Linus Feiten, Dipl.-Inf.
Technische Fakultät Georges Köhler Allee 51 79110 Freiburg Deutschland
Gebäude 51, Raum 01-035
+49 (0)761 203-8183
+49 (0)761 203-8142
fingerprint = CF19 BEB2 B144 8964 96D7 E962 E775 13C8 EC0D 70D2
Liste filtern: Jahre: 2017
2012 | alle anzeigen nach oben zur Jahresübersicht Uwe Wagschal, Bernd Becker, Thomas Metz, Thomas Waldvogel, Linus Feiten Real-time evaluation of political debates at home and abroad with the Debat-O-Meter 2017 Berlin 19th General Online Research Conference (GOR) Due to their role in election campaigns, televised debates between political candidates (“TV-Duelle”) have attracted substantial scholarly attention. A large body of work has used physical feedback devices to measure viewers’ reactions to a debate in real-time. However, this approach is limited to lab-based settings with potential negative ramifications for e.g. external validity. Therefore, a method freeing researchers from the need to use physical devices is called for. Kurzfassung Matthias Sauer, Pascal Raiola, Linus Feiten, Bernd Becker, Ulrich Rührmair, Ilia Polian Sensitized Path PUF: A Lightweight Embedded Physical Unclonable Function 2017 Conf. on Design, Automation and Test in Europe Linus Feiten, Matthias Sauer, Bernd Becker Implementation of Delay-Based PUFs on Altera FPGAs In: Hardware Security and Trust: Design and Deployment of Integrated Circuits in a Threatened Environment 2017, Springer International Publishing, Seiten: 211 - 235, ISBN: 978-3-319-44318-8 This chapter focuses on the implementation of delay-based PUFs on Altera FPGAs. While there has been a manifold of publications on how to evaluate and refine PUFs, a thorough description of the required "handicrafts" enabling a novice to enter this exciting research field has so far been missing. The methods shared in this chapter are not just easily extractable from available standard documentation, but have been compiled by the authors over a long period of trials and consultations with the Altera user community. Designing a delay-based PUF on FPGAs requires fine-tuning which is often like diverting the automated design tools from their intended use. For example, the device-specific delays for the PUF response generation are generally gathered from circuitry looking redundant to the bitstream compiler. Therefore, the automatic reduction of such seemingly redundant circuitry must be prevented. The way the circuitry is placed and routed also has a major impact on delay characteristics, so it is necessary to customise this instead of letting the compiler do it automatically. The reader will be walked through all necessary steps by means of a running example enabling them to embark on further experiments on their own. Along the way, the architecture of Altera Cyclone FPGAs is explained and results from the authors' own experimental studies are shared. Kurzfassung nach oben zur Jahresübersicht Sebastian Volkmann, Linus Feiten, Christian Zimmermann, Sebastian Sester, Laura Wehle, Bernd Becker Digitale Tarnkappe: Anonymisierung in Videoaufnahmen 2016 INFORMATIK 2016 Gesellschaft für Informatik (GI), Heinrich C. Mayr, Martin Pinzger, Band: P-252, Seiten: 413 - 426 Videoüberwachung ist heute allgegenwärtig. Sie dient dazu, Delikte im Nachhinein aufzuklären, zur Echtzeit-Überwachung oder zur Abschreckung. Darüber hinaus gibt es aber auch wirtschaftliche Interessen für eine Videoüberwachung und automatische Erfassung von Personen - z.B. zur Erstellung von Kundenprofilen und somit zur Analyse von Kaufverhalten. Dem gegenüber stehen Rechtsansprüche sowie ethische und gesellschaftliche Grundnormen, etwa dass Menschen nicht unter Generalverdacht gestellt oder ohne Zustimmung aufgezeichnet werden dürfen. In dieser Arbeit wird ein technischer Lösungsansatz behandelt, der eine flexible Handhabung der Videoüberwachung erlaubt. Es werden in diesem Zusammenhang neben der technischen Umsetzung auch ökonomische, ethische und juristische Fragen betrachtet. Der Lösungsansatz besteht darin, Personen auf Videoaufnahmen durch ein kryptographisches Verfahren unkenntlich zu machen, noch bevor die Aufnahmen die Kamera-Elektronik verlassen. Nur mittels eines geheimen kryptographischen Schlüssels können einzelne Zeit- und Bildbereiche einer Aufnahme wieder deanonymisiert werden, wodurch rechtlichen wie ethischen Bedenken Rechnung getragen werden kann. In kommerziellen Szenarien erlaubt es diese digitale Tarnkappe, dass Kunden