We put forward the concepts of universal authentication, restrictive authentication and designated authentication. We then revisit a popular signcryption scheme using a technique similar to the one developed in Schnorr's signature, allowing it respects the restrictive authentication property. Comparing with the modification suggested by Baek et al in 2007, which uses a zero-knowledge proof run between the recipient and the third party, our scheme saves about 1/2 cost. Besides, the security of the revisited scheme can be reduced to that of Schnorr's signature.
This paper first gives out definition of receipt-freeness,and prove necessary and sufficient condition of receipt-freeness. Then by employing homomorphic ElGamal encryption,threshold ElGamal encryption and zero-knowledge proof,this paper designs an efficient electronic voting scheme,which satisfies universal verifiability,receipt-freeness,also eligibility,privacy and so on. Different from the previous protocols,there needs less security requirement on trusted third party in the new scheme,which is more practical.
According to the World Bank, over 80 countries currently plan some form of fiscal decentralization. This group includes Japan, a highly centralized tax state, which in 1995 put in place a law and associated high-profile institutions to promote fiscal and administrative decentralization. But the process in Japan has quickly become bogged down. This dissertation asks why there are hurdles confronting fiscal decentralization in Japan. My research uses the fiscal sociology approach and highlights bureaucratic interests in Japan's intergovernmental tax regime, one that is especially interesting in comparison with other advanced industrial countries. Fully 70 percent of all government spending in Japan is done by subnational levels of government, and 51 percent of the central state's current operating expenditures are transfers downward that serve to support that high rate of local spending. And though Japan is a centralized state, over a third of its taxation is collected locallly. In consequence, Japan is quite anomalous when set alongside a representrative sample of federal and unitary states. No other country among the nine OECD nations used, for comparative purposes, in this dissertation combines such high fiscal transfers with heavy levels of subnational spending and taxation. And no other country gives close control over a large terrain of subnational taxation to a central-state agency (the Ministry of Home Affairs). The ministry's vast bureaucratic turf brings it into conflict with the Ministry of Finance, as both seek to maintain or expand their fiscal jurisdiction. They are thus not interested in fiscal decentralization in large part because they are busy fighting "trench wars" with each other on these tax fields. This dissertation hence undertakes a detailed analysis of intergovernmental fiscal history in Japan, focusing in particular on the Ministry of Home Affairs' ambiguous role in the Japanese state. The case studies of inter-bureaucratic fiscal politics include the Local Allocation Tax (a large general subsidy) as well as an array of taxes on the fields of income, assets and consumption.
Based on information-theoretic hiding commitment scheme and zero-knowledge proof of knowledge,a publicly verifiable secret sharing(PVSS) scheme was constructed.In this scheme,any party could verify the validity of participants' shares in the distribution protocol.Only the receiver could verify validity of these shares gained from the other participants in the reconstruction protocol.This PVSS scheme with information-theoretic security has demostrated that it is more applicable in some cases than any verifiable secrete sharing scheme.
China has the largest urban public transport sector in the world. In principle, strategic policy is determined by the central government, and passed down through the organs of state for implementation. In recent years that strategy has included giving priority to public transport and reforming the supply arrangements to secure a more commercial and competitive sector. In practice, responsibility for implementation is completely decentralized, with municipalities having both complete responsibility for financing urban public transport and substantial freedom to interpret central government guidance at the local level. This paper considers the reforms that have already occurred under this regime, the constraints and limitations on the reform process, and the most recent initiatives being undertaken. It shows that a very wide range of systems are being experimented with simultaneously, with so far no sign that central government would intervene in detail or to provide central government finance specifically for the sector.
