13 research outputs found
Integer Polynomial Recovery from Outputs and its Application to Cryptanalysis of a Protocol for Secure Sorting
{We investigate the problem of recovering integer inputs (up to an affine scaling) when given only the integer monotonic polynomial outputs.
Given integer outputs of a degree- integer monotonic polynomial whose coefficients and inputs are integers within known bounds and , we give an algorithm to recover the polynomial and the integer inputs (up to an affine scaling). A heuristic expected time complexity analysis of our method shows that it is exponential in the size of the degree of the polynomial but polynomial in the size of the polynomial coefficients.
We conduct experiments with real-world data as well as randomly chosen parameters and demonstrate the effectiveness of our algorithm over a wide range of parameters.
Using only the polynomial evaluations at specific integer points, the apparent hardness of recovering the input data served as the basis of security of a recent protocol proposed by Kesarwani et al. for secure -nearest neighbour computation on encrypted data that involved secure sorting. The protocol uses the outputs of randomly chosen monotonic integer polynomial to hide its inputs except to only reveal the ordering of input data. Using our integer polynomial recovery algorithm, we show that we can recover the polynomial and the inputs within a few seconds, thereby demonstrating an attack on the protocol of Kesarwani et al
LLAMA: A Low Latency Math Library for Secure Inference
Secure machine learning (ML) inference can provide meaningful privacy guarantees to both the client (holding sensitive input) and the server (holding sensitive weights of the ML model) while realizing inference-as-a-service. Although many specialized protocols exist for this task, including those in the preprocessing model (where a majority of the overheads are moved to an input independent offline phase), they all still suffer from large online complexity. Specifically, the protocol phase that executes once the parties know their inputs, has high communication, round complexity, and latency. Function Secret Sharing (FSS) based techniques offer an attractive solution to this in the trusted dealer model (where a dealer provides input independent correlated randomness to both parties), and 2PC protocols obtained based on these techniques have a very lightweight online phase.
Unfortunately, current FSS-based 2PC works (AriaNN, PoPETS 2022; Boyle et al. Eurocrypt 2021; Boyle et al. TCC 2019) fall short of providing a complete solution to secure inference. First, they lack support for math functions (e.g., sigmoid, and reciprocal square root) and hence, are insufficient for a large class of inference algorithms (e.g. recurrent neural networks).
Second, they restrict all values in the computation to be of the same bitwidth and this prevents them from benefitting from efficient float-to-fixed converters such as Tensorflow Lite that crucially use low bitwidth representations and mixed bitwidth arithmetic.
In this work, we present LLAMA -- an end-to-end, FSS based, secure inference library supporting precise low bitwidth computations (required by converters) as well as provably precise math functions; thus, overcoming all the drawbacks listed above. We perform an extensive evaluation of LLAMA and show that when compared with non-FSS based libraries supporting mixed bitwidth arithmetic and math functions (SIRNN, IEEE S&P 2021), it has at least an order of magnitude lower communication, rounds, and runtimes.
We integrate LLAMA with the EzPC framework (IEEE EuroS&P 2019) and demonstrate its robustness by evaluating it on large benchmarks (such as ResNet-50 on the ImageNet dataset) as well as on benchmarks considered in AriaNN -- here too LLAMA outperforms prior work
Growth and Functionality of Cells Cultured on Conducting and Semi-Conducting Surfaces Modified with Self-Assembled Monolayers (SAMs)
Bioengineering of dermal and epidermal cells on surface modified substrates is an active area of research. The cytotoxicity, maintenance of cell phenotype and long-term functionality of human dermal fibroblast (HDF) cells on conducting indium tin oxide (ITO) and semi-conducting, silicon (Si) and gallium arsenide (GaAs), surfaces modified with self-assembled monolayers (SAMs) containing amino (–NH2) and methyl (–CH3) end groups have been investigated. Contact angle measurements and infrared spectroscopic studies show that the monolayers are conformal and preserve their functional end groups. Morphological analyses indicate that HDFs grow well on all substrates except GaAs, exhibiting their normal spindle-shaped morphology and exhibit no visible signs of stress or cytoplasmic vacuolation. Cell viability analyses indicate little cell death after one week in culture on all substrates except GaAs, where cells died within 6 h. Cells on all surfaces proliferate except on GaAs and GaAs-ODT. Cell growth is observed to be greater on SAM modified ITO and Si-substrates. Preservation of cellular phenotype assessed through type I collagen immunostaining and positive staining of HDF cells were observed on all modified surfaces except that on GaAs. These results suggest that conducting and semi-conducting SAM-modified surfaces support HDF growth and functionality and represent a promising area of bioengineering research
Will adoption of the 2010 WHO ART guidelines for HIV-infected TB patients increase the demand for ART services in India?
