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Characterizing the Top Cycle via Strategyproofness [article]

Felix Brandt, Patrick Lederer
2021 arXiv   pre-print
Gibbard and Satterthwaite have shown that the only single-valued social choice functions (SCFs) that satisfy non-imposition (i.e., the function's range coincides with its codomain) and strategyproofness (i.e., voters are never better off by misrepresenting their preferences) are dictatorships. In this paper, we consider set-valued social choice correspondences (SCCs) that are strategyproof according to Fishburn's preference extension and, in particular, the top cycle, an attractive SCC that
more » ... rns the maximal elements of the transitive closure of the weak majority relation. Our main theorem implies that, under mild conditions, the top cycle is the only non-imposing strategyproof SCC whose outcome only depends on the quantified pairwise comparisons between alternatives. This result effectively turns the Gibbard-Satterthwaite impossibility into a complete characterization of the top cycle by moving from SCFs to SCCs. It is obtained as a corollary of a more general characterization of strategyproof SCCs.
arXiv:2108.04622v1 fatcat:yqd4c5va5vfk7kxrjsmirswr7u

Incentives in Social Decision Schemes with Pairwise Comparison Preferences [article]

Felix Brandt, Patrick Lederer, Warut Suksompong
2022 arXiv   pre-print
Social decision schemes (SDSs) map the preferences of individual voters over multiple alternatives to a probability distribution over the alternatives. In order to study properties such as efficiency, strategyproofness, and participation for SDSs, preferences over alternatives are typically lifted to preferences over lotteries using the notion of stochastic dominance (SD). However, requiring strategyproofness or participation with respect to this preference extension only leaves room for rather
more » ... undesirable SDSs such as random dictatorships. Hence, we focus on the natural but little understood pairwise comparison (PC) preference extension, which postulates that one lottery is preferred to another if the former is more likely to return a preferred outcome. In particular, we settle three open questions raised by Brandt (2017): (i) there is no Condorcet-consistent SDS that satisfies PC-strategyproofness; (ii) there is no anonymous and neutral SDS that satisfies PC-efficiency and PC-strategyproofness; and (iii) there is no anonymous and neutral SDS that satisfies PC-efficiency and strict PC-participation. All three impossibilities require m >= 4 alternatives and turn into possibilities when m <= 3.
arXiv:2204.12436v1 fatcat:mm65tzn4efdolhk65utlcejp5y

Relaxed Notions of Condorcet-Consistency and Efficiency for Strategyproof Social Decision Schemes [article]

Felix Brandt, Patrick Lederer, René Romen
2022 arXiv   pre-print
Social decision schemes (SDSs) map the preferences of a group of voters over some set of m alternatives to a probability distribution over the alternatives. A seminal characterization of strategyproof SDSs by Gibbard implies that there are no strategyproof Condorcet extensions and that only random dictatorships satisfy ex post efficiency and strategyproofness. The latter is known as the random dictatorship theorem. We relax Condorcet-consistency and ex post efficiency by introducing a lower
more » ... d on the probability of Condorcet winners and an upper bound on the probability of Pareto-dominated alternatives, respectively. We then show that the SDS that assigns probabilities proportional to Copeland scores is the only anonymous, neutral, and strategyproof SDS that can guarantee the Condorcet winner a probability of at least 2/m. Moreover, no strategyproof SDS can exceed this bound, even when dropping anonymity and neutrality. Secondly, we prove a continuous strengthening of Gibbard's random dictatorship theorem: the less probability we put on Pareto-dominated alternatives, the closer to a random dictatorship is the resulting SDS. Finally, we show that the only anonymous, neutral, and strategyproof SDSs that maximize the probability of Condorcet winners while minimizing the probability of Pareto-dominated alternatives are mixtures of the uniform random dictatorship and the randomized Copeland rule.
arXiv:2201.10418v1 fatcat:2etfz5nm7ncd7hxyaik4cbzjdm

NGBPA Next Generation BotNet Protocol Analysis [chapter]

Felix S. Leder, Peter Martini
2009 IFIP Advances in Information and Communication Technology  
As Felix S.  ...  Leder University of Bonn, Institute of Computer Science IV, Roemerstr. 164, 53117 Bonn, Germany, email: leder@cs.uni-bonn.de Peter Martini University of Bonn, Institute of Computer Science IV, Roemerstr  ... 
doi:10.1007/978-3-642-01244-0_27 fatcat:ciq7uf64nfhjbp5kl6xydmwhve

On the Indecisiveness of Kelly-Strategyproof Social Choice Functions [article]

