Dr. Mirco Schönfeld

Mögliche Themen für Abschlussarbeiten

• Schutz der Privatsphäre in Empfehlungssystemen
• Kontext(wieder-)erkennung mit Machine-Learning-Methoden
• Bestimmung der Ähnlichkeit von Kontexten und Kontext-Historien
• Text Mining
• Data Mining in Sozialen Netzen

Die obenstehende Liste ist womöglich nicht vollständig. Am besten sprechen wir bei einem unverbindlichen Treffen über ein mögliches Thema; bei Interesse einfach kurz melden!

Weitere Informationen

Mehr (und womöglich aktuellere) Informationen gibt es auf meiner Webseite.

Publikationen

2017

• E. J. Hoffmann, L. Schauer, M. Schönfeld, and M. Kraus, „Robust Pedestrian Dead Reckoning using Anchor Point Recalibration,“ in Proceedings of Eighth International Conference on Indoor Positioning and Indoor Navigation (IPIN2017), 2017.
  [BibTeX]

  @inproceedings{hoffmann2017robust,
  title = {Robust Pedestrian Dead Reckoning using Anchor Point Recalibration},
  author = {Eike Jens Hoffmann and Lorenz Schauer and Mirco Schönfeld and Maximilian Kraus},
  booktitle = {Proceedings of Eighth International Conference on Indoor Positioning and Indoor Navigation (IPIN2017)},
  year = {2017},
  owner = {ehoffmann},
  timestamp = {2017.09.20}
  }

• C. Linnhoff-Popien, S. Feld, M. Werner, and M. Schönfeld, „Innovationszentrum Mobiles Internet des ZD.B – Methoden der Digitalisierung in der Arbeitswelt,“ in 50 Jahre Universitäts-Informatik in München, Springer Vieweg, Berlin, Heidelberg, 2017, p. 87–95.
  [BibTeX]

  @incollection{linnhoff2017innovationszentrum,
  title = {Innovationszentrum Mobiles Internet des ZD.B -- Methoden der Digitalisierung in der Arbeitswelt},
  author = {Claudia Linnhoff-Popien and Sebastian Feld and Martin Werner and Mirco Schönfeld},
  booktitle = {50 Jahre Universitäts-Informatik in München},
  publisher = {Springer Vieweg, Berlin, Heidelberg},
  year = {2017},
  pages = {87--95},
  owner = {clinnhoff},
  timestamp = {2017.09.12}
  }

2016

• S. Feld, M. Schönfeld, and M. Werner, „Traversing Bitcoin’s P2P network: Insights into the structure of a decentralized currency,“ International Journal of Computational Science and Engineering (IJCSE), Special Issue on Security and Trust Issues in Peer-to-Peer Networks, vol. 13, iss. 2, pp. 122-131, 2016.
  [BibTeX] [Abstract] [Download PDF]
  

  Bitcoin has become increasingly important for several years. While being declared dead in the meantime, it got a boost in 2011. The exchange rate increased from \$14 in January 2013 up to \$240 in April 2013 and even \$900 in early 2014. Lots of existing work addresses the analysis of the publicly available transaction graph. There are evaluations of the user’s anonymity and privacy, but no proper measurements of the underlying network. In this paper, we present novel insights about Bitcoin’s peer-to-peer network, with a focus on its distribution among distinct autonomous systems. The resilience of the Bitcoin ecosystem, the unambiguousness of the blockchain in use, the propagation and verification of transaction blocks, but also the anonymity of Bitcoin’s users depend on the structure of the global peer-to-peer network. Our work is the first thorough analysis of Bitcoin’s underlying peer-to-peer network, especially with regard to its distribution at the autonomous system level. We traversed Bitcoin’s peer-to-peer network in a protocol-compliant manner and made statements about the size of the accessible network and the number of clients. This information is useful when modelling the probability of attacks against the user’s privacy or other aspects. Further, we investigated the distribution of the peer-to-peer network on autonomous systems. The concrete form has an impact on the above-mentioned topics, such as vitality, resilience or privacy. Finally, we analysed the mechanism to announce known peers. It turns out that Bitcoin’s peer announcement is not well distributed, affecting information propagation.

