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  • 201.
    Johansson, Philip
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Blomqvist, Niklas
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    An Approach to Achieve DBMS Vendor Independence for Ides AB's Platform2017Självständigt arbete på grundnivå (högskoleexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Software that is developed with few integration capabilities to different user interfaces or database vendors might lose market share in the long run. To stay competitive, companies that find themselves in situations like these might need to look at options to increase their alternatives. This thesis aims to present and evaluate how Ides AB could achieve vendor independence as it relates to database integration.The proposed solution is based on pre-existing code from an existing product and thus includes theory about the methods and details how one can read, understand and analyse code. The outcome is presented with code examples to give the reader a clear and concise understanding. In the evaluation phase, we take other related work into consideration as it relates to our thesis focus. The proposed approach presented consists of a class to represent different database vendors. It also consists of abstract functions handling the interaction between different databases. Which database the class interacts with is determined by the connection established. The approach also includes what is possible to make database agnostic verified by an evaluation.

  • 202.
    Jägenstedt, Gabriel
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Analysis and Simulation of Threats in an Open, Decentralized, Distributed Spam Filtering System2012Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The existance of spam email has gone from a fairly small amounts of afew hundred in the late 1970’s to several billions per day in 2010. Thiscontinually growing problem is of great concern to both businesses andusers alike.One attempt to combat this problem comes with a spam filtering toolcalled TRAP. The primary design goal of TRAP is to enable tracking ofthe reputation of mail senders in a decentralized and distributed fashion.In order for the tool to be useful, it is important that it does not haveany security issues that will let a spammer bypass the protocol or gain areputation that it should not have.As a piece of this puzzle, this thesis makes an analysis of TRAP’s protocoland design in order to find threats and vulnerabilies capable of bypassingthe protocol safeguards. Based on these threats we also evaluate possiblemitigations both by analysis and simulation. We have found that althoughthe protocol was not designed with regards to certain attacks on the systemitself most of the attacks can be fairly easily stopped.The analysis shows that by adding cryptographic defenses to the protocola lot of the threats would be mitigated. In those cases where cryptographywould not suffice it is generally down to sane design choices in the implementationas well as not always trusting that a node is being truthful andfollowing protocol.

  • 203. Beställ onlineKöp publikationen >>
    Kargén, Ulf
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Scalable Dynamic Analysis of Binary Code2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In recent years, binary code analysis, i.e., applying program analysis directly at the machine code level, has become an increasingly important topic of study. This is driven to a large extent by the information security community, where security auditing of closed-source software and analysis of malware are important applications. Since most of the high-level semantics of the original source code are lost upon compilation to executable code, static analysis is intractable for, e.g., fine-grained information flow analysis of binary code. Dynamic analysis, however, does not suffer in the same way from reduced accuracy in the absence of high-level semantics, and is therefore also more readily applicable to binary code. Since fine-grained dynamic analysis often requires recording detailed information about every instruction execution, scalability can become a significant challenge. In this thesis, we address the scalability challenges of two powerful dynamic analysis methods whose widespread use has, so far, been impeded by their lack of scalability: dynamic slicing and instruction trace alignment. Dynamic slicing provides fine-grained information about dependencies between individual instructions, and can be used both as a powerful debugging aid and as a foundation for other dynamic analysis techniques. Instruction trace alignment provides a means for comparing executions of two similar programs and has important applications in, e.g., malware analysis, security auditing, and plagiarism detection. We also apply our work on scalable dynamic analysis in two novel approaches to improve fuzzing — a popular random testing technique that is widely used in industry to discover security vulnerabilities.

    To use dynamic slicing, detailed information about a program execution must first be recorded. Since the amount of information is often too large to fit in main memory, existing dynamic slicing methods apply various time-versus-space trade-offs to reduce memory requirements. However, these trade-offs result in very high time overheads, limiting the usefulness of dynamic slicing in practice. In this thesis, we show that the speed of dynamic slicing can be greatly improved by carefully designing data structures and algorithms to exploit temporal locality of programs. This allows avoidance of the expensive trade-offs used in earlier methods by accessing recorded runtime information directly from secondary storage without significant random-access overhead. In addition to being a standalone contribution, scalable dynamic slicing also forms integral parts of our contributions to fuzzing. Our first contribution uses dynamic slicing and binary code mutation to automatically turn an existing executable into a test generator. In our experiments, this new approach to fuzzing achieved about an order of magnitude better code coverage than traditional mutational fuzzing and found several bugs in popular Linux software. The second work on fuzzing presented in this thesis uses dynamic slicing to accelerate the state-of-the-art fuzzer AFL by focusing the fuzzing effort on previously unexplored parts of the input space.

    For the second dynamic analysis technique whose scalability we sought to improve — instruction trace alignment — we employed techniques used in speech recognition and information retrieval to design what is, to the best of our knowledge, the first general approach to aligning realistically long program traces. We show in our experiments that this method is capable of producing meaningful alignments even in the presence of significant syntactic differences stemming from, for example, the use of different compilers or optimization levels.

    Delarbeten
    1. Efficient Utilization of Secondary Storage for Scalable Dynamic Slicing
    Öppna denna publikation i ny flik eller fönster >>Efficient Utilization of Secondary Storage for Scalable Dynamic Slicing
    2014 (Engelska)Ingår i: Proceedings of the 2014 IEEE 14th International Working Conference on Source Code Analysis and Manipulation / [ed] Randall Bilof, IEEE , 2014, s. 155-164Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Dynamic program slicing is widely recognized as a powerful aid for e.g. Program comprehension during debugging. However, its widespread use has been impeded in part by scalability issues that occur when constructing the dynamic dependence graph necessary to compute dynamic slices. A few seconds of execution time on a modern CPU can easily yield dynamic dependence graphs on the order of tens of gigabytes in size. Existing methods either produce imprecise slices, incur large time overheads during slice computation, or run out of memory for long program executions. By carefully designing our method to take advantage of locality, we are able to efficiently use secondary storage for dynamic dependence graphs, thus allowing our method to scale to long program executions. Our prototype implementation runs directly on x86 executables, eliminating problems with e.g. Binary-only libraries. We show in our experiments that graphs can be constructed for program runs with billions of executed instructions, at slowdowns ranging from 62x to 173x. Our optimized format also allows graphs to be traversed at speeds of several million dependence edges per second.

    Ort, förlag, år, upplaga, sidor
    IEEE, 2014
    Nyckelord
    binary analysis, debugging, dynamic dependence graph, dynamic slicing, x86
    Nationell ämneskategori
    Datavetenskap (datalogi)
    Identifikatorer
    urn:nbn:se:liu:diva-117289 (URN)10.1109/SCAM.2014.24 (DOI)000358876700020 ()978-0-7695-5304-7 (ISBN)
    Konferens
    14th IEEE International Working Conference on Source Code Analysis and Manipulation, Victoria, British Columbia, Canada, September 28-29, 2014
    Tillgänglig från: 2015-04-22 Skapad: 2015-04-22 Senast uppdaterad: 2019-08-16
    2. Towards Robust Instruction-Level Trace Alignment of Binary Code
    Öppna denna publikation i ny flik eller fönster >>Towards Robust Instruction-Level Trace Alignment of Binary Code
    2017 (Engelska)Ingår i: PROCEEDINGS OF THE 2017 32ND IEEE/ACM INTERNATIONAL CONFERENCE ON AUTOMATED SOFTWARE ENGINEERING (ASE17), IEEE , 2017, s. 342-352Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Program trace alignment is the process of establishing a correspondence between dynamic instruction instances in executions of two semantically similar but syntactically different programs. In this paper we present what is, to the best of our knowledge, the first method capable of aligning realistically long execution traces of real programs. To maximize generality, our method works entirely on the machine code level, i.e. it does not require access to source code. Moreover, the method is based entirely on dynamic analysis, which avoids the many challenges associated with static analysis of binary code, and which additionally makes our approach inherently resilient to e.g. static code obfuscation. Therefore, we believe that our trace alignment method could prove to be a useful aid in many program analysis tasks, such as debugging, reverse-engineering, investigating plagiarism, and malware analysis. We empirically evaluate our method on 11 popular Linux programs, and show that it is capable of producing meaningful alignments in the presence of various code transformations such as optimization or obfuscation, and that it easily scales to traces with tens of millions of instructions.

    Ort, förlag, år, upplaga, sidor
    IEEE, 2017
    Serie
    IEEE ACM International Conference on Automated Software Engineering, ISSN 1527-1366
    Nationell ämneskategori
    Datavetenskap (datalogi)
    Identifikatorer
    urn:nbn:se:liu:diva-143959 (URN)10.1109/ASE.2017.8115647 (DOI)000417469700038 ()978-1-5386-2684-9 (ISBN)978-1-5386-3976-4 (ISBN)
    Konferens
    32nd IEEE/ACM International Conference on Automated Software Engineering (ASE)
    Tillgänglig från: 2017-12-29 Skapad: 2017-12-29 Senast uppdaterad: 2019-08-16
    3. Turning programs against each other: high coverage fuzz-testing using binary-code mutation and dynamic slicing
    Öppna denna publikation i ny flik eller fönster >>Turning programs against each other: high coverage fuzz-testing using binary-code mutation and dynamic slicing
    2015 (Engelska)Ingår i: 2015 10TH JOINT MEETING OF THE EUROPEAN SOFTWARE ENGINEERING CONFERENCE AND THE ACM SIGSOFT SYMPOSIUM ON THE FOUNDATIONS OF SOFTWARE ENGINEERING (ESEC/FSE 2015) PROCEEDINGS, New York, NY, USA: Association for Computing Machinery (ACM), 2015, s. 782-792Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Mutation-based fuzzing is a popular and widely employed black-box testing technique for finding security and robustness bugs in software. It owes much of its success to its simplicity; a well-formed seed input is mutated, e.g. through random bit-flipping, to produce test inputs. While reducing the need for human effort, and enabling security testing even of closed-source programs with undocumented input formats, the simplicity of mutation-based fuzzing comes at the cost of poor code coverage. Often millions of iterations are needed, and the results are highly dependent on configuration parameters and the choice of seed inputs. In this paper we propose a novel method for automated generation of high-coverage test cases for robustness testing. Our method is based on the observation that, even for closed-source programs with proprietary input formats, an implementation that can generate well-formed inputs to the program is typically available. By systematically mutating the program code of such generating programs, we leverage information about the input format encoded in the generating program to produce high-coverage test inputs, capable of reaching deep states in the program under test. Our method works entirely at the machine-code level, enabling use-cases similar to traditional black-box fuzzing. We have implemented the method in our tool MutaGen, and evaluated it on 7 popular Linux programs. We found that, for most programs, our method improves code coverage by one order of magnitude or more, compared to two well-known mutation-based fuzzers. We also found a total of 8 unique bugs.

