Jonathan A. Poritz

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A core security challenge is the integrity verification of the software that is executed on a machine. For example, an enterprise needs to know whether a gateway machine has been infected by malicious code. One prevailing approach is to use directories of configuration check-sums to detect when a configuration has been changed (see These(More)
The pervasive interconnection of systems throughout the world has given computer services a significant socioeconomic value that both accidental faults and malicious activity can affect. The classical approach to security has mostly consisted of trying to prevent bad things from happening-by developing systems without vulnerabilities, for example, or by(More)
This document describes an architecture for secure service replication in an asynchronous network like the Internet, where a malicious adversary may corrupt some servers and control the network. The underlying protocols for Byzantine agreement and for atomic broadcast rely on recent developments in threshold cryptography. These assumptions are discussed in(More)
  • Paulo E. Veríssimo, Nuno F. Neves, +6 authors Paulo E. Verissimo
  • 2004
The pervasive interconnection of systems all over the world has given computer services a significant socio-economic value, which can be affected both by accidental faults and by malicious activity. It would be appealing to address both problems in a seamless manner, through a common approach to security and dependability. This is the proposal of ’intrusion(More)
This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents(More)
This paper analyses the allocative properties of price cap regulation under very general hypotheses on the nature of society’s preferences. We propose a generalised form of price cap formula (GPC) and we show that it ensures the convergence to optimal (second best) prices in the long-run equilibrium for virtually any form of the welfare function. In(More)
A trivial (but very widespread) kind of authentication using hash functions is the practice, within the open source community, of multiply-posting ‘md5 checksums’ of software releases, so that a prospective downloader can compare the checksum (actually the hash digest) of the binary which they actually download to the value they have found on various public(More)
In 1904, Henri Poincaré conjectured: Every compact, connected, simply-connected 3-manifold is the 3-sphere. This conjecture has been near the center of a maelstrom of activity in topology, geometry, analysis, and many allied and sub-disciplines for a hundred years. Recently, Grisha Perelman announced a proof of the conjecture – in fact of the stronger(More)