Blockchain Papers

J. W. Pope

In 1986, Manuel Blum claimed in his paper ”How to Prove a Theo-rem So No One Else Can Claim It ” that he could apply zero-knowledge methods to proving theorems in any proof system. He sketched a proof of this result, but gave no details. We give a background of zero-knowledge proofs and examine their applicability to the propositional calculus. We then examine Blum’s claim, assuming the existence of a proof-verifying program which can be modeled with a finite state machine, and complete the proof. However, we also show that a zero-knowledge proof demon-strating knowledge of a proof is no easier than actually determining a proof of a theorem from scratch. 1

Dorian Goldfeld, Alexander Lubotzky, László Pyber

Let Γ denote the modular group SL(2,Z) and Cn(Γ) the number of congruence subgproups of Γ of index at most n. We prove that lim n→∞ log Cn(Γ) (log n)2/ log log n = 3−2 √ 2 4 . Some extensions of this result for other arithmetic groups are presented as well as a general conjecture. §0. Introduction Let k be an algebraic number field, O its ring of integers, S a finite set of valuations of k (containing all the archimedean ones), and OS = { x ∈ k ∣∣ v(x) ≥ 0, ∀v ∈ S}. Let G be a semisimple, simply connected, connected algebraic group defined over k with a fixed embedding into GLd. Let Γ = G(OS) = G ∩ GLd(OS) be the corresponding S-arithmetic group. We assume that Γ is an infinite group. For every non-zero ideal I of OS let Γ(I) = Ker ( Γ → GLd(OS/I) ) . A subgroup of Γ is called a congruence subgroup if it contains Γ(I) for some I. For n > 0, define Cn(Γ) = # { congruence subgroups of Γ of index at most n } . Theorem 1. There exist two positive real numbers α− and α+ such that for all sufficiently large positive integers n n log n log log nα− ≤ Cn(Γ) ≤ n log n log log nα+ . This theorem is proved in [Lu], although the proof of the lower bound presented there requires the prime number theorem on arithmetic progressions in an interval where its validity depends on the GRH (generalized Riemann hypothesis for arithmetic progressions). The first two authors research is supported in part by the NSF. The third author’s Research is supported in part by OTKA T 034878. All three authors would like to thank Yale University for its hospitality. Typeset by AMS-TEX 1 2 DORIAN GOLDFELD ALEXANDER LUBOTZKY LASZLO PYBER In §2 below, we show that by appealing to a theorem of Linnik [Li1, Li2] on the least prime in an arithmetic progression, the proof can be made unconditional. Following [Lu] we define: α+(Γ) = lim logCn(Γ) λ(n) , α−(Γ) = lim logCn(Γ) λ(n) , where λ(n) = (log n) 2 log log n . It is not difficult to see that α+ and α− are independent of both the choice of the representation of G as a matrix group, as well as independent of the choice of S. Hence α± depend only on G and k. The question whether α+(Γ) = α−(Γ) and the challenge to evaluate them for Γ = SL2(Z) and other groups were presented in [Lu]. It was conjectured by Rademacher that there are only finitely many congruence subgroups of SL2(Z) of genus zero. This counting problem has a long history. Petersson [Pe, 1974] proved that the number of all subgroups of index n and fixed genus goes to infinity exponentially as n → ∞. Dennin [De, 1975] proved that there are only finitely many congruence subgroups of SL2(Z) of given fixed genus and solved Rademacher’s conjecture. It does not seem possible, however, to accurately count all congruence subgroups of index at most n in SL2(Z) by using the theory of Riemann surfaces of fixed genus. Here we prove: Theorem 2. α+(SL2(Z)) = α−(SL2(Z)) = 3−2 √ 2 4 = 0.0428932 . . . We believe that SL2(Z) represents the general case and we expect that α+ = α− for all groups. The proof of the lower bound in Theorem 2 is based on the Bombieri-Vinogradov Theorem [Bo], [Da], [Vi], i.e., the Riemann hypothesis on the average. The upper bound, on the other hand, is proved by first reducing the problem to a counting problem for subgroups of abelian groups and then solving that extremal counting problem. We will, in fact, show a more remarkable result: the answer is independent of O! Theorem 3. Let k be a number field with Galois group g = Gal(k/Q) and with ring of integers O. Let S be a finite set of primes, and OS as above. Assume GRH (generalized Riemann hypothesis) for k and all cyclotomic extensions k(ζ ) with a rational prime and ζ a primitive th root of unity. Then α+(SL2(OS)) = α−(SL2(OS)) = 3 − 2 √ 2 4 . The GRH is needed only for establishing the lower bound. It can be dropped in many cases by appealing to a theorem of Murty and Murty [MM] which generalizes the Bombieri– Vinogradov Theorem cited earlier. COUNTING CONGRUENCE SUBGROUPS 3 Theorem 4. Theorem 3 can be proved unconditionally for k if either (a) g = Gal(k/Q) has an abelian subgroup of index at most 4 (this is true, for example, if k is an abelian extension); (b) d = deg[k : Q] < 42. We conjecture that for every Chevalley group scheme G, the upper and lower limiting constants, α±(G(OS)), depend only on G and not on O. In fact, we have a precise conjecture, for which we need to introduce some additional notation. Let G be a Chevalley group scheme of dimension d = dim(G) and rank = rk(G). Let κ = |Φ+| denote the number of positive roots in the root system of G. Letting R = R(G) = d− 2 = κ , we see that R = +1 2 , (resp. , , −1, 3, 6, 6, 9, 15) if G is of type A (resp. B , C , D , G2, F4, E6, E7, E8). Conjecture. Let k,O, and S be as in Theorem 3, and suppose that G is a simple Chevalley group scheme. Then α+(G(OS)) = α−(G(OS)) = (√ R(R + 1) −R )2 4R2 . The conjecture reflects the belief that “most” subgroups of H = G(Z/mZ) lie between the Borel subgroup B of H and the unipotent radical of B. Our proof covers the case of SL2 and we are quite convinced that this will hold in general. For general G, we do not have such an in depth knowledge of the subgroups of G(Fq) as we do for G = SL2, yet we can still prove: Theorem 5. Let k,O, and S be as in Theorem 3. Let G be a simple Chevalley group scheme of dimension d and rank , and R = R(G) = d− 2 , then: (a) Assuming GRH or the assumptions of Theorem 4; α−(G(OS)) ≥ (√ R(R + 1) −R )2

