68 research outputs found
Distributed Differential Privacy and Applications
Recent growth in the size and scope of databases has resulted in more
research into making productive use of this data. Unfortunately, a
significant stumbling block which remains is protecting the privacy of
the individuals that populate these datasets. As people spend more
time connected to the Internet, and conduct more of their daily lives
online, privacy becomes a more important consideration, just as the
data becomes more useful for researchers, companies, and
individuals. As a result, plenty of important information remains
locked down and unavailable to honest researchers today, due to fears
that data leakages will harm individuals.
Recent research in differential privacy opens a promising pathway to
guarantee individual privacy while simultaneously making use of the
data to answer useful queries. Differential privacy is a theory that
provides provable information theoretic guarantees on what any answer
may reveal about any single individual in the database. This approach
has resulted in a flurry of recent research, presenting novel
algorithms that can compute a rich class of computations in this
setting.
In this dissertation, we focus on some real world challenges that
arise when trying to provide differential privacy guarantees in the
real world. We design and build runtimes that achieve the mathematical
differential privacy guarantee in the face of three real world
challenges: securing the runtimes against adversaries, enabling
readers to verify that the answers are accurate, and dealing with data
distributed across multiple domains
DStress: Efficient Differentially Private Computations on Distributed Data
In this paper, we present DStress, a system that can efficiently perform computations on graphs that contain confidential data. DStress assumes that the graph is physically distributed across many participants, and that each participant only knows a small subgraph; it protects privacy by enforcing tight, provable limits on how much each participant can learn about the rest of the graph. We also study one concrete instance of this problem: measuring systemic risk in financial networks. Systemic risk is the likelihood of cascading bankruptcies – as, e.g., during the financial crisis of 2008 – and it can be quantified based on the dependencies between financial institutions; however, the necessary data is highly sensitive and cannot be safely disclosed. We show that DStress can implement two different systemic risk models from the theoretical economics literature. Our experimental evaluation suggests that DStress can run the corresponding computations in about five hours, whereas a na¨ıve approach could take several decades
The evolution of India’s industrial labour share and its correlates
There has been substantial recent interest in the decline of labour shares across countries. For the most part, attention has been focused on developed countries. We examine the evolution of India’s labour share in its formal industrial sector from 1983- 2014. Using two datasets corresponding to sectoral aggregate data and plant-level data respectively, we document a secular decline in the labour share across all sectors from 1983, with a stabilisation at very low levels (around 8 to 10 percent) starting around 2005. We then use the plant-level data to identify the reasons for the overall decline in the labour share. We find strong evidence to support multiple causes: increased capital intensity, greater informalisation, greater privatisation, and productivity increases in larger firms. As such, we suggest that the declines in labour share experienced are due to a composite set of factors. Conversely, other potential explanations (for example, regional variation in the labour share) have less explanatory power
Secure Network Provenance
This paper introduces secure network provenance (SNP), a novel technique that enables networked systems to explain to their operators why they are in a certain state – e.g., why a suspicious routing table entry is present on a certain router, or where a given cache entry originated. SNP provides network forensics capabilities by permitting operators to track down faulty or misbehaving nodes, and to assess the damage such nodes may have caused to the rest of the system. SNP is designed for adversarial settings and is robust to manipulation; its tamper-evident properties ensure that operators can detect when compromised nodes lie or falsely implicate correct nodes. We also present the design of SNooPy, a general-purpose SNP system. To demonstrate that SNooPy is practical, we apply it to three example applications: the Quagga BGP daemon, a declarative implementation of Chord, and Hadoop MapReduce. Our results indicate that SNooPy can efficiently explain state in an adversarial setting, that it can be applied with minimal effort, and that its costs are low enough to be practical
Mapping India’s Finances 60 Years of Flow of Funds
As a useful adjunct to other macroeconomic accounts, this paper describes financial flows between different sectors of the Indian economy from 1955 to 2015. It finds that the consolidated government sector has the largest net deficit, while the households sector has the largest net surplus. The private corporate sector is running larger deficits than at any other time in the past, implying more reliance on external credits. With liberalisation and globalisation, the rest of the world sector is now the second-largest net surplus sector in the economy
Diagnostic accuracy of non-invasive tests for advanced fibrosis in patients with NAFLD: an individual patient data meta-analysis
Objective Liver biopsy is still needed for fibrosis staging in many patients with non-alcoholic fatty liver disease. The aims of this study were to evaluate the individual diagnostic performance of liver stiffness measurement by vibration controlled transient elastography (LSM-VCTE), Fibrosis-4 Index (FIB-4) and NAFLD (non-alcoholic fatty liver disease) Fibrosis Score (NFS) and to derive diagnostic strategies that could reduce the need for liver biopsies.
