Blockchain Papers

Tassos Dimitriou, Dimitris Foteinakis

No abstract is available for this record.

Balaji Venkatachalam

No abstract is available for this record.

Raphaël C.‐W. Phan, Huo-Chong Ling

Recently, two generic watermarking protocols were proposed, based on a popular zero-knowledge identification protocol. In this paper, we show that both protocols are flawed and therefore fail to achieve their purpose of allowing a prover to prove to a verifier of his ownership of a watermarked image. We also give some suggestions to fix these flaws.

Clifford Neuman, Sultan Almuhammadi

A zero-knowledge proof (ZKP) is an interactive proof between two parties: prover and verifier, where the prover proves the knowledge of a secret without revealing any information about the secret itself. ZKPs were first introduced in 1985 for identity verification systems and became powerful tools for many cryptographic applications. There has been a growing concern about the risk of identity theft in critical situations, like homeland security and e-commerce. ZKPs are the ideal solution to challenges in identification since they allow costumers to prove identities without exchanging sensitive information that may lead to identity theft. Other applications of ZKPs include smart cards, digital cash, anonymous communication, electronic wallets, electronic voting, multimedia security and digital watermarks. Existing ZKPs are iterative in nature; their protocols require multiple communication rounds between parties. Due to the cost of iteration, practitioners see ZKPs as unsuitable in practice and therefore develop other tools to avoid using ZKPs. The proposed approach creates new protocols that allow the prover to prove knowledge of a secret without revealing it. The new approach, called a one-round zero-knowledge-proof, meets all the requirements of ZKPs, yet runs in a single round. The new approach substantially reduces the running-time complexity and communications cost. It eliminates the iteration cost and makes such proofs suitable for practical cryptographic systems for both governmental and commercial applications. The focus of this dissertation is the theory of one-round ZKPs. It presents efficient and secure one-round ZKPs for several classical problems that are used in real life applications. It studies the performance of the proposed one-round ZKPs compared to the existing iterative ZKPs in terms of computation and communication costs. It presents a case study on an identity verification scheme that uses both the iterative ZKP and the new one-round ZKP to compare the results and show the advantages of the new approach.

Hongda Li, Bao Li

No abstract is available for this record.

Andreas Deußen, Annette Pexa, Robert Loncar, Sebastian N. Stehr

Homocysteine may have deleterious effects on the cardiovascular system. It has been hypothesized that these effects may be brought about by a decrease in the adenosine concentration via the S-adenosylhomocysteine hydrolase reaction. A requirement for this causal relationship is proof of a reduction in vascular adenosine concentration during conditions of elevated homocysteine concentrations. In the present communication we summarize published data obtained during systematic variation of the arterial homocysteine concentration. Most of the results reported show that an increase in homocysteine concentration to 100 microM is associated with a 20-50% decrease in vascular adenosine concentration and an increase in tissue S-adenosylhomocysteine level. Homocysteine effects on the adenosine concentration seem to be more pronounced under conditions of impaired oxygenation. Further experiments, in particular on organs and tissue that release high amounts of homocysteine, i.e., the liver, are warranted to study the potential effects of homocysteine on vascular and tissue adenosine concentrations and consequent effects on organ function. The evidence obtained may be relevant for future assessment of risk indicators in conjunction with homocysteine pathogenicity, which might potentially be extended to measurements of adenosine or S-adenosylhomocysteine levels.

Roman Matuszewski, Piotr Rudnicki

The MIZAR project is opus magnum of Andrzej Trybulec. Abstract We present the story of the MIZAR project with focus on the years until 1989. A lot about MIZAR after 1989 is available at the web3. 1.

Omar Khadeer Hussain, Elizabeth Chang, Farookh Khadeer Hussain, Tharam S. Dillon · 5 authors

Risk is associated with almost every activity that is undertaken on a daily life. Risk associated with Trust, Security and Privacy. Risk is associated with transactions, businesses, information systems, environments, networks, partnerships, etc. Generally speaking, risk signifies the likelihood of financial losses, human casualties, business destruction and environmental damages. Risk indicator gives early warning to the party involved and helps avoid deserters. Until now, risk has been discussed extensively in the areas of investment, finance, health, environment, daily life activities and engineering. However, there is no systematic study of risk in Decentralised communication, which involves e-business, computer networks and service oriented environment. In this paper, we define risk associated with trusted communication in e-business and e-transactions; provide risk indicator calculations and basic application areas.