Authors unavailable

1 Arbitration — Applicable law — Relation between concession contract, bilateral investment treaty and ICSID Convention — Dispute with provincial authorities relating to interpretation and application of contract to be submitted to administrative courts Economics, trade and finance — Bilateral investment treaty — Argentina-France bilateral investment treaty, Article 8(2) — “Fork in the road” provision — Relevance to Tribunal’s jurisdiction over treaty claim — Relevance to merits of claim Arbitration — Jurisdiction — Jurisdiction issue joined to merits — Failure to designate or consent to application of ICSID Convention to province under Article 25(1) and (3) does not deprive Tribunal of jurisdiction — Local forum clause in concession contract does not divest Tribunal of jurisdiction for claims against State State responsibility — Imputability — Attribution of responsibility for actions of political subdivisions — Responsibility not limited by federal or decentralized character of State — No factual basis for attribution — State’s obligation under bilateral investment treaty to pursue in good faith and with reasonable efforts the resolution of the dispute — State’s constructive role in renegotiation process Relationship of international law and municipal law — Impossibility of separating claims for breaches of contract from bilateral investment treaty violation without prior resort to administrative courts — Claimant required under contract to assert its rights in proceedings before administrative courts prior to invoking ICSID procedure — Claimant not precluded from asserting its rights in administrative courts — No evidence that courts lacked independence or fairness or would have denied claimant’s rights procedurally or substantively — No principle of exhaustion of remedies Claims — Exhaustion of local remedies — Requirement incompatible with Article 8 of bilateral investment treaty and Article 26 of ICSID Convention — Resort to administrative courts required under contract for purposes of interpretation and application

Stefan Kokot

No abstract is available for this record.

Mário Rui Silva, Hermano de França Rodrigues

In this contribution, we analyse the pattern of the so-called PIP (Partnerships and Public Initiatives) that have been approved between 2000 and mid-2003 in the POE1 framework. In particular, we will evaluate the extent of decentralisation that this new instrument has generated in competitiveness policy. Partnership approaches are a relatively recent phenomenon, but partnerships have received widespread attention and support from economic and political agents, including policy makers at national, regional and local levels. In fact, the term “public-private partnership” covers a wide range of concepts and practices. In our contribution, we will focus on partnerships in a competitiveness policy framework. In a first section, we discuss briefly the meaning and the extent of what we call competitiveness policy. Then, in a second section, we focus our attention in public-private partnerships as a specific instrument for policy. In particular, we make a first assessment on the distinctive principles that differentiate public-private partnerships from more traditional instruments such as direct investment in public agencies or direct subventions to firms. We follow the perspective that these principles, mainly decentralization of policy, may contribute to a greater effectiveness of policy, because a more decentralised policy is supposed to increase focus and accountability and to involve agencies with specialized skills and a more narrow range of objectives. But, also, we will refer that some inefficiencies and some lack of equity may arise from the use of private-public partnerships instrument. Finally, in the main section of this contribution, we will analyse the above-mentioned questions considering the case of the 131 PIP projects approved and financed by the POE between 2000 and mid-2003. As the major part of the variables used are nominal, and in order to define the decentralization pattern induced by this new instrument, we will use multivariate data analysis techniques in order to establish associations between several variables linked to decentralisation criteria and, also, to identify clusters of projects.

