Decentralized Polling with Respectable Participants

International audienceWe consider the polling problem in a social network: participants express support for a given option and expect an outcome reflecting the opinion of the majority. Individuals in a social network care about their reputation: they do not want their vote to be disclosed or any potential misbehavior to be publicly exposed. We exploit this social aspect of users to model dishonest behavior, and show that a simple secret sharing scheme, combined with lightweight verification procedures, enables private and accurate polling without requiring any central authority or cryptography. We present DPol, a simple and scalable distributed polling protocol in which misbehaving nodes are exposed with positive probability and in which the probability of honest participants having their privacy violated is traded off with the impact of dishonest participants on the accuracy of the polling result. The trade-off is captured by a generic parameter of the protocol, an integer k called the privacy parameter. In a system of N nodes with B dishonest participants, the probability of disclosing a participant's vote is bounded by (B/N)^{k+1}, whereas the impact on the score of each polling option is at most (3k+2) B with high probability when dishonest users are a minority (i.e., B < N/2), assuming nodes are uniformly spread across groups used by the system. When dishonest users are few (i.e., B < sqrt{N}), the impact bound holds deterministically and our protocol is asymptotically accurate: there is negligible difference between the true result score of the poll and the outcome of our protocol. To demonstrate the practicality of DPol, we report on its deployment on 400 PlanetLab nodes. The relative error of the polling result is less than 10% when faced with the message loss, crashes and delays inherent in PlanetLab. Our experiments show that the impact on the score of each polling option by dishonest nodes is (2k+1) B on average, consistently lower that the theoretical bound of (3k+2) B

A Distributed Polling with Probabilistic Privacy

In this paper, we present PDP, a distributed polling protocol that enables a set of participants to gather their opinion on a common interest without revealing their point of view. PDP does not rely on any centralized authority or on heavyweight cryptography. PDP is an overlay-based protocol where a subset of participants may use a simple sharing scheme to express their votes. In a system of $M$ participants arranged in groups of size $N$ where at least $2k-1$ participants are honest, PDP bounds the probability for a given participant to have its vote recovered with certainty by a coalition of $B$ dishonest participants by $pi(B/N)^(k+1)$, where $pi$ is the proportion of participants splitting their votes, and $k$ a privacy parameter. PDP bounds the impact of dishonest participants on the global outcome by $2(k&alpha + BN), where represents the number of dishonest nodes using the sharing scheme

Do Off-Label Drug Practices Argue Against FDA Efficacy Requirements? Testing an Argument by Structured Conversations with Experts

The Food, Drug and Cosmetics Act of 1938 with amendments in 1962 is inconsistent regarding FDA certification of a drug’s efficacy. The act requires efficacy certification for the drug’s initial (“on-label”) uses, but does not require certification before physicians may prescribe for subsequent (“off-label”) uses. Are there good reasons for this inconsistency? Using a sequential online survey we carried on a “virtual conversation” with some 500 physicians. The survey asked whether efficacy requirements should be imposed on off-label uses, and almost all physicians said no. It asked whether the efficacy requirements for initial uses should be dropped, and most said no. We then gently challenged respondents asking them whether opposing efficacy requirements in one case but not the other involved an inconsistency. In response to this challenge we received hundreds of written commentaries. This investigation taps the specialized knowledge of hundreds of physicians and organizes their insights into challenges to the consistency argument. Thus, it employs a method of structured conversations with experts to test the merit of an argument. Is the consistency argument a case of “foolish consistency,” or does it hold up even under scrutiny?Food and Drug Administration; drug approval; efficacy requirements; off-label uses; on-label uses; certification; liberalization

