all as a German who could not bear this new Germany. The Jewish destiny was not apparent in its entire horror at the time.”1 Sixty-one years old at the time of emigration, Susman was granted asylum in Switzerland. Soon, she would find a spiritual home among the religious socialists that had begun coalescing around the figure of the Protestant theologian Leonhard Ragaz (1868-1945) almost three decades earlier.2 It is her involvement in this leftist religious movement with its emphasis on dialogue between members of different creeds that constitutes the core of this article.3 The aim of genuine dialogue is to understand one’s partner, not to convert him or her to one’s own viewpoint. “Dialogue speaks to the Other with a full respect of what the Other is and has to say” in the words of religious scholar Edward Kessler. “This is never less than personal but can develop in such a way as to be extended to a group and even to communities. However, it begins with the individual and not with the community.”4 Kessler’s emphasis on the individual basis of dialogue is particularly pertinent to this inquiry. Susman and Ragaz were both interested in how each faith helped illuminate the other, sometimes to the point of blurring crucial doctrinal distinctions. Ultimately, their intellectual engagement centered on the urgent attempt to come to terms with some of the most pressing religious questions of their day. So far, this fascinating encounter has received virtually no scholarly attention, perhaps precisely because of its unorthodox nature and the difficulty of pigeonholing its protagonists.5 An inquiry into Susman’s and Ragaz’s dialogue, or “faith conversation” (Glaubensgespräch) as she called it, is important not only for the light it sheds on the intellectual and spiritual life of one German-Jewish émigré and a renegade Swiss pastor, but also for the time and place of its occurrence. The fact that this interaction took place in unoccupied German-speaking Europe, at a time when Jews had become social pariahs and ultimately victims of genocide, challenges the conventional understanding of the incipience of the Jewish-Christian dialogue after the Holocaust.6 Though Susman’s concern for interreligious dialogue did not amount to formal participation in an institutionalized network – which in any case did not exist at the time – I argue that her and Ragaz’s efforts constituted an important precursor to the phenomenon of interfaith encounter that suddenly burst upon the scene in postwar central Europe. Despite its uncongenial political climate, German-speaking Switzerland provided the essential cultural environment for their dialogue.7 Like so many members of the secularized Jewish bourgeoisie in the German Empire, Margarete Susman grew up largely divorced from her Jewish heritage. A daily prayer and the annual Christmas tree seem to have been the family’s only concessions to religious custom. When Margarete was ten, her family left her native Hamburg for Switzerland, apparently for economic reasons. For the next several years she was educated in the Protestant faith at the public school she attended in Zurich. It was not until she was already in her early twenties, having moved back to Germany, that she sought the instruction of the Reform rabbi Caesar Seligmann. At the time, she was scarcely aware of the differences between Christianity and Judaism, as she later remembered: “Back then the distinction between Judaism and Christianity had almost melted away in my soul. I perceived Christianity in Judaism and Judaism in Christianity. And yet, [my] profound love for Christ notwithstanding, the High Priest’s tearing of the garment in the face of the incarnate son of the One whom no eye may behold has always remained an ultimate truth for me.”8 Whether she actually justified her loyalty to Judaism in these terms at the time is of course doubtful. In any case, Seligmann’s teachings made a profound impact on her.9 To the end of her life she would be attracted to such Reform tenets as Judaism’s role as a ‘world religion’ and the Jews’ messianic mission. Despite a slowly growing interest in the Jewish faith, Susman was still preoccupied with Christianity. This preoccupation received a strong impetus when she became engaged to the non-Jewish painter Eduard von Bendemann. Encouraged by her prospective in-laws, she planned to convert but pulled back from an already scheduled baptism at the last moment. It suddenly became utterly impossible for her, she would subsequently recall, to abandon the “foundations” of her life.10 Her scruples notwithstanding, she would raise her only son Erwin, born in 1906, in the Christian faith – precisely because she herself had so painfully felt her exclusion from the “brilliant” world of Christianity.11 It stands to reason that her sympathy for Christianity affected her understanding of Judaism and what it meant to be Jewish. The decisive fact of her refusal to convert, however, speaks volumes of her life-long loyalty to the ancestral faith. As was the case with many of her intellectual peers, the First World War proved to be an extremely traumatic and transformative event for Susman. For the first time in her life she became aware of the devastating impact of history on human life. It dawned on her that henceforth it would be impossible to live a life of apolitical detachment. This