Carlos Monasterio Escudero

espanolUno de los requisitos esenciales en todo sistema de financiacion descentralizado es la concesion de un grado suficiente de autonomia y corresponsabilidad fiscal a los gobiernos regionales, de modo que estos puedan financiar el nivel de bienes publicos locales que decidan sus ciudadanos En Espana, el sistema de financiacion de las comunidades autonomas de regimen comun incorporo un bajo nivel de corresponsabilidad fiscal entre 1980 y 1996, dada la asimetria entre una amplia descentralizacion del gasto y un modelo de cesion tributaria poco flexible. Desde 1997, y en especial a partir de 2002, la concesion de capacidad normativa y la ampliacion en la cesion tributaria han proporcionado un apreciable nivel de corresponsabilidad fiscal, en el que los tributos cedidos juegan el papel recaudatorio fundamental, constituyendo la imposicion propia un elemento mas de ordenacion economica que recaudatorio. EnglishOne of the essential requirements in any decentralized system of financing is the granting of a sufficient degree of autonomy and fiscal co-responsibility to the regional governments so that they may finance the level of local public amenities decided by their citizens. In Spain, the system of financing of the common regimen autonomous communities included a level of fiscal co-responsibility between 1980 and 1996, given the asymmetry between wide-scale decentralization of expenditure and an inflexible model of tax assignment. Since 1997, and especially from 2002, the conferral of legislative capacity and broader tax assignment have provided a considerable level of fiscal co-responsibility, in which the taxes assigned play an essential role in revenue collection, where the actual taxation is more an element of economic management rather than collection.

Min Zhao

As a basic technology of distributed computing and mobile computation, mobile agent becomes a focus of researches. Due to migration in Internet and then execution in many unknown hosts, a new security problem is presented: how to protect the moving mobile agent? and how to protect the mobile agnet being attacked by some malicious hosts? For those problems, the security problem in current mobile agent system is introduced. Security-authentication mechanism based on zero knowledge proof makes the mobile agent system running more quick and easy.Moreover the system becomes more secure.

Jonathan Putnam

No abstract is available for this record.

Jameson Boex, Jorge Martínez-Vázquez, Andrey Timofeev

Many countries around the world are currently engaged in one way or another in policy debates or reforms of their system of intergovernmental fiscal relations. While the policy dynamics vary greatly from country to country, the focus of such reform efforts can generally be categorized into one of the four main dimensions of intergovernmental fiscal relations, namely the assignment of functional responsibilities (expenditure assignments), the assignment of revenue sources, the provision of intergovernmental fiscal transfers, and the regulatory framework for subnational borrowing and debt. Based on the mantra that “finance should follow function, ” the conceptual starting point of fiscal decentralization reforms is generally held to be the assignment of expenditure responsibilities, which seeks to address the question what functions and expenditure responsibilities should be assigned to each level of government (Bahl 1999). However, a preceding question that is often overlooked pertains to the structure of subnational governments: how should the government sector be structured in order to ensure that fiscal decentralization reforms will result in a more efficient allocation of public resources?

Derek Byerlee

The recent evolution of agricultural research systems in developing countries is described, noting a change in focus from national public sector research organizations to one that emphasizes a diversified public-private system, in which clients, especially farmers, are key partners in financing, planning, implementing and monitoring research. Consistent with these changes, research planning, monitoring and evaluation has evolved from centrally-driven top-down approaches to give greater emphasis to decentralized and participatory approaches, in which client demands and satisfaction are key inputs. Although much progress has been made in reforms to enhance accountability and impacts of research, res systems still face major challenges in ensuring that demand-driven approaches provide coherent research programs consistent with national policy objectives, and in ensuring that they reflect the interests of the poor and are not captured by elites. Media Summary Investment in agricultural research has been one of the major drivers of growth and poverty reduction in developing countries. However, many research systems in developing countries face a crisis of funding and sustainability. New approaches to organizing and managing research systems provide increased participation by farmers in financing, planning and monitoring of agricultural research.