  @article{bitcoinjournal,
  title = {Traversing Bitcoin’s P2P network: Insights into the structure of a decentralized currency},
  author = {Sebastian Feld and Mirco Schönfeld and Martin Werner},
  journal = {International Journal of Computational Science and Engineering (IJCSE), Special Issue on Security and Trust Issues in Peer-to-Peer Networks},
  year = {2016},
  number = {2},
  pages = {122-131},
  volume = {13},
  abstract = {Bitcoin has become increasingly important for several years. While being declared dead in the meantime, it got a boost in 2011. The exchange rate increased from \$14 in January 2013 up to \$240 in April 2013 and even \$900 in early 2014. Lots of existing work addresses the analysis of the publicly available transaction graph. There are evaluations of the user's anonymity and privacy, but no proper measurements of the underlying network. In this paper, we present novel insights about Bitcoin's peer-to-peer network, with a focus on its distribution among distinct autonomous systems. The resilience of the Bitcoin ecosystem, the unambiguousness of the blockchain in use, the propagation and verification of transaction blocks, but also the anonymity of Bitcoin's users depend on the structure of the global peer-to-peer network. Our work is the first thorough analysis of Bitcoin's underlying peer-to-peer network, especially with regard to its distribution at the autonomous system level. We traversed Bitcoin's peer-to-peer network in a protocol-compliant manner and made statements about the size of the accessible network and the number of clients. This information is useful when modelling the probability of attacks against the user's privacy or other aspects. Further, we investigated the distribution of the peer-to-peer network on autonomous systems. The concrete form has an impact on the above-mentioned topics, such as vitality, resilience or privacy. Finally, we analysed the mechanism to announce known peers. It turns out that Bitcoin's peer announcement is not well distributed, affecting information propagation.},
  owner = {sfeld},
  url = {http://www.inderscience.com/offer.php?id=78441}
  }

• M. Schönfeld, Kontextbezug und Authentizität in Sozialen Netzen, Logos Verlag Berlin, 2016.
  [BibTeX] [Download PDF]

  @book{schoenfeld2016,
  title = {Kontextbezug und Authentizität in Sozialen Netzen},
  author = {Mirco Schönfeld},
  publisher = {Logos Verlag Berlin},
  year = {2016},
  isbn = {978-3-8325-4398-3},
  url = {https://edoc.ub.uni-muenchen.de/20232/}
  }

2015

• S. Feld, M. Werner, M. Schönfeld, and S. Hasler, „Archetypes of Alternative Routes in Buildings,“ in 6th International Conference on Indoor Positioning and Indoor Navigation (IPIN 2015), 2015, pp. 1-10.
  [BibTeX] [Abstract]
  

  Alternative routes have found many applications in navigation scenarios. However, alternative routes have only been introduced recently for the indoor space due to the complexity of these environments. Furthermore, the number of alternative routes in buildings can be quite high. With this paper, we propose to organize sets of alternative routes by employing archetypal analysis on a feature space representation of routes and show results in which a set of hundreds of routes between the same start and end point has been compressed to only a few obviously different archetypal routes. Additionally, the framework allows for comparing routes with archetypes and with each other. This comparison does not reveal spatial similarity alone, but rather a measure of routes‘ similarity representing their inherent semantic character.

  @inproceedings{feld2015archetypes,
  title = {Archetypes of Alternative Routes in Buildings},
  author = {Sebastian Feld and Martin Werner and Mirco Schönfeld and Stefanie Hasler},
  booktitle = {6th International Conference on Indoor Positioning and Indoor Navigation (IPIN 2015)},
  year = {2015},
  pages = {1-10},
  abstract = {Alternative routes have found many applications in navigation scenarios. However, alternative routes have only been introduced recently for the indoor space due to the complexity of these environments. Furthermore, the number of alternative routes in buildings can be quite high. With this paper, we propose to organize sets of alternative routes by employing archetypal analysis on a feature space representation of routes and show results in which a set of hundreds of routes between the same start and end point has been compressed to only a few obviously different archetypal routes. Additionally, the framework allows for comparing routes with archetypes and with each other. This comparison does not reveal spatial similarity alone, but rather a measure of routes' similarity representing their inherent semantic character.},
  owner = {sebastian},
  timestamp = {2015.12.01}
  }