Value shifts and management training needs : forecasts for 1990

Thesis (M.A.)--University of Kansas, Communication Studies, 1984

Live Streaming with Gossip

Peer-to-peer (P2P) architectures have emerged as a popular paradigm to support the dynamic and scalable nature of distributed systems. This is particularly relevant today, given the tremendous increase in the intensity of information exchanged over the Internet. A P2P system is typically composed of participants that are willing to contribute resources, such as memory or bandwidth, in the execution of a collaborative task providing a benefit to all participants. File sharing is probably the most widely used collaborative task, where each participant wants to receive an individual copy of some file. Users collaborate by sending fragments of the file they have already downloaded to other participants. Sharing files containing multimedia content, files that typically reach the hundreds of megabytes to gigabytes, introduces a number of challenges. Given typical bandwidths of participants of hundreds of kilobits per second to a couple of megabits per second, it is unacceptable to wait until completion of the download before actually being able to use the file as the download represents a non negligible time. From the point of view of the participant, getting the (entire) file as fast as possible is typically not good enough. As one example, Video on Demand (VoD) is a scenario where a participant would like to start previewing the multimedia content (the stream), offered by a source, even though only a fraction of it has been received, and then continue the viewing while the rest of the content is being received. Following the same line of reasoning, new applications have emerged that rely on live streaming: the source does not own a file that it wants to share with others, but shares content as soon as it is produced. In other words, the content to distribute is live, not pre-recorded and stored. Typical examples include the broadcasting of live sports events, conferences or interviews. The gossip paradigm is a type of data dissemination that relies on random communication between participants in a P2P system, sharing similarities with the epidemic dissemination of diseases. An epidemic starts to spread when the source randomly chooses a set of communication partners, of size fanout, and infects them, i.e., it shares a rumor with them. This set of participants, in turn, randomly picks fanout communication partners each and infects them, i.e., share with them the same rumor. This paradigm has many advantages including fast propagation of rumors, a probabilistic guarantee that each rumor reaches all participants, high resilience to churn (i.e., participants that join and leave) and high scalability. Gossip therefore constitutes a candidate of choice for live streaming in large-scale systems. These advantages, however, come at a price. While disseminating data, gossip creates many duplicates of the same rumor and participants usually receive multiple copies of the same rumor. While this is obviously a feature when it comes to guaranteeing good dissemination of the rumor when churn is high, it is a clear disadvantage when spreading large amounts of multimedia data (i.e., ordered and time-critical) to participants with limited resources, namely upload bandwidth in the case of high-bandwidth content dissemination. This thesis therefore investigates if and how the gossip paradigm can be used as a highly effcient communication system for live streaming under the following specific scenarios: (i) where participants can only contribute limited resources, (ii) when these limited resources are heterogeneously distributed among nodes, and (iii) where only a fraction of participants are contributing their fair share of work while others are freeriding. To meet these challenges, this thesis proposes (i) gossip++: a gossip-based protocol especially tailored for live streaming that separates the dissemination of metadata, i.e., the location of the data, and the dissemination of the data itself. By first spreading the location of the content to interested participants, the protocol avoids wasted bandwidth in sending and receiving duplicates of the payload, (ii) HEAP: a fanout adaptation mechanism that enables gossip to adapt participants' contribution with respect to their resources while still preserving its reliability, and (iii) LiFT: a protocol to secure high-bandwidth gossip-based dissemination protocols against freeriders

GOVERNANCE FROM BELOW A Theory of Local Government With Two Empirical Tests

I examine decentralization through the lens of the local dynamics that it unleashes. The national effects of decentralization are simply the sum of its local-level effects. Hence to understand decentralization we must first understand how local government works. This paper proposes a theory of local government as the confluence of two quasi-markets and one organizational dynamic. Good government results when these three elements - political, economic and civil - are in rough balance, and actors in one cannot distort the others. Specific types of imbalance map into specific forms of government failure. I use comparative analysis to test the theory's predictions with qualitative and quantitative evidence from Bolivia. The combined methodology provides a higher-order empirical rigor than either approach can alone. The theory proves robust.local government, civil society, democratic theory, good governance, decentralization, Q2 (Q-square), Bolivia

Private Actors & (and) Structural Balance: Militia & (and) the Free Rider Problem in Private Provision of Law

Miners in Montana in the 1860s created common law, nongovernmental legal institutions which dispensed millions of dollars of public resources to private individuals. Armed Vigilantes rode across the territory administering private justice. They hung twenty-two men, including an elected sheriff and his deputies. Even as Montana finally became a territory in May 1864, it nevertheless chose still to regard itself as back of beyond, as a remote, independent, and untouchable empire. It resented and continually obstructed, ungratefully, the federal controls which accompanied the blessings of territorial recognition. Such activities were not limited to the early days of the Montana Territory: cattlemen led by Granville Stuart in Montana pursued and hung rustlers in the 1890s, to widespread popular approval. Today the State of Montana and many Montanans celebrate and honor these men and their activities. Montana\u27s state capitol building includes what is almost a shrine to the 1863-64 Vigilantes; the state highway patrol includes the Vigilante symbol on its shoulder patches; Helena\u27s main street, still called Last Chance Gulch, follows the site of mining activity and celebrates as heroic the miners\u27 exploitation of the public domain; guided tours of Bannack State Park glorify the Vigilantes; and cattlemen such as Granville Stuart appear as heroes in most modern Montana history books. Times have changed and celebrating a vigilante past need not mean we want to live in a vigilante present. However, there are striking similarities between the Militias\u27 complaints about the balance between the State and private society and the problems faced by Westerners in the nineteenth century. These links between our past and our present ought to make us hesitate before rejecting the Militias\u27 contributions to political dialogue, even as we recognize the significant flaws in their ideologies. The Militias are a response to changes in the structure of our society. Although these changes have many diverse impacts, one of the most crucial is the increasing reliance on State legal institutions rather than on private, customary legal institutions to solve societal problems. While the Militias are not the only response possible, they are a response well within the traditions of United States political discourse. In Section I, I provide some definitions and describe the free rider problems inherent in private solutions to public problems. In Section II, I discuss the role of different types of law in our society\u27s structure and the Militias\u27 views on these issues, which I compare to historical examples from the nineteenth century American West. I then suggest ways in which the Militias can contribute to solving the problems identified earlier. Finally, I conclude with a brief analysis of the Militias\u27 potential to play a constructive societal role

Private Actors & Structural Balance: Militia & the Free Rider Problem in Private Provision of Law

Private Actors & Structural Balance: Militia & the Free Rider Problem in Private Provision of La