@misc{MitsevaPanchenkoLanzeetal., author = {Mitseva, Asya and Panchenko, Andriy and Lanze, Fabian and Henze, Martin and Engel, Thomas and Wehrle, Klaus}, title = {POSTER: Fingerprinting Tor Hidden Services}, series = {In Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security (CCS '16). Association for Computing Machinery, New York, NY, USA}, journal = {In Proceedings of the 2016 ACM SIGSAC Conference on Computer and Communications Security (CCS '16). Association for Computing Machinery, New York, NY, USA}, publisher = {ACM}, address = {New York}, isbn = {978-1-4503-4139-4}, doi = {10.1145/2976749.2989054}, pages = {1766 -- 1768}, language = {en} } @misc{PennekampHillerReuteretal., author = {Pennekamp, Jan and Hiller, Jens and Reuter, Sebastian and De la Cadena, Wladimir and Mitseva, Asya and Henze, Martin and Engel, Thomas and Wehrle, Klaus and Panchenko, Andriy}, title = {Multipathing Traffic to Reduce Entry Node Exposure in Onion Routing}, series = {Proceedings of the 27th annual IEEE International Conference on Network Protocols (Poster) (IEEE ICNP 2019), Chicago, Illinois, USA, October 2019}, journal = {Proceedings of the 27th annual IEEE International Conference on Network Protocols (Poster) (IEEE ICNP 2019), Chicago, Illinois, USA, October 2019}, publisher = {IEEE Press}, isbn = {978-1-7281-2700-2}, issn = {2643-3303}, doi = {10.1109/ICNP.2019.8888029}, pages = {2}, abstract = {Users of an onion routing network, such as Tor, depend on its anonymity properties. However, especially malicious entry nodes, which know the client's identity, can also observe the whole communication on their link to the client and, thus, conduct several de-anonymization attacks. To limit this exposure and to impede corresponding attacks, we propose to multipath traffic between the client and the middle node to reduce the information an attacker can obtain at a single vantage point. To facilitate the deployment, only clients and selected middle nodes need to implement our approach, which works transparently for the remaining legacy nodes. Furthermore, we let clients control the splitting strategy to prevent any external manipulation.}, language = {en} } @misc{HillerPennekampDahlmannsetal., author = {Hiller, Jens and Pennekamp, Jan and Dahlmanns, Markus and Henze, Martin and Panchenko, Andriy and Wehrle, Klaus}, title = {Tailoring Onion Routing to the Internet of Things: Security and Privacy in Untrusted Environments}, series = {Proceedings of the 27th annual IEEE International Conference on Network Protocols (IEEE ICNP 2019), Chicago, Illinois, USA, October 2019}, journal = {Proceedings of the 27th annual IEEE International Conference on Network Protocols (IEEE ICNP 2019), Chicago, Illinois, USA, October 2019}, publisher = {IEEE Press}, isbn = {978-1-7281-2700-2}, issn = {2643-3303}, doi = {10.1109/ICNP.2019.8888033}, pages = {12}, abstract = {An increasing number of IoT scenarios involve mobile, resource-constrained IoT devices that rely on untrusted networks for Internet connectivity. In such environments, attackers can derive sensitive private information of IoT device owners, e.g., daily routines or secret supply chain procedures, when sniffing on IoT communication and linking IoT devices and owner. Furthermore, untrusted networks do not provide IoT devices with any protection against attacks from the Internet. Anonymous communication using onion routing provides a well-proven mechanism to keep the relationship between communication partners secret and (optionally) protect against network attacks. However, the application of onion routing is challenged by protocol incompatibilities and demanding cryptographic processing on constrained IoT devices, rendering its use infeasible. To close this gap, we tailor onion routing to the IoT by bridging protocol incompatibilities and offloading expensive cryptographic processing to a router or web server of the IoT device owner. Thus, we realize resource-conserving access control and end-toend security for IoT devices. To prove applicability, we deploy onion routing for the IoT within the well-established Tor network enabling IoT devices to leverage its resources to achieve the same grade of anonymity as readily available to traditional devices.