    Ort, förlag, år, upplaga, sidor
    New York, NY, USA: Association for Computing Machinery (ACM), 2015
    Nyckelord
    Fuzz testing, fuzzing, black-box, dynamic slicing, program mutation
    Nationell ämneskategori
    Datavetenskap (datalogi)
    Identifikatorer
    urn:nbn:se:liu:diva-128810 (URN)10.1145/2786805.2786844 (DOI)000382568700067 ()978-1-4503-3675-8 (ISBN)
    Konferens
    10th Joint Meeting on Foundations of Software Engineering
    Tillgänglig från: 2016-05-31 Skapad: 2016-05-31 Senast uppdaterad: 2019-08-16
    4. Speeding Up Bug Finding using Focused Fuzzing
    Öppna denna publikation i ny flik eller fönster >>Speeding Up Bug Finding using Focused Fuzzing
    2019 (Engelska)Ingår i: Proceedings of the 13th International Conference on Availability, Reliability and Security, ACM Digital Library, 2019, artikel-id 7Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Greybox fuzzing has recently emerged as a scalable and practical approach to finding security bugs in software. For example, AFL — the current state-of-the-art greybox fuzzer — has found hundreds of vulnerabilities in popular software since its release in 2013. The combination of lightweight coverage instrumentation and a simple evolutionary algorithm allows AFL to quickly generate inputs that exercise new code. AFL also obviates the need to manually set ad-hoc fuzzing ratios, which has been a major limitation of classical black-box fuzzers. Instead, AFL's first fuzzing pass exhaustively applies a set of mutations to every byte of a program input. While this approach allows for more thorough exploration of the input space, and therefore improves the chances of finding complex bugs, it also drastically slows down the fuzzing progress for "heavyweight" programs, or programs that take large inputs. This makes AFL less suitable for fuzzing input formats with large size overhead, such as various document formats. In this paper, we propose focused fuzzing as a practical trade-off between thoroughness and speed, for fuzzers that employ input mutation. We extend the notion of code coverage to individual bytes of input, and show how forward dynamic slicing can be used to efficiently determine the set of program instructions that are affected by a particular input byte. This information can then be used to restrict expensive mutations to a small subset of input bytes. We implement focused fuzzing on top of AFL, and evaluate it on four "real-life" Linux programs. Our evaluation shows that focused fuzzing noticeably improves bug discovery, compared to vanilla AFL.

    Ort, förlag, år, upplaga, sidor
    ACM Digital Library, 2019
    Nyckelord
    fuzzing, AFL, dynamic slicing, focused fuzzing
    Nationell ämneskategori
    Datavetenskap (datalogi)
    Identifikatorer
    urn:nbn:se:liu:diva-152737 (URN)10.1145/3230833.3230867 (DOI)000477981800013 ()978-1-4503-6448-5 (ISBN)
    Konferens
    13th International Conference on Availability, Reliability and Security, Hamburg, Germany, August 27 - 30, 2018
    Tillgänglig från: 2018-11-19 Skapad: 2018-11-19 Senast uppdaterad: 2019-08-19
  • 204.
    Kargén, Ulf
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Efficient Utilization of Secondary Storage for Scalable Dynamic Slicing2014Ingår i: Proceedings of the 2014 IEEE 14th International Working Conference on Source Code Analysis and Manipulation / [ed] Randall Bilof, IEEE , 2014, s. 155-164Konferensbidrag (Refereegranskat)
    Abstract [en]

    Dynamic program slicing is widely recognized as a powerful aid for e.g. Program comprehension during debugging. However, its widespread use has been impeded in part by scalability issues that occur when constructing the dynamic dependence graph necessary to compute dynamic slices. A few seconds of execution time on a modern CPU can easily yield dynamic dependence graphs on the order of tens of gigabytes in size. Existing methods either produce imprecise slices, incur large time overheads during slice computation, or run out of memory for long program executions. By carefully designing our method to take advantage of locality, we are able to efficiently use secondary storage for dynamic dependence graphs, thus allowing our method to scale to long program executions. Our prototype implementation runs directly on x86 executables, eliminating problems with e.g. Binary-only libraries. We show in our experiments that graphs can be constructed for program runs with billions of executed instructions, at slowdowns ranging from 62x to 173x. Our optimized format also allows graphs to be traversed at speeds of several million dependence edges per second.

  • 205.
    Kargén, Ulf
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    InputTracer: A Data-flow Analysis Tool for Manual Program Comprehension of x86 Binaries2012Ingår i: Proceedings of the 2012 IEEE 12th International Working Conference on Source Code Analysis and Manipulation / [ed] Juan E. Guerrero, IEEE , 2012, s. 138-143Konferensbidrag (Refereegranskat)
    Abstract [en]

    Third-party security analysis of closed-source programs has become an important part of a defense-in-depth approach to software security for many companies. In the absence of efficient tools, the analysis has generally been performed through manual reverse engineering of the machine code. As reverse engineering is an extremely time-consuming and costly task, much research has been performed to develop more powerful methods for analysis of program binaries. One such popular method is dynamic taint analysis (DTA), which is a type of runtime data-flow analysis, where certain input data is marked as tainted. By tracking the flow of tainted data, DTA can, for instance, be used to determine which computations in a program are affected by a certain part of the input. In this paper we present InputTracer, a tool that utilizes DTA for aiding in manual program comprehension and analysis of unmodified x86 executables running in Linux. A brief overview of dynamic taint analysis is given, followed by a description of the tool and its implementation. We also demonstrate the tool’s ability to provide exact information on the origin of tainted data through a detailed use case, where the tool is used to find the root cause of a memory corruption bug.

  • 206.
    Kargén, Ulf
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Speeding Up Bug Finding using Focused Fuzzing2019Ingår i: Proceedings of the 13th International Conference on Availability, Reliability and Security, ACM Digital Library, 2019, artikel-id 7Konferensbidrag (Refereegranskat)
    Abstract [en]

    Greybox fuzzing has recently emerged as a scalable and practical approach to finding security bugs in software. For example, AFL — the current state-of-the-art greybox fuzzer — has found hundreds of vulnerabilities in popular software since its release in 2013. The combination of lightweight coverage instrumentation and a simple evolutionary algorithm allows AFL to quickly generate inputs that exercise new code. AFL also obviates the need to manually set ad-hoc fuzzing ratios, which has been a major limitation of classical black-box fuzzers. Instead, AFL's first fuzzing pass exhaustively applies a set of mutations to every byte of a program input. While this approach allows for more thorough exploration of the input space, and therefore improves the chances of finding complex bugs, it also drastically slows down the fuzzing progress for "heavyweight" programs, or programs that take large inputs. This makes AFL less suitable for fuzzing input formats with large size overhead, such as various document formats. In this paper, we propose focused fuzzing as a practical trade-off between thoroughness and speed, for fuzzers that employ input mutation. We extend the notion of code coverage to individual bytes of input, and show how forward dynamic slicing can be used to efficiently determine the set of program instructions that are affected by a particular input byte. This information can then be used to restrict expensive mutations to a small subset of input bytes. We implement focused fuzzing on top of AFL, and evaluate it on four "real-life" Linux programs. Our evaluation shows that focused fuzzing noticeably improves bug discovery, compared to vanilla AFL.

  • 207.
    Kargén, Ulf
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Towards Accurate Binary Correspondence using Runtime-Observed Values2016Ingår i: 32nd IEEE International Conference on Software Maintenance and Evolution, IEEE Computer Society, 2016, s. 438-442Konferensbidrag (Refereegranskat)
    Abstract [en]

    Establishing binary correspondence is the process of finding corresponding pairs of program elements, e.g., functions or individual instructions, between two semantically equivalent (or nearly-equivalent) but syntactically different program binaries. The binary-correspondence problem has applications in many fields, e.g., plagiarism and clone detection, reverse engineering, and security, and has therefore received significant attention both in industry and academia. Most binary-correspondence methods used in practice today are based on static analysis of the control structure in binaries. Unfortunately, such methods are often highly sensitive to syntactic differences between binaries, and discrepancies in the control structure due to, for example, using different compilers or optimization levels often severely reduce their accuracy. Several recent works have therefore proposed using dynamic analysis and comparing runtime-observed results of computations to establish binary correspondence. In this paper, we study the discriminative power of runtime-values for matching instructions in binaries, and propose several ways to increase the accuracy of value-based analyses. By utilizing techniques from the field of information retrieval combined with dynamic data-flow analysis, we improve matching accuracy by up to 55% in our experiments.

  • 208.
    Kargén, Ulf
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Towards Robust Instruction-Level Trace Alignment of Binary Code2017Ingår i: PROCEEDINGS OF THE 2017 32ND IEEE/ACM INTERNATIONAL CONFERENCE ON AUTOMATED SOFTWARE ENGINEERING (ASE17), IEEE , 2017, s. 342-352Konferensbidrag (Refereegranskat)
    Abstract [en]

    Program trace alignment is the process of establishing a correspondence between dynamic instruction instances in executions of two semantically similar but syntactically different programs. In this paper we present what is, to the best of our knowledge, the first method capable of aligning realistically long execution traces of real programs. To maximize generality, our method works entirely on the machine code level, i.e. it does not require access to source code. Moreover, the method is based entirely on dynamic analysis, which avoids the many challenges associated with static analysis of binary code, and which additionally makes our approach inherently resilient to e.g. static code obfuscation. Therefore, we believe that our trace alignment method could prove to be a useful aid in many program analysis tasks, such as debugging, reverse-engineering, investigating plagiarism, and malware analysis. We empirically evaluate our method on 11 popular Linux programs, and show that it is capable of producing meaningful alignments in the presence of various code transformations such as optimization or obfuscation, and that it easily scales to traces with tens of millions of instructions.

