1,387 research outputs found
USRA/RIACS
The Research Institute for Advanced Computer Science (RIACS) was established by the Universities Space Research Association (USRA) at the NASA Ames Research Center (ARC) on 6 June 1983. RIACS is privately operated by USRA, a consortium of universities with research programs in the aerospace sciences, under a cooperative agreement with NASA. The primary mission of RIACS is to provide research and expertise in computer science and scientific computing to support the scientific missions of NASA ARC. The research carried out at RIACS must change its emphasis from year to year in response to NASA ARC's changing needs and technological opportunities. A flexible scientific staff is provided through a university faculty visitor program, a post doctoral program, and a student visitor program. Not only does this provide appropriate expertise but it also introduces scientists outside of NASA to NASA problems. A small group of core RIACS staff provides continuity and interacts with an ARC technical monitor and scientific advisory group to determine the RIACS mission. RIACS activities are reviewed and monitored by a USRA advisory council and ARC technical monitor. Research at RIACS is currently being done in the following areas: Parallel Computing; Advanced Methods for Scientific Computing; Learning Systems; High Performance Networks and Technology; Graphics, Visualization, and Virtual Environments
Keyword Search in Relational Databases: Architecture, Approaches and Considerations
Questo lavoro di tesi presenta le diverse soluzioni proposte in letteratura per applicare il paradigma keyword search alle basi di dati relazionali, e vuole delineare una architettura generale per definire e sviluppare questi sistemi. A tal proposito, le soluzioni presentate dalla comunitร scientifica sono state analizzate focalizzandosi sui singoli componenti della pipeline di ricerca. Infine, si sono analizzati i processi di valutazione sperimentale di questi sistem
Fixed Points in Discrete Models for Regulatory Genetic Networks
It is desirable to have efficient mathematical methods to extract information about regulatory iterations between genes from repeated measurements of gene transcript concentrations. One piece of information is of interest when the dynamics reaches a steady state. In this paper we develop tools that enable the detection of steady states that are modeled by fixed points in discrete finite dynamical systems. We discuss two algebraic models, a univariate model and a multivariate model. We show that these two models are equivalent and that one can be converted to the other by means of a discrete Fourier transform. We give a new, more general definition of a linear finite dynamical system and we give a necessary and sufficient condition for such a system to be a fixed point system, that is, all cycles are of length one. We show how this result for generalized linear systems can be used to determine when certain nonlinear systems (monomial dynamical systems over finite fields) are fixed point systems. We also show how it is possible to determine in polynomial time when an ordinary linear system (defined over a finite field) is a fixed point system. We conclude with a necessary condition for a univariate finite dynamical system to be a fixed point system
Local, multi-resolution detection of network communities by Markovian dynamics
Complex networks are used to represent systems from many disciplines,
including biology, physics, medicine, engineering and the social sciences;
Many real-world networks are organised into densely connected communi-
ties, whose composition gives some insight into the underlying network.
Most approaches for nding such communities do so by partitioning the
network into disjoint subsets, at the cost of requiring global information
and that nodes belong to exactly one community. In recent years, some effort
has been devoted towards the development of local methods, but these
are either limited in resolution or ignore relevant network features such as
directedness.
Here we show that introducing a dynamic process onto the network allows
us to de ne a community quality function severability which is inherently
multi-resolution, takes into account edge-weight and direction, can accommodate
overlapping communities and orphan nodes and crucially does not
require global knowledge. Both constructive and real-world examples|
drawn from elds as diverse as image segmentation, metabolic networks
and word association|are used to illustrate the characteristics of this approach.
We envision this approach as a starting point for the future analysis
of both evolving networks and networks too large to be readily analysed as
a whole (e.g. the World Wide Web).Open Acces
kLog: A Language for Logical and Relational Learning with Kernels
We introduce kLog, a novel approach to statistical relational learning.