realization did not translate into active political engagement, at least not within the confines of a particular party. Instead, Susman now turned her energies towards lecturing and writing on issues that were more explicitly socio-political as well as Jewish.12 From 1925 onwards she contributed to some of the Weimar Republic’s most prominent Jewish periodicals including Der Jude and Die Kreatur.13 Professional success might have alleviated, but could not undo, personal calamity. In the late twenties her marriage fell apart, and Susman suffered a deep depression from which she recovered only slowly. No doubt work provided a palliative to her misery. When she finally left Germany at the end of 1933, never to return to the land of her birth, she had gained a reputation as one of Germany’s most insightful commentators on intellectual, religious, and literary trends. In emigration Susman’s material situation In to a she had to her which in her having to for an she did not from up she was to herself for a time by writing for and including Ragaz’s a particularly had attracted the eye of the she was a left and from and – a she to in by a a she now on the of including the Ragaz family who helped her way of life in a on the and her in by her Leonhard Ragaz in particular became a intellectual and Susman’s by Ragaz had up as one of of a in Despite the family’s economic it was that the Leonhard school and On in and to work as a Protestant pastor, first in a then at the In the of for at by the a German and of Ragaz it to with what the and of the and the at As a felt from the Christian with their emphasis on the In a to towards the end of the First World that it had not been for their would have up years and become a In finally the to from and on what true From now on Ragaz would all energies to the religious and political of which took place in the a and for that in a in Zurich. At the of this was Ragaz’s to the religious of and only did Jews the at the some also to the Judaism was the of of the In a religious with several explicitly to even so as to the to No that the Jewish him to on Judaism and Christianity and that the Jewish on the of a new Ragaz was of the of Christian the but to have no understanding for Jewish In of Judaism to be of in a in Der for the Jewish were the central of the among the may well have to Jews more to but it at a In a on at the Ragaz of the figure of many the of Christ and profound to the of the to this of as the of the Jewish religious was a of Christianity. the Jews had only Ragaz in a that still one had so and To this the of and – that is It was a Susman to made Ragaz so a in dialogue with Jews was to and In at the had that sought to the Christian and with the of is no had is how I and it Ragaz’s on this to Jews in dialogue on a of is and to have its in emphasis on the of a true in can be to the of the as well as the movement that helped religious The to to interested from different and was precisely for its Ragaz any or at or An of the and to not any of of any Whether was always to to this to be As the and then the Ragaz became more by of and both of which were with of the of To the Swiss were from towards Jews and political who the border from 1933 Ragaz and family had their for The Ragaz became the first point for many in Susman having been one of In in Ragaz and family were to live up to the of the of and on from a to a renegade and social was did the between and Jews into In an late in life Margarete Susman her understanding of the or of Judaism and Christianity as Judaism for the Christianity has already … the as well as the the of the is on the it is one and faith and the the love which the the among as the true in both As Ragaz had in early Judaism and Christianity were in one from one to one of the that from what called the with nature and above life and And it was understanding of that had to and true – in the of the Susman as the Ragaz to be and that human history In were one and the Like Ragaz the as a of history – more not only as any but as most important of was that the not only in history in but that it actually as in the to Die As a of the world as and still in the of and not only was still in the of As it, is the of the new and the new in which did the Jews into this and for Ragaz the of could not be the the Jews were the had been the messianic for on the had even as that the had already was in was Judaism’s of the figure of Christ as the and return to – only then would the true as Ragaz it come into this the of a point that Ragaz’s of a true that a messianic Christianity with a Judaism that Christ even to a of Jews of The in of Ragaz’s in the of religious by such as and the perhaps more than any with individual Ragaz’s for the interreligious dialogue and the not respect among Jewish The impact of to not be as the Jewish German religious the years of the Jews such as from Ragaz’s in a a which would never be by the This was Ragaz that had more in with Jews such as than with most for having recovered the and that felt almost to than to and to than to Christian the in a to of in the true of even when the political had begun to it from the notwithstanding, it would be to that and Ragaz’s in the with one of particularly with that had to be and of a new would be however, in this as or as an attempt at Jews into the Christian was at was a of both Judaism and