On asymptotically good ramp secret sharing schemes

Asymptotically good sequences of linear ramp secret sharing schemes have been intensively studied by Cramer et al. in terms of sequences of pairs of nested algebraic geometric codes. In those works the focus is on full privacy and full reconstruction. In this paper we analyze additional parameters describing the asymptotic behavior of partial information leakage and possibly also partial reconstruction giving a more complete picture of the access structure for sequences of linear ramp secret sharing schemes. Our study involves a detailed treatment of the (relative) generalized Hamming weights of the considered codes

Saving, Microinsurance: Why You Should Do Both or Nothing. A Behavioral Experiment on the Philippines

This paper analyzes data from a novel field experiment designed to test the impact of two different insurance products and a secret saving device on solidarity in risk-sharing groups among rural villagers in the Philippines. Risk is simulated by a lottery, risk-sharing is possible in solidarity groups of three and insurance is introduced via less risky lotteries. Our main hypothesis is that formal market-based products lead to lower transfers among network members. We also test for the persistence of this crowding-out of solidarity. We find evidence for a reduction of solidarity by insurance if shocks are observable. Depending on insurance design, there is also evidence for persistence of this effect even if insurance is removed. Simulations using our regression results show that the benefits of insurance are completely offset by the reduction in transfers. However, if secret saving is possible solidarity is very low in general and there is no crowding out effect of insurance. This suggests that introducing formal insurance is not as effective as it is hoped for when the monetary situation can be closely monitored, but that it might be a very important complement when savings inhibit observing financial resources. --

Usability of Humanly Computable Passwords

Reusing passwords across multiple websites is a common practice that compromises security. Recently, Blum and Vempala have proposed password strategies to help people calculate, in their heads, passwords for different sites without dependence on third-party tools or external devices. Thus far, the security and efficiency of these "mental algorithms" has been analyzed only theoretically. But are such methods usable? We present the first usability study of humanly computable password strategies, involving a learning phase (to learn a password strategy), then a rehearsal phase (to login to a few websites), and multiple follow-up tests. In our user study, with training, participants were able to calculate a deterministic eight-character password for an arbitrary new website in under 20 seconds

Report of the 6th Tanzania Joint Annual Health Sector Review 4th-6th April 2005 Kunduchi Beach Hotel,Dar es Salaam

The 6th Annual Joint Health Sector Review was concluded successfully at Kunduchi Beach hotel,between 4th and 6th April 2005. It was preceded by a Technical preparatory meeting, held at Belinda Hotel. This year’s was the largest review yet, with over 200 participants. As well as government and donor representatives, the meeting was attended by a variety of civil society and NGO representatives. The Honourable Minister of Health opened the meeting. Judged by the milestones, performance over the last year has been mixed. The advent of the Joint Rehabilitation Fund, the successful integration of Health into MKUKUTA, the scaling up of AIDS Care and Treatment and a steep budget increase (FY2004/5) were all registered as achievements. However, little if any progress was achieved in tackling the Human Resources crisis. The meeting resolved to address the issue with renewed commitment and urgency. A good deal of quantitative data was presented at the meeting, including the State of Health report, the updated health sector performance profile, and the ten-district study. In most respects these reports point to improvement in health service delivery between 2000 and 2003. The major areas of concern were maternal health services and child malnutrition – neither of which seem to have made any improvement over the last 2 decades. Weaknesses in the routine information system mean that data for 2004 is still patchy. Public Private Partnership was the theme of the technical review this year. The clearest message emerging in plenary was the need to replace the current government subsidy to faith-based providers by a service agreement, linked to outputs. Another resonating theme was the need to expand the opportunity for NGOs (including FBOs) to participate in health planning and management at district level. More generally, there was a commitment by both public and private stakeholders to deepen their collaboration. The recommendations of the Technical Review extended well beyond these two themes. However, lack of time in plenary precluded reaching consensus on most of the recommendations in the report. A good start has been made with the rehabilitation of district health infrastructure. This is expected to accelerate in the year ahead. Participants called for a holistic approach towards prioritisation and effective monitoring of implementation. The Honourable Minister called for a new approach and renewed urgency in tackling the human resources crisis. The challenges and the priorities are clear enough. But the shared commitment of MOF, PO-PSM, PORALG and MOH will be needed in order to move forward. A cabinet paper was seen as one way to secure this joint commitment. The financing situation for Health has improved markedly. The PER demonstrates a 33% nominal rise in health budget between 2003/4 and this budget year. FY2005/6 will witness a further steep increase. This good news is tempered by the fact that payroll expenditure is not keeping up with “other charges”, and central government expenditure is expanding much faster than local government. Even these increases are not sufficient to cover the requirements of the health sector. A 167 billion resource gap was documented by the MOH. New financial commitments continue to come on stream, often initiated by short-term donor funding. Moreover, a substantial portion of new money coming into the sector is tightly earmarked. Flexible, discretionary resources remain highly constrained and tough choices on resource allocation will have to be made. Detailed discussion of health financing in general, and user charges / CHF in particular, was deferred to the Health Financing Workshop due in early May.\u

Entanglement-secured single-qubit quantum secret-sharing

In single-qubit quantum secret sharing, a secret is shared between N parties via manipulation and measurement of one qubit at a time. Each qubit is sent to all N parties in sequence; the secret is encoded in the first participant's preparation of the qubit state and the subsequent participants' choices of state rotation or measurement basis. We present a protocol for single-qubit quantum secret sharing using polarization entanglement of photon pairs produced in type-I spontaneous parametric downconversion. We investigate the protocol's security against eavesdropping attack under common experimental conditions: a lossy channel for photon transmission, and imperfect preparation of the initial qubit state. A protocol which exploits entanglement between photons, rather than simply polarization correlation, is more robustly secure. We implement the entanglement-based secret-sharing protocol with 87% secret-sharing fidelity, limited by the purity of the entangled state produced by our present apparatus. We demonstrate a photon-number splitting eavesdropping attack, which achieves no success against the entanglement-based protocol while showing the predicted rate of success against a correlation-based protocol.Comment: 10 pages, 8 figure

Auctioning Conservation Contracts: An Application to the Flemish Afforestation Policy

This paper studies the possibility of using auctions as a policy instrument in conservation programs. In particular, it provides insight into the main concerns that need to be dealt with when implementing conservation auctions. To show the cost saving potential of this policy instrument, we also calculate the social welfare improvement that can be obtained for an afforestation project in Flanders. Creation-Date: 2006-03Auctions; Conservation contracts; Afforestation