• M. Schönfeld, „HbbRadio oder der personalisierte Rundfunk,“ in Marktplätze im Umbruch – Digitale Strategien fuer Services im Mobilen Internet, C. Linnhoff-Popien, M. Zaddach, and A. Grahl, Eds., Springer Berlin Heidelberg, 2015, pp. 203-211. doi:10.1007/978-3-662-43782-7_23
  [BibTeX] [Download PDF]

  @incollection{HbbRadioBuch,
  title = {HbbRadio oder der personalisierte Rundfunk},
  author = {Mirco Schönfeld},
  booktitle = {Marktplätze im Umbruch - Digitale Strategien fuer Services im Mobilen Internet},
  publisher = {Springer Berlin Heidelberg},
  year = {2015},
  editor = {Claudia Linnhoff-Popien and Michael Zaddach and Andreas Grahl},
  pages = {203-211},
  doi = {10.1007/978-3-662-43782-7_23},
  owner = {mschönfeld},
  timestamp = {2015.08.06},
  url = {http://dx.doi.org/10.1007/978-3-662-43782-7_23}
  }

• M. Schönfeld, M. Werner, C. Linnhoff-Popien, and A. Erk, „Towards a Privacy-Preserving Hybrid Radio Network: Design and Open Challenges,“ in 15th International Conference on Innovations for Community Services (I4CS 2015), 2015, pp. 1-6.
  [BibTeX] [Download PDF]

  @inproceedings{RadioNetwork,
  title = {Towards a Privacy-Preserving Hybrid Radio Network: Design and Open Challenges},
  author = {Mirco Schönfeld and Martin Werner and Claudia Linnhoff-Popien and Alexander Erk},
  booktitle = {15th International Conference on Innovations for Community Services (I4CS 2015)},
  year = {2015},
  pages = {1-6},
  owner = {mschönfeld},
  timestamp = {2015.08.06},
  url = {http://publications.mircoschoenfeld.de/2015-RadioNetwork.pdf}
  }

• M. Werner, F. Dorfmeister, and M. Schönfeld, „AMBIENCE: A Context-Centric Online Social Network,“ in Accepted for Inclusion in the 12th Workshop on Positioning, Navigation and Communications (WPNC 2015), 2015.
  [BibTeX] [Download PDF]

  @inproceedings{ambience,
  title = {AMBIENCE: A Context-Centric Online Social Network},
  author = {Martin Werner and Florian Dorfmeister and Mirco Schönfeld},
  booktitle = {Accepted for Inclusion in the 12th Workshop on Positioning, Navigation and Communications (WPNC 2015)},
  year = {2015},
  publisher = {IEEE},
  file = {2015-Ambience.pdf:http\://publications.mircoschoenfeld.de/2015-Ambience.pdf:PDF},
  url = {http://publications.mircoschoenfeld.de/2015-Ambience.pdf}
  }

• M. Werner and M. Schönfeld, „The Gaussian Bloom Filter,“ in 20th International Conference on Database Systems for Advanced Applications (DASFAA 2015), 2015, pp. 191-206.
  [BibTeX]

  @inproceedings{gaussianbloom,
  title = {The Gaussian Bloom Filter},
  author = {Martin Werner and Mirco Schönfeld},
  booktitle = {20th International Conference on Database Systems for Advanced Applications (DASFAA 2015)},
  year = {2015},
  pages = {191-206}
  }

2014

• S. Feld, M. Schönfeld, and M. Werner, „Analyzing the Deployment of Bitcoin’s P2P Network under an AS-level Perspective,“ in 5th International Conference on Ambient Systems, Networks and Technologies (ANT 2014) and 4th International Conference on Sustainable Energy Information Technology (SEIT 2014), 2014, pp. 1121-1126.
  [BibTeX] [Abstract] [Download PDF]
  

  Bitcoin has become increasingly important in recent years. The exchange rate raised from \$14 in January 2013 up to \$240 in April 2013 and even \$900 in early 2014. In this paper, we present novel insights about Bitcoin’s peer-to-peer (P2P) network with a special focus on its distribution among distinct autonomous systems. We traversed Bitcoin’s P2P network in a protocol-compliant manner and collected information about the network size, the number of clients, and the network distribution among autonomous systems. Our findings lead to conclusions about the resilience of the Bitcoin ecosystem, the unambiguousness of the blockchain in use, and the propagation and verification of transaction blocks.