Christianity that Ragaz essential for the of the In Ragaz a which as a and In the the to a – perhaps to Susman’s of the in an on in the Weimar The to to illuminate the and that made an encounter from different The up Ragaz’s as first had to become true and Jews true only then could work towards the realization of for faith had to with the that the of on was its ultimate that is with the of a point of that was to both true in Ragaz’s meant the of as of Jewish in as the last of a of in had to that the of the of had not been ultimate was still was some for both – to with the of the a basis for an encounter in the and This and between true and true Jews was to be in the by the of one the other, by of all by but in a different by of a the of each to and then by the of each to that which the had the of of and now a new for the the to Christ in this not only to Christ but was to be in In a personal Susman later to be in the Ragaz explicitly her on the of the Her to it had been to but not only in the of had of Though the Jewish of was an important concern to and the not place of Judaism in in In this as to Judaism was and is only a of my this to my faith in the of For the of the of the One all of and many Jews received Ragaz’s of a with to the The a of Though the was by no Ragaz was in role in the Swiss it him that efforts to a between the creeds were not perceived as the not have been it the of when the and with which even the Jews to the had the of to was now on a has and have – – not even Ragaz to would at least have constituted a genuine a Ragaz aware of the nature of For the Jews had been of and all of a the who one of their precisely of the that of having to Ragaz’s particularly the of in the of the Jews was in full full to the Susman him the as of Swiss less of as a In a Jewish on of she had for the first time, she how the Jews felt by the figure of In their she Christ was a to their own and to their loyalty and Ragaz that by no had all Jews on and then a crucial in one when of It was a she herself had Susman’s notwithstanding, it that she would have with of what called Her own had provided her with to the and nature of the what would she have that the and of the of had always been in the of a It was this Ragaz that had had to the of who had to be the the situation was no destiny in the of the to this as well to her, and as was not that she convert, for it was precisely her that her to between Jews and Susman took her role as she with Ragaz’s is from her for the but ultimately in the religious Der Ragaz could have for a more from a The was of an understanding so and the of which have not in the entire history of Susman The was in of Judaism and Christianity and did not to for the figure of both had Ragaz did not engaged in a between of the the Jewish was at this particular it was upon Susman to to this that did not to convert but to For this was not the of faith that had place the Weimar had genuine she these efforts which had of the in an as she it, Ragaz’s attempt had from within the and was less than a for the of was particularly Susman in of the fact that Ragaz was to the Jews in be no the particular Jewish the as the realization of the true The ultimate aim of – how could it be – was ultimate aim of history to all Christ as the of all was this not in Christianity the all to the as for Ragaz’s and Susman’s and for the of their one but at the of such at a time when a Christian was in the of to the Jewish Susman’s of her her in Jews such as the her of not how she to this Though she by she her role as an Ragaz and the is she to her I have now how and how of a I even for the Susman’s to Ragaz and her in a in of the fact that towards the end of life Ragaz to a for a of the in Christian than to some Judaism would it did not to was not and the in to the with and the of could be As in the of the Jewish or to last on Judaism and Christianity had in a from of the to the tree no in Judaism and Christianity of I Christianity … to be and Judaism the Susman is no she would it be for it to at the of the destiny as it so in her Judaism and Christianity the the one as a the as an individual In Ragaz had made the The of from the that also Christianity. The fact that this the of Christianity not It is an of that Christianity and Judaism on the Christianity – of the that the – and as well as in and many of its this was a more devastating and on the In to understand to such Susman to the of could the Jewish destiny be in light of the of the of the and years of writing what would to be her most important Susman was in with both in and by and In this in of its most or were at least in the dialogue with In its a of the of with of the entire Jewish In this the destiny of the by a of more stands as the of the Jewish the destiny of a with the of for it has not For to live in the full of and the of this is what the of is ultimately meant to be Jewish – to and not to the of the even only Susman that it was not up to to no how and might to the of the had the of in the this had only been with and to she it had not been the by the on life that had a new among the a that after of and had finally the to no Susman is not to the of a return to a but to the of the – the of a to the world for the of the The way she it, was of a of faith, a of life. the is it in The however, an to the end of And a crucial in Jews to the Like