16,778 research outputs found

    FLAIM: A Multi-level Anonymization Framework for Computer and Network Logs

    Full text link
    FLAIM (Framework for Log Anonymization and Information Management) addresses two important needs not well addressed by current log anonymizers. First, it is extremely modular and not tied to the specific log being anonymized. Second, it supports multi-level anonymization, allowing system administrators to make fine-grained trade-offs between information loss and privacy/security concerns. In this paper, we examine anonymization solutions to date and note the above limitations in each. We further describe how FLAIM addresses these problems, and we describe FLAIM's architecture and features in detail.Comment: 16 pages, 4 figures, in submission to USENIX Lis

    수치 문자열의 순서를 보존하는 매칭 기법

    Get PDF
    학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2014. 2. 박근수.String matching is a fundamental problem in computer science and has been extensively studied. Sometimes a string consists of numeric values instead of alphabet characters, and we are interested in some trends in the text rather than specific patterns. We introduce a new string matching problem called order-preserving matching on numeric strings, where a pattern matches a text substring of the same length if the relative orders in the substring coincide with those of the pattern. Order-preserving matching is applicable to many scenarios such as stock price analysis and musical melody matching. In this thesis, we define order-preserving matching in numeric strings, and present various representations of order relations and efficient algorithms of order-preserving matching with those representations. For single pattern matching, we give an O(n log m) time algorithm with the prefix representation based on the KMP algorithm, and optimize it further to obtain O(n + m log m) time with the nearest neighbor representation, where n and m are the lengths of the text and the pattern, respectively. For multiple pattern matching, we present an O((n+m) log m) time algorithm with the prefix representation based on the Aho-Corasick algorithm, where n is the text length and m is the sum of the lengths of the patterns. Our algorithms are presented in binary order relations first, and then extended to ternary order relations. With our extensions, the time complexities in binary order relations can be achieved in ternary order relations as well.Contents Abstract i Contents ii List of Figures iv List of Tables v Chapter 1 Introduction 1 1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Contribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.3 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.4 Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Chapter 2 Order-Preserving Pattern Matching 6 2.1 Preliminaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.1 Definitions of Order Relations . . . . . . . . . . . . . . . . 6 2.1.2 Number of Representations . . . . . . . . . . . . . . . . . 8 2.1.3 Problem Formulation . . . . . . . . . . . . . . . . . . . . 8 2.2 O(n logm) Algorithm . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2.1 Prefix Representation . . . . . . . . . . . . . . . . . . . . 10 2.2.2 KMP Failure Function . . . . . . . . . . . . . . . . . . . . 11 ii 2.2.3 Text Search . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.2.4 Construction of KMP Failure Function . . . . . . . . . . . 15 2.2.5 Correctness and Time Complexity . . . . . . . . . . . . . 17 2.3 O(n + mlogm) Algorithm . . . . . . . . . . . . . . . . . . . . . . 17 2.3.1 Nearest Neighbor Representation . . . . . . . . . . . . . . 17 2.3.2 Text Search . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.3.3 Construction of KMP Failure Function . . . . . . . . . . . 21 2.3.4 Correctness and Time Complexity . . . . . . . . . . . . . 22 2.3.5 Generalized Order-Preserving Matching . . . . . . . . . . 23 2.3.6 Remark on Alphabet Size . . . . . . . . . . . . . . . . . . 23 Chapter 3 Order-Preserving Multiple Pattern Matching 25 3.1 O((n + m) logm) Algorithm . . . . . . . . . . . . . . . . . . . . . 25 3.1.1 Aho-Corasick Automaton . . . . . . . . . . . . . . . . . . 26 3.1.2 Aho-Corasick Failure Function . . . . . . . . . . . . . . . 27 3.1.3 Text Search . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.1.4 Construction of Aho-Corasick Failure Function . . . . . . 29 3.1.5 Correctness and Time Complexity . . . . . . . . . . . . . 32 Chapter 4 Extensions to Ternary Order Relations 33 4.1 Preliminaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 4.2 Extension of Prefix Representation . . . . . . . . . . . . . . . . . 34 4.3 Extension of Nearest Neighbor Representation . . . . . . . . . . . 38 4.4 Generalized Order-Preserving KMP Algorithm . . . . . . . . . . 42 Chapter 5 Conclusion 45 Bibliography 47Docto

    From Cooperative Scans to Predictive Buffer Management

    Get PDF
    In analytical applications, database systems often need to sustain workloads with multiple concurrent scans hitting the same table. The Cooperative Scans (CScans) framework, which introduces an Active Buffer Manager (ABM) component into the database architecture, has been the most effective and elaborate response to this problem, and was initially developed in the X100 research prototype. We now report on the the experiences of integrating Cooperative Scans into its industrial-strength successor, the Vectorwise database product. During this implementation we invented a simpler optimization of concurrent scan buffer management, called Predictive Buffer Management (PBM). PBM is based on the observation that in a workload with long-running scans, the buffer manager has quite a bit of information on the workload in the immediate future, such that an approximation of the ideal OPT algorithm becomes feasible. In the evaluation on both synthetic benchmarks as well as a TPC-H throughput run we compare the benefits of naive buffer management (LRU) versus CScans, PBM and OPT; showing that PBM achieves benefits close to Cooperative Scans, while incurring much lower architectural impact.Comment: VLDB201

    Bernoulli measure on strings, and Thompson-Higman monoids

    Full text link
    The Bernoulli measure on strings is used to define height functions for the dense R- and L-orders of the Thompson-Higman monoids M_{k,1}. The measure can also be used to characterize the D-relation of certain submonoids of M_{k,1}. The computational complexity of computing the Bernoulli measure of certain sets, and in particular, of computing the R- and L-height of an element of M_{k,1} is investigated.Comment: 27 pages

    Traffic engineering in multihomed sites

    Get PDF
    It is expected that IPv6 multihomed sites will obtain as many global prefixes as direct providers they have, so traffic engineering techniques currently used in IPv4 multihomed sites is no longer suitable. However, traffic engineering is required for several reasons, and in particular, for being able to properly support multimedia communications. In this paper we present a framework for traffic engineering in IPv6 multihomed sites with multiple global prefixes. Within this framework, we have included several tools such as DNS record manipulation and proper configuration of the policy table defined in RFC 3484. To provide automation in the management of traffic engineering, we analyzed the usage of two mechanisms to configure the policy table.This work has been partly supported by the European Union under the E-Next Project FP6-506869 and by the OPTINET6 project TIC-2003-09042-C03-01.Publicad

    End-Site Routing Support for IPv6 Multihoming

    Get PDF
    Multihoming is currently widely used to provide fault tolerance and traffic engineering capabilities. It is expected that, as telecommunication costs decrease, its adoption will become more and more prevalent. Current multihoming support is not designed to scale up to the expected number of multihomed sites, so alternative solutions are required, especially for IPv6. In order to preserve interdomain routing scalability, the new multihoming solution has to be compatible with Provider Aggregatable addressing. However, such addressing scheme imposes the configuration of multiple prefixes in multihomed sites, which in turn causes several operational difficulties within those sites that may even result in communication failures when all the ISPs are working properly. In this paper we propose the adoption of Source Address Dependent routing within the multihomed site to overcome the identified difficulties.Publicad
    corecore