Quantitative Information-Flow Tracking for C and Related Languages

We present a new approach for tracking programs' use of data througharbitrary calculations, to determine how much information about secretinputs is revealed by public outputs. Using a fine-grained dynamicbit-tracking analysis, the technique measures the information revealedduring a particular execution. The technique accounts for indirectflows, e.g. via branches and pointer operations. Two kinds ofuntrusted annotation improve the precision of the analysis. Animplementation of the technique based on dynamic binary translation isdemonstrated on real C, C++, and Objective C programs of up to half amillion lines of code. In case studies, the tool checked multiplesecurity policies, including one that was violated by a previouslyunknown bug

Edge stabilization in reduced-dimensional perovskites

Reduced-dimensional perovskites are attractive light-emitting materials due to their efficient luminescence, color purity, tunable bandgap, and structural diversity. A major limitation in perovskite light-emitting diodes is their limited operational stability. Here we demonstrate that rapid photodegradation arises from edge-initiated photooxidation, wherein oxidative attack is powered by photogenerated and electrically-injected carriers that diffuse to the nanoplatelet edges and produce superoxide. We report an edge-stabilization strategy wherein phosphine oxides passivate unsaturated lead sites during perovskite crystallization. With this approach, we synthesize reduced-dimensional perovskites that exhibit 97 ± 3% photoluminescence quantum yields and stabilities that exceed 300 h upon continuous illumination in an air ambient. We achieve green-emitting devices with a peak external quantum efficiency (EQE) of 14% at 1000 cd m-2; their maximum luminance is 4.5 × 104 cd m-2 (corresponding to an EQE of 5%); and, at 4000 cd m-2, they achieve an operational half-lifetime of 3.5 h.This publication is based in part on work supported by an award (KUS-11-009-21) from the King Abdullah University of Science and Technology (KAUST), by the Ontario Research Fund Research Excellence Program, by the Ontario Research Fund (ORF), by the Natural Sciences and Engineering Research Council (NSERC) of Canada, and by the US Department of Navy, Office of Naval Research (Grant Award No. N00014-17-1-2524). H.Y. acknowledges the Research Foundation-Flanders (FWO Vlaanderen) for a postdoctoral fellowship. E.B. gratefully acknowledges financial support by the Research Foundation-Flanders (FWO Vlaanderen). S.B. acknowledges financial support from European Research Council (ERC Starting Grant #815128-REALNANO). M.B.J.R. and J.H. acknowledge the Research Foundation-Flanders (FWO, Grants G.0962.13, G.0B39.15, AKUL/11/14 and G0H6316N), KU Leuven Research Fund (C14/15/053) and the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. [307523], ERC-Stg LIGHT to M.B.J.R. DFT calculations were performed on the IBM BlueGene Q supercomputer with support from the Southern Ontario Smart Computing Innovation Platform (SOSCIP). M.I.S. acknowledges the Banting Postdoctoral Fellowship program from the Natural Sciences and Engineering Research Council of Canada (NSERC). H.T. acknowledges the Netherlands Organisation for Scientific Research (NWO) for a Rubicon grant (680-50-1511)

The mechanics of housing collectivism: How forms and functions affect affordability

In countries worldwide, limited access to affordable housing is fuelling interest in collectivist solutions. Different organizational models are being developed to enable groups of people to own and control housing collectively. The benefits of such models have been widely promoted, not least in terms of delivering enhanced housing affordability for residents. However, evidence to support such claims is scarce and it remains unclear whether affordability is the product of collective forms and functions, or some other factor(s). To address this gap in knowledge, the paper presents findings from three case studies of English and Canadian housing collectives. Applying realist theories of causation, the processes affecting housing affordability are explained, conceptualizing two causal mechanisms which depict how organizational form, internal rules and regulatory activity, along with the unique role of the resident-owner, influence the setting of rents and prices. Further research is required to understand the prevalence of these mechanisms and their general application