z.B. im Rahmen eines Prämien-Programms freiwillig auf Anonymisierung verzichten. Während in der Literatur der Informatik bereits seit längerem Technologien für solche System beschrieben werden, werden in dieser Arbeit Wege gezeigt, wie dessen Einbettung in die Gesellschaft wirklich realisiert werden könnte. Kurzfassung Linus Feiten, Matthias Sauer, Bernd Becker On Metrics to Quantify the Inter-Device Uniqueness of PUFs 2016 TRUDEVICE Workshop, Dresden Physically Unclonable Functions (PUFs) have been an emerging topic in hardware security and trust in recent years, and many different kinds of PUFs have been presented in the literature. An important criterion is always the diversity of PUF responses for different devices, called inter-device uniqueness. A very popular uniqueness metric consists of calculating the pairwise hamming distance between the response bit-strings of all devices, assuming that all response bits are uncorrelated. Such correlations, however, should be regarded when a statement about inter-device uniqueness is made. We therefore propose a novel correlation metric to fulfil this requirement. Furthermore, we show that the hamming distance metric is actually redundant when at the same time the also popular bit-aliasing metric is applied. Kurzfassung Thomas Metz, Uwe Wagschal, Thomas Waldvogel, Marko Bachl, Linus Feiten, Bernd Becker Das Debat-O-Meter: ein neues Instrument zur Analyse von TV-Duellen 2016 ZSE Zeitschrift für Staats- und Europawissenschaften, Band: 14, Nummer: 1, Seiten: 124 - 149 Linus Feiten, Sebastian Sester, Christian Zimmermann, Sebastian Volkmann, Laura Wehle, Bernd Becker Revocable Anonymisation in Video Surveillance: A "Digital Cloak of Invisibility" In: Technology and Intimacy: Choice or Coercion 2016, Springer International Publishing, Seiten: 314 - 327, ISBN: 978-3-319-44804-6 Video surveillance is an omnipresent phenomenon in today's metropolitan life. Mainly intended to solve crimes, to prevent them by realtime-monitoring or simply as a deterrent, video surveillance has also become interesting in economical contexts; e.g. to create customer profiles and analyse patterns of their shopping behaviour. The extensive use of video surveillance is challenged by legal claims and societal norms like not putting everybody under generalised suspicion or not recording people without their consent. In this work we propose a technological solution to balance the positive and negative effects of video surveillance. With automatic image recognition algorithms on the rise, we suggest to use that technology to not just automatically identify people but blacken their images. This blackening is done with a cryptographic procedure allowing to revoke it with an appropriate key. Many of the legal and ethical objections to video surveillance could thereby be accommodated. In commercial scenarios, the operator of a customer profiling program could offer enticements for voluntarily renouncing one's anonymity. Customers could e.g. wear a small infrared LED to signal their agreement to being tracked. After explaining the implementation details, this work outlines a multidisciplinary discussion incorporating an economic, ethical and legal viewpoint. Kurzfassung Bernd Becker, Katrin Weber, Linus Feiten SMartphones In der LEhre (SMILE) In: Kreativ, Innovativ, Motivierend - Lehrkonzepte in der Praxis: Der Instructional Development Award (IDA) der Universität Freiburg 2016, Universitäts Verlag Webler (UVW), Seiten: 117 - 133, ISBN: 978-3-946017-01-1 Linus Feiten, Jonathan Oesterle, Tobias Martin, Matthias Sauer, Bernd Becker Systematic Frequency Biases in Ring Oscillator PUFs on FPGAs
2016 IEEE Transactions on Multi-Scale Computing Systems (TMSCS), Band: PP, Nummer: 99 Physically unclonable functions (PUFs) are an emerging primitive in hardware security, enabling the identification of computer-chips. A promising type particularly for FPGA implementations is the Ring Oscillator (RO) PUF, where signal delays – stemming from uncontrollable variations in the manufacturing process – are used as device-specific characteristics. Based on experimental results gathered with 38 identical Altera FPGAs, we show the existence of nondevice- specific i.e. systemic RO frequency biases, traced back to (1) the internal routing within the RO’s look-up tables, (2) the RO locations on the FPGAs, or (3) the non-PUF payload activity. As these biases are the same for all devices, the