  @inproceedings{bitcoin,
  title = {Analyzing the Deployment of Bitcoin's P2P Network under an AS-level Perspective},
  author = {Sebastian Feld and Mirco Schönfeld and Martin Werner},
  booktitle = {5th International Conference on Ambient Systems, Networks and Technologies (ANT 2014) and 4th International Conference on Sustainable Energy Information Technology (SEIT 2014)},
  year = {2014},
  pages = {1121-1126},
  abstract = {Bitcoin has become increasingly important in recent years. The exchange rate raised from \$14 in January 2013 up to \$240 in April 2013 and even \$900 in early 2014. In this paper, we present novel insights about Bitcoin's peer-to-peer (P2P) network with a special focus on its distribution among distinct autonomous systems. We traversed Bitcoin's P2P network in a protocol-compliant manner and collected information about the network size, the number of clients, and the network distribution among autonomous systems. Our findings lead to conclusions about the resilience of the Bitcoin ecosystem, the unambiguousness of the blockchain in use, and the propagation and verification of transaction blocks.},
  file = {pdf?md5=2a5efb534e0d4dc1e12ba9b4157ae4c9&pid=1-s2.0-S187705091400742X-main.pdf:http\://www.sciencedirect.com/science/article/pii/S187705091400742X/pdf?md5=2a5efb534e0d4dc1e12ba9b4157ae4c9&pid=1-s2.0-S187705091400742X-main.pdf:PDF},
  owner = {sfeld},
  url = {http://www.sciencedirect.com/science/article/pii/S187705091400742X}
  }

• M. Schönfeld and M. Werner, „Distributed Privacy-Preserving Mean Estimation,“ in 2nd International Conference on Privacy and Security in Mobile Systems (PRISMS 2014), 2014, pp. 1-8.
  [BibTeX] [Abstract] [Download PDF]
  

  Due to the rise of mobile computing and smartphones, a lot of information about groups has become accessible. This information shall often be kept secret. Hence distributed algorithms for privacy-preserving distribution estimation are needed. Most research currently focuses on privacy in a database, where a single entity has collected the secret information and privacy is ensured between query results and the database. In fully distributed systems such as sensor networks it is often infeasible to move the data towards a central entity for processing. Instead, distributed algorithms are needed. With this paper we propose a fully distributed, privacy-friendly, consensus-based approach. In our approach all nodes cooperate to generate a sufficiently random obfuscation of their secret values until the estimated and obfuscated values of the individual nodes can be safely published. Then the calculations can be done on this replacement containing only non-secret values but recovering some aspects (mean, standard deviation) of the original distribution.

  @inproceedings{distributedmeanestim,
  title = {Distributed Privacy-Preserving Mean Estimation},
  author = {Mirco Schönfeld and Martin Werner},
  booktitle = {2nd International Conference on Privacy and Security in Mobile Systems (PRISMS 2014)},
  year = {2014},
  pages = {1-8},
  publisher = {IEEE},
  abstract = {Due to the rise of mobile computing and smartphones, a lot of information about groups has become accessible. This information shall often be kept secret. Hence distributed algorithms for privacy-preserving distribution estimation are needed. Most research currently focuses on privacy in a database, where a single entity has collected the secret information and privacy is ensured between query results and the database. In fully distributed systems such as sensor networks it is often infeasible to move the data towards a central entity for processing. Instead, distributed algorithms are needed. With this paper we propose a fully distributed, privacy-friendly, consensus-based approach. In our approach all nodes cooperate to generate a sufficiently random obfuscation of their secret values until the estimated and obfuscated values of the individual nodes can be safely published. Then the calculations can be done on this replacement containing only non-secret values but recovering some aspects (mean, standard deviation) of the original distribution.},
  file = {2014-DistrPrivPresMeanEstim.pdf:http\://publications.mircoschoenfeld.de/2014-DistrPrivPresMeanEstim.pdf:PDF},
  keywords = {Mobile Systems; Privacy; Distributed Privacy;},
  url = {http://publications.mircoschoenfeld.de/2014-DistrPrivPresMeanEstim.pdf}
  }