The global dimensions of the credit crisis of 2008 have become increasingly apparent. Bank failures, credit freeze-ups, and sharp stock market declines have spread well beyond the borders of the United States, the original epicenter of the crisis. What role, then, should international institutions play in addressing the crisis? Much public discussion of the crisis has underestimated the relevance of such international institutions, often assuming that they do not exist, or that they are so weak that we will have to relay to rely on nation-states for any meaningful response. In contrast, I argue in this article that a relatively well-established set of existing international institutions should and will play a central role in response to the crisis. (1) However, I also argue that policy makers, regulators, and financial elites have displayed too much complacency and self-interest in their attitudes toward these institutions, and these failings need to be corrected with greater public awareness and pressure regarding the role that these institutions can play. To see the potential of existing international institutions to address the current credit crisis, it is necessary to go beyond the assumption that only states or formal intergovernmental organizations can have influence. Faced with extraordinary complexity, including the need to manage the negative effects of fast-paced global markets, public authorities have increasingly shifted from centralized command and control to rely more on hybrid mixes of decentralized public and private regulation, a phenomenon that has been called regulatory capitalism. (2) A risk in this shift is that policy and processes will be captured and manipulated by the private sector actors that they are supposed to regulate. However, such capture is not inevitable, especially if mechanisms for asserting the public interest in these processes are strengthened. Transnational Private Sector Institutions in Global Finance While the financial products involved in the present crisis are often seen as toxic, mysterious, and chaotic, they also signify an increase in the institutionalization of global financial markets. The current crisis is the first transnational one involving personal credit. There are direct linkages between individual borrowers and global financial markets, in which creditors and investors are much more widely dispersed than previously. Such connections have been enabled by the growth of a variety of now well-established transnational practices, institutions, clearing houses, and networks that transmit information, calculate risk, record contractual commitments, and transfer ownership claims. This institutionalization involves inertia, benefits, and sunk costs for the participants that will make transnational financial practices difficult to abandon. At the same time, this institutionalization can also provide opportunities for public and private authorities to strengthen the governance of global finance. In the financial sector, as elsewhere, commercial firms may use their trade associations to propose self-regulatory arrangements as an alternative to public regulation. Such practices are very well established domestically and are becoming more evident in global finance as well. For example, the CEOs of leading international banks forestalled effective public regulation of hedge funds at the time of the 1998 Long-Term Capital Management (LTCM) crisis by organizing themselves into the Counterparty Risk Management Policy Group (CRMPG) and creating best practices. Ironically, this group's second major initiative, the CRMPG II report of 2005, predicted a number of the key elements of the current crisis, but evidently without significant effect. The influence of CRMPG I and II was undoubtedly enhanced by the reputation of the chair, E. Gerald Corrigan, managing director at Goldman Sachs and formerly head of the New York Federal Reserve and chair of the Basel Committee on Banking Supervision. …
It is very important to choose the most approproate finance control mode for the enterprise's development.On the basis of analyzing the characters of three typical modes,the paper compare their advantages and disadvantages.Considering these factors such as the guoup's developing strategic,developing stage,choosing industry,the subsidiary's influence on the parent company and so on,a conclusion is drawn that currently the business should adopt the finance control mode mixed by the centralization and decentralization.
A fine-grained property attestation based on the components is proposed to prove that the user platform satisfies the security property predefined by remote relying party. Compared with other remote attestation schemes, CPBA (component property based attestation) has the advantage of semantic and property expression to some extent. It is not only more fine-grained and extensive, but also easier to implement issuing, verifying and revoking the property certificate. CPBA guarantees the authenticity of attestation by component commitment, and protects the privacy of platform components by zero-knowledge proof. It is proved secure in Random Oracle Model under strong RSA Assumption. The experimental result of its prototype system indicates that CPBA is a flexible, usable, highly efficient attestation, and has no influence on system performance.
Certificate-based cryptography solves certificate revocation problem and eliminate third-party queries in the traditional PKI and avoid key escrow in the ID-based cryptography. It is a better alternative for the traditional public key system. In this paper, we proposed an efficient certificate based signature scheme based on Schnorr signature and zero-knowledge proof technique. Our proposed scheme doesn't use pairing operator which is the most expensive computation. Then we show that our proposed scheme is proven to be against two forgeable attacks in the random oracles model, and the security is related to that of Schnorr signature.
Reuse of intellectual property (IP) of VLSI physical design facilitates integration of more components on a single chip in shrinking time-to-market. For intellectual property protection (IPP), various kinds of IP marks are embedded into the design for establishing the veracity of a legal owner. However, public verification of IP marks is not leakage-proof. Current techniques include a sufficiently large set of public marks containing a header and a message body in addition to private ones to facilitate only public verification at the cost of significant increase in design overhead. But these techniques are not effective, as attackers manage to obtain potential clues to tamper public marks rendering public verification invalid and may also suitably override the marks to include own signature resulting in wrong public identification of IP owner. Here we propose a zero-knowledge protocol to ensure robust and absolutely leakage proof convincing public verification with the help of private marks. We have tested our protocol for FPGA benchmarks. The results on overhead and robustness are encouraging.