Unlike standard approaches, kLog does not represent a probability distribution
directly. It is rather a language to perform kernel-based learning on
expressive logical and relational representations. kLog allows users to specify
learning problems declaratively. It builds on simple but powerful concepts:
learning from interpretations, entity/relationship data modeling, logic
programming, and deductive databases. Access by the kernel to the rich
representation is mediated by a technique we call graphicalization: the
relational representation is first transformed into a graph --- in particular,
a grounded entity/relationship diagram. Subsequently, a choice of graph kernel
defines the feature space. kLog supports mixed numerical and symbolic data, as
well as background knowledge in the form of Prolog or Datalog programs as in
inductive logic programming systems. The kLog framework can be applied to
tackle the same range of tasks that has made statistical relational learning so
popular, including classification, regression, multitask learning, and
collective classification. We also report about empirical comparisons, showing
that kLog can be either more accurate, or much faster at the same level of
accuracy, than Tilde and Alchemy. kLog is GPLv3 licensed and is available at
http://klog.dinfo.unifi.it along with tutorials
Recommended from our members
Formal Analysis of Arithmetic Circuits using Computer Algebra - Verification, Abstraction and Reverse Engineering
Despite a considerable progress in verification and abstraction of random and control logic, advances in formal verification of arithmetic designs have been lagging. This can be attributed mostly to the difficulty in an efficient modeling of arithmetic circuits and datapaths without resorting to computationally expensive Boolean methods, such as Binary Decision Diagrams (BDDs) and Boolean Satisfiability (SAT), that require โbit blastingโ, i.e., flattening the design to a bit-level netlist. Approaches that rely on computer algebra and Satisfiability Modulo Theories (SMT) methods are either too abstract to handle the bit-level nature of arithmetic designs or require solving computationally expensive decision or satisfiability problems. The work proposed in this thesis aims at overcoming the limitations of analyzing arithmetic circuits, specifically at the post-synthesized phase. It addresses the verification, abstraction and reverse engineering problems of arithmetic circuits at an algebraic level, treating an arithmetic circuit and its specification as a properly constructed algebraic system. The proposed technique solves these problems by function extraction, i.e., by deriving arithmetic function computed by the circuit from its low-level circuit implementation using computer algebraic rewriting technique. The proposed techniques work on large integer arithmetic circuits and finite field arithmetic circuits, up to 512-bit wide containing millions of logic gates
BCH ๋ถํธ๋ฅผ ์ด์ฉํ FrodoKEM์ ์ฑ๋ฅ ๊ฐ์ ๋ฐ ๋ํ ๋น๊ต๋ฅผ ์ํ ํฉ์ฑํจ์์ ์ํ ๋ถํธ ํจ์์ ๋ฏธ๋๋งฅ์ค ๊ทผ์ฌ
ํ์๋
ผ๋ฌธ (๋ฐ์ฌ) -- ์์ธ๋ํ๊ต ๋ํ์ : ๊ณต๊ณผ๋ํ ์ ๊ธฐยท์ ๋ณด๊ณตํ๋ถ, 2020. 8. ๋
ธ์ข
์ .In this dissertation, two main contributions are given as;
Performance improvement of FrodoKEM using Gray and error-correcting codes (ECCs).
Optimal minimax polynomial approximation of sign function by composite polynomial for homomorphic comparison.
First, modification of FrodoKEM using Gray codes and ECCs is studied. Lattice-based scheme is one of the most promising schemes for post-quantum cryptography (PQC). Among many lattice-based cryptosystems, FrodoKEM is a well-known key-encapsulation mechanism (KEM) based on (plain) learning with errors problems and is advantageous in that the hardness is based on the problem of unstructured lattices. Many lattice-based cryptosystems adopt ECCs to improve their performance, such as LAC, Three Bears, and Round5 which were presented in the NIST PQC Standardization Round 2 conference. However, for lattice-based cryptosystems that do not use ring structures such as FrodoKEM, it is difficult to use ECCs because the number of transmitted symbols is small. In this dissertation, I propose a method to apply Gray and ECCs to FrodoKEM by encoding the bits converted from the encrypted symbols. It is shown that the proposed method improves the security level and/or the bandwidth of FrodoKEM, and 192 message bits, 50\% more than the original 128 bits, can be transmitted using one of the modified Frodo-640's.