Ragaz as the of who with and who among the of Ragaz as the of Susman as the of the messianic as it was not to as in the of In Susman had Ragaz how she had been by one of on the of a this new world were to Ragaz apparently had it would largely be to in world history – a that had her however, she her difficulty in to the that had actually in her Susman had to the Jewish of the of her she was in for a The to the because of its non-Jewish her one of the of the her that her had to essential it did not with between Judaism and and it than the Jewish towards and the of Judaism however, as a to the in which as spiritual Susman had no more with non-Jewish and of the on of its which of as an In the the was by of Zurich. the its for a by Susman’s Like her a German-Jewish the to Other Jewish were for the scholar of the was affected by the particularly its first and in a way that Susman as and Susman’s first of Judaism, Caesar to be by the had it three and each time had been more Susman’s who had been from the in Susman had to and Jewish in its entire with all the and with all and and with an and that was To be was with her on a Jewish which a Christian may as but it at a Susman’s by a no a Jewish Christian up on the of and between the An for Susman that a group of and were to Susman have to this for several later that her was for because it is a for to the understanding of with and an could such such as these the Christian were to from Susman’s Whether the of her is a different A at the impact of is important for what it the Susman was and by both Jews and To be her unorthodox to the of in with her left her to from the Jewish as well as the Christian Susman to have some of these still in the of she to to as I had suddenly a new of Ragaz’s and I – for more than one Susman on a crucial point her with not to Jews such as her of having come to And Susman’s to that she was aware of how her had from was a but so was of would have engaged in dialogue with the had it not been for their on the of their And – and this point to be and – were from the of a and a As Susman herself had to the Jews and had to each on a basis of to to as Christian and In the she never of that Leonhard Ragaz on after the end of the World War in Europe. did not live to the of interreligious and that to the German and Swiss social after Margarete however, was a of and in this In she took in a of and Jews by the At the she helped the Her involvement with Ragaz had the way for her engagement in the Jewish-Christian Susman and Ragaz engaged in what constitutes a provided the essential basis for this dialogue because it was the religious in the of in some that such a than to an and religious religious socialists sought the realization of what Ragaz called the of a even the of as Ragaz it in on the their as from the institutionalized dialogue that after as from such as in it an of of different religious and for some of their most pressing and of interreligious dialogue not to the different such took in the the of the in which Ragaz and Susman to each be When Jews Christian to in religious in the Weimar these were all by what one might the between the only did the almost always with Jews – a of interest on the Christian – but respect was in these At its most this of respect was in and at to and the of Christianity the essential of a interreligious dialogue were from these between the in dialogue and of all of In the case of Margarete Susman and the religious socialists around however, the three for dialogue were all the to the of the the of the and the of the for the This last is of particular I would to all from what by the of dialogue to to the of the of the in the words of the of the three As have Susman was to Christianity than many of her Jews felt can be no however, that she of herself as a In a a Jewish the by which and their in their with and is the one can to the Jewish individual within the individual aim the first of the – and is almost strong a – that first when in the of the world and by that for the first time to the to an old for Though Susman to in some way her understanding of what was to be of a to When her only son Erwin, whom she had as a was to Judaism, she a even a is the of that only a who has no of Judaism is of One not convert to Judaism as to one has it in or it by The is one is not born a but a by to in this of destiny In a of of as a daily might of the daily to be of the Jewish And for Susman this a faith between Jews and As as Ragaz was for the of the and have been well aware that sympathy for and the left made him in their but this did not him from at did not doubt the genuine nature of Christianity. sympathy for Judaism, and the of at a time when such were the of in the of this inquiry was as a to with And this was and No Ragaz would have been moved by the fact that the him as one of the the was to the who had to a true understanding between the of and a true of an as which would on a Jewish a Christian but on that of the of and of the of the between the personal and the of the dialogue with by of by and in the was for him the dialogue between these The to Susman who was even more aware of the of the Jewish-Christian dialogue and of the and of the attempt to a a At the time of the Jews’ Margarete Susman the the of the which the world to up with its true between a and a of constitutes a of from a of the messianic