Physical Unclonable Functions (PUFs) and Hardware Security
Learning is a central task in computer science, and there are various formalisms for capturing the notion. One important model studied in computational learning theory is the PAC model of Valiant (CACM 1984). On the other hand, in cryptography the notion of "learning nothing'' is often modelled by the simulation paradigm: in an interactive protocol, a party learns nothing if it can produce a transcript of the protocol by itself that is indistinguishable from what it gets by interacting with other parties. The most famous example of this paradigm is zero knowledge proofs, introduced by Goldwasser, Micali, and Rackoff (SICOMP 1989). Applebaum et al. (FOCS 2008) observed that a theorem of Ostrovsky and Wigderson (ISTCS 1993) combined with the transformation of one-way functions to pseudo-random functions (Hastad et al. SICOMP 1999, Goldreich et al. J. ACM 1986) implies that if there exist non-trivial languages with zero-knowledge arguments, then no efficient algorithm can PAC learn polynomial-size circuits. They also prove a weak reverse implication, that if a certain non-standard learning task is hard, then zero knowledge is non-trivial. This motivates the question we explore here: can one prove that hardness of PAC learning is equivalent to non-triviality of zero-knowledge? We show that this statement cannot be proven via the following techniques: 1. Relativizing techniques: there exists an oracle relative to which learning polynomial-size circuits is hard and yet the class of languages with zero knowledge arguments is trivial. 2. Semi-black-box techniques: if there is a black-box construction of a zero-knowledge argument for an NP-complete language (possibly with a non-black-box security reduction) based on hardness of PAC learning, then NP has statistical zero knowledge proofs, namely NP is contained in SZK. Under the standard conjecture that NP is not contained in SZK, our results imply that most standard techniques do not suffice to prove the equivalence between the non-triviality of zero knowledge and the hardness of PAC learning. Our results hold even when considering non-uniform hardness of PAC learning with membership queries. In addition, our technique relies on a new kind of separating oracle that may be of independent interest.
Decentralization reforms in CEE countries have been an essential component of the overall transformation process that took place after the collapse of the former communist regimes. It entered public thought as a panacea to the political, economical and social problems that emerged because of and during the transformation. It also featured prominently in social policy reforms, particularly in the case of social assistance. Local government involvement in the financing and administration of social assistance schemes has been widely promoted by various international organizations as holding the key to reducing the financial cost of such schemes through improved targeting. However, the theory of fiscal federalism provides us with sound theoretical arguments against decentralization of social assistance. According to this theoretical framework, fundamental constraints on redistribution by lower level governments would negatively affect the generosity of poverty relief systems and facilitate a ‘race to the bottom’.
In this paper, we prove classical coin-flipping secure in the presence of quantum adversaries. The proof uses a recent result of Watrous [Wat09] that allows quantum rewinding for protocols of a certain form. We then discuss two applications. First, the combination of coin-flipping with any non-interactive zero-knowledge protocol leads to an easy transformation from non-interactive zero-knowledge to interactive quantum zero-knowledge. Second, we discuss how our protocol can be applied to a recently proposed method for improving the security of quantum protocols [DFL+09], resulting in an implementation without set-up assumptions. Finally, we sketch how to achieve efficient simulation for an extended construction in the common-reference-string model.