}, language = {en} } @misc{DeLaCadenaMitsevaPennekampetal., author = {De La Cadena, Wladimir and Mitseva, Asya and Pennekamp, Jan and Hiller, Jens and Lanze, Fabian and Engel, Thomas and Wehrle, Klaus and Panchenko, Andriy}, title = {POSTER: Traffic Splitting to Counter Website Fingerprinting}, series = {CCS '19 Proceedings of the 2019 ACM SIGSAC Conference on Computer and Communications Security , London, UK, November 11 - 15, 2019.}, journal = {CCS '19 Proceedings of the 2019 ACM SIGSAC Conference on Computer and Communications Security , London, UK, November 11 - 15, 2019.}, publisher = {ACM Press}, address = {New York}, isbn = {978-1-4503-6747-9}, doi = {10.1145/3319535.3363249}, pages = {2533 -- 2535}, abstract = {Website fingerprinting (WFP) is a special type of traffic analysis, which aims to infer the websites visited by a user. Recent studies have shown that WFP targeting Tor users is notably more effective than previously expected. Concurrently, state-of-the-art defenses have been proven to be less effective. In response, we present a novel WFP defense that splits traffic over multiple entry nodes to limit the data a single malicious entry can use. Here, we explore several traffic-splitting strategies to distribute user traffic. We establish that our weighted random strategy dramatically reduces the accuracy from nearly 95\% to less than 35\% for four state-of-the-art WFP attacks without adding any artificial delays or dummy traffic.}, language = {en} } @misc{PennekampHenzeHohlfeldetal., author = {Pennekamp, Jan and Henze, Martin and Hohlfeld, Oliver and Panchenko, Andriy}, title = {Hi Doppelg{\"a}nger: Towards Detecting Manipulation in News Comments}, series = {Companion Proceedings of the 2019 World Wide Web Conference (WWW '19 Companion), 4th Workshop on Computational Methods in Online Misbehavior (CyberSafety '19), May 13-17, 2019, San Francisco, CA, USA}, journal = {Companion Proceedings of the 2019 World Wide Web Conference (WWW '19 Companion), 4th Workshop on Computational Methods in Online Misbehavior (CyberSafety '19), May 13-17, 2019, San Francisco, CA, USA}, publisher = {ACM}, address = {New York}, isbn = {978-1-4503-6675-5}, doi = {10.1145/3308560.3316496}, pages = {197 -- 205}, language = {en} } @misc{DelaCadenaKaiserMitsevaetal., author = {De la Cadena, Wladimir and Kaiser, Daniel and Mitseva, Asya and Panchenko, Andriy and Engel, Thomas}, title = {Analysis of Multi-path Onion Routing-based Anonymization Networks}, series = {Data and Applications Security and Privacy XXXIII : 33rd Annual IFIP WG 11.3 Conference, DBSec 2019, Charleston, SC, USA, July 15-17, 2019, Proceedings}, journal = {Data and Applications Security and Privacy XXXIII : 33rd Annual IFIP WG 11.3 Conference, DBSec 2019, Charleston, SC, USA, July 15-17, 2019, Proceedings}, editor = {Foley, Simon N.}, publisher = {Springer}, address = {Frankfurt am Main}, isbn = {978-3-030-22478-3}, issn = {0302-9743}, doi = {10.1007/978-3-030-22479-0_13}, pages = {240 -- 258}, language = {en} } @misc{MitsevaEngelPanchenko, author = {Mitseva, Asya and Engel, Thomas and Panchenko, Andriy}, title = {Analyzing PeerFlow - A Bandwidth Estimation System for Untrustworthy Environments}, series = {Sicherheit 2020 : Sicherheit, Schutz und Zuverl{\"a}ssigkeit ; Konferenzband der 10. Jahrestagung des Fachbereichs Sicherheit der Gesellschaft f{\"u}r Informatik e.V. (GI) ; 17.- 20. M{\"a}rz 2020 in G{\"o}ttingen}, journal = {Sicherheit 2020 : Sicherheit, Schutz und Zuverl{\"a}ssigkeit ; Konferenzband der 10. Jahrestagung des Fachbereichs Sicherheit der Gesellschaft f{\"u}r Informatik e.V. (GI) ; 17.- 20. M{\"a}rz 2020 in G{\"o}ttingen}, editor = {Reinhardt, Delphine and Langweg, Hanno and Witt, Bernhard C. and Fischer, Mathias}, publisher = {Gesellschaft f{\"u}r Informatik}, address = {Bonn}, isbn = {978-3-88579-695-4}, doi = {10.18420/sicherheit2020_02}, pages = {29 -- 40}, language = {en} } @misc{MitsevaAleksandrovaEngeletal., author = {Mitseva, Asya and Aleksandrova, Marharyta and Engel, Thomas and Panchenko, Andriy}, title = {Security and Performance Implications of BGP Rerouting-resistant Guard Selection Algorithms for Tor}, series = {ICT Systems Security and Privacy Protection : 35th IFIP TC 11 International Conference, SEC 2020, Maribor, Slovenia, September 21-23, 2020}, journal = {ICT Systems Security and Privacy Protection : 35th IFIP TC 11 International Conference, SEC 2020, Maribor, Slovenia, September 21-23, 2020}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-58201-2}, issn = {1868-4238}, doi = {10.1007/978-3-030-58201-2_15}, pages = {219 -- 233}, language = {en} } @misc{DelaCadenaMitsevaHilleretal., author = {De la Cadena, Wladimir and Mitseva, Asya and Hiller, Jens and Pennekamp, Jan and Reuter, Sebastian and Filter, Julian and Engel, Thomas and Wehrle, Klaus and Panchenko, Andriy}, title = {TrafficSliver: Fighting Website Fingerprinting Attacks with Traffic Splitting}, series = {CCS '20: Proceedings of the 2020 ACM SIGSAC Conference on Computer and Communications Security, October 2020}, journal = {CCS '20: Proceedings of the 2020 ACM SIGSAC Conference on Computer and Communications Security, October 2020}, publisher = {Association for Computing Machinery}, address = {New York}, isbn = {978-1-4503-7089-9}, doi = {10.1145/3372297.3423351}, pages = {1971 -- 1985}, abstract = {Website fingerprinting (WFP) aims to infer information about the content of encrypted and anonymized connections by observing patterns of data flows based on the size and direction of packets. By collecting traffic traces at a malicious Tor entry node — one of the weakest adversaries in the attacker model of Tor — a passive eavesdropper can leverage the captured meta-data to reveal the websites visited by a Tor user. As recently shown, WFP is significantly more effective and realistic than assumed. Concurrently, former WFP defenses are either infeasible for deployment in real-world settings or defend against specific WFP attacks only. To limit the exposure of Tor users to WFP, we propose novel lightweight WFP defenses, TrafficSliver, which successfully counter today's WFP classifiers with reasonable bandwidth and latency overheads and, thus, make them attractive candidates for adoption in Tor. Through user-controlled splitting of traffic over multiple Tor entry nodes, TrafficSliver limits the data a single entry node can observe and distorts repeatable traffic patterns exploited by WFP attacks.We first propose a network-layer defense, in which we apply the concept of multipathing entirely within the Tor network. We show that our network-layer defense reduces the accuracy from more than 98\% to less than 16\% for all state-of-the-art WFP attacks without adding any artificial delays or dummy traffic. We further suggest an elegant client-side application-layer defense, which is independent of the underlying anonymization network. By sending single HTTP requests for different web objects over distinct Tor entry nodes, our application-layer defense reduces the detection rate of WFP classifiers by almost 50 percentage points. Although it offers lower protection than our network-layer defense, it provides a security boost at the cost of a very low implementation overhead and is fully compatible with today's Tor network.}, language = {en} } @misc{DelaCadenaKaiserPanchenkoetal., author = {De la Cadena, Wladimir and Kaiser, Daniel and Panchenko, Andriy and Engel, Thomas}, title = {Out-of-the-box Multipath TCP as a Tor Transport Protocol: Performance and Privacy Implications}, series = {2020 IEEE 19th International Symposium on Network Computing and Applications (NCA), 24-27 Nov. 2020, Cambridge, MA, USA}, journal = {2020 IEEE 19th International Symposium on Network Computing and Applications (NCA), 24-27 Nov. 2020, Cambridge, MA, USA}, isbn = {978-1-7281-8326-8}, issn = {2643-7929}, doi = {10.1109/NCA51143.2020.9306702}, pages = {6}, language = {en} } @misc{MitsevaPennekampLohmoelleretal., author = {Mitseva, Asya and Pennekamp, Jan and Lohm{\"o}ller, Johannes and Ziemann, Torsten and Hoerchner, Carl and Wehrle, Klaus and Panchenko, Andriy}, title = {POSTER: How Dangerous is My Click? Boosting Website Fingerprinting By Considering Sequences of Webpages}, series = {Proceedings of the 28th ACM Conference on Computer and Communications Security (ACM CCS 2021), Seoul, Virtual Event, South Korea, November 2021}, journal = {Proceedings of the 28th ACM Conference on Computer and Communications Security (ACM CCS 2021), Seoul, Virtual Event, South Korea, November 2021}, publisher = {ACM Press}, address = {New York}, isbn = {978-1-4503-8454-4}, doi = {10.1145/3460120.3485347}, pages = {2411 -- 2413}, language = {en} } @misc{PanchenkoMitsevaKnabe, author = {Panchenko, Andriy and Mitseva, Asya and Knabe, Sara}, title = {WhisperChord: Scalable and Secure Node Discovery for Overlay Networks}, series = {IEEE 46th Conference on Local Computer Networks (LCN), Edmonton, AB, Canada , 4-7 Oct. 2021}, journal = {IEEE 46th Conference on Local Computer Networks (LCN), Edmonton, AB, Canada , 4-7 