2013

• M. Schönfeld and M. Werner, „Node Wake-Up via OVSF-Coded Bloom Filters in Wireless Sensor Networks,“ in 5th International Conference on Ad Hoc Networks (ADHOCNETS 2013), 2013.
  [BibTeX] [Abstract] [Download PDF]
  

  Interest dissemination in constrained environments such as wireless sensor networks utilizes Bloom filters commonly. A Bloom filter is a probabilistic data structure of fixed length, which can be used to encode the set of sensor nodes to be awake. In this way an application can disseminate interest in specific sensor nodes by broadcasting the Bloom filter throughout the complete wireless sensor network. The probabilistic nature of a Bloom filter induces false positives, that is some sensor nodes will be awake without the application having interest in their sensor values. As the interest is often depending on location such as in adaptive sampling applications, we present a novel method to encode both interest and possible location of information into one probabilistic data structure simultaneously. While our algorithm is able to encode any kind of tree-structured information into a fixed length bit array we exemplify its use through a wireless sensor network. In comparison to traditional Bloom encoding techniques we are able to reduce the overall number of false positives and furthermore reduce the average distance of false positives from the next true positive of the same interest. In our example this helps to reduce the overall energy consumption of the sensor network by only requesting sensor nodes that are likely to store the requested information.

  @inproceedings{bloomwakeup,
  title = {Node Wake-Up via OVSF-Coded Bloom Filters in Wireless Sensor Networks},
  author = {Mirco Schönfeld and Martin Werner},
  booktitle = {5th International Conference on Ad Hoc Networks (ADHOCNETS 2013)},
  year = {2013},
  abstract = {Interest dissemination in constrained environments such as wireless sensor networks utilizes Bloom filters commonly. A Bloom filter is a probabilistic data structure of fixed length, which can be used to encode the set of sensor nodes to be awake. In this way an application can disseminate interest in specific sensor nodes by broadcasting the Bloom filter throughout the complete wireless sensor network. The probabilistic nature of a Bloom filter induces false positives, that is some sensor nodes will be awake without the application having interest in their sensor values. As the interest is often depending on location such as in adaptive sampling applications, we present a novel method to encode both interest and possible location of information into one probabilistic data structure simultaneously. While our algorithm is able to encode any kind of tree-structured information into a fixed length bit array we exemplify its use through a wireless sensor network. In comparison to traditional Bloom encoding techniques we are able to reduce the overall number of false positives and furthermore reduce the average distance of false positives from the next true positive of the same interest. In our example this helps to reduce the overall energy consumption of the sensor network by only requesting sensor nodes that are likely to store the requested information.},
  file = {2013-HierarchicalHashing.pdf:http\://publications.mircoschoenfeld.de/2013-HierarchicalHashing.pdf:PDF},
  url = {http://publications.mircoschoenfeld.de/2013-HierarchicalHashing.pdf}
  }

2012

• F. Dorfmeister, M. Maier, M. Schönfeld, and S. A. W. Verclas, „SmartBEEs: Enabling Smart Business Environments Based on Location Information and Sensor Networks,“ in 9. GI/ITG KuVS Fachgespräch Ortsbezogene Anwendungen und Dienste, 2012, pp. 43-56.
  [BibTeX]

  @inproceedings{smartbeees,
  title = {SmartBEEs: Enabling Smart Business Environments Based on Location Information and Sensor Networks},
  author = {Florian Dorfmeister and Marco Maier and Mirco Schönfeld and Stephan A. W. Verclas},
  booktitle = {9. GI/ITG KuVS Fachgespräch Ortsbezogene Anwendungen und Dienste},
  year = {2012},
  pages = {43-56}
  }