The purpose of this study was to investigate the impact of recurrent of famine in Wajir district between the years 2002 -2008 despite the Government and Non-Governmental Organization intervention. The objectives of the study were: a) to find out the impact of famine on the people of Wajir District, b) to establish the nature of assistance given to the people in the district during famine period by stake-holders, c) to find out perception of the Wajir people towards the assistance given to them during famine, d) to find out the measures the people in Wajir district employ in order to manage famine effectively, and e) to assess the relationship that exists between clans living in Wajir district during famine time and their neighbors. \n \nThe study adopted descriptive survey design and data was largely descriptive by nature. The studies main aim was to find out the impact of famine on people living in Wajir district, the following factors were gathered: It emerged that 40% of the families had 6 to 10 members while 28% had 1 to 5 members. About a quarter of the families (26%) had 4 to 5 members. The average family size was eight members. The study also showed that up to 48% of respondents were employed or self employed while the others 52% were not. Concerning the form of employment, the study indicated that up to 54% of the respondents were self employed while 46% were in formal employment. The number of family members engaged in economic activities was an important factor that determined the impact of famine on the people living in the area. \n \nThe study showed that in up to 82% of the families whose respondents were employed, less that 5 of the family members were employed. Combination of income generating activities as practiced by 46% of the respondents was seen as important diversification strategy to shield the community from the impacts of famine. The people employ a variety of coping mechanisms to manage famine they included: frequent migration within the district and into the republic of Somalia more than ever before, reduction in the frequency of food intake, migration to towns including Wajir town, Nairobi and as far as Bungoma in western province. \n \nConcerning the assistance given to the local people of Wajir, it emerged that food aid was the major assistance given by both the Government and NGOs during famine. This was reported to be 92% and 71% for both the government and the NGOs respectively. Regarding rating of the value of assistance from the government and the NGOs to the local community, the study found out that the most adequate assistance was medicine at only 8% followed by water at 6%. Communities that live in Wajir possessed a rich repertoire of responses against famine as reported by the respondents. These ranged from reducing food intake (65%) to gathering forest products (52%) such as fruits, firewood, medicine, and honey. \n \nThe study sought to understand the community's satisfaction with the manner the watering points were managed. It found that up to 70% of the respondents were not satisfied with the management of the watering points while only 30% were satisfied. About the frequency of droughts, the majority of respondents (52%) indicated that droughts were occurring twice a year. Up to 38% of the respondents reported that they were occurring once per year. The study also sought to understand the problems encountered by the people ofWajir. \n \nThe recommendations were: famine vulnerability is best tackled through institutionbuilding and strengthening the ability of government to design and implement sound propoor policies, the government to step up efforts to make its economy more climate proof through diversification, the government to take bold steps to reduce marginalization of the dry lands and incorporate them into mainstream social and economic systems, establishment of vibrant livestock market and slaughter houses in the district where pastoralists can easily sell their livestock to avoid losses, the government and its development partners to emphasize real development instead of relief.
Digital signatures are fundamental cryptographic primitives. They are useful as a stand-alone application and building blocks of complex cryptographic systems. Accumulators are another useful cryptographic primitive which provide a way to combine a set of values into one short value. They are useful in improving efficiency of cryptographic systems. In particular, these two primitives are key components in privacy-preserving cryptographic systems. In this thesis, we study the use of digital signatures and accumulators in cryptographic applications. We design digital signature schemes and accumulators with different features that are suitable for a wide range of applications. We are interested in privacy-preserving cryptographic applications including anonymous electronic cash systems, anonymous authentication schemes and anonymous credential systems. We construct three different digital signature schemes, each with distinctive features. We also propose two novel constructions of accumulators. Based on our signature schemes and accumulators, we design two compact electronic cash schemes and a divisible electronic cash scheme. All our schemes are truly anonymous, meaning that privacy of the users is well-protected. We also explore other applications of our newly proposed signatures and accumulators. Specifically, we give a construction of k-times anonymous authentication schemes and attribute-based anonymous credential systems. During the course of the development of the thesis, we generalise existing techniques of zero-knowledge proof-of-knowledge protocol of double-discrete logarithms into zero-knowledge proof-of-knowledge protocol of representation of a committed value. Our protocol is compatible with existing zero-knowledge proof-of-knowledge protocols that demonstrate relationship amongst discrete logarithms. We believe that this protocol, together with the newly introduced primitives, are of independent interest.
We propose a distributed key generation protocol for pairing-based cryptosystems which is adaptively secure in the erasure-free and secure channel model, and at the same time completely avoids the use of interactive zero-knowledge proofs. Utilizing it as the threshold key generation protocol, we present a secure (t,n) threshold signature scheme based on the Waters' signature scheme. We prove that our scheme is unforgeable and robust against any adaptive adversary who can choose players for corruption at any time during the run of the protocols and make adaptive chosen-message attacks. And the security proof of ours is in the standard model (without random oracles). In addition our scheme achieves optimal resilience, that is, the adversary can corrupt any t<n/2 players.
This paper studies mobile devices mediated electronic voting system based on the distributed Pailler's encryptions; We apply the standard cut-of-the-choose technique to avoid the computational zero-knowledge proofs and show that the proposed scheme is efficient yet somewhat provably secure in the simulation-based paradigm.