Oct. 2021}, publisher = {IEEE}, isbn = {978-1-6654-1886-7}, issn = {0742-1303}, doi = {10.1109/LCN52139.2021.9525008}, pages = {170 -- 177}, abstract = {Node discovery is a fundamental service for any overlay network, including anonymization networks. Although anonymization and node discovery are two disjoint services, the node discovery has a direct impact on the anonymization. Centralized methods require a trusted third party, limit the network scalability, and are vulnerable to intersection (statistical disclosure) attacks. Therefore, several distributed node discovery methods were proposed to meet the security requirements of anonymization networks through additional structures within Distributed Hash Tables (DHTs). However, they require a high management overhead, a strict cooperation between nodes, and are susceptible to active and passive attacks.We propose WhisperChord—an alternative distributed node discovery approach, which incorporates gossiping into structured overlays. WhisperChord is based on a Chord DHT and neither creates any additional structures within the DHT nor requires any trusted third party. Via simulations, we show that our method provides superior protection against active attacks than prior methods and can effectively thwart information leakages.}, language = {en} } @misc{PanchenkoMitsevaZiemannetal., author = {Panchenko, Andriy and Mitseva, Asya and Ziemann, Torsten and Hering, Till}, title = {GuardedGossip: Secure and Anonymous Node Discovery in Untrustworthy Networks}, series = {Security and Privacy in Communication Networks : 17th EAI International Conference, SecureComm 2021, Virtual Event, September 6-9, 2021, Proceedings, Part I}, journal = {Security and Privacy in Communication Networks : 17th EAI International Conference, SecureComm 2021, Virtual Event, September 6-9, 2021, Proceedings, Part I}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-90018-2}, issn = {1867-8211}, doi = {10.1007/978-3-030-90019-9_7}, pages = {123 -- 143}, abstract = {Node discovery is a fundamental service for any overlay network. It is a particular challenge to provide unbiased discovery in untrustworthy environments, e.g., anonymization networks. Although a major line of research focused on solving this problem, proposed methods have been shown to be vulnerable either to active attacks or to leak routing information, both threatening the anonymity of users. In response, we propose GuardedGossip—a novel gossip-based node discovery protocol—that achieves an unbiased random node discovery in a fully-decentralized and highly-scalable fashion. It is built on top of a Chord distributed hash table (DHT) and relies on witness nodes and bound checks to resist active attacks. To limit routing information leakages, GuardedGossip uses gossiping to create uncertainty in the process of node discovery. By incorporating the principles of DHTs with the unstructured nature of gossiping in a subtle way, we profit from the strengths of both techniques while carefully mitigating their shortcomings. We show that GuardedGossip provides a sufficient level of security for users even if 20\% of the participating nodes are malicious. Concurrently, our system scales gracefully and provides an adequate overhead for its security and privacy benefits.}, language = {en} } @misc{VogelSchusterKoppetal., author = {Vogel, Michael and Schuster, Franka and Kopp, Fabian Malte and K{\"o}nig, Hartmut}, title = {Data Volume Reduction for Deep Packet Inspection by Multi-layer Application Determination}, series = {2022 IEEE International Conference on Cyber Security and Resilience (CSR), 27-29 July 2022, Rhodes, Greece}, journal = {2022 IEEE International Conference on Cyber Security and Resilience (CSR), 27-29 July 2022, Rhodes, Greece}, publisher = {IEEE}, isbn = {978-1-6654-9952-1}, doi = {10.1109/CSR54599.2022.9850293}, pages = {6}, abstract = {Attack detection in enterprise networks is increasingly faced with large data volumes, in part high data bursts, and heavily fluctuating data flows that often cause arbitrary discarding of data packets in overload situations which can be used by attackers to hide attack activities. Attack detection systems usually configure a comprehensive set of signatures for known vulnerabilities in different operating systems, protocols, and applications. Many of these signatures, however, are not relevant in each context, since certain vulnerabilities have already been eliminated, or the vulnerable applications or operating system versions, respectively, are not installed on the involved systems. In this paper, we present an approach for clustering data flows to assign them to dedicated analysis units that contain only signature sets relevant for the analysis of these flows. We discuss the performance of this clustering and show how it can be used in practice to improve the efficiency of an analysis pipeline.