Ramon H. Myers, Fiki Ardiansyah

Key messages<br><ul><li>In different provinces or districts, the same laws can be applied in very different ways.</li><li>Participation of customary land users and local communities remains ad hoc and requires that implementing regulations are strengthened, as the existing safeguarding laws are not sufficiently specific.</li><li>Further developments of safeguarding laws and regulations (specifically the distribution of benefits from carbon financing) need to be well defined and better aligned with decentralization processes.</li><li>Subnational actors are unclear on their role in a national REDD+ strategy and how they will be involved in decision making.</li><li>REDD+ is challenged by a misalignment between land use decision-making powers and REDD+ management powers allocated to different bodies and levels.

John Michael Grant

This paper explores legal and economic issues related to a fascinating new technology called the blockchain protocol. The most popular and important blockchain commodity is currently bitcoin (Part I). Bitcoin is intuitively understood as a “virtual currency.” However, it is possible that bitcoin fails to meet an economist’s definition of money (Part II). In Part III, I survey the academic literature and conduct an empirical study of my own that compares bitcoin prices and other assets from July 12, 2013 until December 16, 2014. Ultimately, I conclude that bitcoin is not money and does not behave like money. Later, I analyze two potential legal questions connected to the question of whether bitcoin is money: how will bitcoin derivatives be regulated? (Part IV), and whether transferred bitcoins are free of security interests under Article 9 of the Uniform Commercial Code (Part V).

Pim Vullers

In a world where computers are involved in most aspects of our lives, it becomes more and more important to digitally identify entities. To achieve this goal, many existing systems use unique identifiers. This is a simple solution, but also makes it easy to trace the user’s actions. A privacy-friendly alternative is to use attributebased credentials as a basis for authentication and authorisation. Such credentials serve as a cryptographic container for attributes, that is, properties of the user, which are certified by an authority. With these attributes the user can be authenticated to access a resource or receive a service solely on the properties that are relevant for that specific resource or service. In this thesis we discuss three attribute-based credential technologies for which we have developed efficient smart card implementations. These technologies are: Self-blindable Credentials These credentials are based on elliptic curve cryptography with bilinear pairings. This technology shifts the computational burden to the terminal which makes a very compact smart card implementation possible. Unfortunately the support for elliptic curve cryptography on smart cards is limited to standard algorithms, which made it hard to develop other variants of this technology. This results in a minimal feature set compared to the other technologies. U-Prove The U-Prove issuance and verification protocols are, respectively, based on Schnorr’s blind signature scheme and zero-knowledge proofs. This technology offers the fastest implementation for attribute verification. With respect to privacy there is only one important drawback: U-Prove does not protect against linking multiple verification sessions to each other. This means that these credentials basically act as a pseudonym for the user. Identity Mixer This technology is based on the Camenisch-Lysyanskaya signature scheme which provides a blind signature protocol, which can be used for credential issuance, and zero-knowledge proofs for attribute verification. The performance of this implementation is not the best among these technologies, but this technology provides a broad feature set and offers proper unlinkability. This makes it possible to use a credential multiple times without becoming traceable. The goal of the research presented in this thesis has been to develop efficient smart card implementations of attribute-based credentials and compare various cryptographic systems for attribute-based credentials. This has resulted in a detailed

Ivan Damgård, Bernardo David, Irene Giacomelli, Jesper Buus Nielsen

We present a new compact verifiable secret sharing scheme, based on this we present the first construction of a homomorphic UC commitment scheme that requires only cheap symmetric cryptography, except for a small number of seed OTs. To commit to a k -bit string, the amortized communication cost is O ( k ) bits. Assuming a sufficiently efficient pseudorandom generator, the computational complexity is O ( k ) for the verifier and O ( k 1 + ε ) for the committer (where ε < 1 is a constant). In an alternative variant of the construction, all complexities are O ( k · polylog ( k )). Our commitment scheme extends to vectors over any finite field and is additively homomorphic. By sending one extra message, the prover can allow the verifier to also check multiplicative relations on committed strings, as well as verifying that committed vectors a , b satisfy a = φ ( b ) for a linear function φ . These properties allow us to non-interactively implement any one-sided functionality where only one party has input (this includes UC secure zero-knowledge proofs of knowledge). We also present a perfectly secure implementation of any multiparty functionality, based directly on our VSS. The communication required is proportional to a circuit implementing the functionality, up to a logarithmic factor. For a large natural class of circuits the overhead is even constant. We also improve earlier results by Ranellucci et al. on the amount of correlated randomness required for string commitments with individual opening of bits. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Takashi Shiraishi

Indonesia underwent enormous political and institutional changes in the wake of the 1997&#8211;98 economic crisis and the collapse of Soeharto's authoritarian regime. Yet something curious happened under President Yudhoyono: a politics of economic growth has returned in post-crisis decentralized, democratic Indonesia. The politics of economic growth is politics that transforms political issues of redistribution into problems of output and attempts to neutralize social conflict in favor of a consensus on growth. Under Soeharto, this politics provided ideological legitimation to his authoritarian regime. The new politics of economic growth in post-Soeharto Indonesia works differently. Decentralized democracy created a new set of conditions for doing politics: social divisions along ethnic and religious lines are no longer suppressed but are contained locally. A new institutional framework was also created for the economic policy-making. The 1999 Central Bank Law guarantees the independence of the Bank Indonesia (BI) from the government. The Law on State Finance requires the government to keep the annual budget deficit below 3% of the GDP while also expanding the powers of the Ministry of Finance (MOF) at the expense of National Development Planning Agency. No longer insulated in a state of political demobilization as under Soeharto, Indonesian technocracy depends for its performance on who runs these institutions and the complex political processes that inform their decisions and operations.