Carolyn Hart

Clients should never leave a clinic empty-handed because the product they need is out of stock. Health and family planning programs can succeed only if the clients they serve have access to medicines vaccines contraceptives and other essential health products whenever they are needed. Many international programs focus on improving service delivery promoting demand and donating drugs and other health commodities which fill up port warehouses and central medical stores. But most programs overlook the need to improve the logistics supply chain to ensure that products move from central warehouses to the health facilities where they are needed. Worse well intentioned changes in health delivery—including health reforms such as decentralization or integration of services—can exacerbate storage and distribution problems and in some cases wreak havoc on once smooth-functioning logistics systems. Furthermore donor support for commodities is diminishing relative to needs especially for contraceptives and vaccines. Countries are adapting to this situation by accessing a variety of multilateral funding mechanisms to finance commodity procurements. In addition to traditional World Bank loans these mechanisms include the Global Drug Facility of the Stop TB initiative the Children’s Vaccine Fund and the Global Fund to Fight AIDS Tuberculosis and Malaria. (excerpt)

Zhong Xiao-min

Local government fiscal competition means a series of fiscal activities competing for various economic resources taken by local governments by means of finance in order to enhance the economic power and improve the potential welfare of the regions. Local government fiscal competition includes expenditure competition and tax competition, whose theoretical basis is fiscal decentralization theory. At the different stages of a national e-conomic development, the manifestation of local government fiscal competition is different. China has experienced the fiscal competition characterized mainly by tax competition toward the fiscal competition including tax competition and expenditure competition as well since reform and opening-up. With her access to the WTO and further fiscal decentralization, the expenditure competition is getting more and more important. Based on fiscal competition , the paper attempts to analyze China's economic reform of market from a new approach.

Shigeru Takami

No abstract is available for this record.

Yong Li, Dingyi Pei

Previous designated confirmer signature schemes were less e#cient because complex zero-knowledge proof employed in confirmation and disavowal protocol. In this paper, we propose a new e#cient signature scheme which is recipient-specific and confirmer-specific. The new scheme is transformed from ID-based chameleon signature and inherits its advantage in simplicity and e#ciency. The scheme&amp;apos;s security relies on the underlying secure chameleon signature and public key encryption scheme. We also considers the case of confirmer as an adversary in security proof.

John M. de Figueiredo, Elizabeth Garrett

Even in the wake of the most sweeping campaign finance reform law to be enacted in three decades, further significant reform is inevitable. Special interest money continues to flow through loopholes in the Act, and the Presidential Election Campaign Fund is near collapse. The next reform should encourage broader participation in the political process by individual citizens, both to dilute the power of special interests and to serve independent democratic values that recent Supreme Court jurisprudence has identified as vital to meaningful reform. We propose adopting a refundable tax credit of $100/taxpayer for political contributions to federal candidates and national parties; the credit would be targeted to lowerand middle-income Americans. A refundable tax credit is equivalent to giving each eligible citizen up to $100 annually to use for political contributions. We also present data about the relative importance of political contributions by special interests (corporate, labor and other PACs) and individuals that undermine many of the assumptions on which past reform has been based and that have not been discussed in the legal literature. The data clearly show that small contributions by individuals are the dominant source of money in campaigns, and that the influence of special interest money is subtle, appearing to “purchase” benefits like access, a place on the agenda, and minor policy details. Working from an accurate picture of who really pays for politics, and drawing from the experience at the federal and state levels with similar tax refund programs, we present the tax credit as a reform that is simple, easy to administer, and likely to improve political participation by average Americans. Thus, our proposal, unlike the complicated voucher plan with anonymity put forward by Ackerman and Ayres, is likely to be adopted by Congress; moreover, it will appeal to a bipartisan consensus because it mixes public funding with a decentralized allocation mechanism using a tax subsidy.