result is poor inter-device uniqueness and unreliable signatures under changing payloads. After characterising these biases with a newly developed set of metrics, we suggest a method to overcome them: Using only a small sample of devices, the average bias over all devices for each RO is predicted and the relative differences caused by systemic biases are nullified. We demonstrate the viability of this method by determining the sufficient random sample sizes and showing that the inter-device uniqueness is drastically increased and the PUF signatures become reliable even under changing payload activities. Kurzfassung Matthias Sauer, Linus Feiten, Bernd Becker, Ulrich Rührmair, Ilia Polian Utilizing Intrinsic Delay Variability in Complex Digital Circuits for Defining PUF Behavior 2016 TRUDEVICE Workshop, Dresden nach oben zur Jahresübersicht Linus Feiten, Tobias Martin, Matthias Sauer, Bernd Becker Improving RO-PUF Quality on FPGAs by Incorporating Design-Dependent Frequency Biases 2015 IEEE European Test Symposium Physically unclonable functions (PUFs) based on ring oscillators (ROs) are a popular primitive in hardware security, meant to enable the unambiguous and tamper-proof identification of computer chips. This is achieved by exploiting different signal delays on each chip stemming from uncontrollable variations during the manufacturing process. Thus, the relation between RO frequencies on an individual chip can be used as the chip's unique PUF signature. In this work, we show how ROs implemented on a larger number of Altera Cyclone IV FPGAs are biased towards slower or faster frequencies in non-uniform ways depending on the FPGA's programming with different design; even though the ROs are placed and routed equally. Without considering these biases, inter-device uniqueness of the PUF signatures is degraded. We demonstrate that subtracting
the mean frequency of each RO - derived using only a small training set of devices - from the sampled frequencies overcomes this disadvantage; i.e. the uniqueness is increased drastically while maintaining reliability. Kurzfassung Linus Feiten, Tobias Martin, Matthias Sauer, Bernd Becker Analysis and utilisation of deviations in RO-PUFs under altered FPGA designs 2015 TRUDEVICE Workshop, Grenoble Physically unclonable functions (PUFs) based on ring oscillators (ROs) are a popular primitive in hardware security, enabling the unambiguous and tamper-proof identification of computer chips. This is achieved by exploiting uncontrollable variations in the chip manufacturing process, leading to different signal delays of each chip. Thus, if all ROs on a chip are affected uniformly by ageing and temperature effects, the relation between their frequencies can be used as the chip's unique finger print. A problem arises when the RO frequencies change in a non-uniform way.
Here, we are sharing our experiences from analyses on 70 FPGAs about how ROs implemented on Altera Cyclone IV FPGAs are affected in non-uniform ways depending on the non-PUF circuitry of the design. As specific ROs are affected towards faster or slower frequencies on all devices, this leads to bad inter-device uniqueness. We suggest that subtracting the mean frequency - derived with a training set of devices - from the sampled frequencies per RO on all devices will overcome this disadvantage. Kurzfassung Linus Feiten, Matthias Sauer Extracting the RC4 secret key of the Open Smart Grid Protocol (OSGP) 2015 Industrial Control System Security (ICSS) Workshop The Open Smart Grid Protocol (OSGP) is a widely used industry standard for exchanging sensitive data between devices inside of smart grids. For message confidentiality, OSGP implements a customised form of the RC4 stream cipher. In this work, we show how already known weaknesses of RC4 can be exploited to successfully attack the OSGP implementation as well. The attack modification is able to effectively derive the secret OSGP encryption and decryption key, given that an attacker can accumulate the cipher streams of approximately 90,000 messages. The possession of this key allows the attacker to decrypt all data intercepted on the OSGP smart grid and thereby obtain privacy critical information of its participants. Kurzfassung Linus Feiten, Matthias Sauer, Tobias Schubert, Victor Tomashevich, Ilia Polian, Bernd Becker Formal Vulnerability Analysis of Security Components 2015 IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems (TCAD), Band: 34, Nummer: 8, Seiten: 1358 - 1369 Vulnerability to malicious fault attacks is an emerging concern for hardware circuits that are employed in mobile and embedded systems and process sensitive data. We describe a new methodology to assess the vulnerability of a circuit to such attacks, taking into account built-in protection mechanisms. Our method is based on accurate modeling of fault effects and detection status expressed by Boolean satisfiability (SAT) formulas. Vulnerability is quantified based on the number of solutions of these formulas, which are determined by an efficient #SAT solver. We demonstrate the applicability of this method for design space exploration of a pseudo random number generator and for calculating the attack success rate in a multiplier circuit protected by robust error-detecting codes. Kurzfassung nach oben zur Jahresübersicht Linus Feiten, Andreas Spilla, Matthias Sauer, Tobias Schubert, Bernd Becker Implementation and Analysis of Ring Oscillator PUFs on 60 nm Altera Cyclone FPGAs 2014 Information Security Journal: A Global Perspective, Band: 22, Nummer: 5-6, Seiten: 265 - 273 Ring Oscillator (RO) physically unclonable functions (PUFs) on field programmable gate arrays (FPGAs) have drawn much attention in recent years. Making each FPGA uniquely identifiable, they allow for protection of intellectual property (IP) or generation of secret encryption keys. Their implementation has been widely discussed, but most experiments have been conducted on Xilinx platforms. In this paper, we report the statistical results from an analysis spanning 20 Cyclone IV FPGAs with 60 nm technology. We parameterize the RO length, placement, ambient temperature, and non-PUF switching activity and discuss the observed effects on PUF quality. Kurzfassung nach oben zur Jahresübersicht Linus Feiten, Katrin Weber, Bernd Becker SMILE: Smartphones in der Lehre – ein Rück- und Überblick 2013 INFORMATIK 2013 Gesellschaft für Informatik (GI), Matthias Horbach, Band: P-220, Seiten: 255 - 269 Bei SMILE handelt es sich um ein Projekt, das im Wintersemester 2010 gestartet wurde. Sein fortlaufendes Ziel ist die Erforschung von Möglichkeiten, die universitäre Lehre - insbesondere Vorlesungen mit über hundert Studierenden - durch den Einsatz von IT zu bereichern. Hierfür wurden Apps für Studierende und Dozierenden entwickelt, die auf allen gängigen Geräten laufen. Die konzeptionelle Planung liegt bei einem interdisziplinären Team aus Informatikern und Instructional Designern; für die Implementierung wird eng mit einem studentischen Entwicklerteam zusammen gearbeitet. Zwei Preisauszeichnungen zeigen die positive Resonanz, die SMILE bisher hervor gerufen hat. Im Sommersemester 2013 wird SMILE zum vierten Mal in einer größeren Vorlesung eingesetzt. In diesem Workshop-Paper beschreiben wir den bisherigen Verlauf des Projekts und die Kernfunktionalitäten der Software. Kurzfassung Linus Feiten, Matthias Sauer, Tobias Schubert, Alexander Czutro, Victor Tomashevich, Eberhard Böhl, Ilia Polian, Bernd Becker #SAT for Vulnerability Analysis of Security Components 2013 (Workshop-Paper, Informal Proceedings) IEEE European Test Symposium Vulnerability to malicious fault attacks is an emerging concern for hardware circuits that process sensitive data.We describe a new methodology to assess the vulnerability to such attacks, taking into account built-in protection mechanisms. Our method is based on accurate modeling of fault effects and their detection status expressed as Boolean satisfiability (SAT) formulae. Vulnerability is quantified based on the number of solutions of such formulae, which are computed by an eficient #SAT solver. We demonstrate the applicability of this method by analyzing a sequential pseudo random number generator and a combinatorial multiplier circuit both protected by robust error-detecting codes. Kurzfassung Linus Feiten, Andreas Spilla, Matthias Sauer, Tobias Schubert, Bernd Becker Analysis of Ring Oscillator PUFs on 60nm FPGAs 2013 TRUDEVICE Workshop, Avignon In hardware security and trusted computing it is often desired to uniquely and unambiguously identify a device among several others of the same brand. Physically unclonable functions (PUFs) take advantage of subtle variations in the devices' production process to achieve this. A ring oscillator (RO) PUF exploits differing time delays of circuits to yield a unique response from each device.