Second, an optimal minimax polynomial approximation of sign function by a composite polynomial is studied. The comparison function of the two numbers is one of the most commonly used operations in many applications including deep learning and data processing systems. Several studies have been conducted to efficiently evaluate the comparison function in homomorphic encryption schemes which only allow addition and multiplication for the ciphertext. Recently, new comparison methods that approximate sign function using composite polynomial in the homomorphic encryption, called homomorphic comparison operation, were proposed and it was proved that the methods have optimal asymptotic complexity. In this dissertation, I propose new optimal algorithms that approximate the sign function in the homomorphic encryption by using composite polynomials of the minimax approximate polynomials, which are constructed by the modified Remez algorithm. It is proved that the number of required non-scalar multiplications and depth consumption for the proposed algorithms are less than those for any methods that use a composite polynomial of component polynomials with odd degree terms approximating the sign function, respectively. In addition, an optimal polynomial-time algorithm for the proposed homomorphic comparison operation is proposed by using dynamic programming. As a result of numerical analysis, for the case that I want to minimize the number of non-scalar multiplications, the proposed algorithm reduces the required number of non-scalar multiplications and depth consumption by about 33% and 35%, respectively, compared to those for the previous work. In addition, for the case that I want to minimize the depth consumption, the proposed algorithm reduces the required number of non-scalar multiplications and depth consumption by about 10% and 47%, respectively, compared to those for the previous work.์ด ํ์ ๋
ผ๋ฌธ์์๋, ๋ค์ ๋ ๊ฐ์ง ๋ด์ฉ์ด ์ฐ๊ตฌ๋์๋ค.
FrodoKEM์ ๊ทธ๋ ์ด ๋ถํธ ๋ฐ ์ค๋ฅ์ ์ ๋ถํธ๋ฅผ ์ฌ์ฉํ์ฌ ๊ฐ์
๋ํ ๋น๊ต ์ฐ์ฐ์ ์ํด ํฉ์ฑ ๋คํญ์์ ์ฌ์ฉํ ๋ถํธ ํจ์์ ์ต์ ๋ฏธ๋๋งฅ์ค ๋คํญ์ ๊ทผ์ฌ
๋จผ์ , ๊ทธ๋ ์ด ๋ถํธ ๋ฐ ์ค๋ฅ์ ์ ๋ถํธ๋ฅผ ์ฌ์ฉํ์ฌ FrodoKEM์ ๋ณํ์ํค๋ ๋ฐฉ๋ฒ์ด ์ฐ๊ตฌ๋์๋ค. ๊ฒฉ์๊ธฐ๋ฐ์ํธ๋ ๊ฐ์ฅ ์ ๋งํ ํฌ์คํธ ์์ ์ํธ ์คํด์ด๋ค. ๋ง์ ๊ฒฉ์๊ธฐ๋ฐ์ํธ ์์คํ
์ค์์ FrodoKEM์ learning with errors (LWE) ๋ฌธ์ ์ ๊ธฐ๋ฐ์ ๋ ์ ์๋ ค์ง ํค-์บก์ํ ๋ฉ์ปค๋์ฆ (KEM) ์ด๋ฉฐ ๊ตฌ์กฐ๋ฅผ ๊ฐ์ง ์์ ๊ฒฉ์ ๋ฌธ์ ์ ๊ธฐ๋ฐ์ ๋ ์ด๋ ค์์ ๊ฐ์ง๋ค๋ ์ฅ์ ์ด ์๋ค. NIST ํฌ์คํธ ์์ ์ํธ ํ์คํ ๋ผ์ด๋ 2์ ๋ฐํ๋ LAC, Three Bears, Round5์ ๊ฐ์ด ์ฑ๋ฅ ๊ฐ์ ์ ์ํด ์ค๋ฅ์ ์ ๋ถํธ๋ฅผ ์ฌ์ฉํ๋ ๋ง์ ์ํธ ์์คํ
๋ค์ด ์๋ค. ๊ทธ๋ฌ๋ FrodoKEM๊ณผ ๊ฐ์ด ๋ง ๊ตฌ์กฐ๋ฅผ ์ฌ์ฉํ์ง ์๋ ๊ฒฉ์๊ธฐ๋ฐ ์ํธ ์์คํ
์์๋ ์ ์ก๋๋ ์ฌ๋ณผ ๊ฐ์๊ฐ ์๊ธฐ ๋๋ฌธ์ ์ค๋ฅ์ ์ ๋ถํธ๋ฅผ ์ฌ์ฉํ๊ธฐ ์ด๋ ต๋ค. ๋๋ ์ํธํ๋ ์ฌ๋ณผ๋ก๋ถํฐ ๋ณํ๋ ๋นํธ๋ค์ ๋ถํธํํ์ฌ ์ค๋ฅ์ ์ ๋ถํธ์ ๊ทธ๋ ์ด ๋ถํธ๋ฅผ FrodoKEM์ ์ ์ฉํ๋ ๋ฐฉ๋ฒ์ ์ ์ํ์๋ค. ์ ์ํ ์๊ณ ๋ฆฌ์ฆ์ FrodoKEM์ ๋ณด์์ฑ ๋ ๋ฒจ ํน์ ๋ฐ์ดํฐ์ ์ก๋์ ํฅ์ํ๊ณ ๊ธฐ์กด 128๋นํธ๋ณด๋ค 50\% ๋ง์ 192๋นํธ๊ฐ ๋ณํ๋ Frodo-640์์ ์ ์ก๋ ์ ์์์ ๋ณด์ฌ์ฃผ์๋ค.