Marius-Cǎlin Silaghi

Mix-nets can be used to shuffle vectors of shared secrets. This operation can be an important building block for solving combinatorial problems where constraints depend on secrets of different participants. A main contribution of this paper is to show how participants in the mix-net can provide Zero-Knowledge proofs to convince each other that they do not tamper with the shuffled secrets, and that inverse permutations are correctly applied at unshu#ing. The approach is related to the proof of knowing an isomorphism between large graphs. We also make a detailed review and comparison with rationales and analysis of Chaum's and Merritt's mix-nets. Another

Jens Groth, Rafail Ostrovsky, Amit Sahai

No abstract is available for this record.

Rosario G. M Anasan

Twelve years into the implementation of the Local Government Code of 1991, it is but opportune to assess how the key features of this landmark legislation has contributed to (or detracted from) achieving the balance between local autonomy and accountability. The literature on fiscal decentralization suggests that these two goals are not incompatible. In fact, real autonomy (in the sense of subnational governments being able to link their spending decisions with their revenue/tax decisions) promotes fiscal responsibility. In the context of the ongoing debate in the Philippines, however, local autonomy has been equated (by many LGUs officials) with the independence of LGUs from central government interference. As such, LGU officials have focused more on securing even higher levels of block grants in order to address the widely perceived vertical fiscal imbalance. However, closer scrutiny of the problem indicates that greater tax decentralization, coupled with a well-designed intergovernmental transfer system that includes elements of fiscal equalization and categorical grants conditional on the achievement of minimum service standards, would better enhance the gains that are forthcoming from the decentralization process while minimizing the risks of macro-instability.

Nicole Milne, Patrick Christie

No abstract is available for this record.

Bunnan Men, John Grundy, Jeff Cane, Lon Chan Rasmey · 10 authors

The following study was conducted as part of a review of management systems at a Provincial Health Department (Kampong Cham Province) and a National Health Programme (National Immunization Program) in 2002-2003 in Cambodia. The aim of this paper is to identify, analyse and recommend those management system factors that are critical to the success of health management performance, with a particular focus on provincial management. The review has identified critical success factors associated with health management performance at the sub-national level that include a stronger role for effective human resource management in health sector reform, elevation of the status of planning in senior level management, and the development of a more comprehensive and transparent finance system. These success factors will position the provincial level of health management to respond more effectively to the reform challenges of administrative de-concentration and political decentralization that are currently underway across a range of government sectors in Cambodia.

Michael Szydlo

No abstract is available for this record.

Craig Gentry, Dávid Molnár, Zulfikar Ramzan

Abstract. Most prior designated confirmer signature schemes either prove security in the random oracle model (ROM) or use general zeroknowledge proofs for NP statements (making them impractical). By slightly modifying the definition of designated confirmer signatures, Goldwasser and Waisbard presented an approach in which the Confirm and ConfirmedSign protocols could be implemented without appealing to general zero-knowledge proofs for NP statements (their Disavow protocol still requires them). The Goldwasser-Waisbard approach could be instantiated using Cramer-Shoup, GMR, or Gennaro-Halevi-Rabin signatures. In this paper, we provide an alternate generic transformation to convert any signature scheme into a designated confirmer signature scheme, without adding random oracles. Our key technique involves the use of a signature on a commitment and a separate encryption of the random string used for commitment. By adding this “layer of indirection, ” the underlying protocols in our schemes admit efficient instantiations (i.e., we can avoid appealing to general zero-knowledge proofs for NP statements) and furthermore the performance of these protocols is not tied to the choice of underlying signature scheme. We illustrate this using the Camenisch-Shoup variation on Paillier’s cryptosystem and Pedersen commitments. The confirm protocol in our resulting scheme requires 10 modular exponentiations (compared to 320 for Goldwasser-Waisbard) and our disavow protocol requires 41 modular exponentiations (compared to using a general zero-knowledge proof for Goldwasser-Waisbard). Previous schemes use the encryption of a signature paradigm, and thus run into problems when trying to implement the confirm and disavow protocols efficiently. 1