Felix Brandt and Martin Bullinger and Patrick Lederer
2022 arXiv   pre-print
Social choice functions (SCFs) map the preferences of a group of agents over some set of alternatives to a non-empty subset of alternatives. The Gibbard-Satterthwaite theorem has shown that only extremely restrictive SCFs are strategyproof when there are more than two alternatives. For set-valued SCFs, or so-called social choice correspondences, the situation is less clear. There are miscellaneous - mostly negative - results using a variety of strategyproofness notions and additional
more » ... s. The simple and intuitive notion of Kelly-strategyproofness has turned out to be particularly compelling because it is weak enough to still allow for positive results. For example, the Pareto rule is strategyproof even when preferences are weak, and a number of attractive SCFs (such as the top cycle, the uncovered set, and the essential set) are strategyproof for strict preferences. In this paper, we show that, for weak preferences, only indecisive SCFs can satisfy strategyproofness. In particular, (i) every strategyproof rank-based SCF violates Pareto-optimality, (ii) every strategyproof support-based SCF (which generalize Fishburn's C2 SCFs) that satisfies Pareto-optimality returns at least one most preferred alternative of every voter, and (iii) every strategyproof non-imposing SCF returns the Condorcet loser in at least one profile. We also discuss the consequences of these results for randomized social choice.
arXiv:2102.00499v2 fatcat:ngkjegtms5ff3n5xcngdsu5wuq

Finding and extracting crypto routines from malware

Felix Leder, Peter Martini, Andre Wichmann
2009 2009 IEEE 28th International Performance Computing and Communications Conference  
In this paper we present a new approach for identifying the crypto routines in different types of malware. In traditional malware analysis, like sandboxing, network data is examined as seen on the wire or data is collected as it is written to a file. The use of proprietary binary formats, obfuscation, or encryption hides important details, which are necessary for investigating malicious behavior. It is hardly possible to create decryptors just from monitored sandbox data. Our approach not only
more » ... xamines the data when leaving or entering the malware but also correlates it with information from inside the malware. By monitoring the data at I/O interfaces as well as data dependencies our approach automatically reveals the data origin. Knowing the data origin enables an analyst to easily find the crypto functions. Using this approach, we were able to identify the encryption, decryption, and command parser in different malware samples each within minutes. In our evaluation, we present the results for the Kraken command&control protocol encryption and for the file encryption of the Srvcp trojan.
doi:10.1109/pccc.2009.5403858 dblp:conf/ipccc/LederMW09 fatcat:t4ctiutw4jeehlok35v6jqeumy

On the Indecisiveness of Kelly-Strategyproof Social Choice Functions

Felix Brandt, Martin Bullinger, Patrick Lederer
2022 The Journal of Artificial Intelligence Research  
Social choice functions (SCFs) map the preferences of a group of agents over some set of alternatives to a non-empty subset of alternatives. The Gibbard-Satterthwaite theorem has shown that only extremely restrictive SCFs are strategyproof when there are more than two alternatives. For set-valued SCFs, or so-called social choice correspondences, the situation is less clear. There are miscellaneous -- mostly negative -- results using a variety of strategyproofness notions and additional
more » ... nts. The simple and intuitive notion of Kelly-strategyproofness has turned out to be particularly compelling because it is weak enough to still allow for positive results. For example, the Pareto rule is strategyproof even when preferences are weak, and a number of attractive SCFs (such as the top cycle, the uncovered set, and the essential set) are strategyproof for strict preferences. In this paper, we show that, for weak preferences, only indecisive SCFs can satisfy strategyproofness. In particular, (i) every strategyproof rank-based SCF violates Pareto-optimality, (ii) every strategyproof support-based SCF (which generalize Fishburn's C2 SCFs) that satisfies Pareto-optimality returns at least one most preferred alternative of every voter, and (iii) every strategyproof non-imposing SCF returns the Condorcet loser in at least one profile. We also discuss the consequences of these results for randomized social choice.
doi:10.1613/jair.1.13449 fatcat:dwjlt5yvcrgynm5w4albekcbra

A Case Study in Ethical Decision Making Regarding Remote Mitigation of Botnets [chapter]

David Dittrich, Felix Leder, Tillmann Werner
2010 Lecture Notes in Computer Science  
It is becoming more common for researchers to find themselves in a position of being able to take over control of a malicious botnet. If this happens, should they use this knowledge to clean up all the infected hosts? How would this affect not only the owners and operators of the zombie computers, but also other researchers, law enforcement agents serving justice, or even the criminals themselves? What dire circumstances would change the calculus about what is or is not appropriate action to
more » ... e? We review two case studies of long-lived malicious botnets that present serious challenges to researchers and responders and use them to illuminate many ethical issues regarding aggressive mitigation. We make no judgments about the questions raised, instead laying out the pros and cons of possible choices and allowing workshop attendees to consider how and where they would draw lines. By this, we hope to expose where there is clear community consensus as well as where controversy or uncertainty exists. Copyright c 2010, IFCA. Primary source of publication is
doi:10.1007/978-3-642-14992-4_20 fatcat:dlxzzbq7v5ah5ohesjdiwz7nge