๋ ๋ฒ์งธ๋ก, ํฉ์ฑ ๋คํญ์์ ์ฌ์ฉํ ๋ถํธ ํจ์์ ์ต์ ๋ฏธ๋๋งฅ์ค ๋คํญ์ ๊ทผ์ฌ๊ฐ ์ฐ๊ตฌ๋์๋ค. ๋ ์ซ์์ ๋น๊ต ํจ์๋ ๋ฅ๋ฌ๋ ๋ฐ ๋ฐ์ดํฐ ์ฒ๋ฆฌ ์์คํ
์ ํฌํจํ ๋ง์ ์์ฉ์์ ๊ฐ์ฅ ๋ง์ด ์ฌ์ฉ๋๋ ์ฐ์ฐ ์ค ํ๋์ด๋ค. ์ํธ๋ฌธ ์์์์ ๋ง์
๊ณผ ๊ณฑ์
๋ง ์ง์ํ๋ ๋ํ ์ํธ์์ ๋น๊ต ํจ์๋ฅผ ํจ์จ์ ์ผ๋ก ๊ณ์ฐํ๋ ๋ช๋ช ์ฐ๊ตฌ๊ฐ ์งํ๋์๋ค. ๋ํ ์ํธ์์ ํฉ์ฑ ๋คํญ์์ ์ฌ์ฉํ์ฌ ๋ถํธ ํจ์๋ฅผ ๊ทผ์ฌํ๋ ๋น๊ต ๋ฐฉ๋ฒ์ ๋ํ ๋น๊ต ์ฐ์ฐ์ด๋ผ๊ณ ๋ถ๋ฆฌ๋๋ฐ ์ต๊ทผ ์๋ก์ด ๋ํ ๋น๊ต ์ฐ์ฐ ๋ฐฉ๋ฒ์ด ์ ์๋์๊ณ ๊ทธ ๋ฐฉ๋ฒ์ด ์ต์ ์ ๊ทผ์ ๋ณต์ก๋๋ฅผ ๊ฐ์ง๋ค๋ ๊ฒ์ด ์ฆ๋ช
๋์๋ค. ๋ณธ ๋
ผ๋ฌธ์์ ๋๋ ๋ฏธ๋๋งฅ์ค ๊ทผ์ฌ๋คํญ์์ ํฉ์ฑํจ์๋ฅผ ์ฌ์ฉํ์ฌ ๋ํ์ํธ์์ ๋ถํธ ํจ์๋ฅผ ๊ทผ์ฌํ๋ ์๋ก์ด ์ต์ ์๊ณ ๋ฆฌ์ฆ์ ์ ์ํ๋ค. ๋ฏธ๋๋งฅ์ค ๊ทผ์ฌ ๋คํญ์์ modified Remez ์๊ณ ๋ฆฌ์ฆ์ ์ํด ์ป์ ์ ์๋ค.