  • 209.
    Kargén, Ulf
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Turning programs against each other: high coverage fuzz-testing using binary-code mutation and dynamic slicing2015Ingår i: 2015 10TH JOINT MEETING OF THE EUROPEAN SOFTWARE ENGINEERING CONFERENCE AND THE ACM SIGSOFT SYMPOSIUM ON THE FOUNDATIONS OF SOFTWARE ENGINEERING (ESEC/FSE 2015) PROCEEDINGS, New York, NY, USA: Association for Computing Machinery (ACM), 2015, s. 782-792Konferensbidrag (Refereegranskat)
    Abstract [en]

    Mutation-based fuzzing is a popular and widely employed black-box testing technique for finding security and robustness bugs in software. It owes much of its success to its simplicity; a well-formed seed input is mutated, e.g. through random bit-flipping, to produce test inputs. While reducing the need for human effort, and enabling security testing even of closed-source programs with undocumented input formats, the simplicity of mutation-based fuzzing comes at the cost of poor code coverage. Often millions of iterations are needed, and the results are highly dependent on configuration parameters and the choice of seed inputs. In this paper we propose a novel method for automated generation of high-coverage test cases for robustness testing. Our method is based on the observation that, even for closed-source programs with proprietary input formats, an implementation that can generate well-formed inputs to the program is typically available. By systematically mutating the program code of such generating programs, we leverage information about the input format encoded in the generating program to produce high-coverage test inputs, capable of reaching deep states in the program under test. Our method works entirely at the machine-code level, enabling use-cases similar to traditional black-box fuzzing. We have implemented the method in our tool MutaGen, and evaluated it on 7 popular Linux programs. We found that, for most programs, our method improves code coverage by one order of magnitude or more, compared to two well-known mutation-based fuzzers. We also found a total of 8 unique bugs.

  • 210.
    Karlsson, Axel
    et al.
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Wångblad, Christian
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    En kvantitativ jämförelse av opensource-navigeringsprogram med OpenStreetMap som kartdatabas2018Självständigt arbete på grundnivå (högskoleexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Under detta arbete testades och utvärderades navigeringsverktyg mot varandra för att sedan se om de, tillsammans med kartsystemet OpenStreetMap, kunde fungera som substitut till programmet Google Maps och användas för att navigera vid en rutt. Navigeringssystemen som jämfördes hade alla öppen källkod och det gick att sätta upp och köra lokalt på en personlig dator med hjälp av stickprovsdata för att navigera i olika delar av världen.

  • 211.
    Karresand, Martin
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    File Type Identification of Data Fragments by Their Binary Structure2006Ingår i: IEEE Systems, Man and Cybernetics Society Information Assurance Workshop,2006, Piscataway, NJ, USA: IEEE , 2006, s. 140-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Rapidly gaining information superiority is vital when fighting an enemy, but current computer forensics tools, which require file headers or a working file system to function, do not enable us to quickly map out the contents of corrupted hard disks or other fragmented storage media found at crime scenes. The lack of proper tools slows down the hunt for information, which would otherwise help in gaining the upper hand against IT based perpetrators. To address this problem, this paper presents an algorithm which allows categorization of data fragments based solely on their structure, without the need for any meta data. The algorithm is based on measuring the rate of change of the byte contents of digital media and extends the byte frequency distribution based Oscar method presented in an earlier paper. The evaluation of the new method shows a detection rate of 99.2 %, without generating any false positives, when used to scan for JPEG data. The slowest implementation of the algorithm scans a 72.2 MB file in approximately 2.5 seconds and scales linearly.

  • 212.
    Karresand, Martin
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Oscar - File Type and Camera Identification Using the Structure of Binary Data Fragments2006Ingår i: First Conference on Advances in Computer Security and Forensics, ACSF 2006 / [ed] John Haggerty, Madjid Merabti, Liverpool, UK: School of Computing and Mathematical Sciences, John Moores University , 2006, s. 11-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Mapping out the contents of fragmented storage media is hard if the file system has been corrupted, especially as the current forensic tools rely on meta information to do their job. If it were possible to find all fragments belonging to a certain file type, it might also be possible to recover a lost file. The Oscar method identifies the file type of data fragments based on their structure. This paper presents an improvement of the Oscar method. The new version is built on using 2-grams to create a model of different file types. The method is evaluated for JPEG, Windows executables, and zip files, reaching a 100% detection rate with 0.12% false positives for JPEG. We also use the method to identify the camera make used to capture a JPEG picture from a fragment of the picture.

  • 213.
    Karresand, Martin
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Oscar - File Type Identification of Binary Data in Disk Clusters and RAM Pages2006Ingår i: IFIP TC-11 International Information Security Conference SEC,2006, New York, NY, USA: Springer , 2006, s. 413-Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper proposes a method, called Oscar, for determining the probable file type of binary data fragments. The Oscar method is based on building models, called centroids, of the mean and standard deviation of the byte frequency distribution of different file types. A weighted quadratic distance metric is then used to measure the distance between the centroid and sample data fragments. If the distance falls below a threshold, the sample is categorized as probably belonging to the modelled file type. Oscar is tested using JPEG pictures and is shown to give a high categorization accuracy, i.e. high detection rate and low false positives rate. By using a practical example we demonstrate how to use the Oscar method to prove the existence of known pictures based on fragments of them found in RAM and the swap partition of a computer.

  • 214.
    Karresand, Martin
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Oscar — Using Byte Pairs to Find File Type and Camera Make of Data Fragments2007Ingår i: EC2ND 2006: Proceedings of the Second European Conference on Computer Network Defence, in conjunction with the First Workshop on Digital Forensics and Incident Analysis Faculty of Advanced Technology, University of Glamorgan, Wales, UK / [ed] Andrew Blyth, Iain Sutherland, Springer London, 2007, s. 85-94Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Mapping out the contents of fragmented storage media is hard if the file system has been corrupted, especially as the current forensic tools rely on meta information to do their job. If it was possible to find all fragments belonging to a certain file type, it would also be possible to recover a lost file. Such a tool could for example be used in the hunt for child pornography. The Oscar method identifies the file type of data fragments based solely on statistics calculated from their structure. The method does not need any meta data to work. We have previously used the byte frequency distribution and the rate of change between consecutive bytes as basis for the statistics, as well as calculating the 2-gram frequency distribution to create a model of different file types. This paper present a variant of the 2-gram method, in that it uses a dynamic smoothing factor. In this way we take the amount of data used to create the centroid into consideration. A previous experiment on file type identification is extended with .mp3 files reaching a detection rate of 76\% with a false positives rate of 0.4\%. We also use the method to identify the camera make used to capture a .jpg picture from a fragment of the picture. The result shows that we can clearly separate a picture fragment coming from a Fuji or Olympus cameras from a fragment of a picture of the other camera makes used in our test.

  • 215.
    Karresand, Martin
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Reassembly of Fragmented JPEG Images Containing Restart Markers2008Ingår i: Proceedings - 4th Annual European Conference on Computer Network Defense, EC2ND 2008, Los Alamitos, CA, USA: IEEE Computer Society , 2008, s. 25-32Konferensbidrag (Refereegranskat)
    Abstract [en]

    A fragmented JPEG image is currently not possible to reassemble without knowing the ordering of the fragments. This is a problem for the police when they search for illegal digital images. This paper presents a method to reassemble fragmented JPEG images containing restart markers. Empirical evaluations show that it is possible to reassemble images taken from a set containing fragments of several images.

  • 216.
    Keivani, Omid
    et al.
    Wichita State University, USA.
    Peña, Jose M.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Uni- and Multi-Dimensional Clustering Via Bayesian Networks2016Ingår i: Unsupervised Learning Algorithms / [ed] Emre Celebi, Kemal Aydin, Cham: Springer, 2016, s. 163-192Kapitel i bok, del av antologi (Refereegranskat)
  • 217.
    Keskisärkkä, Robin
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Interaktiva och kognitiva system. Linköpings universitet, Tekniska fakulteten.
    Li, Huanyu
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Cheng, Sijin
    Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Carlsson, Niklas
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Lambrix, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    An Ontology for Ice Hockey2019Ingår i: ISWC 2019 Satellites: Proceedings of the ISWC 2019 Satellite Tracks (Posters & Demonstrations, Industry, and Outrageous Ideas) co-located with 18th International Semantic Web Conference (ISWC 2019), 2019, s. 13-16Konferensbidrag (Refereegranskat)
    Abstract [en]

    Ice hockey is a highly popular sport that has seen significant increase in the use of sport analytics. To aid in such analytics, most major leagues collect and share increasing amounts of play-by-play data and other statistics. Additionally, some websites specialize in making such data available to the public in user-friendly forms. However, these sites fail to capture the semantic information of the data, and cannot be used to support more complex data requirements. In this paper, we present the design and development of an ice hockey ontology that provides improved knowledge representation, enables intelligent search and information acquisition, and helps when using information from multiple databases. Our ontology is substantially larger than previous ice hockey ontologies (that cover only a small part of the domain) and provides a formal and explicit representation of the ice hockey domain, supports information retrieval, data reuse, and complex performance metrics.

  • 218.
    Khodari, Mohammad
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Decentralized firmware attestation for in-vehicle networks2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Today's vehicles are controlled by several so called electronic control units (ECUs). ECUs can be seen as small computers that work together in order to perform a common task. They control everything from critical tasks such as engine control to less critical functionality such as window control. The most prominent trend that can be observed today is the development of self-driving functionality. Due to inherent complexity of self-driving functionality, ECUs are becoming more dependent on each other. A fundamental problem in today's vehicles is that there does not exist any efficient way of achieving trust in the vehicle's internal-network. How can ECUs be assured that the output of other ECUs can be trusted? If an ECU produces the wrong output when the vehicle is in autonomous mode it can lead to the vehicle performing unsafe actions and risking the lives of the passengers and driver.

