In spite of a long history of institutional reforms, Mexico still cannot assure adequate water services to its population and its aquifers and ecosystems are being degraded. Although decentralization is a principal theme of administrative reform, the National Water Commission (CNA) remains a powerful semi-autonomous organization charged with the oversight and control of local water agencies. Local urban water administrations are under intense pressure to change their management structures to ...
A proof is whatever convinces me. Shimon Even, 1978. Zero-knowledge proof is usual proof, but you must not give more information to verifier, than your statement (which you prove) can give alone. So, in this paper, some facts about zero-knowledge, interactive protocols and proofs will be given. Also, with examples.
We examine the pyramidal ownership structure of a large sample of newly listed Chinese companies controlled by local governments or private entrepreneurs. Both types of the owners use layers of intermediate companies to control their firms. However, their pyramiding behaviors are likely affected by different property rights constraints. Local governments are constrained by the Chinese laws prohibiting free transfer of state ownership. Pyramiding allows them to credibly decentralize their firm decision rights to firm management without selling off their ownership. Private entrepreneurs are constrained by their lack of access to external funds. Pyramiding creates internal capital markets that help relieving their external financing constraints. Our empirical results support these conjectures. Local governments build more extensive corporate pyramids when they are less burdened with fiscal or unemployment problems, when they have more long-term goals, and when their firm decisions are more subject to market and legal disciplines. The more extensive pyramids are also associated with smaller "underpricing" when the firms go public. Entrepreneur owners construct more complex corporate pyramids when they do not have a very deep pocket - as indicated by whether they are among the top-100 richest people in China.
Abstract. A shuffle consists of a permutation and re-encryption of a set of input ciphertexts. One application of shuffles is to build mix-nets. We suggest an honest verifier zero-knowledge argument for the correctness of a shuffle of homomorphic encryptions. Our scheme is more efficient than previous schemes both in terms of communication and computation. The honest verifier zero-knowledge argument has a size that is independent of the actual cryptosystem being used and will typically be smaller than the size of the shuffle itself. Moreover, our scheme is well suited for the use of multi-exponentiation and batch-verification techniques. Additionally, we suggest a more efficient honest verifier zero-knowledge argument for a commitment containing a permutation of a set of publicly known messages. We also suggest an honest verifier zero-knowledge argument for the correctness of a combined shuffle-and-decrypt operation that can be used in connection with decrypting mix-nets based on ElGamal encryption. All our honest verifier zero-knowledge arguments can be turned into honest verifier zero-knowledge proofs. We use homomorphic commitments as an essential part of our schemes. When the commitment scheme is statistically hiding we obtain statistical honest verifier zero-knowledge arguments; when the commitment scheme is statistically binding we obtain computational honest verifier zero-knowledge proofs. Key words. Shuffle, Honest verifier zero-knowledge argument, Homomorphic encryption, Mix-net. 1
We present a constant-round protocol for general secure multiparty computation which makes a black-box use of a pseudorandom generator. In particular, the protocol does not require expensive zero-knowledge proofs and its communication complexity does not depend on the computational complexity of the underlying cryptographic primitive. Our protocol withstands an active, adaptive adversary corrupting a minority of the parties. Previous constant-round protocols of this type were only known in the semi-honest model or for restricted classes of functionlities.
The Nordic countries have decentralized government spending more than any other country and consequently the local public sector needs more financing. This is generally solved by income tax revenue sharing systems and central government grants. Another characteristic is the emphasis on tax equalization. While this centralized financing generates considerable revenue for the local governments, the design implies vertical fiscal imbalance and a challenge for local accountability. Overall the system is better understood as public sector decentralization than traditional fiscal federalism. The Nordic countries represent an interesting puzzle in local government financing. The financing of local governments must be arranged nationally when decentralization is extensive. The resulting degree of local autonomy varies, and the local discretion in income taxation in Denmark and Sweden seems to help strengthen the locals. But all the Nordic countries struggle with the balance between central government control and local self rule.
In this paper we define a decentralized management mechanism for the dynamic coalition characteristic of virtual organization. We propose an identity-based threshold signature scheme for joint management. We also propose the policy mode for joint management, which uses role-based access control mechanism for authorization policies definition, and voting mechanism for authorization decision-making. Our solution can satisfy the dynamic coalition requirement of virtual organization, and also guarantee the autonomous characteristic of participant organizations and grid entities. Privacy preservation is also provided for grid entities to interact with authorized entities. Authorization revocation mechanism is taken into consideration in this paper. The experimental performance also shows the scalability of the solution.