}, language = {en} } @misc{SchusterLarisch, author = {Schuster, Franka and Larisch, Ren{\´e}}, title = {KI-basierte Angriffserkennung: Von der Blackbox zum verst{\"a}ndlichen System}, series = {54. Kraftwerkstechni­sches Kolloquium 2022}, journal = {54. Kraftwerkstechni­sches Kolloquium 2022}, language = {de} } @misc{PennekampHenzeZinnenetal., author = {Pennekamp, Jan and Henze, Martin and Zinnen, Andreas and Lanze, Fabian and Wehrle, Klaus and Panchenko, Andriy}, title = {CUMUL \& Co: High-Impact Artifacts for Website Fingerprinting Research}, series = {38th Annual Computer Security Applications Conference (ACSAC 2022), Austin, Texas, USA, December 5-9, 2022.}, journal = {38th Annual Computer Security Applications Conference (ACSAC 2022), Austin, Texas, USA, December 5-9, 2022.}, pages = {6}, abstract = {Anonymous communication on the Internet is about hiding the relationship between communicating parties. At NDSS '16, we presented a new website fingerprinting approach, CUMUL, that utilizes novel features and a simple yet powerful algorithm to attack anonymization networks such as Tor. Based on pattern observation of data flows, this attack aims at identifying the content of encrypted and anonymized connections. Apart from the feature generation and the used classifier, we also provided a large dataset to the research community to study the attack at Internet scale. In this paper, we emphasize the impact of our artifacts by analyzing publications referring to our work with respect to the dataset, feature extraction method, and source code of the implementation. Based on this data, we draw conclusions about the impact of our artifacts on the research field and discuss their influence on related cybersecurity topics. Overall, from 393 unique citations, we discover more than 130 academic references that utilize our artifacts, 61 among them are highly influential (according to SemanticScholar), and at least 43 are from top-ranked security venues. This data underlines the significant relevance and impact of our work as well as of our artifacts in the community and beyond.}, language = {en} } @misc{ReuterHillerPennekampetal., author = {Reuter, Sebastian and Hiller, Jens and Pennekamp, Jan and Panchenko, Andriy and Wehrle, Klaus}, title = {Demo: Traffic Splitting for Tor - A Defense against Fingerprinting Attacks}, series = {Conference on Networked Systems 2021 (NetSys 2021)}, journal = {Conference on Networked Systems 2021 (NetSys 2021)}, issn = {1863-2122}, doi = {10.14279/tuj.eceasst.80.1151.1128}, pages = {4}, abstract = {Website fingerprinting (WFP) attacks on the anonymity network Tor have become ever more effective. Furthermore, research discovered that proposed defenses are insufficient or cause high overhead. In previous work, we presented a new WFP defense for Tor that incorporates multipath transmissions to repel malicious Tor nodes from conducting WFP attacks. In this demo, we showcase the operation of our traffic splitting defense by visually illustrating the underlying Tor multipath transmission using LED-equipped Raspberry Pis.}, language = {en} } @misc{YiWuXietal., author = {Yi, Chao and Wu, Shunxiang and Xi, Bin and Ming, Daodong and Zhang, Yisong and Zhou, Zhenwen}, title = {Terrorist Video Detection System Based on Faster R-CNN and LightGBM}, series = {CSAE '20: Proceedings of the 4th International Conference on Computer Science and Application Engineering}, journal = {CSAE '20: Proceedings of the 4th International Conference on Computer Science and Application Engineering}, isbn = {978-1-4503-7772-0}, doi = {10.1145/3424978.3425121}, pages = {1 -- 8}, abstract = {Nowadays the mobile phone has become an indispensable tool in the lives of many people. While facilitating people's lives, it also provides criminals with a very important tool for spreading the terrorist video. Traditional manual detection of the terrorist video has the problem of low accuracy and inefficiency. To address the issue, this