    In this thesis we evaluate different already established firmware attestation solutions for achieving trust in a decentralized network. Furthermore, three new firmware attestation solutions specially tailored for the automotive domain are proposed. We demonstrate that all the found existing solutions have a fundamental flaw, they all have a single point of failure. Meaning that if you eliminate the correct node, the entire attestation process stops functioning. Thus, a new more robust solution specially tailored for the automotive domain needed to be developed. Three different consistency verification mechanisms were designed. One parallel solution, one serial solution and one merkle-tree solution. Two of the three proposed solutions, the parallel solution and serial solution, were implemented and assessed. Two tests were conducted, a detection performance test and a timing performance test.

    By assessing the detection performance test and timing performance test of the serial and parallel solutions, it was concluded that the parallel solution showed a significant improvement in both stability and performance over the serial solution.

  • 219.
    Klingström, Tomas
    et al.
    Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Soldatova, Larissa
    Aberystwyth University, UK.
    Stevens, Robert
    Universtity of Manchester, UK.
    Roos, T. Erik
    University of Groningen, The Netherlands.
    Swertz, Morris A.
    University of Groningen, The Netherlands.
    Müller, Kristian M.
    University of Potsdam, Germany.
    Kalas, Matus
    University of Bergen, Norway.
    Lambrix, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Taussig, Michael J.
    Babraham Bioscience Technologies, Cambridge, UK.
    Litton, Jan-Eric
    Karolinska Institutet, Stockholm, Sweden.
    Landegren, Ulf
    Uppsala University, Sweden.
    Bongcam-Rudloff, Erik
    Swedish University of Agricultural Sciences and Uppsala University, Sweden.
    Workshop on laboratory protocol standards for the molecular methods database2013Ingår i: New Biotechnology, ISSN 1871-6784, E-ISSN 1876-4347, Vol. 30, nr 2, s. 109-113Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Management of data to produce scientific knowledge is a key challenge for biological research in the 21st century. Emerging high-throughput technologies allow life science researchers to produce big data at speeds and in amounts that were unthinkable just a few years ago. This places high demands on all aspects of the workflow: from data capture (including the experimental constraints of the experiment), analysis and preservation, to peer-reviewed publication of results. Failure to recognise the issues at each level can lead to serious conflicts and mistakes; research may then be compromised as a result of the publication of non-coherent protocols, or the misinterpretation of published data. In this report, we present the results from a workshop that was organised to create an ontological data-modelling framework for Laboratory Protocol Standards for the Molecular Methods Database (MolMeth). The workshop provided a set of short- and long-term goals for the MolMeth database, the most important being the decision to use the established EXACT description of biomedical ontologies as a starting point.

  • 220.
    Knuth, Magnus
    et al.
    Hasso Plattner Institute, University of PotsdamPotsdamGermany.
    Hartig, Olaf
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Scheduling Refresh Queries for Keeping Results from a SPARQL Endpoint Up-to-Date2016Ingår i: On the Move to Meaningful Internet Systems: OTM 2016 Conferences, 2016, Vol. 10033, s. 780-791Konferensbidrag (Refereegranskat)
    Abstract [en]

    Many datasets change over time. As a consequence, long-running applications that cache and repeatedly use query results obtained from a SPARQL endpoint may resubmit the queries regularly to ensure up-to-dateness of the results. While this approach may be feasible if the number of such regular refresh queries is manageable, with an increasing number of applications adopting this approach, the SPARQL endpoint may become overloaded with such refresh queries. A more scalable approach would be to use a middle-ware component at which the applications register their queries and get notified with updated query results once the results have changed. Then, this middle-ware can schedule the repeated execution of the refresh queries without overloading the endpoint. In this paper, we study the problem of scheduling refresh queries for a large number of registered queries by assuming an overload-avoiding upper bound on the length of a regular time slot available for testing refresh queries. We investigate a variety of scheduling strategies and compare them experimentally in terms of time slots needed before they recognize changes and number of changes that they miss.

  • 221.
    Kodoth, Sruthi
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Jiménez Ramos, Juan Manuel
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Enhance user experience based on traffic in operator network2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The increasing usage of numerous mobile applications can cause impairments in cellular network performance. Such impairments result in performance degradation that can reduce the satisfaction level of subscribers. Consequently, subscribers may switch between different network operators to get good user experience. Thus the success of any network operator will primarily depend on the ability to ensure quality of experience (QoE), where QoE is a measure of the subscriber’s satisfaction level and is closely related to the performance of networks. Our work aims to identify the key performance indicators (KPI)which in turn can comprehensively model the QoE. Since the popularity of web browsing and video streaming applications continues to increase rapidly, analyzing the KPI of such applications will help to identify the parameters which degrade network performance the most. The analyzed KPIs are tested with different user equipments and different network load. This thesis work also includes tuning the Radio Network Controller (RNC) parameters to analyze the variation in user experience. Important performance metrics of webbrowsing and video streaming applications have been considered to measure the QoE. Atest environment for QoE estimation was developed using real Radio Network Controller(RNC) and simulatable models of the Core Network(CN) and User Equipments (UEs). Simulations with this test set up and subsequent analyses help to identify some of the RNC parameters which influence the QoE. Furthermore, simulatable models of widely used UEssuch as iPhone 6 and iPhone 3 were included in the test environment to assess their relative performance for web browsing and video streaming applications. Our simulation results confirm the superior performance of iPhone 6 which reinforces the reliability of our testbed. Finally, the simulations also helped to illustrate the degradation in QoE caused by the increase in RNC load.

  • 222.
    Korzun, Dmitry
    et al.
    Department of Computer Science, Petrozavodsk State University, Petrozavodsk, Russian Federation.
    Kuptsov, Dmitriy
    Helsinki Institute for Information Technology, Helsinki, Finland.
    Gurtov, Andrei
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    A comparative simulation study of deterministic and stochastic strategies for reduction of packet reordering in multipath data streaming2016Ingår i: International journal of simulation. Systems, Science and Technology, ISSN 1473-8031, E-ISSN 1473-804X, Vol. 17, nr 33, s. 10.1-10.8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multipath routing gains clear network performance advantages for data streaming in networked systems with high path diversity. The level of packet reordering, however, becomes higher: distant packets are reordered, the application performance is reduced due to head-of-line blocking at the destination, and a large resequencing buffer is needed for sorting incoming packets. In this paper, we study by simulation the stochastic compensation effect to reduce packet reordering. If a source randomizes packet scheduling into multiple paths of random transmission delays, then these two sides of randomness “quench” each other. We perform comparison experiments to test this hypothesis in various multipath configurations, focusing on deterministic vs. randomized strategies of packet scheduling. The experiments confirm the existence of the stochastic compensation effect and its considerable influence on the application performance. © 2016, UK Simulation Society. All rights reserved.

  • 223. Beställ onlineKöp publikationen >>
    Krishnamoorthi, Vengatanathan
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Efficient and Adaptive Content Delivery of Linear and Interactive Branched Videos2016Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Video streaming over the Internet has gained tremendous popularity over recent years and currently constitutes the majority of Internet traffic. The on-demand delivery of high quality video streaming has been enabled by a combination of consistent improvements in residential download speeds, HTTP-based Adaptive Streaming (HAS), extensive content caching, and the use of Content Distribution Networks (CDNs). However, as large-scale on-demand streaming is gaining popularity, several important questions and challenges remain unanswered, including determining how the infrastructure can best be leveraged to provide users with the best possible playback experience. In addition, it is important to develop new techniques and protocols that facilitate the next generation of streaming applications. Innovative services such as interactive branched streaming are gaining popularity and are expected to be the next big thing in on-demand entertainment.

    The major contributions of this thesis are in the area of efficient content delivery of video streams using HAS. To address the two challenges above, the work utilizes a combination of different methods and tools, ranging from real-world measurements, characterization of system performance, proof-of-concept implementations, protocol optimization, and evaluation under realistic environments. First, through careful experiments, we evaluate the performance impact and interaction of HAS clients with proxy caches. Having studied the typical interactions between HAS clients and caches, we then design and evaluate content-aware policies to be used by the proxy caches, which parse the client requests and prefetch the chunks that are most likely to be requested next. In addition, we also design cooperative policies in which clients and proxies share information about the playback session. Our evaluations reveal that, in general, the bottleneck location and network conditions play central roles in which policy choices are most advantageous, and the location of the bottlenecks significantly impact the relative performance differences between policy classes. We also show that careful design and policy selection is important when trying to enhance HAS performance using proxy assistance.

    Second, this thesis proposes, models, designs, and evaluates novel streaming applications such as interactive branched videos. In such videos, users can influence the content that is being shown to them. We design and evaluate careful prefetching policies that provides seamless playback even when the users defer their path choices to the last possible moment. We derive optimized prefetching policies using an optimization framework, design and implement effective buffer management techniques for seamless playback at branch points, and use parallel TCP connections to achieve efficient buffer workahead. Through performance evaluations, we show that our policies can effectively prefetch data of carefully adapted qualities along multiple alternative paths so to ensure seamless playback, offering users a pleasant viewing experience without playback interruptions.

  • 224. Beställ onlineKöp publikationen >>
    Krishnamoorthi, Vengatanathan
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Efficient HTTP-based Adaptive Streaming of Linear and Interactive Videos2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Online video streaming has gained tremendous popularity over recent years and currently constitutes the majority of Internet traffic. As large-scale on-demand streaming continues to gain popularity, several important questions and challenges remain unanswered. This thesis addresses open questions in the areas of efficient content delivery for HTTP-based Adaptive Streaming (HAS) from different perspectives (client, network and content provider) and in the design, implementation, and evaluation of interactive streaming applications over HAS.