Joe Walton

Cryptocurrency – including a particular initial denomination known as Bitcoins – has received since 2009 wide and growing publicity in technology, finance, U.S. and international law enforcement, as well as general public journalism and popular press. This recent popular press coverage of cryptocurrency (how and from where do Bitcoins originate?, how much is one worth today or tomorrow?, will it last with all the stumbling implementation and technical intricacies?, purchasing illegal drugs and guns with Bitcoins!) overshadows cryptocurrency’s applicability to financial and currency system theories which have been developed and predicted for decades or more: the fundamental theory of currency; currency denationalization; a return to an international standard monetary unit (before nationalized fiat); the inefficiency of costly 3rd-party-trust currency models; and global concerns about currency hegemonies as well as political influence of monetary policy, and currency hedge/speculation. As the moral panic of Bitcoin and similar initial implementations of cryptocurrency fade and cryptocurrency systems gain traction underground or aboveground anywhere in the world, U.S. and international public policymakers and regulators will need to surveil, understand, and evolve public policy to accommodate any aspect of cryptocurrency which develops from technical novelty to realization of predicted grand monetary theories. Some of those areas of evolution include: national central bank monetary control; public sector dependence (oversight, taxing, fees) on private sector financial models and structures; and viability of traditional national and international law enforcement techniques U.S. federal and major subnational public sector policymakers and regulators must remain vigilant for and educated about cryptocurrency usage whether in nationalized or denationalized use cases or they risk missing early opportunities to shape the rapidly changing landscape of digital financial systems in the U.S and abroad. This vigilance and awareness could be in the form of continued congressional hearings and regulatory surveillance. But a more proactive approach including federal grants for research and study of cryptocurrency, promotion of national and international symposia regarding currency technology and implications should be pursued. The nature of cryptocurrency’s raison d'être and early-adopter motivation foretells a disruptive network-effect adoption despite entrenched interests’ efforts at preclusion similar to numerous recent technical innovations in the private sector like music or other intellectual property downloads, retail shopping, taxis services, hotel lodging, traditional print journalism, and traditional communication systems.

Diana Sirila

No abstract is available for this record.

W L Brown

Bitcoins have the potential to fundamentally change the way value is transferred globally. Their rapid adoption over the past four years has led many to consider the possible results of such a technology. To be a viable currency, however, it is imperative that the market for trading Bitcoins is efficient. By examining the changes in availability of predictable outsized returns and market liquidity over time, this paper examines historical Bitcoin market efficiency and establishes correlations between market liquidity, price predictability, and return data. The results provide insight into the turbulent nature of Bitcoin market efficiency over the past years, but cannot definitively measure the magnitude of the change due to the limitations in efficiency analysis. The most meaningful result of this study, however, is the statistically significant short-horizon price predictability that existed over the duration of the study, which has implications for Bitcoin market efficiency as well as for continued research in short-horizon Bitcoin price forecasting models.

Maria Letizia Perugini, Cesare Maioli

The considerable diffusion of bitcoins over the Internet that took place in the last two years has highlighted some important issue about the use of anonym tools of payment in e-commerce. Even though bitcoins are largely considered to be a digital currency, the legal and economic analysis draws the attention to a concomitant structure of financial commodity with risky features related to derivative instruments making the possibility of a bubble a case to consider. The significant growth in value and the intense volatility characterizing bitcoins are more likely to be the consequence of remarkable investments made by hedge funds and the effect of specific Institutional measures, than the outcome this efficient instrument has achieved on the Internet. The following article is analyzing bitcoins in their twofold nature: the structural considerations we will express are referred to virtual coins in general, whereas the financial evaluation is related to the specific volatility of our analysis target.