• M. Kessel, M. Maier, M. Schönfeld, and F. Dorfmeister, „Testing Sensor Fusion Algorithms in Indoor Positioning Scenarios,“ in 9. GI/ITG KuVS Fachgespräch Ortsbezogene Anwendungen und Dienste, 2012, pp. 133-142.
  [BibTeX] [Abstract]
  

  Location information is the foundation for location based services. However, a cheap and global indoor positioning solution offering a sufficiently high accuracy and precision for most applications is not yet available and detains location based services from indoor areas. This is also due to missing comparability and standards in the field of indoor positioning, resulting in a large number of proprietary research prototypes of varying capabilities. In this paper we present a software environment for testing and comparing sensor fusion algorithms in indoor positioning scenarios. For this purpose an extendable tool for evaluating accuracy, precision, robustness, complexity, and storage is designed and the results from a first implementation presented and discussed.

  @inproceedings{sensorfusiontool,
  title = {Testing Sensor Fusion Algorithms in Indoor Positioning Scenarios},
  author = {Moritz Kessel and Marco Maier and Mirco Schönfeld and Florian Dorfmeister},
  booktitle = {9. GI/ITG KuVS Fachgespräch Ortsbezogene Anwendungen und Dienste},
  year = {2012},
  pages = {133-142},
  abstract = {Location information is the foundation for location based services. However, a cheap and global indoor positioning solution offering a sufficiently high accuracy and precision for most applications is not yet available and detains location based services from indoor areas. This is also due to missing comparability and standards in the field of indoor positioning, resulting in a large number of proprietary research prototypes of varying capabilities. In this paper we present a software environment for testing and comparing sensor fusion algorithms in indoor positioning scenarios. For this purpose an extendable tool for evaluating accuracy, precision, robustness, complexity, and storage is designed and the results from a first implementation presented and discussed.}
  }

• M. Maier, F. Dorfmeister, M. Schönfeld, and M. Kessel, „A Tool for Visualizing and Editing Multiple Parallel Tracks of Time Series Data from Sensor Logs,“ in 9. GI/ITG KuVS Fachgespräch Ortsbezogene Anwendungen und Dienste, 2012, pp. 99-108.
  [BibTeX] [Abstract]
  

  In the last couple of years, the number of smartphone users has proliferated. As smartphones contain a lot of different sensors, research interest in algorithms combining data of several sensors to derive meaningful information about a user’s context, e.g. her location, is increasing. Ideas for reasonable algorithms often can be found by looking at examples of raw (or somehow pre-processed) sensor data. Still, the research community lacks a simple means to intuitively work with several parallel tracks of time series data. We present a tool which can be used to visualize and edit time dependent data from various sensors along with ground truth recordings like audio or video files. It is complemented by an optional application for logging all kinds of sensor data on Android devices. The tool has already been used to analyze a large data set containing hundreds of walking traces, intended to improve pedestrian dead reckoning algorithms.

  @inproceedings{paralleltrackstool,
  title = {A Tool for Visualizing and Editing Multiple Parallel Tracks of Time Series Data from Sensor Logs},
  author = {Marco Maier and Florian Dorfmeister and Mirco Schönfeld and Moritz Kessel},
  booktitle = {9. GI/ITG KuVS Fachgespräch Ortsbezogene Anwendungen und Dienste},
  year = {2012},
  pages = {99-108},
  abstract = {In the last couple of years, the number of smartphone users has proliferated. As smartphones contain a lot of different sensors, research interest in algorithms combining data of several sensors to derive meaningful information about a user's context, e.g. her location, is increasing. Ideas for reasonable algorithms often can be found by looking at examples of raw (or somehow pre-processed) sensor data. Still, the research community lacks a simple means to intuitively work with several parallel tracks of time series data. We present a tool which can be used to visualize and edit time dependent data from various sensors along with ground truth recordings like audio or video files. It is complemented by an optional application for logging all kinds of sensor data on Android devices. The tool has already been used to analyze a large data set containing hundreds of walking traces, intended to improve pedestrian dead reckoning algorithms.}
  }