Kjeld Møller Pedersen, Terkel Christiansen, Mickael Bech

The Danish health care system has undergone gradual changes, but not radical reforms, from 1970 until 2004. Theoretically, the development can be viewed from the perspective of fiscal federalism, decentralization, and incentives embodied in reimbursement systems. Furthermore, path dependence and incrementalism have characterized the system. The Danish health care system is decentralized politically, financially, and operationally. The counties are responsible for health care, and finance it out of county income and property taxes along with block grants from the state. Hospitals are publicly owned while general practitioners are private entrepreneurs working on contract with the counties. Hospital services and GP and specialist services are free, while there are co-payments for drugs, adult dental care, physiotherapy and the like. Co-payments make up close to 19% of total health expenditures. The system has been characterized by expenditure control, reasonable positive development in productivity, and a high degree of patient and citizen satisfaction despite waiting lists. Free choice of hospital was introduced more than 10 years ago. It has recently been expanded so that after waiting 2 months for treatments like elective surgery at public hospitals, citizens can choose either private hospitals or go abroad with full payment from public funds. The thinking behind decentralization gradually has been eroded for a number of reasons. This has led to a reform that will be effective as of January 2007. The number of counties will be reduced, but the new regions retain responsibility for health care. A national earmarked health tax will be introduced so that the regions will receive revenues from state block grants and municipal co-payment, for instance an amount per hospitalization.

Armando Arredondo, Emanuel Orozco, Esteban de Icaza

OBJECTIVE: The main objective was to identify trends and evidence on health financing after health care decentralization. STUDY DESIGN: Evaluative research with a before-after design integrating qualitative and quantitative analysis. Taking into account feasibility, political and technical criteria, three Latin American countries were selected as study populations: Mexico, Nicaragua and Peru. DATA SOURCES: The methodology had two main phases. In the first phase, the study referred to secondary sources of data and documents to obtain information about the following variables: type of decentralization implemented, source of finance, funds of financing, providers, final use of resources and mechanisms for resource allocation. In the second phase, the study referred to primary data collected in a survey of key personnel from the health sectors of each country. FINDINGS: The trends and evidence reported in all five financing indicators may identify major weaknesses and strengths in health financing. CONCLUSIONS: Weaknesses: a lack of human resources trained in health economics who can implement changes, a lack of financial resource independence between the local and central levels, the negative behavior of the main macro-economic variables, and the difficulty in developing new financing alternatives. Strengths: the sharing between the central level and local levels of responsibility for financing health services, the implementation of new organizational structures for the follow-up of financial changes at the local level, the development and implementation of new financial allocation mechanisms taking as a basis the efficiency and equity principles, new technique of a per-capita adjustment factor corrected at the local health needs, and the increase of financing contributions from households and local levels of government.

Joan Costa‐Font, Jordi Pons‐Novell

One of the limitations of cross-country health expenditure analysis refers to the fact that the financing, the internal organization and political restraints of health care decision-making are country-specific and heterogeneous. Yet, a way through is to examine the influence of such effects in those countries that have undertaken decentralization processes. In such a setting, it is possible to examine potential expenditure spillovers across the geography of a country as well as the influence of the political ideology of regional incumbents and institutional factors on public health expenditure. This paper examines the determinants of public health expenditure within Spanish region-states (Autonomous Communities, ACs), most of them subject to similar financing structures although exhibiting significant heterogeneity as a result of the increasing decentralization, region-specific political factors along with different use of health care inputs, economic dimension and spatial interactions.

Yevgeniy Dodis, Shien Jin Ong, Manoj Prabhakaran, Arun Sahai

We investigate the feasibility of a variety of cryptographic tasks with imperfect randomness. The kind of imperfect randomness we consider are entropy sources, such as those considered by Santha and Vazirani, Chor and Goldreich, and Zuckerman. We show the following: (1) certain cryptographic tasks like bit commitment, encryption, secret sharing, zero-knowledge, non-interactive zero-knowledge, and secure two-party computation for any non-trivial junction are impossible to realize if parties have access to entropy sources with slightly less-than-perfect entropy, i.e., sources with imperfect randomness. These results are unconditional and do not rely on any un-proven assumption. (2) On the other hand, based on stronger variants of standard assumptions, secure signature schemes are possible with imperfect entropy sources. As another positive result, we show (without any unproven assumption) that interactive proofs can be made sound with respect to imperfect entropy sources.

Salil Vadhan

We prove a number of general theorems about CZK, the class of problems possessing computational zero knowledge proofs. Our results are unconditional, in contrast to most previous works on CZK which rely on the assumption that one-way functions exist. We establish several new characterizations of CZK, and use these characterizations to prove results such as: 1) Honest-verifier CZK equals general CZK. 2) Public-coin CZK equals private-coin CZK. 3) CZK is closed under union (and more generally, "monotone formula closure"). 4) CZK with imperfect completeness equals CZK with perfect completeness. 5) Any problem in CZK /spl cap/ NP can be proven in computational zero knowledge by a BPP/sup NP/ prover. 6) CZK with black-box simulators equals CZK with general, non-black-box simulators. The above equalities refer to the resulting class of problems (and do not necessarily preserve other efficiency measures such as round complexity). Our approach is to combine the conditional techniques previously used in the study of CZK with the unconditional techniques developed in the study of SZK, the class of problems possessing statistical zero knowledge proofs. To enable this combination, we prove that every problem in CZK can be decomposed into a problem in SZK together with a set of instances from which a one-way function can be constructed.