paper proposes a terrorist video detection system based on Light Gradient Boosting Machine (LightGBM) and Faster Region-based Convolutional Neural Network (Faster R-CNN) for mobile phone forensics system, which is used to quickly detect whether there is a terrorist video in the suspect's mobile phone. The system uses a multi-model method for detection, which includes preliminary detection and deep detection in two stages. Experimental research shows that it can effectively and accurately detect terrorist videos in mobile phones, thereby helping criminal investigation personnel to quickly grasp criminal evidence and provide some clues for the detection of the case.}, language = {en} } @misc{GaoLinZhangetal., author = {Gao, Yunlong and Lin, Tingting and Zhang, Yisong and Luo, Sizhe and Nie, Feiping}, title = {Robust principal component analysis based on discriminant information}, series = {IEEE Transactions on Knowledge and Data Engineering}, volume = {35}, journal = {IEEE Transactions on Knowledge and Data Engineering}, number = {2}, publisher = {IEEE}, issn = {1558-2191}, doi = {10.1109/TKDE.2021.3093447}, pages = {1991 -- 2003}, abstract = {Recently, several robust principal component analysis (RPCA) models were presented to enhance the robustness of PCA by exploiting the robust norms as their loss functions. But an important problem is that they have no ability to discriminate outliers from correct samples. To solve this problem, we propose a robust principal component analysis based on discriminant information (RPCA-DI). RPCA-DI disentangles the robust PCA with a two-step fashion: the identification and the processing of outliers. To identity outliers, a sample representation model based on entropy regularization is constructed to analyze the membership of data belonging to the principal component space(PC) and its orthogonal complement(OC), the discriminative information of data will be extracted based on measuring the differences of retained information on PC(or OC) of data. By this way, we can discriminate correct samples when we deal with outliers, which is more reasonable for robustness learning respective to previous works. In the noise processing step, in addition to considering the levels of noise, the resistance of the sample points to noise is also considered to prevent overfitting, thereby improving the generalization performance of RPCA-DI. Finally, an iterative algorithm is designed to solve the corresponding model. Compared with some state-of-art RPCA methods on artificial datasets, UCI datasets and face databases that verifies the effectiveness of our proposed algorithm.}, language = {en} } @misc{ZhangAalst, author = {Zhang, Yisong and Aalst, Wil van der}, title = {Explorative Process Discovery Using Activity Projections}, series = {International Conference on Applications and Theory of Petri Nets and Concurrency, PETRI NETS 2023}, journal = {International Conference on Applications and Theory of Petri Nets and Concurrency, PETRI NETS 2023}, publisher = {Springer, Cham}, isbn = {978-3-031-33619-5}, doi = {10.1007/978-3-031-33620-1_13}, pages = {229 -- 239}, abstract = {This paper presents a tool to Explore Process Discovery (EPD) results using activity projection. Our EPD-Tool aims at exploring quality changes after removing activities from an event log. The main idea is to create a projected event log for every non-empty subset of activities and apply process discovery and conformance checking on them. The tool has been implemented as a plugin in ProM. First, EPD-Tool uses a process discovery algorithm to discover Petri net models for each projected event log. Then, EPD-Tool uses a conformance checking technique to compute conformance measures for each projected event log and model pair (L, N), e.g., fitness, precision, and F1-score. Finally, a dendrogram is generated to visualize the relationship between each log-model pair, thus enabling the systematic exploration of the different models using the dendrogram to find the best-performing node, i.e., a best log-model pair. This method prioritizes activities and detects redundancy in the process, which contributes to process enhancement. Conversely, critical activities are uncovered to help to shorten the processing time or save the process cost. This paper presents the EPD-Tool implementation and some example results.