์ ์ํ๋ ์๊ณ ๋ฆฌ์ฆ์ ์์์ ๋ถํธ ํจ์๋ฅผ ๊ทผ์ฌํ๋ ํ์ ์ฐจ์ ํญ๋ค์ ๊ฐ์ง ๋คํญ์์ ํฉ์ฑ ๋คํญ์์ ์ฌ์ฉํ๋ ๋ฐฉ๋ฒ๋ณด๋ค ๋ ์ ์ ๋์ค์นผ๋ผ ๊ณฑ ๋ฐ ๋์ค ์๋ชจ๋ฅผ ์ฌ์ฉํ๋ค๋ ๊ฒ์ด ์ฆ๋ช
๋์๋ค. ๋ํ, ์ ์ํ ๋ํ ๋น๊ต ์ฐ์ฐ์ ๋ํ ๋ค์ด๋๋ฏน ํ๋ก๊ทธ๋๋ฐ์ ์ฌ์ฉํ ์ต์ ๋คํญ์๊ฐ ์๊ณ ๋ฆฌ์ฆ์ด ์ ์๋์๋ค. ์์น ๋ถ์ ๊ฒฐ๊ณผ, ๋์ค์นผ๋ผ ๊ณฑ ๊ฐ์๋ฅผ ์ต์๋ก ํ ๋, ์ ์ํ๋ ์๊ณ ๋ฆฌ์ฆ์ ํ์ํ ๋์ค์นผ๋ผ ๊ณฑ ๊ฐ์์ ๋์ค ์๋ชจ๋ฅผ ๊ธฐ์กด ๋ฐฉ๋ฒ์ ํ์ํ ๋์ค์นผ๋ผ ๊ณฑ ๊ฐ์ ๋ฐ ๋์ค ์๋ชจ๋ณด๋ค ๊ฐ๊ฐ 33%, 35%์ ๋ ๊ฐ์์ํจ๋ค. ๋ํ, ๋์ค ์๋ชจ๋ฅผ ์ต์๋ก ํ ๋, ์ ์ํ๋ ์๊ณ ๋ฆฌ์ฆ์ ํ์ํ ๋์ค์นผ๋ผ ๊ณฑ ๊ฐ์์ ๋์ค ์๋ชจ๋ฅผ ๊ธฐ์กด ๋ฐฉ๋ฒ์ ํ์ํ ๋์ค์นผ๋ผ ๊ณฑ ๊ฐ์ ๋ฐ ๋์ค ์๋ชจ๋ณด๋ค ๊ฐ๊ฐ 10%, 47%์ ๋ ๊ฐ์์ํจ๋ค.1 Introduction 1
1.1 Background 1
1.2 Overview of Dissertation 3
1.3 Notations 5
2 Preliminaries 6
2.1 NIST Post-Quantum Cryptography Standardization 6
2.1.1 Background 6
2.1.2 Categories for Security Level 7
2.1.3 List of Algorithms in NIST PQC Round 2 8
2.2 Public-Key Encryption and Key-Encapsulation Mechanism 10
2.3 Lattice-Based Cryptogaphy 13
2.3.1 Learning with Errors Problem 13
2.3.2 Overview of FrodoPKE Algorithm 14
2.3.3 Parameters of FrodoKEM 17
2.4 BCH and Gray Codes 18
2.5 Fully Homomorphic Encryption 20
2.5.1 Homomorphic Encryption 20
2.5.2 Comparison Operation in Fully Homomorphic Encryption 21
2.6 Approximation Theory 22
2.7 Algorithms for Minimax Approximation 24
3. Improvement of FrodoKEM Using Gray and BCH Codes 29
3.1 Modification of FrodoKEM with Gray and Error-Correcting Codes 33
3.1.1 Viewing FrodoPKE as a Digital Communication System 33
3.1.2 Error-Correcting Codes for FrodoPKE 34
3.1.3 Gray Coding 36
3.1.4 IND-CCA Security of Modified FrodoKEM 38
3.1.5 Evaluation of DFR 40
3.1.6 Error Dependency 43
3.2 Performance Improvement of FrodoKEM Using Gray and BCH Codes 43
3.2.1 Improving the Security Level of FrodoKEM 43
3.2.2 Increasing the Message Size of Frodo-640 47
3.2.3 Reducing the Bandwidth of Frodo-640 50
4. Homomorphic Comparison Using Optimal Composition of Minimax Approximate Polynomials 54
4.1 Introduction 54
4.1.1 Previous Works 55
4.1.2 My Contributions 56
4.2 Approximation of Sign Function by Using Optimal Composition of Minimax Approximate Polynomials 58
4.2.1 New Approximation Method for Sine Function Using Composition of the Minimax Approximate Polynomials 58
4.2.2 Optimality of Approximation of the Sign Function by a Minimax Composite Polynomial 64
4.2.3 Achieving Polynomial-Time Algorithm for New Approximation Method by Using Dynamic Programming 68
4.3 Numerical Results 80
4.3.1 Computation of the Required Non-Scalar Multiplications and Depth Consumption 81
4.3.2 Comparisons 81
5. Conclusions 88
Abstract (In Korean) 97Docto
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