김명용

The 21st century is transforming itself from age of Centralization and Concentration into age of Decentralization. The contemporary paradigm is shifted from age of State and Efficiency into age of Development. Among many countries which try to meet great changes of our times, especially Japan is driving forward decentralization and decentralization policy to improve national competitiveness. For purpose of nation's balanced development, and to remedy ill effect of centralization, discussions on decentralization steadily took place in Korea. The Participatory Government, which promised decentralization policy as its presidential campaign pledge, designated decentralization and nation's balanced development as its core tasks and pushing them forward, To realize and Balanced Participatory Government set up Government Innovation Decentralization Committee under immediate control of government and announced the Participatory Government Decentralization Promotion Road Map. On basis of this Road Map, government enacted so-called Special Laws for Decentralization, namely Decentralization Special Law, Nation's Balanced Development Special Law and Special Measure Law For Construction Of New Administrative Capital. However, in reality, government is confronting political, social and legal conflicts and disputes in relation to methods, time and applicable region to drive forward decentralization policy and to bring an end to centralized system. The Three Special Laws for Decentralization emphasize that centralization of national powers, lack of local autonomy experience, lack of capacity for autonomy, insufficient citizen participation and poor local finance impedes development into decentralized developed nation and also that centralized system in age of compressional economic growth is not functioning efficiently anymore and hinders national competitiveness instead. The Three Laws have its origin in recognition above and are intended to promote increased local vitality by citizen participation and reinforced national competitiveness through answering to needs for decentralization. In contemporary Korean society take place heated discussions over decentralization and construction of new administrative capital. The government party and opposition party argue over national referendum for relocation of administrative capital. In this essay will be reviewed basic ideas of decentralization and contents and problems of decentralization special laws. The future tasks in pushing forward decentralization policy under Decentralization Special Law will also be presented.