Quantitative information-flow tracking for C and related languages

We present a new approach for tracking programs ’ use of data through arbitrary calculations, to determine how much information about secret inputs is revealed by public outputs. Using a fine-grained dynamic bit-tracking analysis, the technique measures the information revealed during a particular execution. The technique accounts for indirect flows, e.g. via branches and pointer operations. Two kinds of untrusted annotation improve the precision of the analysis. An implementation of the technique based on dynamic binary translation is demonstrated on real C, C++, and Objective C programs of up to half a million lines of code. In case studies, the tool checked multiple security policies, including one that was violated by a previously unknown bug.

Formalizing lightweight verification of software component composition

Software errors often occur at the interfaces between separately developed components. Incompatibilities are an especially acute problem when upgrading software components, as new versions may be accidentally incompatible with old ones. As an inexpensive mechanism to detect many such problems, previous work proposed a technique that adapts methods from formal verification to use component abstractions that can be automatically generated from implementations. The technique reports, before performing the replacement or integrating the new component into a system, whether the upgrade might be problematic for that particular system. The technique is based on a rich model of components that support internal state, callbacks, and simultaneous upgrades of multiple components, and component abstractions may contain arbitrary logical properties including unbounded-state ones. This paper motivates this (somewhat non-standard) approach to component verification. The paper also refines the formal model of components, provides a formal model of software system safety, gives an algorithm for constructing a consistency condition, proves that the algorithm’s result guarantees system safety in the case of a single-component upgrade, and gives a proof outline of the algorithm’s correctness in the case of an arbitrary upgrade. 1

TOXOPLASMOSIS, A SUMMARY OF THE DISEASE WITH REPORT OF A CASE

This report presents a new, automatic technique to assess whether replacing a component of a software system by a purportedly compatible component may change the behavior of the system. The technique operates before integrating the new component into the system or running system tests, permitting quicker and cheaper identification of problems. It takes into account the system’s use of the component, because a particular component upgrade may be desirable in one context but undesirable in another. No formal specifications are required, permitting detection of problems due either to errors in the component or to errors in the system. Both external and internal behaviors can be compared, enabling detection of problems that are not immediately reflected in the output. The technique generates an operational abstraction for the old component in the context of the system, and one for the new component in the context of its test suite. An operational abstraction is a set of program properties that generalizes over observed run-time behavior. Modeling a system as divided into modules, and taking into account the control and data flow between the modules, we formulate a logical condition to guarantee that the system’s behavior is preserved across a component replacement. If automated logical comparison indicates that the new component does not make all the guarantees that the old one did, the

A Simulation-based Proof Technique forDynamic Information Flow

Abstract Information-flow analysis can prevent programs from improperlyrevealing secret information, and a dynamic approach can mak

Femtosecond stimulated Raman study of excited-state evolution in bacteriorhodopsin.

Femtosecond time-resolved stimulated Raman spectroscopy (FSRS) is used to examine the photoisomerization dynamics in the excited state of bacteriorhodopsin. Near-IR stimulated emission is observed in the FSRS probe window that decays with a 400-600-fs time constant. Additionally, dispersive vibrational lines appear at the locations of the ground-state vibrational frequencies and decay with a 260-fs time constant. The dispersive line shapes are caused by a nonlinear effect we term Raman initiated by nonlinear emission (RINE) that generates vibrational coherence on the ground-state surface. Theoretical expressions for the RINE line shapes are developed and used to fit the spectral and temporal evolution of the spectra. The rapid 260-fs decay of the RINE peak intensity, compared to the slower evolution of the stimulated emission, indicates that the excited-state population moves in approximately 260 fs to a region on the potential energy surface where the RINE signal is attenuated. This loss of RINE signal is best explained by structural evolution of the excited-state population along multiple low-frequency modes that carry the molecule out of the harmonic photochemically inactive Franck-Condon region and into the photochemically active geometry