| 1. |
- Hasselquist, David, et al.
(författare)
-
Twitch Chat Fingerprinting
- 2022
-
Ingår i: Proc. IFIP Network Traffic Measurement and Analysis Conference (TMA) 2022.
-
Konferensbidrag (refereegranskat)abstract
- The streaming content that we choose to watch canreveal much about our thoughts, opinions, and interests. Anadversary capable of determining what users watch thereforepresents a significant privacy threat. In this paper, we presentand evaluate the first fingerprinting attack on Twitch that allowsviewers of individual live streams to be identified despite thetraffic being encrypted. The attack targets the traffic patternsassociated with chat messages associated with each stream. Ourresults show that high accuracy can be achieved by eavesdroppingonly for a short time (e.g., 90 seconds) and that the accuracy canbe increased even further by interacting with the stream. We alsotake a closer look at how the accuracy and activity level differbetween different Twitch channels and provide insights into theaccuracy that attackers using different strategies for selectingtarget channels may have. Finally, we study countermeasures toprotect against such attacks and demonstrate that the naive use ofVPN is not enough. We instead present countermeasures alteringpacket timing and sizes. Our large-scale evaluation of differentcountermeasures provides important insights that help both thestreaming providers and users better protect their privacy.
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| 2. |
- Aaro, Gustav, 1995-, et al.
(författare)
-
Toolset for Run-time Dataset Collection of Deep-scene Information
- 2020
-
Ingår i: Symposium on Modelling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS). - Cham : Springer. - 9783030681098 ; , s. 224-236
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Konferensbidrag (refereegranskat)abstract
- Virtual reality (VR) provides many exciting new application opportunities, but also present new challenges. In contrast to 360° videos that only allow a user to select its viewing direction, in fully immersive VR, users can also move around and interact with objects in the virtual world. To most effectively deliver such services it is therefore important to understand how users move around in relation to such objects. In this paper, we present a methodology and software tool for generating run-time datasets capturing a user’s interactions with such 3D environments, evaluate and compare different object identification methods that we implement within the tool, and use datasets collected with the tool to demonstrate example uses. The tool was developed in Unity, easily integrates with existing Unity applications through the use of periodic calls that extracts information about the environment using different ray-casting methods. The software tool and example datasets are made available with this paper.
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| 3. |
- Arvanitaki, Antonia, 1991-, et al.
(författare)
-
Delay Performance of a Two-User Broadcast Channel with Security Constraints
- 2020
-
Ingår i: SN Computer Science. - : Springer. - 2661-8907 .- 2662-995X. ; 1:1
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we consider the two-user broadcast channel with security constraints. We assume that a source broadcasts packets to two receivers, and that one of them has secrecy constraints, i.e., its packets need to be kept secret from the other receiver. The receiver with secrecy constraint has full-duplex capability, allowing it to transmit a jamming signal to increase its secrecy. We derive the average delay per packet and provide simulations and numerical results, where we compare different performance metrics for the cases when both receivers treat interference as noise, when the legitimate receiver performs successive decoding, and when the eavesdropper performs successive decoding. The results show that successive decoding provides better average packet delay for the legitimate user. Furthermore, we define a new metric that characterizes the reduction on the success probability for the legitimate user that is caused by the secrecy constraint. The results show that secrecy poses a significant amount of packet delay for the legitimate receiver when either receiver performs successive decoding. We also formulate an optimization problem, wherein the throughput of the eavesdropper is maximized under delay and secrecy rate constraints at the legitimate receiver. We provide numerical results for the optimization problem, where we show the trade-off between the transmission power for the jamming and the throughput of the non-legitimate receiver. The results provide insights into how channel ordering and encoding differences can be exploited to improve performance under different interference conditions.
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| 4. |
- Arvanitaki, Antonia, 1991-, et al.
(författare)
-
Secrecy in Congestion-Aware Broadcast Channels
- 2021
-
Ingår i: Proc. Wireless Days Conference (WD) 2021. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665425599 - 9781665425605
-
Konferensbidrag (refereegranskat)abstract
- Congestion-aware scheduling in the case of traditional downlink cellular communication has neglected the heterogeneity in terms of secrecy among different clients. In this paper, we study a two-user congestion-aware broadcast channel with heterogeneous traffic and different security requirements. The traffic with security requirements is intended for a legitimate user and it has bursty nature. The incoming packets are stored in a queue at the source. Furthermore, there is a second traffic flow intended for another user, it is delay tolerant and does not have secrecy constraints. The receiver which needs to be served with confidential data has full-duplex capabilities, and it can send a jamming signal to hinder eavesdropping of its data at the other user. We consider two randomized policies for selecting which packets to transmit, one is congestion-aware by taking into consideration the queue size, whereas the other one is non-congestion-aware. We analyse the throughput and the delay performance under two decoding schemes at the receivers and provide insights into their relative security performance and into how congestion control at the queue holding confidential information can help decrease the average delay per packet. We show that the two policies have the same secrecy performance for large random access probabilities. The derived results also take account of the self-interference caused at the receiver for whom confidential data is intended due to its full-duplex operation while jamming the communication at the other user.