Haixia Jia, Cristopher Moore

Many backtracking algorithms exhibit heavy-tailed distributions, in which their running time is often much longer than their median. We analyze the behavior of two natural variants of the Davis-Putnam-Logemann-Loveland (DPLL) algorithm for Graph 3-Coloring on sparse random graphs G(n,p=c/n). Let P_c(b) be the probability that DPLL backtracks b times. First, we calculate analytically the probability P_c(0) that these algorithms find a 3-coloring with no backtracking at all, and show that it goes to zero faster than any analytic function as c \to c^* = 3.847... Then we show that even in the ``easy'' phase 1 &lt; c &lt; c^* where P_c(0) &gt; 0, including just above the emergence of the giant component, the expected number of backtracks is exponentially large with positive probability. To our knowledge this is the first rigorous proof that the running time of a natural backtracking algorithm has a heavy tail for graph coloring. Moreover, our results show that these algorithms take exponential time, not just below the 3-colorability threshold, but just above the degree c=1 at which the giant component first appears. In addition, we give experimental evidence and heuristic arguments that this tail takes the form P_c(b) ~ b^{-1} up to an exponential cutoff.

Toru Nakanishi, Daisuke Yamamoto, Yuji Sugiyama

No abstract is available for this record.

Gerald Baumgartner, A.J. Chakravarti

Current approaches to utilizing computational resources on large, unstructured networks like the Internet, require either centralized servers or extensive system knowledge, limiting their scalability. In a radical departure from current models, we follow a fully-decentralized approach in which mobile agents autonomously organize themselves on a peer-to-peer network so as to maximize resource utilization. Computation and scheduling behavior are encapsulated into agents and thus decoupled from the underlying infrastructure. The following design objectives are achieved: near-zero knowledge of network topology, zero knowledge of system status, distributed computation, lack of specialized roles. Every node is equally responsible for scheduling and computation, both of which are performed with minimal information about the system. This model avoids the extensive system knowledge requirements of traditional Grid scheduling approaches. Unlike popular master/worker organizations of current large-scale grids, our model is not reliant on specialized super-servers or on application-specific clients. Strong mobility allows the asynchronous and transparent migration of multi-threaded agents, and is a powerful mechanism for realizing a peer-to-peer computing environment. We have implemented and evaluated an agent system that endows Java with strong mobility. Through the careful design of agent behavior, the global organization of computation can be customized for different classes of applications. We describe our scheduling framework and demonstrate the flexibility of our approach by applying it to two problems that are vastly different in terms of the synchrony of their communication patterns: an Independent Task Application and Cannon's Matrix Multiplication.

Ting Wu

By using restrictive blind signature and zero knowledge proofs of knowledge, a new proxy signature scheme with proxy signer privacy protection is proposed, which has two characteristics listed as follows: (1)Being encrypted by ElGamal encryption, the ID information of the proxy signer is included in the proxy signature, so no one, except the revoker, can find the identity of the proxy signer, while with the help of the revoker, the identity of the proxy signer can be revealed; (2)By using the zero knowledge proofs of knowledge, only the legitimate proxy signer can give a proxy signature on behalf of the original signer Meanwhile, since the security of the proposed scheme is based on the restrictive blind signature hypothesis and the random oracle model, the revoker can not make a cheat and only when the proxy signer follows the scheme, he can get the power of attorney At the same time, it is proved that it satisfies the security requirements such as verifiability, strong unforgeability, strong non repudiation, proxy privacy, and privacy revocation

Anderson C. A. Nascimento, Joern Mueller-Quade, Akira Otsuka, Goichiro Hanaoka · 5 authors

No abstract is available for this record.

Iftach Haitner

No abstract is available for this record.

Benjamin J. Priester

No abstract is available for this record.

Andrew T. Young, Matthew J. Higgins, Daniel Lévy

No abstract is available for this record.

Armando Arredondo, Irene Parada, Emanuel Orozco, Eunice García

Objective To identify trends and to describe the impact of health care decentralization on health financing policies in Mexico. Methods The study population comprised four states selected according with six technical criteria: socioeconomic development, implementation of decentralization process, database on economical features, data consistency and reliability, and technical Apoyo financiero del International Development Research Centre (Canada) (Expediente # 100 191) . Recibido en 21/10/2002. Representado en 24/6/2003. Aprobado en 23/7/2003. 122 Rev Saude Publica 2004;38(1):121-9 www.fsp.usp.br/rsp El fnanciamiento de la salud en Mexico Arredondo A et al support from a multidisciplinary team. In-depth interviews with key personnel as well as analysis of technical reports of state budgets for health in the period 1990-2000 were conducted. Results The analysis model applied allowed to determine the trends and the impact of health care decentralization on main financing sources: householders, and federal, state and municipal governments. There was evidence of different change effectiveness, especially regarding trends of financing per source. Conclusions There are states where householders and state and municipal governments effectively increased financing support for health care system. But there are also states where householders and state and municipal governments do not agree on the increase of financing support for health care system.