}, language = {en} } @misc{GiustolisiSheikhi‐GarjanSchuermann, author = {Giustolisi, Rosario and Sheikhi-Garjan, Maryam and Schuermann, Carsten}, title = {Thwarting Last-Minute Voter Coercion}, series = {45th IEEE Symposium on Security and Privacy Sponsored by the IEEE Computer Society Technical Committee on Security and Privacy in cooperation with the International Association for Cryptologic Research}, journal = {45th IEEE Symposium on Security and Privacy Sponsored by the IEEE Computer Society Technical Committee on Security and Privacy in cooperation with the International Association for Cryptologic Research}, pages = {10}, language = {en} } @misc{MitsevaPanchenko, author = {Mitseva, Asya and Panchenko, Andriy}, title = {Stop, don't click here anymore: boosting website fingerprinting by considering sets of subpages}, series = {Proceedings of the 33rd USENIX Security Symposium (USENIX Sec 2024), Philadelphia, PA, USA, August 14-16, 2024}, journal = {Proceedings of the 33rd USENIX Security Symposium (USENIX Sec 2024), Philadelphia, PA, USA, August 14-16, 2024}, isbn = {978-1-939133-44-1}, pages = {4139 -- 4156}, abstract = {A type of traffic analysis, website fingerprinting (WFP), aims to reveal the website a user visits over an encrypted and anonymized connection by observing and analyzing data flow patterns. Its efficiency against anonymization networks such as Tor has been widely studied, resulting in methods that have steadily increased in both complexity and power. While modern WFP attacks have proven to be highly accurate in laboratory settings, their real-world feasibility is highly debated. These attacks also exclude valuable information by ignoring typical user browsing behavior: users often visit multiple pages of a single website sequentially, e.g., by following links. In this paper, we aim to provide a more realistic assessment of the degree to which Tor users are exposed to WFP. We propose both a novel WFP attack and efficient strategies for adapting existing methods to account for sequential visits of pages within a website. While existing WFP attacks fail to detect almost any website in real-world settings, our novel methods achieve F1-scores of 1.0 for more than half of the target websites. Our attacks remain robust against state-of- the-art WFP defenses, achieving 2.5 to 5 times the accuracy of prior work, and in some cases even rendering the defenses useless. Our methods enable to estimate and to communicate to the user the risk of successive page visits within a website (even in the presence of noise pages) to stop before the WFP attack reaches a critical level of confidence.}, language = {en} } @misc{GiustolisiSheikhi‐Garjan, author = {Giustolisi, Rosario and Sheikhi-Garjan, Maryam}, title = {Efficient cleansing in coercion-resistant voting}, series = {Electronic Voting : 9th International Joint Conference, E-Vote-ID 2024, Tarragona, Spain, October 2-4, 2024, Proceedings}, journal = {Electronic Voting : 9th International Joint Conference, E-Vote-ID 2024, Tarragona, Spain, October 2-4, 2024, Proceedings}, publisher = {Springer, Cham}, isbn = {978-3-031-72243-1}, doi = {10.1007/978-3-031-72244-8_5}, pages = {72 -- 88}, abstract = {Coercion resistance is a strong security property of electronic voting that prevents adversaries from forcing voters to vote in a specific way by using threats or rewards. There exist clever techniques aimed at preventing voter coercion based on fake credentials, but they are either inefficient or cannot support features such as revoting without leaking more information than necessary to coercers. One of the reasons is that invalid ballots cast due to revoting or coercion need to be removed before the tallying. In this paper, we propose a coercion-resistant Internet voting scheme that does not require the removal of invalid ballots, hence avoids the leakage of information, but still supports revoting. The scheme is very efficient and achieves linear tallying.}, language = {en} } @misc{HainesMosahebMuelleretal., author = {Haines, Thomas and Mosaheb, Rafieh and M{\"u}ller, Johannes and Pryvalov, Ivan}, title = {SoK: Secure E-Voting with Everlasting Privacy.}, series = {Thomas Haines, Rafieh Mosaheb, Johannes M{\"u}ller, Ivan Pryvalov. "SoK: Secure E-Voting with Everlasting Privacy." In Proceedings on Privacy Enhancing Technologies (PoPETS), 2023.}, journal = {Thomas Haines, Rafieh Mosaheb, Johannes M{\"u}ller, Ivan Pryvalov. "SoK: Secure E-Voting with Everlasting Privacy." In Proceedings on Privacy Enhancing Technologies (PoPETS), 2023.