Ole Christian Andreas Valstad, Kristian Vagstad

Alloreactivity after transplantation is associated with profound immune suppression, and consequent opportunistic infection results in high morbidity and mortality. This immune suppression is most profound during GVHD after bone marrow transplantation where an inflammatory cytokine storm dominates. Contrary to current dogma, which avers that this is a T-cell defect, we demonstrate that the impairment lies within conventional dendritic cells (cDCs). Significantly, exogenous antigens can only be presented by the CD8(-) cDC subset after bone marrow transplantation, and inflammation during GVHD specifically renders the MHC class II presentation pathway in this population incompetent. In contrast, both classic and cross-presentation within MHC class I remain largely intact. Importantly, this defect in antigen processing can be partially reversed by TNF inhibition or the adoptive transfer of donor cDCs generated in the absence of inflammation.

Džemail Zornić, Šemsudin Plojović, Enis Ujkanović, Senadin Plojović

Bitcoin is actually a new kind of money. It is a brand new concept and it is a digital currency that is not issued by a central bank. Bitcoin is not created by a corporation. Instead, anyone who participates in the Bitcoin network - anyone who uses the Bitcoin software on his computer and communicates with a network of other people, who are doing the same thing, all these people together perform the function normally performed by a central bank. In this paper, we will try to bring closer the currency Bitcoin. Researchers are recommended to conduct research about Bitcoin, in order to receive objective advantages and disadvantages of Bitcoin as a currency.

Karl Lauschke

Although academic and practical interest in non-fungible tokens (NFTs) has continuously increased over the last few years, there is still a need to better understand their social acceptability. The aim of the study was to explore the double edge of NFT legitimacy for NFTs by unveiling the role of sustainability and by adopting technology legitimacy and the field of sustainability transition studies as a theoretical lens. Specifically, this research investigates the role of sustainability in securing and maintaining technology legitimacy within NFT projects. We interviewed 12 experts through exploratory qualitative research. The findings highlight three main ways in which sustainability participates in the legitimation of NFT projects. While sustainability can be inherent in the NFT project itself, this legitimation can also be derived from the perceived sustainability of the NFT technology or be part of innovative business models. Theoretical contributions and managerial implications are then discussed. JEL CODES: O33, O35, O50

Essam Ghadafi

Abstract. In this work, we first formalize the notion of dynamic group signatures with distributed traceability, where the capability to trace signatures is distributed among nmanagers without requiring any interaction. This ensures that only the participation of all tracing managers permits tracing a signature, which reduces the trust placed in a single tracing manager. The threshold variant follows easily from our definitions and constructions. Our model offers strong security requirements. Our second contribution is a generic construction for the notion which has a concurrent join protocol, meets strong security requirements, and offers efficient traceability, i.e. without requiring tracing managers to produce expensive zero-knowledge proofs for tracing correctness. To dispense with the expensive zero-knowledge proofs required in the tracing, we deploy a distributed tag-based encryption with public verifiability. Finally, we provide some concrete instantiations, which, to the best of our knowledge, are the first efficient provably secure realizations in the standard model simultaneously offering all the aforementioned properties. To realize our constructions efficiently, we construct an efficient distributed (and threshold) tag-based encryption scheme that works in the efficient Type-III asymmetric bilinear groups. Our distributed tag-based encryption scheme yields short ciphertexts (only 1280 bits at 128-bit security), and is secure under an existing variant of the standard decisional linear assumption. Our tag-based encryption scheme is of independent interest and is useful for many applications beyond the scope of this paper. As a special case of our distributed tag-based encryption scheme, we get an efficient tag-based encryption scheme in Type-III asymmetric bilinear groups that is secure in the standard model.

Charanjit S. Jutla, Arnab Roy

We introduce a novel concept of dual-system simulation-sound non-interactive zero-knowledge (NIZK) proofs. Dual-system NIZK proof system can be seen as a two-tier proof system. As op-posed to the usual notion of zero-knowledge proofs, dual-system defines an intermediate partial-simulation world, where the proof simulator may have access to additional auxiliary information about the potential language member, for example a membership bit, and simulation of proofs is only guaranteed if the membership bit is correct. Further, dual-system NIZK proofs allow a quasi-adaptive setting where the CRS can be generated based on language parameters. This allows for the further possibility that the partial-world CRS simulator may have access to fur-ther trapdoors related to the language parameters. We show that for important hard languages like the Diffie-Hellman language, such dual-system proof systems can be given which allow unbounded partial simulation soundness, and which further allow transition between partial simulation world and single-theorem full simulation world even when proofs are sought on non-members. The construction is surprisingly simple, involving only two additional group elements in asymmetric bilinear pairing groups.

Ajibola Ogunbadewa

No abstract is available for this record.