Separating Two-Round Secure Computation From Oblivious Transfer

We consider the question of minimizing the round complexity of protocols for secure multiparty computation (MPC) with security against an arbitrary number of semi-honest parties. Very recently, Garg and Srinivasan (Eurocrypt 2018) and Benhamouda and Lin (Eurocrypt 2018) constructed such 2-round MPC protocols from minimal assumptions. This was done by showing a round preserving reduction to the task of secure 2-party computation of the oblivious transfer functionality (OT). These constructions made a novel non-black-box use of the underlying OT protocol. The question remained whether this can be done by only making black-box use of 2-round OT. This is of theoretical and potentially also practical value as black-box use of primitives tends to lead to more efficient constructions. Our main result proves that such a black-box construction is impossible, namely that non-black-box use of OT is necessary. As a corollary, a similar separation holds when starting with any 2-party functionality other than OT. As a secondary contribution, we prove several additional results that further clarify the landscape of black-box MPC with minimal interaction. In particular, we complement the separation from 2-party functionalities by presenting a complete 4-party functionality, give evidence for the difficulty of ruling out a complete 3-party functionality and for the difficulty of ruling out black-box constructions of 3-round MPC from 2-round OT, and separate a relaxed "non-compact" variant of 2-party homomorphic secret sharing from 2-round OT

Ion propulsion cost effectivity

Ion propulsion modules employing 8-cm thrusters and 30-cm thrusters were studied for Multimission Modular Spacecraft (MMS) applications. Recurring and nonrecurring cost elements were generated for these modules. As a result, ion propulsion cost drivers were identified to be Shuttle charges, solar array, power processing, and thruster costs. Cost effective design approaches included short length module configurations, array power sharing, operation at reduced thruster input power, simplified power processing units, and power processor output switching. The MMS mission model employed indicated that nonrecurring costs have to be shared with other programs unless the mission model grows. Extended performance missions exhibited the greatest benefits when compared with monopropellant hydrazine propulsion

Multiple-View Tracing for Haskell: a New Hat

Different tracing systems for Haskell give different views of a program at work. In practice, several views are complementary and can productively be used together. Until now each system has generated its own trace, containing only the information needed for its particular view. Here we present the design of a trace that can serve several views. The trace is generated and written to file as the computation proceeds. We have implemented both the generation of the trace and several different viewers

Computing Stable Coalitions: Approximation Algorithms for Reward Sharing

Consider a setting where selfish agents are to be assigned to coalitions or projects from a fixed set P. Each project k is characterized by a valuation function; v_k(S) is the value generated by a set S of agents working on project k. We study the following classic problem in this setting: "how should the agents divide the value that they collectively create?". One traditional approach in cooperative game theory is to study core stability with the implicit assumption that there are infinite copies of one project, and agents can partition themselves into any number of coalitions. In contrast, we consider a model with a finite number of non-identical projects; this makes computing both high-welfare solutions and core payments highly non-trivial. The main contribution of this paper is a black-box mechanism that reduces the problem of computing a near-optimal core stable solution to the purely algorithmic problem of welfare maximization; we apply this to compute an approximately core stable solution that extracts one-fourth of the optimal social welfare for the class of subadditive valuations. We also show much stronger results for several popular sub-classes: anonymous, fractionally subadditive, and submodular valuations, as well as provide new approximation algorithms for welfare maximization with anonymous functions. Finally, we establish a connection between our setting and the well-studied simultaneous auctions with item bidding; we adapt our results to compute approximate pure Nash equilibria for these auctions.Comment: Under Revie

Empirical evidence on the success of R&D co-operation: Happy together?