}, doi = {10.56553/popets-2023-0017}, pages = {279 -- 293}, abstract = {Vote privacy is a fundamental right, which needs to be protected not only during an election, or for a limited time afterwards, but for the foreseeable future. Numerous electronic voting (e-voting) protocols have been proposed to address this challenge, striving for everlasting privacy. This property guarantees that even computationally unbounded adversaries cannot break privacy of past elections. The broad interest in secure e-voting with everlasting privacy has spawned a large variety of protocols over the last three decades. These protocols differ in many aspects, in particular the precise security properties they aim for, the threat scenarios they consider, and the privacy-preserving techniques they employ. Unfortunately, these differences are often opaque, making analysis and comparison cumbersome. In order to overcome this non-transparent state of affairs, we systematically analyze all e-voting protocols designed to provide everlasting privacy. First, we illustrate the relations and dependencies between all these different protocols. Next, we analyze in depth which protocols do provide secure and efficient approaches to e-voting with everlasting privacy under realistic assumptions, and which ones do not. Eventually, based on our extensive and detailed treatment, we identify which research problems in this field have already been solved, and which ones are still open. Altogether, our work offers a well - founded reference point for conducting research on secure e - voting with everlasting privacy as well as for future - proofing privacy in real - world electronic elections.}, language = {en} } @misc{BackesBerrangHanzliketal., author = {Backes, Michael and Berrang, Pascal and Hanzlik, Lucjan and Pryvalov, Ivan}, title = {A Framework for Constructing Single Secret Leader Election from MPC.}, series = {Michael Backes, Pascal Berrang, Lucjan Hanzlik, Ivan Pryvalov. "A Framework for Constructing Single Secret Leader Election from MPC." In Computer Security - ESORICS 2022 - 27th European Symposium on Research in Computer Security, Copenhagen, Denmark, September 26-30, 2022, Proceedings, Part II, pp.672-691, Springer.}, journal = {Michael Backes, Pascal Berrang, Lucjan Hanzlik, Ivan Pryvalov. "A Framework for Constructing Single Secret Leader Election from MPC." In Computer Security - ESORICS 2022 - 27th European Symposium on Research in Computer Security, Copenhagen, Denmark, September 26-30, 2022, Proceedings, Part II, pp.672-691, Springer.}, publisher = {Springer}, doi = {10.1007/978-3-031-17146-8_33}, pages = {672 -- 691}, abstract = {The emergence of distributed digital currencies has raised the need for a reliable consensus mechanism. In proof-of-stake cryptocurrencies, the participants periodically choose a closed set of validators, who can vote and append transactions to the blockchain. Each validator can become a leader with the probability proportional to its stake. Keeping the leader private yet unique until it publishes a new block can significantly reduce the attack vector of an adversary and improve the throughput of the network. The problem of Single Secret Leader Election (SSLE) was first formally defined by Boneh et al. in 2020. In this work, we propose a novel framework for constructing SSLE protocols, which relies on secure multi-party computation (MPC) and satisfies the desired security properties. Our framework does not use any shuffle or sort operations and has a computational cost for N parties as low as O(N) of basic MPC operations per party. We improve the stateof-the-art for SSLE protocols that do not assume a trusted setup. Moreover, our SSLE scheme efficiently handles weighted elections. That is, for a total weight S of N parties, the associated costs are only increased by a factor of log S. When the MPC layer is instantiated with techniques based on Shamir's secret-sharing, our SSLE has a communication cost of O(N2) which is spread over O(logN) rounds, can tolerate up to t < N/2 of faulty nodes without restarting the protocol, and its security relies on DDH in the random oracle model. When the MPC layer is instantiated with more efficient techniques based on garbled circuits, our SSLE requires all parties to participate, up to N -1 of which can be malicious, and its security is based on the random oracle model.}, language = {en} }