CIS: The Crypto Intelligence System for automatic detection and localization of cryptographic functions in current malware

Felix Matenaar, Andre Wichmann, Felix Leder, Elmar Gerhards-Padilla
2012 2012 7th International Conference on Malicious and Unwanted Software  
Finding and extracting crypto algorithms in binary code is often a tedious reverse engineering task. A significant amount of manual work is required when unknown implementations are used. This is especially true for malware that contains variants of existing or even completely new algorithms. So far, no flexible and generic crypto detection framework exists that can support analysts in this task. The framework must be able to handle various heuristics that each are ideal to detect specific
more » ... of cryptographic algorithms. In addition, a suitable set of heuristics must be selected that can identify a wide range of crypto algorithms from various classes since the type of crypto implemented in a binary is not always known. In this paper, we present the architecture of CIS, the Crypto Intelligence System, that fulfills the requirements for such a framework. Furthermore, we evaluate different heuristics for the real-world usage in the framework. The overall evaluation, using real programs, shows that CIS simplifies the job of an analysts significantly with a high detection and low false positive ratio.
doi:10.1109/malware.2012.6461007 dblp:conf/malware/MatenaarWLG12 fatcat:vjokrqozqnd3bfynkf2szom6ba

Bonah, Christian: L'expérimentation humaine. Discours et pratiques en France, 1900–1940. Préface de Susan E. Lederer. Paris, Les Belles Lettres, 2007. 423 p. (Médecine & Sciences humaines). € 25.–. ISBN 978-2-251-43016-4

Félix Ullmann
2008 Gesnerus  
Félix Ullmann, Lausanne Céline Eidenbenz, Lausanne Bonah, Christian: L'expérimentation humaine. Discours et pratiques en France, 1900-1940. Préface de Susan E. Lederer.  ... 
doi:10.1163/22977953-0650304007 fatcat:4kgryfm3vjanxlkawzaqtuxb5q

Serum Transaminase Levels in Experimental Myocardial Infarction

CLARENCE M. AGRESS, HOWARD I. JACOBS, HARVEY F. GLASSNER, MARIANNE A. LEDERER, WM. G. CLARK, FELIX WROBLEWSKI, ARTHUR KARMEN, JOHN S. LADUE
1955 Circulation  
doi:10.1161/01.cir.11.5.711 pmid:14364745 fatcat:73tuxg6tf5cj5itmknx63nq2u4

Amphiphilic block copolymers featuring a reversible hetero Diels-Alder linkage

Marcel Langer, Josef Brandt, Albena Lederer, Anja S. Goldmann, Felix H. Schacher, Christopher Barner-Kowollik
2014 Polymer Chemistry  
The present article reports the preparation of a novel class of switchable amphiphilic diblock copolymers with a temperature switchable linkage. Reversible addition fragmentation chain transfer (RAFT) polymerization was used to synthesize the individual blocks: for the preparation of the non-polar block, i.e. poly(isoprene-co-styrene) (P(I-co-S)) (9200 g mol À1 # M n # 50 000 g mol À1 , 1.22 # Đ # 1.36), a chain transfer agent (CTA, 3-((2-bromo-2-methylpropanoyl)oxy)propyl
more » ... nothioyl) thio)-2-methylpropanoate) carrying a bromine group was employed, ready for subsequent cyclopentadienyl (Cp) transformation. For the preparation of the polar block, triethylene glycol methyl ether acrylate (TEGA) was polymerized (6600 g mol À1 # M n # 35 000 g mol À1 , 1.12 # Đ # 1.30) using a RAFT agent carrying a phosphoryl Z-group, which is able to undergo hetero Diels-Alder (HDA) ligation with Cp moieties. Both building blocks were conjugated at ambient temperature in the presence of ZnCl 2 as catalyst yielding the amphiphilic block copolymer P(I-co-S)-b-PTEGA (16 000 g mol À1 # M n # 68 000 g mol À1 , 1.15 # Đ # 1.32). To investigate the bonding/debonding capability of the HDA linkage, high temperature nuclear magnetic resonance (HT-NMR) spectroscopy, high temperature dynamic light scattering (HT-DLS) and high temperature size exclusion chromatography (HT-SEC) were carried out, evidencing that efficiently switchable amphiphilic block copolymers were generated (>4 cycles). † Electronic supplementary information (ESI) available: The experimental part, including the used materials, synthetic procedures and used characterization methods, 1 H-, 13 C-NMR and ESI-MS spectra of the new RAFT agent, kinetic studies of the polymerization and SEC traces of the polymers before and aer Cp-transformation, 1 H-NMR spectra of the building blocks and the resulting block copolymer, a table of the calculated ratios from both block copolymers and the content of isoprene and all measured HT-SEC traces. See Scheme 1 Synthetic strategy for the preparation of amphiphilic P(S-co-I)-b-PTEGA block copolymers with a reversible hetero Diels-Alder linkage. 5332 | Polym. Chem., 2014, 5, 5330-5338 This journal is
doi:10.1039/c4py00644e fatcat:z2vmg5w4yrbxfmykptij2wtpre