    As streaming usage scales and new streaming services emerge, continuous improvements are required to both the infrastructure and the techniques used to deliver high-quality streams. In the context of Content Delivery Network (CDN) nodes or proxies, this thesis investigates the interaction between HAS clients and proxy caches. In particular, we propose and evaluate classes of content-aware and collaborative policies that take advantage of information that is already available, or share information among elements in the delivery chain, where all involved parties can benefit. Asides from the users’ playback experience, it is also important for content providers to minimize users’ startup times. We have designed and evaluated different classes of client-side policies that can prefetch data from the videos that the users are most likely to watch next, without negatively affecting the currently watched video. To help network providers to monitor and ensure that their customers enjoy good playback experiences, we have proposed and evaluated techniques that can be used to estimate clients’ current buffer conditions. Since several services today stream over HTTPS, our solution is adapted to predict client buffer conditions by only observing encrypted network-level traffic. Our solution allows the operator to identify clients with low-buffer conditions and implement policies that help avoid playback stalls.

    The emergence of HAS as the de facto standard for delivering streaming content also opens the door to use it to deliver the next generation of streaming services, such as various forms of interactive services. This class of services is gaining popularity and is expected to be the next big thing in entertainment. For the area of interactive streaming, this thesis proposes, models, designs, and evaluates novel streaming applications such as interactive branched videos and multi-video stream bundles. For these applications, we design and evaluate careful prefetching policies that provides seamless playback (without stalls or switching delay) even when interactive branched video viewers defer their choices to the last possible moment and when users switches between alternative streams within multi-video stream bundles. Using optimization frameworks, we design and implement effective buffer management techniques for seamless playback experiences and evaluate several tradeoffs using our policies.  

    Delarbeten
    1. Helping Hand or Hidden Hurdle: Proxy-assisted HTTP-based Adaptive Streaming Performance
    Öppna denna publikation i ny flik eller fönster >>Helping Hand or Hidden Hurdle: Proxy-assisted HTTP-based Adaptive Streaming Performance
    Visa övriga...
    2013 (Engelska)Ingår i: Modeling, Analysis & Simulation of Computer and Telecommunication Systems (MASCOTS), 2013 IEEE 21st International Symposium, IEEE , 2013, s. 182-191Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    HTTP-based Adaptive Streaming (HAS) has become a widely-used video delivery technology. Use of HTTP enables relatively easy firewall/NAT traversal and content caching. While caching is an important aspect of HAS, there is not much public research on the performance impact proxies and their policies have on HAS. In this paper we build an experimental framework using open source Squid proxies and the most recent Open Source Media Framework (OSMF). A range of content-aware policies can be implemented in the proxies and tested, while the player software can be instrumented to measure performance as seen at the client. Using this framework, the paper makes three main contributions. First, we present a scenario-based performance evaluation of the latest version of the OSMF player. Second, we quantify the benefits using different proxy-assisted solutions, including basic best effort policies and more advanced content quality aware prefetching policies. Finally, we present and evaluate a cooperative framework in which clients and proxies share information to improve performance. In general, the bottleneck location and network conditions play central roles in which policy choices are most advantageous, as they significantly impact the relative performance differences between policy classes. We conclude that careful design and policy selection is important when trying to enhance HAS performance using proxy assistance.

    Ort, förlag, år, upplaga, sidor
    IEEE, 2013
    Serie
    Modeling, Analysis, and Simulation of Com puter and Telecommunications Systems, ISSN 1526-7539
    Nyckelord
    HTTP-based adaptive streaming, Proxy assisted
    Nationell ämneskategori
    Datavetenskap (datalogi)
    Identifikatorer
    urn:nbn:se:liu:diva-105282 (URN)10.1109/MASCOTS.2013.26 (DOI)000347906000019 ()978-0-7695-5102-9 (ISBN)978-1-4799-1209-4 (ISBN)
    Konferens
    IEEE 21st International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunication Systems (MASCOTS), 14-16 August 2013, San Francisco, CA, USA
    Tillgänglig från: 2014-03-15 Skapad: 2014-03-15 Senast uppdaterad: 2019-07-03Bibliografiskt granskad
    2. Bandwidth-aware Prefetching for Proactive Multi-video Preloading and Improved HAS Performance
    Öppna denna publikation i ny flik eller fönster >>Bandwidth-aware Prefetching for Proactive Multi-video Preloading and Improved HAS Performance
    Visa övriga...
    2015 (Engelska)Ingår i: Proceedings of the ACM International Conference on Multimedia (ACM Multimedia), New York, USA: Association for Computing Machinery (ACM), 2015, s. 551-560Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    This paper considers the problem of providing users playing one streaming video the option of instantaneous and seamless playback of alternative videos. Recommendation systems can easily provide a list of alternative videos, but there is little research on how to best eliminate the startup time for these alternative videos. The problem is motivated by services that want to retain increasingly impatient users, who frequently watch the beginning of multiple videos, before viewing a video to the end. We present the design, implementation, and evaluation of an HTTP-based Adaptive Streaming (HAS) solution that provides careful prefetching and buffer management. We also present the design and evaluation of three fundamental policy classes that provide different tradeoffs between how aggressively new alternative videos are prefetched versus the importance of ensuring high playback quality. We show that our solution allows us to reduce the startup times of alternative videos by an order of magnitude and effectively adapt the quality such as to ensure the highest possible playback quality of the video being viewed. By improving the channel utilization we also address the discrimination problem that HAS clients often suffer from, allowing us to in some cases simultaneously improve the playback quality of the video being viewed and provide the value-added service of allowing instantaneous playback of the prefetched alternative videos.

    Ort, förlag, år, upplaga, sidor
    New York, USA: Association for Computing Machinery (ACM), 2015
    Nyckelord
    HTTP-based adaptive streaming (HAS); Bandwidth-aware prefetching; Multi-video preloading; Seamless playback
    Nationell ämneskategori
    Datorsystem
    Identifikatorer
    urn:nbn:se:liu:diva-128168 (URN)10.1145/2733373.2806270 (DOI)000387861300064 ()978-1-4503-3459-4 (ISBN)
    Konferens
    ACM Multimedia 2015
    Tillgänglig från: 2016-05-20 Skapad: 2016-05-19 Senast uppdaterad: 2018-02-06
    3. BUFFEST: Predicting Buffer Conditions and Real-time Requirements of HTTP(S) Adaptive Streaming Clients
    Öppna denna publikation i ny flik eller fönster >>BUFFEST: Predicting Buffer Conditions and Real-time Requirements of HTTP(S) Adaptive Streaming Clients
    2017 (Engelska)Ingår i: MMSys’17, Proceedings of the 8th ACM on Multimedia Systems Conference, ACM , 2017, s. 76-87Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Stalls during video playback are perhaps the most important indicator of a client's viewing experience. To provide the best possible service, a proactive network operator may therefore want to know the buffer conditions of streaming clients and use this information to help avoid stalls due to empty buffers. However, estimation of clients' buffer conditions is complicated by most streaming services being rate-adaptive, and many of them also encrypted. Rate adaptation reduces the correlation between network throughput and client buffer conditions. Usage of HTTPS prevents operators from observing information related to video chunk requests, such as indications of rate adaptation or other HTTP-level information.; AB@This paper presents BUFFEST, a novel classification framework that can be used to classify and predict streaming clients' buffer conditions from both HTTP and HTTPS traffic. To illustrate the tradeoffs between prediction accuracy and the available information used by classifiers, we design and evaluate classifiers of different complexity. At the core of BUFFEST is an event-based buffer emulator module for detailed analysis of clients' buffer levels throughout a streaming session, as well as for automated training and evaluation of online packet-level classifiers. We then present example results using simple threshold-based classifiers and machine learning classifiers that only use TCP/IP packet-level information. Our results are encouraging and show that BUFFEST can distinguish streaming clients with low buffer conditions from clients with significant buffer margin during a session even when HTTPS is used.

    Ort, förlag, år, upplaga, sidor
    ACM, 2017
    Nyckelord
    Buffer condition estimation, HTTP-based adaptive streaming, HTTPS, Real-time requirements
    Nationell ämneskategori
    Data- och informationsvetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-140913 (URN)10.1145/3083187.3083193 (DOI)978-1-4503-5002-0 (ISBN)
    Konferens
    8th ACM Conference on Multimedia Systems, June 20-23, 2017, Taipei, Taiwan
    Tillgänglig från: 2017-09-15 Skapad: 2017-09-15 Senast uppdaterad: 2018-02-06
    4. Empowering the creative user: personalized HTTP-based adaptive streaming of multi-path nonlinear video
    Öppna denna publikation i ny flik eller fönster >>Empowering the creative user: personalized HTTP-based adaptive streaming of multi-path nonlinear video
    Visa övriga...
    2013 (Engelska)Ingår i: FhMN '13 Proceedings of the 2013 ACM SIGCOMM workshop on Future human-centric multimedia networking, New York, USA: Association for Computing Machinery (ACM), 2013, s. 53-58Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    This paper presents the design, implementation, and validation of a novel system that supports streaming and playout of personalized, multi-path, nonlinear video. In contrast to regular video, in which the file content is played sequentially, our design allows multiple nonlinear video sequences of the underlying (linear) video to be stitched together and played in any personalized order, and clients can be provided multiple path choices. The design combines the ideas of HTTP-based adaptive streaming (HAS) and multi-path nonlinear video. Personalization of the content is achieved with the use of a customized metafile, which is downloaded separately from the underlying media and the manifest file that defines the HAS structure. An extension to the user interface allows path choices to be presented to and made by the user. Novel buffer management and prefetching policies are used to ensure seamless uninterrupted playback regardless of client path choices, even under scenarios in which clients defer their choices until the last possible moment. Our solution allows creative home users to easily create their own multi-path nonlinear video, opening the door to an endless possibility of new opportunities and media forms.