Olivier Saint‐Jean

The French health-care system is almost totally under the supervision of the government, which defines the general orientation of health policy. For example, a health-care policy for cancer treatment will be developed in France within the next 5 years. The government organizes the initial formation of all categories of health professionals and so controls the number of professionals in each category. In France, 4500 medical students graduate each year. Demographic problems at the present time are caused by the quota for all medical professions. The government also ensures that the number and location of hospitals are adequate for the needs of the French population. It supervises public hospitals and the management of private clinics, with the objective of providing a consistent standard of care in all health-care structures. The government also proposes the health budget for parliament's approval. In 1996, in line with the concept of decentralization, which means ‘to think globally but act locally’, regional agencies for hospital care were created in each administrative region. They are responsible for the strategic and economic supervision of hospitals, and for the organization of regional health care. However, they have no authority with regard to ambulatory care, thus creating a gap between hospital and ambulatory care in France, which represents a great obstacle to the coordination of care for disabled and elderly people. The French health-care system is a mixed system, being both etatic and liberal. There is a collective health insurance program in place based on incomes; the premium payments are automatically deducted from salaries. The rate is determined each year by the government for an equilibrated budget. Patients have completely free access to all medical care, including hospitals and choice of practitioners. They can have as many consultations and hospitalizations as they want. Furthermore, public and private health structures coexist. Sixty-five percent of hospitals are public and 35% are private. Ambulatory care structures are mainly private (95%). Therefore, although the French system is complex, comprising etatic and private organizations, it functions well. Furthermore, freedom and heterogeneity are probably the main guarantees of quality of health care in France, even if the cost is high and constantly increasing. In France, the number of available hospital beds for acute care (short-stay units), rehabilitation, long-term care and psychiatry is high (Table 1). The rates per 1000 people are the highest in Europe. However, the number of beds for disabled geriatric patients is low: 400 000 beds in retirement homes and 68 000 beds in long-term care units. There is a very long queue to get into such establishments. For psychiatric institutions, there are a total of 6430 beds. The number of health professionals is quite high (Table 2), but they are growing older and demographic problems will arise in the next 10 years. To finance the health-care system, including ambulatory and hospital care, a budget is approved by parliament annually. Ten percent of the gross domestic product (GDP) is devoted to the health-care system (130bn euros), including public hospitals, private hospitals, ambulatory care organizations and pharmacies (Table 3). The budget is being constantly increased. Patients can get a refund of the total cost of health care. For example, refunds for hospitalization costs are between 80% and 100%. For ambulatory care, refunds are between 70% and 100% and for drugs, between 35% and 100%. Health care is free for the homeless and poor people (100% refund). There is a list of 30 severe diseases, including Alzheimer's disease (AD), for which patients are entitled to a 100% refund. Last year, the treatment of AD was listed as a national priority and the government established a care program for the disease. Two main initiatives were proposed. The first one is diagnosis, particularly early diagnosis, as only half of the patients are diagnosed in France. In regard to this, the program proposed the development of memory clinics and regional expert centers. The second initiative is to provide better care for people with AD. This covers ethical issues, the possibility of family caregivers benefiting from some help, financial aid, and the creation of social day-care centers. Hospital care for people with AD is totally paid for by the social security system. Various options are available: short-stay units, rehabilitation units, and day hospitals (of which there are too few) for diagnosis and rehabilitation. Furthermore, people with AD are generally not very welcome in traditional short-stay and rehabilitation units, and it is very difficult to get them a place in such units. Memory clinics are being developed and regional expert centers will be created next year to assist in the early diagnosis of the disease. An expert center must meet specific defined criteria. It must have a multidisciplinary team (neurologists, geriatricians, psychiatrists, and neuropsychologists) and a day hospital for disease diagnosis (capable of handling at least 100 new patients a year). It must also be a source of expertise in research, possess postgraduate knowledge about dementia, and be the centre of a network including general practitioners, ambulatory neurologists and memory clinics of the first degree. Ambulatory care for people with AD is provided by neurologists and psychiatrists (both in insufficient numbers), and by general practitioners, who are not accurately trained for dementia care. Very few geriatricians are included in ambulatory care. Nurses, orthophonists, and physiotherapists are also involved, but again, they are insufficient in number. In other words, social day-care centers should be developed. Social support for patients is financed by a new prestation, the ‘APA’ (personalized prestation for the promotion of autonomy). This prestation was defined in 2002. The amount of the prestation is calculated according to the loss of autonomy. Patients are classified into six groups upon evaluation of their autonomy. It is possible for patients to buy the time of professional social workers and caregivers. The highest level of financial aid they can obtain is 1200 euros per month. Today, 50% of patients are being looked after only by family caregivers. Nursing homes are currently evolving in France. Retirement homes and long-term care units now belong to a single category. The total living expenses comprise three parts: food and housing costs are borne by the patients (through family or social aid); nursing costs are covered by the APA prestation and patients (or their families); and the total cost of medical care is covered by social security (100%). In conclusion, the French health-care system is quite unique since it involves both etatic and liberal organizations. It is an excellent system for patients because of low medical costs, but it requires a high cost of maintenance.

William E. Thro

In America free public education is a constitutional value. Yet, although free public education for all is a constitutional value, America's public schools remain ravaged by savage inequalities, many of which are the direct result of significant financial disparities. Given the obvious conflict between the constitutional value of free public education for all and the funding parities created by the States' school finance systems, it is not surprising that the courts have been asked to intervene and vindicate the constitutional value of free public education for all by declaring that the current system of financing the schools is unconstitutional. However, a judicial solution to the problem has proved as elusive as a legislative or executive solution. Paradoxically, a major reason for the States' failure to adequately finance the achievement - the constitutional value of quality education for all - is the existence of other constitutional values. In other words, there are values within the American constitutional system that make it extremely difficult to achieve another constitutional value. This article explains how two American constitutional values - judicial restraint and decentralization - work together to prevent adequate funding of another constitutional value - a quality education for all.

JaeGwi Choi, Kyung-Hyune Rhee

In this paper, we are concerned with a digital fingerprinting scheme for multi-purchase where a buyer wants to buy more than a digital content. If we apply previous schemes to multi-purchase protocol, the number of execution of registration step and decryption key should be increased in proportion to that of digital contents to be purchased in order to keep unlinkability. More worse, most of fingerprinting schemes in the literature are based on either secure multi-party computation or general zero-knowledge proofs with very high computational complexity. These high complexities complicate materialization of fingerprinting protocol more and more. In this paper, we propose a multi-purchase fingerprinting scheme with lower computational complexity. In the proposed scheme, a buyer executes just one-time registration step regardless of the number of contents to be purchased. The number of decryption key is constant and independent of the number of contents to be purchased. We can also reduce the computational costs of buyers by introducing a concept of proxy-based fingerprinting protocol.