Quantitative Information Flow Research Articles

Quantitative information flow in interactive systems

We consider the problem of defining the information leakage in interactive systems where secrets and observables can alternate during the computation. We show that the information-theoretic approach which interprets such systems as (simple) noisy cha

On bounding problems of quantitative information flow

Researchers have proposed formal definitions of quantitative information flow based on information theoretic notions such as the Shannon entropy, the min entropy, the guessing entropy, belief, and channel capacity. This paper investigates the hardnes

Quantitative information flow as network flow capacity

We present a new technique for determining how much information about a program's secret inputs is revealed by its public outputs. In contrast to previous techniques based on reachability from secret inputs (tainting), it achieves a more precise quantitative result by computing a maximum flow of information between the inputs and outputs. The technique uses static control-flow regions to soundly account for implicit flows via branches and pointer operations, but operates dynamically by observing one or more program executions and giving numeric flow bounds specific to them (e.g., "17 bits"). The maximum flow in a network also gives a minimum cut (a set of edges that separate the secret input from the output), which can be used to efficiently check that the same policy is satisfied on future executions. We performed case studies on 5 real C, C++, and Objective C programs, 3 of which had more than 250K lines of code. The tool checked multiple security policies, including one that was violated by a previously unknown bug.

Linking Models of Land Use, Resources, and Economy to Simulate the Development of Mountain Regions (ALPSCAPE)

We present a framework of a scenario-based model that simulates the development of the municipality of Davos (Swiss Alps). We illustrate our method with the calculation of the scenario for 2050 "Decrease in subsidies for mountain agriculture and liberalization of markets." The main objective was to link submodels of land-use allocation (regression-based approach), material and energy flows submodels (Material and Energy Flux Analysis), and economic submodels (Input-Output Analysis). Letting qualitative and quantitative information flow from one submodel to the next, following the storyline describing a scenario, has proven to be suitable for linking submodels. The succession of the submodels is then strongly dependent on the scenario. Qualitative information flows are simulated with microsimulations of actor choices. Links between the submodels show different degrees of robustness: although the links involving microsimulations are the weakest, the uncertainty introduced by the land-use allocation model is actually advantageous because it allows one possible change in the landscape in the future to be simulated. The modeling results for the scenario here presented show that the disappearance of agriculture only marginally affects the region's factor income, but that the consequences for the self-sufficiency rate, for various landscape-related indicators and ecosystem services, and for the economy in the long term may be considerable. These benefits compensate for agriculture's modest direct economic value. The framework presented can potentially be applied to any region and scenario. This framework provides a basis for a learning package that allows potential detrimental consequences of regional development to be anticipated at an early stage.

Quantitative Information Flow, Relations and Polymorphic Types

This paper uses Shannon's information theory to give a quantitative definition of information flow in systems that transform inputs to outputs. For deterministic systems, the definition is shown to specialize to a simpler form when the information source and the known inputs jointly determine all inputs uniquely. For this special case, the definition is related to the classical security condition of non-interference and an equivalence is established between non-interference and independence of random variables. Quantitative information flow for deterministic systems is then presented in relational form. With this presentation, it is shown how relational parametricity can be used to derive upper and lower bounds on information flows through families of functions defined in the second-order lambda calculus.

Imagerie du péricarde et des valves : apport du scanner multicoupe et de l’IRM

Color Doppler echocardiography has limitations, particularly in the assessment of valvular regurgitation and pericardial diseases. MRI, with the help of three dimensional morphologic data, dynamic acquisitions with cine techniques and functional evaluation with flow sensitive techniques can be envisioned as a complementary noninvasive procedure able to provide the complete information required for planning therapeutic options. Qualitative as well as accurate and reproducible quantitative information (volume measurements, cardiac function and flow velocity profiles) are unique for the evaluation of the severity of valve or pericardial diseases. Multislice CT is unique in precisely demonstrating valvular and pericardial calcifications. This article reviews both imaging techniques used in assessing valvular and pericardial disease and discusses the advantages and limitations of these techniques in current clinical applications.

Imagerie du péricarde et des valves : apport du scanner multicoupe et de l’IRM

Color Doppler echocardiography has limitations, particularly in the assessment of valvular regurgitation and pericardial diseases. MRI, with the help of three dimensional morphologic data, dynamic acquisitions with cine techniques and functional evaluation with flow sensitive techniques can be envisioned as a complementary noninvasive procedure able to provide the complete information required for planning therapeutic options. Qualitative as well as accurate and reproducible quantitative information (volume measurements, cardiac function and flow velocity profiles) are unique for the evaluation of the severity of valve or pericardial diseases. Multislice CT is unique in precisely demonstrating valvular and pericardial calcifications. This article reviews both imaging techniques used in assessing valvular and pericardial disease and discusses the advantages and limitations of these techniques in current clinical applications.