In this paper we analyse the effect of R&D co-operation on firms? innovation performance. We investigate the effect of past co-operation on current sales of innovative products, distinguishing between products new to the firm and new to the market, and on cost reductions due to innovative processes. Particular attention is paid to the impact of different co-operation partners. The analysis rests on firm-level data from two consecutive waves of the annual German innovation survey. We find that innovative firms that cooperate have a higher share of turnover with market novelties and a higher share of cost reduction due to process innovations than non-cooperating firms. In particular, R&D cooperation with research institutes has a positive influence on a firm's economic success with market novelties, while R&D co-operation with competitors leads to an increase in the cost reduction attributable to innovative processes. --R&D Co-operation,Innovation Success,Germany,Applied Econometrics

Reconstructing Climate Policy: Beyond Kyoto

In their comprehensive analysis of the Kyoto Protocol and climate policy, Richard B. Stewart and Jonathan B. Wiener examine the current impasse in climate policy and the potential steps nations can take to reduce greenhouse gases. They summarize the current state of information regarding the extent of global warming that would be caused by increasing uncontrolled greenhouse gas emissions. They explain why participation by all major greenhouse gas-emitting countries is essential to curb future greenhouse gas emissions and also note the significant obstacles to obtaining such participation. Stewart and Wiener argue it is in the national interest of the United States to participate in such a regime, provided that it is well designed. They discuss the elements of sound climate regulatory design, including maximum use of economic incentives, the comprehensive approach, and other flexibility mechanisms; participation by all major emitting countries, including developing countries; regulatory targets based on longer-term emissions pathways set to maximize net social benefits; and effective arrangements to ensure compliance with regulatory obligations by nations and sources. After evaluating the successes and failures of the Kyoto Protocol in light of those elements, the authors propose a series of U.S. initiatives at the international and domestic levels, with the aim of engaging the United States and major developing country emitters such as China in the global greenhouse gas regulatory effort and correcting the remaining defects in the design of the Kyoto Protocol. Although several alternatives to the current Kyoto Protocol regime have been proposed, Stewart and Wiener argue that the best approach for surmounting the current global climate policy impasse is a new strategy that would lead, sooner or later, to simultaneous accession by the United States and China (and other major developing country emitters) to a modified and improved version of the Kyoto Protocol agreement

State of Watershed Payments: An Emerging Marketplace

A global research effort conducted by Ecosystem Marketplace identified a total of approximately 288 payments for watershed services (PWS) and water quality trading (WQT) programs in varying stages of activity over the past 30 years. In 2008, the baseline year, about 127 programs were actively receiving payments or transacting credits. The total transaction value from all programs actively engaged in 2008 is estimated at US$9.3 billion. Over the entire time span of recorded activity, total transaction value is estimated at slightly more than US$50 billion, impacting some 3.24 billion hectares

Reconstructing Climate Policy: Beyond Kyoto

In their comprehensive analysis of the Kyoto Protocol and climate policy, Richard B. Stewart and Jonathan B. Wiener examine the current impasse in climate policy and the potential steps nations can take to reduce greenhouse gases. They summarize the current state of information regarding the extent of global warming that would be caused by increasing uncontrolled greenhouse gas emissions. They explain why participation by all major greenhouse gas-emitting countries is essential to curb future greenhouse gas emissions and also note the significant obstacles to obtaining such participation. Stewart and Wiener argue it is in the national interest of the United States to participate in such a regime, provided that it is well designed. They discuss the elements of sound climate regulatory design, including maximum use of economic incentives, the comprehensive approach, and other flexibility mechanisms; participation by all major emitting countries, including developing countries; regulatory targets based on longer-term emissions pathways set to maximize net social benefits; and effective arrangements to ensure compliance with regulatory obligations by nations and sources. After evaluating the successes and failures of the Kyoto Protocol in light of those elements, the authors propose a series of U.S. initiatives at the international and domestic levels, with the aim of engaging the United States and major developing country emitters such as China in the global greenhouse gas regulatory effort and correcting the remaining defects in the design of the Kyoto Protocol. Although several alternatives to the current Kyoto Protocol regime have been proposed, Stewart and Wiener argue that the best approach for surmounting the current global climate policy impasse is a new strategy that would lead, sooner or later, to simultaneous accession by the United States and China (and other major developing country emitters) to a modified and improved version of the Kyoto Protocol agreement