Design Individual patient data meta-analysis of studies evaluating LSM-VCTE against liver histology was conducted. FIB-4 and NFS were computed where possible. Sensitivity, specificity and area under the receiver operating curve (AUROC) were calculated. Biomarkers were assessed individually and in sequential combinations.
Results Data were included from 37 primary studies (n=5735; 45% women; median age: 54 years; median body mass index: 30 kg/m2; 33% had type 2 diabetes; 30% had advanced fibrosis). AUROCs of individual LSM-VCTE, FIB-4 and NFS for advanced fibrosis were 0.85, 0.76 and 0.73. Sequential combination of FIB-4 cut-offs (<1.3; ≥2.67) followed by LSM-VCTE cut-offs (<8.0; ≥10.0 kPa) to rule-in or rule-out advanced fibrosis had sensitivity and specificity (95% CI) of 66% (63–68) and 86% (84–87) with 33% needing a biopsy to establish a final diagnosis. FIB-4 cut-offs (<1.3; ≥3.48) followed by LSM cut-offs (<8.0; ≥20.0 kPa) to rule out advanced fibrosis or rule in cirrhosis had a sensitivity of 38% (37–39) and specificity of 90% (89–91) with 19% needing biopsy.
Conclusion Sequential combinations of markers with a lower cut-off to rule-out advanced fibrosis and a higher cut-off to rule-in cirrhosis can reduce the need for liver biopsies
Conclave: secure multi-party computation on big data (extended TR)
Secure Multi-Party Computation (MPC) allows mutually distrusting parties to
run joint computations without revealing private data. Current MPC algorithms
scale poorly with data size, which makes MPC on "big data" prohibitively slow
and inhibits its practical use.
Many relational analytics queries can maintain MPC's end-to-end security
guarantee without using cryptographic MPC techniques for all operations.
Conclave is a query compiler that accelerates such queries by transforming them
into a combination of data-parallel, local cleartext processing and small MPC
steps. When parties trust others with specific subsets of the data, Conclave
applies new hybrid MPC-cleartext protocols to run additional steps outside of
MPC and improve scalability further.
Our Conclave prototype generates code for cleartext processing in Python and
Spark, and for secure MPC using the Sharemind and Obliv-C frameworks. Conclave
scales to data sets between three and six orders of magnitude larger than
state-of-the-art MPC frameworks support on their own. Thanks to its hybrid
protocols, Conclave also substantially outperforms SMCQL, the most similar
existing system.Comment: Extended technical report for EuroSys 2019 pape
Unusual magnetic and transport properties in HoMnSn kagome magnet
With intricate lattice structures, kagome materials are an excellent platform
to study various fascinating topological quantum states. In particular, kagome
materials, revealing large responses to external stimuli such as pressure or
magnetic field, are subject to special investigation. Here, we study the
kagome-net HoMnSn magnet that undergoes paramagnetic to ferrimagnetic
transition (below 376 K) and reveals spin-reorientation transition below 200 K.
In this compound, we observe the topological Hall effect and substantial
contribution of anomalous Hall effect above 100 K. We unveil the pressure
effects on magnetic ordering at a low magnetic field from the pressure tunable
magnetization measurement. By utilizing high-resolution angle-resolved
photoemission spectroscopy, Dirac-like dispersion at the high-symmetry point K
is revealed in the vicinity of the Fermi level, which is well supported by the
first-principles calculations, suggesting a possible Chern-gapped Dirac cone in
this compound. Our investigation will pave the way to understand the
magneto-transport and electronic properties of various rare-earth-based kagome
magnets
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