DM - Comunicaciones en Congresos y otros eventos
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Publication Modular Sumcheck Proofs With Applications to Machine Learning and Image Processing(Association for Computing Machinery (ACM), 2023-11-21) Balbás, David; Fiore, Dario; González Vasco, María Isabel; Robissout, Damien; Soriente, ClaudioCryptographic proof systems provide integrity, fairness, and privacy in applications that outsource data processing tasks. However, general-purpose proof systems do not scale well to large inputs. At the same time, ad-hoc solutions for concrete applications - e.g., machine learning or image processing - are more efficient but lack modularity, hence they are hard to extend or to compose with other tools of a data-processing pipeline. In this paper, we combine the performance of tailored solutions with the versatility of general-purpose proof systems. We do so by introducing a modular framework for verifiable computation of sequential operations. The main tool of our framework is a new information-theoretic primitive called Verifiable Evaluation Scheme on Fingerprinted Data (VE) that captures the properties of diverse sumcheck-based interactive proofs, including the well-established GKR protocol. Thus, we show how to compose VEs for specific functions to obtain verifiability of a data-processing pipeline. We propose a novel VE for convolution operations that can handle multiple input-output channels and batching, and we use it in our framework to build proofs for (convolutional) neural networks and image processing. We realize a prototype implementation of our proof systems, and show that we achieve up to 5x faster proving time and 10x shorter proofs compared to the state-of-the-art, in addition to asymptotic improvements.Publication (Password) authenticated key establishment: From 2-party to group(Springer, 2007) Abdalla, Michel; Bohli, Jens Matthias; González Vasco, María Isabel; Steinwandt, Rainer; European CommissionA protocol compiler is described, that transforms any provably secure authenticated 2-party key establishment into a provably secure authenticated group key establishment with 2 more rounds of communication. The compiler introduces neither idealizing assumptions nor high-entropy secrets, e.g., for signing. In particular, applying the compiler to a password-authenticated 2-party key establishment without random oracle assumption, yields a password-authenticated group key establishment without random oracle assumption. Our main technical tools are non-interactive and non-malleable commitment schemes that can be implemented in the common reference string (CRS) model.Publication A new cramer-shoup like methodology for group based provably secure encryption schemes(Springer, 2005) González Vasco, María Isabel; Martínez, Consuelo; Steinwandt, Rainer; Villar, Jorge L.A theoretical framework for the design of - in the sense of IND-CCA - provably secure public key cryptosystems taking non-abelian groups as a base is given. Our construction is inspired by Cramer and Shoup's general framework for developing secure encryption schemes from certain language membership problems; thus all our proofs are in the standard model, without any idealization assumptions. The skeleton we present is conceived as a guiding tool towards the construction of secure concrete schemes from finite non-abelian groups (although it is possible to use it also in conjunction with finite abelian groups).Publication A policy iteration algorithm for nonzero-sum stochastic impulse games(EDP Science, 2019-02) Aïd, René; Bernal Martínez, Francisco Manuel; Mnif, Mohamed; Zabaljauregui, Diego; Zubelli, Jorge P.This work presents a novel policy iteration algorithm to tackle nonzero-sum stochastic impulse games arising naturally in many applications. Despite the obvious impact of solving such problems, there are no suitable numerical methods available, to the best of our knowledge. Our method relies on the recently introduced characterisation of the value functions and Nash equilibrium via a system of quasi-variational inequalities. While our algorithm is heuristic and we do not provide a convergence analysis, numerical tests show that it performs convincingly in a wide range of situations, including the only analytically solvable example available in the literature at the time of writing.Publication Numerical solution of the viscous flow past a cylinder with a non-global yet spectrally convergent meshless collocation method(Springer, 2017-08-22) Bernal Martínez, Francisco Manuel; Heryudono, Alfa R.H.; Larsson, ElisabethThe flow of a viscous fluid past a cylinder is a classical problem in fluid-structure interaction and a benchmark for numerical methods in computational fluid dynamics. We solve it with the recently introduced radial basis function-based partition of unity method (RBF-PUM), which is a spectrally convergent collocation meshless scheme well suited to this kind of problem. The resulting discrete system of nonlinear equations is tackled with a trust-region algorithm, whose performance is much enhanced by the analytic Jacobian which is provided alongside. Preliminary results up to Re = 60 with just 1292 nodes are shown.Publication Solving Non-Smooth Delay Differential Equations with Multiquadrics(Springer Verlag Berlin-Heidelberg, 2012-01-14) Bernal Martínez, Francisco ManuelWe put forward a discretization scheme for the numerical solution of neutral differential equations (NDEs). The solution to the NDE in an interval I = [a, b] is approximated by a multiquadric (MQ) interpolant, whose coefficients are found by collocation on a set of N nodes in I. This approach, also known as Kansa’s method, enjoys an exponential rate of convergence and great flexibility regarding the location of the nodes, as long as the solution to the differential equation is smooth. However, the critical difficulty posed by NDEs is precisely that they propagate, forward in time and without damping, low-order discontinuities of the history function. Here, we exploit the sensitivity of the MQ interpolant to discontinuities in order to detect them in computing time. This allows for a partition of I into smooth subintervals, which are then sequentially solved by Kansa’s method.Publication Meshless Simulation of Hele-Shaw Flow(Springer, 2008-06-01) Bernal Martínez, Francisco Manuel; Kindelan Segura, Manuel; Comunidad de Madrid; Ministerio de Educación, Cultura y Deporte (España)A novel meshless approach was proposed for solving the Hele-Shaw flow which models plastic injection molding, in the case of a Newtonian fluid. Here, we have extended this idea to non-Newtonian Hele-Shaw flow via a Newton algorithm for the resulting nonlinear PDE.Publication The Groenewold-Moyal plane and its quantum physics(American Institute of Physics, 2009-12-15) Balachandran, Aiyalan P.; Padmanabhan, PramodQuantum theories constructed on the noncommutative spacetime called the Groenewold-Moyal(GM) plane exhibit many interesting properties such as causality violation, Lorentz and CPT non-invariance and twisted statistics. Such violations lead to many striking features that may be tested experimentally. Thus these theories predict Pauli-forbidden transitions due to twisted statistics, anisotropies and acausal effects in the cosmic microwave background radiation in correlations of observables and Lorentz and CPT violations in scattering amplitudes. Such features of quantum physics on the GM plane are surveyed in this review.