    Ort, förlag, år, upplaga, sidor
    New York, USA: Association for Computing Machinery (ACM), 2013
    Nyckelord
    HTTP-based adaptive streaming, Multi-path video, Nonlinear video, Seamless playback
    Nationell ämneskategori
    Datorsystem
    Identifikatorer
    urn:nbn:se:liu:diva-96695 (URN)10.1145/2491172.2491183 (DOI)978-1-4503-2183-9 (ISBN)
    Konferens
    ACM SIGCOMM 2013, Hong Kong, China, 12-16 August 2013
    Anmärkning

    Nominated as the Best Paper in the 2013 ACM SIGCOMM workshop on Future human-centric Multimedia Networking (FhMN)

    Tillgänglig från: 2013-08-23 Skapad: 2013-08-23 Senast uppdaterad: 2018-02-06Bibliografiskt granskad
    5. Quality-adaptive prefetching for interactive branched video using HTTP-based Adaptive Streaming
    Öppna denna publikation i ny flik eller fönster >>Quality-adaptive prefetching for interactive branched video using HTTP-based Adaptive Streaming
    Visa övriga...
    2014 (Engelska)Ingår i: MM 2014 - Proceedings of the 2014 ACM Conference on Multimedia, Association for Computing Machinery, Inc , 2014, s. 317-326Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Interactive branched video that allows users to select their own paths through the video, provides creative content designers with great personalization opportunities; however, such video also introduces significant new challenges for the system developer. For example, without careful prefetching and buffer management, the use of multiple alternative playback paths can easily result in playback interruptions. In this paper, we present a full implementation of an interactive branched video player using HTTP-based Adaptive Streaming (HAS) that provides seamless playback even when the users defer their branch path choices to the last possible moment. Our design includes optimized prefetching policies that we derive under a simple optimization framework, effective buffer management of prefetched data, and the use of parallel TCP connections to achieve efficient buffer workahead. Through performance evaluation under a wide range of scenarios, we show that our optimized policies can effectively prefetch data of carefully selected qualities along multiple alternative paths such as to ensure seamless playback, offering users a pleasant viewing experience without playback interruptions.

    Ort, förlag, år, upplaga, sidor
    Association for Computing Machinery, Inc, 2014
    Serie
    MM 2014 - Proceedings of the 2014 ACM Conference on Multimedia
    Nyckelord
    Branched video; HTTP-based Adaptive Streaming (HAS); Multipath/nonlinear streaming; Seamless playback
    Nationell ämneskategori
    Data- och informationsvetenskap
    Identifikatorer
    urn:nbn:se:liu:diva-116449 (URN)10.1145/2647868.2654951 (DOI)2-s2.0-84913597570 (Scopus ID)9781450330633 (ISBN)
    Konferens
    2014 ACM Conference on Multimedia, MM 2014
    Tillgänglig från: 2015-03-27 Skapad: 2015-03-26 Senast uppdaterad: 2018-02-06
    6. Optimized Adaptive Streaming of Multi-video Stream Bundles
    Öppna denna publikation i ny flik eller fönster >>Optimized Adaptive Streaming of Multi-video Stream Bundles
    2017 (Engelska)Ingår i: IEEE transactions on multimedia, ISSN 1520-9210, E-ISSN 1941-0077, Vol. 19, nr 7, s. 1637-1653Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In contrast to traditional video, multi-view video streaming allows viewers to interactively switch among multiple perspectives provided by different cameras. One approach to achieve such a service is to encode the video from all of the cameras into a single stream, but this has the disadvantage that only a portion of the received video data will be used, namely that required for the selected view at each point in time. In this paper, we introduce the concept of a multi-video stream bundle that consists of multiple parallel video streams that are synchronized in time, each providing the video from a different camera capturing the same event or movie. For delivery we leverage the adaptive features and time-based chunking of HTTP-based adaptive streaming, but now employing adaptation in both content and rate. Users are able to change their viewpoint on-demand and the client player adapts the rate at which data are retrieved from each stream based on the users current view, the probabilities of switching to other views, and the users current bandwidth conditions. A crucial component of such a system is the prefetching policy. For this we present an optimization model as well as a simpler heuristic that can balance the playback quality and the probability of playback interruptions. After analytically and numerically characterizing the optimal solution, we present a prototype implementation and sample results. Our prefetching and buffer management solution is shown to provide close to seamless playback switching when there is sufficient bandwidth to prefetch the parallel streams.

    Ort, förlag, år, upplaga, sidor
    IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2017
    Nyckelord
    HTTP-based adaptive streaming (HAS); multi-view video streaming; multi-video stream bundles; optimized prefetching; seamless stream switching
    Nationell ämneskategori
    Telekommunikation
    Identifikatorer
    urn:nbn:se:liu:diva-139270 (URN)10.1109/TMM.2017.2673412 (DOI)000404061800019 ()
    Anmärkning

    Funding Agencies|Swedish Research Council (VR); Center for Industrial Information Technology (CENIIT); Natural Sciences and Engineering Research Council of Canada

    Tillgänglig från: 2017-07-07 Skapad: 2017-07-07 Senast uppdaterad: 2018-02-06
  • 225.
    Krishnamoorthi, Vengatanathan
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Bergström, Patrik
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Carlsson, Niklas
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Eager, Derek
    University of Saskatchewan, Canada.
    Mahanti, Anirban
    NICTA, Australia.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Empowering the Creative User: Personalized HTTP-based Adaptive Streaming of Multi-path Nonlinear Video2013Ingår i: Computer communication review, ISSN 0146-4833, E-ISSN 1943-5819, Vol. 43, nr 4, s. 591-596Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents the design, implementation, and validation of a novel system that supports streaming and playout of personalized, multi-path, nonlinear video. In contrast to regular video, in which the file content is played sequentially, our design allows multiple nonlinear video sequences of the underlying (linear) video to be stitched together and played in any personalized order, and clients can be provided multiple path choices. The design combines the ideas of HTTP-based adaptive streaming (HAS) and multi-path nonlinear video. Personalization of the content is achieved with the use of a customized metafile, which is downloaded separately from the underlying media and the manifest file that defines the HAS structure. An extension to the user interface allows path choices to be presented to and made by the user. Novel buffer management and prefetching policies are used to ensure seamless uninterrupted playback regardless of client path choices, even under scenarios in which clients defer their choices until the last possible moment. Our solution allows creative home users to easily create their own multi-path nonlinear video, opening the door to an endless possibility of new opportunities and media forms.

  • 226.
    Krishnamoorthi, Vengatanathan
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Bergström, Patrik
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Carlsson, Niklas
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Eager, Derek
    University of Saskatchewan.
    Mahanti, Anirban
    NICTA, Sydney, Australia.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Empowering the creative user: personalized HTTP-based adaptive streaming of multi-path nonlinear video2013Ingår i: FhMN '13 Proceedings of the 2013 ACM SIGCOMM workshop on Future human-centric multimedia networking, New York, USA: Association for Computing Machinery (ACM), 2013, s. 53-58Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents the design, implementation, and validation of a novel system that supports streaming and playout of personalized, multi-path, nonlinear video. In contrast to regular video, in which the file content is played sequentially, our design allows multiple nonlinear video sequences of the underlying (linear) video to be stitched together and played in any personalized order, and clients can be provided multiple path choices. The design combines the ideas of HTTP-based adaptive streaming (HAS) and multi-path nonlinear video. Personalization of the content is achieved with the use of a customized metafile, which is downloaded separately from the underlying media and the manifest file that defines the HAS structure. An extension to the user interface allows path choices to be presented to and made by the user. Novel buffer management and prefetching policies are used to ensure seamless uninterrupted playback regardless of client path choices, even under scenarios in which clients defer their choices until the last possible moment. Our solution allows creative home users to easily create their own multi-path nonlinear video, opening the door to an endless possibility of new opportunities and media forms.

  • 227.
    Krishnamoorthi, Vengatanathan
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Carlsson, Niklas
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Eager, D.
    University of of Saskatchewan, Canada.
    Mahanti, A.
    NICTA, Australia.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Quality-adaptive prefetching for interactive branched video using HTTP-based Adaptive Streaming2014Ingår i: MM 2014 - Proceedings of the 2014 ACM Conference on Multimedia, Association for Computing Machinery, Inc , 2014, s. 317-326Konferensbidrag (Refereegranskat)
    Abstract [en]

    Interactive branched video that allows users to select their own paths through the video, provides creative content designers with great personalization opportunities; however, such video also introduces significant new challenges for the system developer. For example, without careful prefetching and buffer management, the use of multiple alternative playback paths can easily result in playback interruptions. In this paper, we present a full implementation of an interactive branched video player using HTTP-based Adaptive Streaming (HAS) that provides seamless playback even when the users defer their branch path choices to the last possible moment. Our design includes optimized prefetching policies that we derive under a simple optimization framework, effective buffer management of prefetched data, and the use of parallel TCP connections to achieve efficient buffer workahead. Through performance evaluation under a wide range of scenarios, we show that our optimized policies can effectively prefetch data of carefully selected qualities along multiple alternative paths such as to ensure seamless playback, offering users a pleasant viewing experience without playback interruptions.

  • 228.
    Krishnamoorthi, Vengatanathan
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Carlsson, Niklas
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Eager, Derek
    University of Saskatchewan, Canada.
    Mahanti, Anirban
    NICTA, Australia.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Bandwidth-aware Prefetching for Proactive Multi-video Preloading and Improved HAS Performance2015Ingår i: Proceedings of the ACM International Conference on Multimedia (ACM Multimedia), New York, USA: Association for Computing Machinery (ACM), 2015, s. 551-560Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper considers the problem of providing users playing one streaming video the option of instantaneous and seamless playback of alternative videos. Recommendation systems can easily provide a list of alternative videos, but there is little research on how to best eliminate the startup time for these alternative videos. The problem is motivated by services that want to retain increasingly impatient users, who frequently watch the beginning of multiple videos, before viewing a video to the end. We present the design, implementation, and evaluation of an HTTP-based Adaptive Streaming (HAS) solution that provides careful prefetching and buffer management. We also present the design and evaluation of three fundamental policy classes that provide different tradeoffs between how aggressively new alternative videos are prefetched versus the importance of ensuring high playback quality. We show that our solution allows us to reduce the startup times of alternative videos by an order of magnitude and effectively adapt the quality such as to ensure the highest possible playback quality of the video being viewed. By improving the channel utilization we also address the discrimination problem that HAS clients often suffer from, allowing us to in some cases simultaneously improve the playback quality of the video being viewed and provide the value-added service of allowing instantaneous playback of the prefetched alternative videos.