Classification and detection of metamorphic malware using value set analysis

Felix Leder, Bastian Steinbock, Peter Martini
2009 2009 4th International Conference on Malicious and Unwanted Software (MALWARE)  
Metamorphic malware changes the structure of its code from infection to infection. This makes it very hard to classify or to detect. While the byte-sequence of two variants may be completely different, the core functionality of the malware has to stay the same. This includes the use of flags and constants that have to be consistent at specific points. We present a novel approach that allows us to detect metamorphic variants. Based on this detection, it is also possible to classify new samples
more » ... a metamorphic family. Our approach identifies variants by tracking the use of consistent values throughout the malware. Our evaluation shows a 100% detection rate with 0 false positives for all metamorphic samples that do not change their behavior.
doi:10.1109/malware.2009.5403019 dblp:conf/malware/LederSM09 fatcat:2slzikex3vgo7oznu24qundtde

Computer Controlled Automated Assay for Comprehensive Studies of Enzyme Kinetic Parameters

Felix Bonowski, Ana Kitanovic, Peter Ruoff, Jinda Holzwarth, Igor Kitanovic, Van Ngoc Bui, Elke Lederer, Stefan Wölfl, Vladimir Brusic
2010 PLoS ONE  
Stability and biological activity of proteins is highly dependent on their physicochemical environment. The development of realistic models of biological systems necessitates quantitative information on the response to changes of external conditions like pH, salinity and concentrations of substrates and allosteric modulators. Changes in just a few variable parameters rapidly lead to large numbers of experimental conditions, which go beyond the experimental capacity of most research groups. We
more » ... plemented a computer-aided experimenting framework ("robot lab assistant") that allows us to parameterize abstract, human-readable descriptions of micro-plate based experiments with variable parameters and execute them on a conventional 8 channel liquid handling robot fitted with a sensitive plate reader. A set of newly developed R-packages translates the instructions into machine commands, executes them, collects the data and processes it without user-interaction. By combining script-driven experimental planning, execution and data-analysis, our system can react to experimental outcomes autonomously, allowing outcome-based iterative experimental strategies. The framework was applied in a response-surface model based iterative optimization of buffer conditions and investigation of substrate, allosteric effector, pH and salt dependent activity profiles of pyruvate kinase (PYK). A diprotic model of enzyme kinetics was used to model the combined effects of changing pH and substrate concentrations. The 8 parameters of the model could be estimated from a single two-hour experiment using nonlinear least-squares regression. The model with the estimated parameters successfully predicted pH and PEP dependence of initial reaction rates, while the PEP concentration dependent shift of optimal pH could only be reproduced with a set of manually tweaked parameters. Differences between modelpredictions and experimental observations at low pH suggest additional protonation-sites at the enzyme or substrates critical for enzymatic activity. The developed framework is a powerful tool to investigate enzyme reaction specifics and explore biological system behaviour in a wide range of experimental conditions.
doi:10.1371/journal.pone.0010727 pmid:20502716 pmcid:PMC2873295 fatcat:fyd4ui7n4zginexgxcdjv4u6x4

Detecting VoIP based DoS attacks at the public safety answering point

Christoph Fuchs, Nils Aschenbruck, Felix Leder, Peter Martini
2008 Proceedings of the 2008 ACM symposium on Information, computer and communications security - ASIACCS '08  
In the recent years Voice over IP (VoIP) telephony started to migrate from research to the market. In the future, All-IP networks will substitute the classical Public Switched Telephone Networks (PSTNs). Nowadays, there is no All-IP network yet, but many VoIP-providers already enable calls from VoIP to a PSTN and vice versa. Thus, critical infrastructures within the PSTN like the emergency call service, are accessible from the VoIP network (e.g. the Internet) and get exposed to new security
more » ... ats. In particular, there is the risk of Denial of Service (DoS) attacks originating from the VoIP network. An attacker could jam the emergency call service by generating a massive load of faked emergency calls, which could lead to the loss of lives in the worst case. For us, this was the motivation to analyse the applicability of the concept of Intrusion Detection (ID) in the emergency call context and develop an adapted ID-architecture including its implementation. In an evaluation of the IDarchitecture, using real emergency call traces from the fire department of Cologne, we show that the developed concept can reliably detect emerging DoS attacks from VoIP networks up to a certain VoIP diffusion rate.
doi:10.1145/1368310.1368333 dblp:conf/ccs/FuchsALM08 fatcat:gos2hfvgi5hprjjk76zupfpv2i
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