@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{HillerHenzeZimmermannetal., author = {Hiller, Jens and Henze, Martin and Zimmermann, Torsten and Hohlfeld, Oliver and Wehrle, Klaus}, title = {The Case for Session Sharing: Relieving Clients from TLS Handshake Overheads}, series = {2019 IEEE 44th LCN Symposium on Emerging Topics in Networking (LCN Symposium), 14-17 Oct. 2019, Osnabr{\"u}ck, Germany}, journal = {2019 IEEE 44th LCN Symposium on Emerging Topics in Networking (LCN Symposium), 14-17 Oct. 2019, Osnabr{\"u}ck, Germany}, publisher = {IEEE}, isbn = {978-1-7281-2561-9}, doi = {10.1109/LCNSymposium47956.2019.9000667}, pages = {9}, abstract = {In recent years, the amount of traffic protected with Transport Layer Security (TLS) has significantly increased and new protocols such as HTTP/2 and QUIC further foster this emerging trend. However, protecting traffic with TLS has significant impacts on network entities. While the restrictions for middleboxes have been extensively studied, addressing the impact of TLS on clients and servers has been mostly neglected so far. Especially mobile clients in emerging 5G and IoT deployments suffer from significantly increased latency, traffic, and energy overheads when protecting traffic with TLS. In this paper, we address this emerging topic by thoroughly analyzing the impact of TLS on clients and servers and derive opportunities for significantly decreasing latency of TLS communication and downsizing TLS management traffic, thereby also reducing TLSinduced server load. We propose a protocol compatible redesign of TLS session management to use these opportunities and showcase their potential based on mobile device traffic and mobile web-browsing traces. These show promising potentials for latency improvements by up to 25.8\% and energy savings of up to 26.3\%.}, 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{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} }