Efficient Secure Computation for Real-world Settings and Security Models

Secure computation involves multiple parties computing a common function while keeping their inputs private, and is a growing field of cryptography due to its potential for maintaining privacy guarantees in real-world applications. However, current secure computation protocols are not yet efficient enough to be used in practice. We argue that this is due to much of the research effort being focused on generality rather than specificity. Namely, current research tends to focus on constructing and improving protocols for the strongest notions of security or for an arbitrary number of parties. However, in real-world deployments, these security notions are often too strong, or the number of parties running a protocol would be smaller. In this thesis we make several steps towards bridging the efficiency gap of secure computation by focusing on constructing efficient protocols for specific real-world settings and security models. In particular, we make the following four contributions: - We show an efficient (when amortized over multiple runs) maliciously secure two-party secure computation (2PC) protocol in the multiple-execution setting, where the same function is computed multiple times by the same pair of parties. - We improve the efficiency of 2PC protocols in the publicly verifiable covert security model, where a party can cheat with some probability but if it gets caught then the honest party obtains a certificate proving that the given party cheated. - We show how to optimize existing 2PC protocols when the function to be computed includes predicate checks on its inputs. - We demonstrate an efficient maliciously secure protocol in the three-party setting.

Argo quality control manual for dissolved oxygen concentration

This document is the Argo quality control manual for Dissolved oxygen concentration. It describes two levels of quality control: • The first level is the real-time system that performs a set of agreed automatic checks. • Adjustment in real-time can also be performed and the real-time system can evaluate quality flags for adjusted fields • The second level is the delayed-mode quality control system.

Fitting phase type distribution to service process with sequential phases

The work of this thesis is concerned with fitting Hypo-exponential and Erlang phase type distributions for modeling real life processes with non-exponential service time. There exist situations where exponential distributions cannot explain the distribution of service time properly. This thesis presents the application of two traditional statistical estimation techniques to approximate the service distributions of processes with coefficient of variation less than one. It also presents an algorithm to fit Hypo-exponential distribution for complex situations which can’t be handled properly with traditional estimation techniques. The result shows the effect of variation of sample size and other parameters on the efficiency of the estimation techniques by comparing their respective outputs. Furthermore it checks how accurately the proposed algorithm approximates a given distribution.

Rigidez ou flexibilidade governamental? Discursos anti-corrupção e pró-eficiência sobre contratações com orçamento sigilogo

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciência Política, Programa de Pós-Graduação em Ciência Política, 2016.

Pelas mãos do socioeducativo : práticas disciplinares na medida socioeducativa de internação

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Humanas, Departamento de Serviço Social, Programa de Pós-Graduação em Política Social, 2016.

Analysis of the failure of cracked biscuits

Cracks or checks in biscuits weaken the material and cause the product to break at low load levels that are perceived as injurious to product quality. In this work, the structural response of circular digestive biscuits, with diameter 72 mm and thickness 7.2 mm, simply supported around the circumference and loaded by a central concentrated force was investigated by experiment and theory. Tests were conducted to quantify the distribution in breakage strength for structurally sound biscuits, biscuits with natural checks and biscuits with a single known part-through crack. For sound biscuits the breakage force is Normally distributed with a mean of 12.5 N and standard deviation of 1.2 N. For biscuits with checks, the corresponding statistics are 9.6 N ± 2.62 N respectively. The presence of a crack weakens the biscuit and strength, as measured by breakage force falls almost linearly with crack length and crack depth. The orientation of the crack, whether radial or tangential, and its location (i.e. position of the crack mid-point on the biscuit surface) are also important. Deep, radial, cracks located close to the biscuit centre can reduce the strength by up to 50%. Two separate failure criteria were examined for sound and cracked biscuits respectively. The results from these tests were in good accord with theory. For a biscuit without defects, breakage occurred when maximum biscuit stress reached or exceeded the failure stress of 420 kPa. For a biscuit with cracks, breakage occurred as above or alternatively when its critical stress intensity factor of 18 kPam0.5 was reached.

Propuesta para el mejoramiento de la seguridad de Inversiones ABC S.A.S

Inversiones ABC S.A.S es una empresa colombiana situada en la ciudad de Bogotá, la cual ofrece servicios cambiarios y de intermediación financiera al segmento específico de las empresas de transporte terrestre de carga en la capital del país. La actividad principal de la empresa consiste en el cambio de cheques y la compra de facturas (factoring). Derivados de dicha actividad se ofrecen los siguientes servicios; servicio por ventanilla, servicio puerta a puerta (a domicilio) y consignaciones y giros en bancos y otras entidades como Efecty, Super giros, Western Union (giros y finanzas) y demás casas de giros presentes actualmente en el país. Con base en lo anterior, es posible afirmar que la liquidez constituye en elemento fundamental para el óptimo funcionamiento de los procesos de la compañía. Sin embargo, la tenencia de altas sumas de dinero en efectivo supone también una serie de riesgos asociados a la problemática de inseguridad en la capital del país. Anteriormente, se han presentado asaltos a la sede principal los cuales generalmente resultan en pérdidas económicas que afectan los resultados de la compañía al igual que acciones violentas contra los empleados que atentan contra su integridad física. 1 Teniendo en cuenta que la inseguridad en Bogotá es una amenaza constante, que afecta la operación de la empresa y podría inclusive amenazar su perdurabilidad, el presente trabajo tiene como fin determinar estrategias viables que permitan a la compañía contrarrestar el accionar delictivo de los grupos criminales que amenazan su operación.