BACKGROUND: In 2010, WHO expanded previously-recommended indications for anti-retroviral treatment to include all HIV-infected TB patients irrespective of CD4 count. India, however, still limits ART to those TB patients with CD4 counts <350/mm(3) or with extrapulmonary TB manifestations. We sought to evaluate the additional number of patients that would be initiated on ART if India adopted the current 2010 WHO ART guidelines for HIV-infected TB patients. METHODS: We evaluated all TB patients recorded in treatment registers of the Revised National TB Control Programme in June 2010 in the high-HIV prevalence state of Karnataka, and cross-matched HIV-infected TB patients with ART programme records. RESULTS: Of 6182 TB patients registered, HIV status was ascertained for 5761(93%) and 710(12%) were HIV-infected. 146(21%) HIV-infected TB patients were on ART prior to TB diagnosis. Of the remaining 564, 497(88%) were assessed for ART eligibility; of these, 436(88%) were eligible for ART according to 2006 WHO ART guidelines. Altogether, 487(69%) HIV-infected TB patients received ART during TB treatment. About 80% started ART within 8 weeks of TB treatment and 95% received an efavirenz based regimen. CONCLUSION: In Karnataka, India, about nine out of ten HIV-infected TB patients were eligible for ART according to 2006 WHO ART guidelines. The efficiency of HIV case finding, ART evaluation, and ART initiation was relatively high, with 78% of eligible HIV-infected patients actually initiated on ART, and 80% within 8 weeks of diagnosis. ART could be extended to all HIV-infected TB patients irrespective of CD4 count with relatively little additional burden on the national ART programme
Soft Colloidal Scaffolds Capable of Elastic Recovery after Large Compressive Strains
Assemblies of inorganic or glassy
particles are typically brittle
and cannot sustain even moderate deformations. This restricts the
use of such materials to applications where they do not experience
significant loading or deformation. Here, we demonstrate a general
strategy to create centimeter-size macroporous monoliths, composed
primarily (>90 wt %) of colloidal particles, that recover elastically
after compression to about one-tenth their original size. We employ
ice templating of an aqueous dispersion of particles, polymer, and
cross-linker such that cross-linking happens in the frozen state.
This method yields elastic composite scaffolds for starting materials
ranging from nanoparticles to micron-sized dispersions of inorganics
or glassy lattices. The mechanical response of the monoliths is also
qualitatively independent of polymer type, molecular weight, and even
cross-linking chemistry. Our results suggest that the monolith mechanical
properties arise from the formation of a unique hybrid microstructure,
generated by cross-linking the polymer during ice templating. Particles
that comprise the scaffold walls are connected by a cross-linked polymeric
mesh. This microstructure results in soft monoliths, with moduli ∼O
(10<sup>4</sup> Pa), despite the very high particle content in their
walls. A remarkable consequence of this microstructure is that the
monolith mechanical response is entropic in origin: the modulus of
these scaffolds increases with temperature over a range of 140 K.
We show that interparticle connections formed by cross-linking during
ice templating determine the monolith modulus and also allow relative
motion between connected particles, resulting in entropic elasticity
Fluorinated Nanocellulose-Reinforced All-Organic Flexible Ferroelectric Nanocomposites for Energy Generation
We report here enhanced ferroelectric
crystal formation and energy
generation properties of polyvinylidene fluoride (PVDF) in the presence
of surface-modified crystalline nanocellulose. Incorporation of only
2–5 wt % fluorinated nanocellulose (FNC) in PVDF has been found
to significantly induce polar β/γ-phase crystallization
as compared to the addition of unmodified nanocellulose (carboxylated
nanocellulose). A device made up of electrically poled PVDF/FNC composite
films yielded 2 orders of magnitude higher voltage output than neat
PVDF in vibrational energy harvesting. This remarkable increase in
energy generation properties of PVDF at such a low loading of an organic
natural biopolymer could be attributed to the tailored surface chemistry
of nanocellulose, facilitating strong interfacial interactions between
PVDF and FNC. Interestingly, energy harvesting devices fabricated
from PVDF/FNC nanocomposites charged a 4.7 μF capacitor at significantly
faster rate and the accumulated voltage on capacitor was 3.8 times
greater than neat PVDF. The fact that PVDF/FNC nanocomposites still
retain a strain at break of 10–15% and can charge a capacitor
in few seconds suggests potential use of these nanocomposites as flexible
energy harvesting materials at large strain conditions
Timing of ART initiation and ART regimen in HIV-infected TB patients registered in Karnataka state, India, in June 2010.
<p>TB-Tuberculosis; HIV-Human immunodeficiency virus; ART-antiretroviral treatment.</p