  • 229.
    Krishnamoorthi, Vengatanathan
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Carlsson, Niklas
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Eager, Derek
    University of Saskatchewan, Canada.
    Mahanti, Anirban
    NICTA, Australia.
    Shahmehri, Nahid
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Helping Hand or Hidden Hurdle: Proxy-assisted HTTP-based Adaptive Streaming Performance2013Ingår i: Modeling, Analysis & Simulation of Computer and Telecommunication Systems (MASCOTS), 2013 IEEE 21st International Symposium, IEEE , 2013, s. 182-191Konferensbidrag (Refereegranskat)
    Abstract [en]

    HTTP-based Adaptive Streaming (HAS) has become a widely-used video delivery technology. Use of HTTP enables relatively easy firewall/NAT traversal and content caching. While caching is an important aspect of HAS, there is not much public research on the performance impact proxies and their policies have on HAS. In this paper we build an experimental framework using open source Squid proxies and the most recent Open Source Media Framework (OSMF). A range of content-aware policies can be implemented in the proxies and tested, while the player software can be instrumented to measure performance as seen at the client. Using this framework, the paper makes three main contributions. First, we present a scenario-based performance evaluation of the latest version of the OSMF player. Second, we quantify the benefits using different proxy-assisted solutions, including basic best effort policies and more advanced content quality aware prefetching policies. Finally, we present and evaluate a cooperative framework in which clients and proxies share information to improve performance. In general, the bottleneck location and network conditions play central roles in which policy choices are most advantageous, as they significantly impact the relative performance differences between policy classes. We conclude that careful design and policy selection is important when trying to enhance HAS performance using proxy assistance.

  • 230.
    Krishnamoorthi, Vengatanathan
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Carlsson, Niklas
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Halepovic, Emir
    ATandT Labs Res, NJ USA.
    Slow but Steady: Cap-based Client-Network Interaction for Improved Streaming Experience2018Ingår i: 2018 IEEE/ACM 26TH INTERNATIONAL SYMPOSIUM ON QUALITY OF SERVICE (IWQOS), IEEE , 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Due to widespread popularity of streaming services, many streaming clients typically compete over bottleneck links for their own bandwidth share. However, in such environments, the rate adaptation algorithms used by modern streaming clients often result in instability and unfairness, which negatively affects the playback experience. In addition, mobile clients often waste bandwidth by trying to stream excessively high video bitrates. We present and evaluate a cap-based framework in which the network and clients cooperate to improve the overall Quality of Experience (QoE). First, to motivate the framework, we conduct a comprehensive study using the lab setup showing that a fixed rate cap comes with both benefits (e.g., data savings, improved stability and fairness) and drawbacks (e.g., higher startup times and slower recovery after stalls). To address the drawbacks while keeping the benefits, we then introduce and evaluate a framework that includes (i) buffer-aware rate caps in which the network temporarily boosts the rate cap of clients during video startup and under low buffer conditions, and (ii) boost-aware client-side adaptation algorithms that optimize the bitrate selection during the boost periods. Combined with information sharing between the network and clients, these mechanisms are shown to improve QoE, while reducing wasted bandwidth.

  • 231.
    Krishnamoorthi, Vengatanathan
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Carlsson, Niklas
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Halepovic, Emir
    AT&T Labs, USA.
    Petajan, Eric
    AT&T Labs, USA.
    BUFFEST: Predicting Buffer Conditions and Real-time Requirements of HTTP(S) Adaptive Streaming Clients2017Ingår i: MMSys’17, Proceedings of the 8th ACM on Multimedia Systems Conference, ACM , 2017, s. 76-87Konferensbidrag (Refereegranskat)
    Abstract [en]

    Stalls during video playback are perhaps the most important indicator of a client's viewing experience. To provide the best possible service, a proactive network operator may therefore want to know the buffer conditions of streaming clients and use this information to help avoid stalls due to empty buffers. However, estimation of clients' buffer conditions is complicated by most streaming services being rate-adaptive, and many of them also encrypted. Rate adaptation reduces the correlation between network throughput and client buffer conditions. Usage of HTTPS prevents operators from observing information related to video chunk requests, such as indications of rate adaptation or other HTTP-level information.; AB@This paper presents BUFFEST, a novel classification framework that can be used to classify and predict streaming clients' buffer conditions from both HTTP and HTTPS traffic. To illustrate the tradeoffs between prediction accuracy and the available information used by classifiers, we design and evaluate classifiers of different complexity. At the core of BUFFEST is an event-based buffer emulator module for detailed analysis of clients' buffer levels throughout a streaming session, as well as for automated training and evaluation of online packet-level classifiers. We then present example results using simple threshold-based classifiers and machine learning classifiers that only use TCP/IP packet-level information. Our results are encouraging and show that BUFFEST can distinguish streaming clients with low buffer conditions from clients with significant buffer margin during a session even when HTTPS is used.

  • 232.
    Kumar, Pardeep
    et al.
    University of Oxford, England.
    Braeken, An
    Vrije University of Brussel, Belgium.
    Gurtov, Andrei
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten. ITMO University, Russia.
    Iinatti, Jari
    University of Oulu, Finland.
    Hoai Ha, Phuong
    University of Tromso, Norway.
    Anonymous Secure Framework in Connected Smart Home Environments2017Ingår i: IEEE Transactions on Information Forensics and Security, ISSN 1556-6013, E-ISSN 1556-6021, Vol. 12, nr 4, s. 968-979Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The smart home is an environment, where heterogeneous electronic devices and appliances are networked together to provide smart services in a ubiquitous manner to the individuals. As the homes become smarter, more complex, and technology dependent, the need for an adequate security mechanism with minimum individuals intervention is growing. The recent serious security attacks have shown how the Internet-enabled smart homes can be turned into very dangerous spots for various ill intentions, and thus lead the privacy concerns for the individuals. For instance, an eavesdropper is able to derive the identity of a particular device/appliance via public channels that can be used to infer in the life pattern of an individual within the home area network. This paper proposes an anonymous secure framework (ASF) in connected smart home environments, using solely lightweight operations. The proposed framework in this paper provides efficient authentication and key agreement, and enables devices (identity and data) anonymity and unlinkability. One-time session key progression regularly renews the session key for the smart devices and dilutes the risk of using a compromised session key in the ASF. It is demonstrated that computation complexity of the proposed framework is low as compared with the existing schemes, while security has been significantly improved.

  • 233.
    Kumar, Pardeep
    et al.
    UiT Arctic University of Norway, Norway.
    Gurtov, Andrei
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten. ITMO University, Russia.
    Iinatti, Jari
    University of Oulu, Finland.
    Sain, Mangal
    Dongseo University, South Korea.
    Ha, Phuong H.
    UiT Arctic University of Norway, Norway.
    Access Control Protocol With Node Privacy in Wireless Sensor Networks2016Ingår i: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 16, nr 22, s. 8142-8150Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For preventing malicious nodes joining wireless sensor networks (WSNs), an access control mechanism is necessary for the trustworthy cooperation between the nodes. In addition to access control, recently, privacy has been an important topic regarding how to achieve privacy without disclosing the real identity of communicating entities in the WSNs. Based on elliptic curve cryptography, in this paper, we present an access control protocol with node privacy (called ACP) for the WSN. The proposed scheme not only accomplishes the node authentication but also provides the identity privacy (i.e., source to destination and vice-versa) for the communicating entities. Compared with the current state of the art, the proposed solution can defend actively against attacks. The efficacy and the efficiency of the proposed ACP are confirmed through the test bed analysis and performance evaluations.

  • 234.
    Kumar, Pardeep
    et al.
    University of Oxford, Oxford, United Kingdom.
    Gurtov, Andrei
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten. ITMO University, Saint Petersburg, Russian Federation.
    Sain, Mangal
    Dongseo University, South Korea.
    Martin, Andrew
    University of Oxford, Oxford, United Kingdom.
    Ha, Phuong H.
    Arctic University of Norway, Norway.
    Lightweight Authentication and Key Agreement for Smart Metering in Smart Energy Networks2019Ingår i: IEEE Transactions on Smart Grid, ISSN 1949-3053, E-ISSN 1949-3061, Vol. 10, nr 4, s. 4349-4359Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Smart meters are considered as foundational part of the smart metering infrastructure (SMI) in smart energy networks. Smart meter is a digital device that makes use of twoway communication between consumer and utility to exchange, manage and control energy consumptions within a home. However, despite all the features, a smart meter raises several securityrelated concerns. For instance, how to exchange data between the legal entities (e.g., smart meter and utility server) while maintaining privacy of the consumer. To address these concerns, authentication and key agreement in SMI can provide important security properties that not only to maintain a trust between the legitimate entities but also to satisfy other security services. This work presents a lightweight authentication and key agreement (LAKA) that enables trust, anonymity, integrity and adequate security in the domain of smart energy network. The proposed scheme employs hybrid cryptography to facilitate mutual trust (authentication), dynamic session key, integrity, and anonymity. We justify the feasibility of the proposed scheme with a testbed using 802.15.4 based device (i.e., smart meter). Moreover, through the security and performance analysis, we show that the proposed scheme is more effective and energy efficient compared to the previous schemes.

  • 235.
    Lambrix, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    A framework for session-based ontology alignment2011Ingår i: Proceedings of the 6th International Workshop on Ontology Matching, CEUR Workshop Proceedings , 2011, s. 238-239Konferensbidrag (Refereegranskat)
    Abstract [en]

    [No abstract available]

  • 236.
    Lambrix, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Advances in Secure and Networked Information Systems – The ADIT Perspective: Festschrift in honor of professor NAHID SHAHMEHRI2012Samlingsverk (redaktörskap) (Övrigt vetenskapligt)
    Abstract [en]

    This book contains contributions by current and former colleagues and PhD students of professor Nahid Shahmehri in celebration of her 60th birthday. Although it would be difficult to cover the full range of her academic contributions, we have at least been able to hint the importance and the breadth of her work. We have chosen the title ‘Advances in Secure and Networked Information Systems - The ADIT Perspective’ as many of the contributions of Nahid and her group have been in these areas, given a fairly broad interpretation of “networked information systems”. In this collection we have gathered both republications of past work as well as newly written articles.