• M. Schönfeld, M. Werner, and F. Dorfmeister, „Location-based Access Control Providing One-Time Passwords Through 2D Barcodes,“ in 9. GI/ITG KuVS Fachgespräch Ortsbezogene Anwendungen und Dienste, 2012, pp. 165-168.
  [BibTeX] [Abstract] [Download PDF]
  

  Location-based Access Control often relies a location proof, which ensures that a specific user is at a specific location. These locations are most often inferred from measurements. As a consequence, such systems are never trustworthy. An attacker can simply fake sensor measurements or even sensor data in absence of a trusted measurement module. Moreover, the measurement data is typically stable over time at a fixed location and can thus be replayed at later times. With this paper, we propose a system, which can provide functionality for a location proof, which does not rely on measurements and does not suffer from replay attacks. Therefore, a self-contained system is generating signed one-time passwords and communicates them via 2D barcodes for authentication of camera-enabled devices being in a specific location.

  @inproceedings{qrcodelocationproof,
  title = {Location-based Access Control Providing One-Time Passwords Through 2D Barcodes},
  author = {Mirco Schönfeld and Martin Werner and Florian Dorfmeister},
  booktitle = {9. GI/ITG KuVS Fachgespräch Ortsbezogene Anwendungen und Dienste},
  year = {2012},
  pages = {165-168},
  abstract = {Location-based Access Control often relies a location proof, which ensures that a specific user is at a specific location. These locations are most often inferred from measurements. As a consequence, such systems are never trustworthy. An attacker can simply fake sensor measurements or even sensor data in absence of a trusted measurement module. Moreover, the measurement data is typically stable over time at a fixed location and can thus be replayed at later times. With this paper, we propose a system, which can provide functionality for a location proof, which does not rely on measurements and does not suffer from replay attacks. Therefore, a self-contained system is generating signed one-time passwords and communicates them via 2D barcodes for authentication of camera-enabled devices being in a specific location.},
  file = {2012-LBAC.pdf:http\://publications.mircoschoenfeld.de/2012-LBAC.pdf:PDF},
  url = {http://publications.mircoschoenfeld.de/2012-LBAC.pdf}
  }

• M. Werner and M. Schönfeld, „DualCodes: Backward-Compatible Multi-Layer 2D-Barcodes,“ in 9th Annual International Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services (MOBIQUITOUS 2012), 2012, pp. 25-36.
  [BibTeX] [Abstract] [Download PDF]
  

  Matrix codes enable a coupling between virtual and physical worlds for ubiquitous computing applications. With this paper, we propose a technique, which can be used to increase the amount of information contained in a matrix barcode in a backward compatible way. This enables applications to fully utilize the wide spread of QR Codes or Data Matrix Codes for service discovery or basic service, while being able to transmit much more information during one scan for advanced applications. We present the approach, explain difficulties in decoding typical camera images, a simulatory evaluation of decoding performance, and application examples.

  @inproceedings{dualcodes,
  title = {DualCodes: Backward-Compatible Multi-Layer 2D-Barcodes},
  author = {Martin Werner and Mirco Schönfeld},
  booktitle = {9th Annual International Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services (MOBIQUITOUS 2012)},
  year = {2012},
  pages = {25-36},
  abstract = {Matrix codes enable a coupling between virtual and physical worlds for ubiquitous computing applications. With this paper, we propose a technique, which can be used to increase the amount of information contained in a matrix barcode in a backward compatible way. This enables applications to fully utilize the wide spread of QR Codes or Data Matrix Codes for service discovery or basic service, while being able to transmit much more information during one scan for advanced applications. We present the approach, explain difficulties in decoding typical camera images, a simulatory evaluation of decoding performance, and application examples.},
  file = {2012-DualCodes.pdf:http\://publications.mircoschoenfeld.de/2012-DualCodes.pdf:PDF},
  url = {http://www.springer.com/computer/communication+networks/book/978-3-642-40237-1}
  }