We introduce the first El Gamal based mix-net in which each mix-server partially decrypts and permutes its input, i.e., no reencryption is necessary. An interesting property of the construction is that a sender can verify non-interactively that its message is processed correctly. We call this sender verifiability. The mix-net is provably UC-secure against static adversaries corrupting any minority of the mix-servers. The result holds under the decision Diffie-Hellman assumption, and assuming an ideal bulletin board and an ideal zero-knowledge proof of knowledge of a correct shuffle. Then we construct the first proof of a decryption-permutation shuffle, and show how this can be transformed into a zero-knowledge proof of knowledge in the UC-framework. The protocol is sound under the strong RSA-assumption and the discrete logarithm assumption. Our proof of a shuffle is not a variation of existing methods. It is based on a novel idea of independent interest, and we argue that it is at least as efficient as previous constructions.
Abstract. Micali, Rabin, and Kilian [9] recently introduced zero-knowledge sets and databases, in which a prover sets up a database by publishing a commitment, and then gives proofs about particular values. While an elegant and useful primitive, zero-knowledge databases do not offer any good way to perform updates. We explore the issue of updating zero-knowledge databases. We define and discuss transparent updates, which (1) allow holders of proofs that are still valid to update their proofs, but (2) otherwise maintain secrecy about the update. We give rigorous definitions for transparently updatable zero-knowledge databases, and give a practical construction based on the Chase et al [2] construction, assuming that verifiable random functions exist and that mercurial commitments exist, in the random oracle model. We also investigate the idea of updatable commitments, an attempt to make simple commitments transparently updatable. We define this new primitive and give a simple secure construction.
Daniele Micciancio, Shien Jin Ong, Amit Sahai, Salil Vadhan
Abstract. We provide unconditional constructions of concurrent statistical zero-knowledge proofs for a variety of non-trivial problems (not known to have probabilistic polynomial-time algorithms). The problems include Graph Isomorphism, Graph Nonisomorphism, Quadratic Residuosity, Quadratic Nonresiduosity, a restricted version of Statistical Difference, and approximate versions of the (coNP forms of the) Shortest Vector Problem and Closest Vector Problem in lattices. For some of the problems, such as Graph Isomorphism and Quadratic Residuosity, the proof systems have provers that can be implemented in polynomial time (given an NP witness) and have ~O(log n) rounds, which is known to be essentially optimal for black-box simulation.
India has set out ambitious goals for itself in the health sector in its Tenth Five Year Plan (2002-07). It is also a signatory to the United Nations Millennium Development Goals. Attainment of these goals which are time-bound will require a massive scaling up of investment in health, especially in public primary health care. We argue for a ‘Health for All’ initiative on the part of the government akin to the ‘Education for All’ scheme which was launched nation-wide in 2001. The large amount of resources required for scaling up public investment in primary health need not be the constraint it is purported to be. We discuss several options that are available to the government for generating the necessary funds. Among the options that can generate resources domestically are reform of the government’s subsidies regime including implementing life-line tariffs, ear-marking taxes and disinvestment of loss-making public sector units. Health for All can also be financed by raising more resources via external assistance. Official development assistance to India at present is rather low given India’s per capita income and the scale of its needs in human development terms. The scale of official development aid to India should increase several folds and committed use of funds should be made by the government in health and other priority sectors. With the 73rd and 74th amendments to the Indian Constitution which created a third tier of government comprising of elected local bodies at the village and town ward levels, a decentralized system of service delivery will eventually become a reality in India and needs to be a part of any debate on the means and modes of improving human development outcomes in India. The current system of planning and allocation of funds at the sub-national level however needs to be over-hauled if fiscal decentralization is also to become a reality.
In a pioneering work, Jeffrey Fear overturns the dominant understanding of German management as "backward" relative to the United States and uncovers an autonomous and sophisticated German managerial tradition. Beginning with founder August Thyssen - the Andrew Carnegie of Germany - Fear traces the evolution of management inside the Thyssen-Konzern and the Vereinigte Stahlwerke (United Steel Works) between 1871 and 1934.". "Fear focuses on the organization and internal dynamics of the company. He demonstrates that initiatives often flowed from middle managers, rather than from the top down. Shattering stereotypes of the overly bureaucratic and rigid German firm, Fear portrays a decentralized and flexible system that underscores the dynamic and entrepreneurial nature of German business." "This work will generate much debate among historians, organizational theorists, and management and accounting scholars.