     

  • 237.
    Lambrix, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Extending Standard Description Logics1994Ingår i: Proceedings of the International Workshop on Description Logics, 1994, s. 42-44Konferensbidrag (Refereegranskat)
  • 238.
    Lambrix, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Introduction to Description Logics2001Ingår i: Ontologies and Search - Proceedings of the 2nd OntoQuery Workshop, 2001, s. 53-56Konferensbidrag (Refereegranskat)
  • 239.
    Lambrix, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Filosofiska fakulteten.
    Ontologies in Bioinformatics and Systems Biology2004Ingår i: Artificial Intelligence Methods and Tools for Systems Biology / [ed] Werner Dubitzky and Francisco Azuaje, Springer Science+Business Media B.V., 2004, 5, s. 129-145Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    Ontologies are being used in bioinformatics and systems biology, among others, for communication between people and organizations, as the basis for interoperability between systems, and as query models and indexes to repositories of information. In this chapter we give a background of the area and provide a state of the art overview. We present different possible definitions of ontology, examples of bio-ontologies and their use, formalisms that can be used to represent ontologies as well as tools that support the different stages in the life cycle of an ontology.

  • 240.
    Lambrix, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Part-Whole Reasoning in an Object-Centered Framework2000Bok (Refereegranskat)
    Abstract [en]

    In this book, the author develops an object-centered framework with specialized support of the part-of relation based on description logics. These logics are a family of object-centered knowledge representation languages tailored for describing knowledge about concepts and is-a hierarchies of these concepts. In addition to the representation and reasoning facilities provided by description logics for is-a, representation and reasoning facilities are introduced for part-of. Finally, the feasibility and the usefulness of the approach is demonstrated by applying the framework to various areas including domain modeling, agent-oriented scenarios, document management and retrieval, and composite concept learning.

  • 241.
    Lambrix, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Semantic Web, Ontologies and Linked Data2014Ingår i: Comprehensive Biomedical Physics: Volume 6: Bioinformatics / [ed] Brahme (ed in chief), Persson, (ed), Amsterdam: Elsevier, 2014, s. 67-76Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Researchers in various areas in the life sciences use biomedical data sources and tools for their research. However, with the explosion of the amountof available data sources and tools, researchers also face the difficulties of finding and retrieving relevant information and tools as well as integratinginformation from different sources. The vision of the Semantic Web alleviates these difficulties. In this chapter, we introduce the Semantic Web anddiscuss steps that have been taken toward this vision. We discuss ontologies as a key technology as well as the recent development of Linked Data. Further, for each of these, we list issues for future research.

  • 242.
    Lambrix, Patrick
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Towards a semantic web for bioinformatics using ontology-based annotation2005Ingår i: 14th IEEE International Workshops on Enabling Technologies: Infrastructures for Collaborative Enterprises,2005, Institute of Electrical and Electronics Engineers (IEEE), 2005, s. 3-7Konferensbidrag (Refereegranskat)
    Abstract [en]

    Nowadays, biologists use biological data sources and tools to find relevant information for their research. However, with the explosion of the amount of online accessible data and tools, finding the relevant sources and retrieving the relevant information is not an easy task. Further, often information from different sources needs to be integrated. The vision of a Semantic Web alleviates these difficulties. The Semantic Web is an extension of the current Web in which information is given a well-defined meaning by annotating Web content with ontology terms. In this paper we discuss the Semantic Web vision and focus on an important technology, ontologies, that is needed to make this vision happen.

  • 243.
    Lambrix, Patrick
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Armiento, Rickard
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Delin, Anna
    School of Science and Engineering (SCI) at the Royal Institute of Technology, KTH, Sweden.
    Li, Huanyu
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Big Semantic Data Processing in the Materials Design Domain2018Ingår i: Encyclopedia of Big Data Technologies / [ed] Sherif Sakr and Albert Zomaya, Cham: Springer, 2018Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    To speed up the progress in the field of materials design, a number of challenges related to big data need to be addressed. This entry discusses these challenges and shows the semantic technologies that alleviate the problems related to variety, variability, and veracity.

  • 244.
    Lambrix, Patrick
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Borgida, AlexRutgers University, NJ, USA.Lenzerini, MaurizioUniversita degli Studi di Roma "La Sapienza", Italy..Möller, RalfUniversity of Hamburg, Germany.Patel-Schneider, PeterBell Labs Research, NJ, USA.
    Proceedings of the 1999 International Workshop on Description Logics1999Proceedings (redaktörskap) (Refereegranskat)
    Abstract [en]

    The International Workshop on Description Logics was held in Linköping Sweden from July to August. It was an a affiliate event with the Sixteenth International Joint Conference on Articial Intelligence IJCAI Stockholm July 31 - August 6 and with the Sixth International Workshop on Knowledge Representation meets Databases KRDB Linköoping July 29-30.

    The workshop was organized in sessions on theoretical advances in de scription logics (2 sessions), applications of description logics (2 sessions), description logic systems (2 sessions) and extensions of description logics (1 session). Further there was a joint session with the Sixth International Workshop on Knowledge Representation Meets Databases. There were two invited talks Natasha Alechina gave a tutorial on logics for semi-structured data Robert MacGregor and Deborah McGuinness gave a presentation on DARPAs High Performance Knowledge Base project.

    The workshop was sponsored by the Swedish Research Council for Engineering Sciences TFR Telefonaktiebolaget LM Ericssons Stiftelse for främjande av elektroteknisk forskning, Linköpings kommun, Erda AB andthe Laboratory for Intelligent Information Systems, Linköpings universitet.Thanks go also to Lotta Nissen Yelena Turetskaya and a number of studentsfor their contribution to the organization.

  • 245.
    Lambrix, Patrick
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Dragisic, Zlatan
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Ivanova, Valentina
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Get my pizza right: Repairing missing is-a relations in ALC ontologies2012Ingår i: Second Joint International Semantic Technology Conference, Springer Berlin/Heidelberg, 2012, s. 17-32Konferensbidrag (Refereegranskat)
    Abstract [en]

    With the increased use of ontologies in semantically-enabled applications, the issue of debugging defects in ontologies has become increasingly important. These defects can lead to wrong or incomplete results for the applications. Debugging consists of the phases of detection and repairing. In this paper we focus on the repairing phase of a particular kind of defects, i.e. the missing relations in the is-a hierarchy. Previous work has dealt with the case of taxonomies. In this work we extend the scope to deal with ALC ontologies that can be represented using acyclic terminologies. We present algorithms and discuss a system.

  • 246.
    Lambrix, Patrick
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Dragisic, Zlatan
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Ivanova, Valentina
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Anslow, Craig
    Middlesex University, London, UK.
    Visualization for Ontology Evolution2016Ingår i: VOILA 2016 Visualization and Interaction for Ontologies and Linked Data: Proceedings of the 2nd  International Workshop on Visualization and Interaction for Ontologies and Linked Data / [ed] Valentina Ivanova; Patrick Lambrix; Steffen Lohmann; Catia Pesquita, Rheinisch-Westfaelische Technische Hochschule Aachen University , 2016, s. 54-67Konferensbidrag (Refereegranskat)
    Abstract [en]

    One of the challenges for the ontology engineering community is theuser involvement in the engineering process. Ontologies are not static entities andthere is a demand for tools to support the user during the ontology evolution pro-cess. This paper aims to provide a set of functionality requirements for ontologyevolution systems, with a particular focus on the visualization of the ontologies,their versions and information needed for ontology evolution tasks. Further, wereview the current state of the art in ontology evolution systems with respect tothe requirements and the visualization. We also view ontologies as software anddiscuss approaches from the software visualization area that could be used forontology evolution visualization.

  • 247.
    Lambrix, Patrick
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Edberg, Anna
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Evaluation of ontology merging tools2003Ingår i: Pacific Symposium on Biocomputing, World Scientific , 2003, s. 589-600Konferensbidrag (Refereegranskat)
    Abstract [en]

    Ontologies are being used nowadays in many areas, including bioinformatics. One of the issues in ontology research is the aligning and merging of ontologies. Tools have been developed for ontology merging, but they have not been evaluated for their use in bioinformatics. In this paper we evaluate two of the most well-known ontology merging tools with a bioinformatics perspective. As test ontologies we have used Gene Ontology and Signal-Ontology.

  • 248.
    Lambrix, Patrick
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Edberg, Anna
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Manis, Carolyn
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Tan, He
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Merging DAML+OIL bio-ontologies2003Ingår i: International workshop on description logics, 2003Konferensbidrag (Refereegranskat)
  • 249.
    Lambrix, Patrick
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska fakulteten.
    Göthe Lundgren, Maud
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Kamkar, Mariam
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Computer science as an integrated part of engineering education1997Ingår i: Proceedings of the ACM SIGCSE/SIGCUE Conference on Integrating Technology into Computer Science Education, 1997, s. 151-Konferensbidrag (Refereegranskat)
  • 250.
    Lambrix, Patrick
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Habbouche, Manal
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik.
    Perez, Marta
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Evaluation of ontology development tools for bioinformatics2003Ingår i: Bioinformatics, ISSN 1367-4803, E-ISSN 1367-4811, Vol. 19, nr 12, s. 1564-1571Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ontologies are being used nowadays in many areas, including bioinformatics. To assist users in developing and maintaining ontologies a number of tools have been developed. In this paper we compare four such tools, Protégé-2000, Chimaera, DAG-Edit and OilEd. As test ontologies we have used ontologies from the Gene Ontology Consortium. No system is preferred in all situations, but each system has its own strengths and weaknesses.

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