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| 5. |
- Bertmar, Sofia, et al.
(författare)
-
Who's Most Targeted and Does My New Adblocker Really Help : A Profile-based Evaluation of Personalized Advertising
- 2021
-
Ingår i: Proc. ACM CCS Workshop on Privacy in the Electronic Society (ACM WPES @CCS). - New York, NY, USA : ACM Digital Library. - 9781450385275
-
Konferensbidrag (refereegranskat)abstract
- There is limited prior work studying how the ad personalization experienced by different users is impacted by the use of adblockers, geographic location, the user's persona, or what browser they use. To address this void, this paper presents a novel profile-based evaluation of the personalization experienced by carefully crafted user profiles. Our evaluation framework impersonates different users and captures how the personalization changes over time, how it changes when adding or removing an extension, and perhaps most importantly how the results differ depending on the profile's persona (e.g., interest, occupation, age, gender), geographic location (US East, US West, UK), what browser extension they use (none, AdBlock, AdBlock Plus, Ghostery, CatBlock), what browser they use (Chrome, Firefox), and whether they are logged in to their Google account. By comparing and contrasting observed differences we provide insights that help explain why some user groups may feel more targeted than others and why some people may feel even more targeted after having turned on their adblocker.
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| 6. |
- Bruhner, Carl Magnus, 1988-, et al.
(författare)
-
Bridging the Privacy Gap: Enhanced User Consent Mechanisms on the Web
- 2023
-
Ingår i: Proc. NDSS Workshop on Measurements, Attacks, and Defenses for the Web (MADWeb @NDSS). - Reston, VA : Internet Society. - 1891562878
-
Konferensbidrag (refereegranskat)abstract
- In the age of the General Data Protection Regula-tion (GDPR) and the California Consumer Privacy Act (CCPA),privacy and consent control have become even more apparent forevery-day web users. Privacy banners in all shapes and sizes askfor permission through more or less challenging designs and makeprivacy control more of a struggle than they help users’ privacy.In this paper, we present a novel solution expanding the AdvancedData Protection Control (ADPC) mechanism to bridge currentgaps in user data and privacy control. Our solution moves theconsent control to the browser interface to give users a seamlessand hassle-free experience, while at the same time offering contentproviders a way to be legally compliant with legislation. Throughan extensive review, we evaluate previous works and identifycurrent gaps in user data control. We then present a blueprintfor future implementation and suggest features to support privacycontrol online for users globally. Given browser support, thesolution provides a tangible path to effectively achieve legallycompliant privacy and consent control in a user-oriented mannerthat could allow them to again browse the web seamlessly.
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| 7. |
- Carlsson, Niklas, 1977-, et al.
(författare)
-
Cross-user Similarities in Viewing Behavior for 360°Video and Caching Implications
- 2023
-
Ingår i: ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP). - : ASSOC COMPUTING MACHINERY. - 1551-6857 .- 1551-6865. ; 19:5
-
Tidskriftsartikel (refereegranskat)abstract
- The demand and usage of 360°video services are expected to increase. However, despite these services being highly bandwidth intensive, not much is known about the potential value that basic bandwidth saving techniques such as server or edge-network on-demand caching (e.g., in a CDN) could have when used for delivery of such services. This problem is both important and complicated as client-side solutions have been developed that split the full 360°view into multiple tiles, and adapt the quality of the downloaded tiles based on the user’s expected viewing direction and bandwidth conditions. This paper presents new trace-based analysis methods that incorporate users’ viewports (the area of the full 360°view the user actually sees), a first characterization of the cross-user similarities of the users’ viewports, and a trace-based analysis of the potential bandwidth savings that caching-based techniques may offer under different conditions. Our analysis takes into account differences in the time granularity over which viewport overlaps can be beneficial for resource saving techniques, compares and contrasts differences between video categories, and accounts for uncertainties in the network conditions and the prediction of the future viewing direction when prefetching. The results provide substantial insight into the conditions under which overlap can be considerable and caching effective, and inform the design of new caching system policies tailored for 360°video.
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| 8. |
- Carlsson, Niklas, 1977-, et al.
(författare)
-
Optimized Dynamic Cache Instantiation and Accurate LRU Approximations under Time-varying Request Volume
- 2023
-
Ingår i: IEEE Transactions on Cloud Computing. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2168-7161 .- 2372-0018. ; 11:1, s. 779-797
-
Tidskriftsartikel (refereegranskat)abstract
- Content-delivery applications can achieve scalability and reduce wide-area network traffic using geographically distributed caches. However, each deployed cache has an associated cost, and under time-varying request rates (e.g., a daily cycle) there may be long periods when the request rate from the local region is not high enough to justify this cost. Cloud computing offers a solution to problems of this kind, by supporting dynamic allocation and release of resources. In this paper, we analyze the potential benefits from dynamically instantiating caches using resources from cloud service providers. We develop novel analytic caching models that accommodate time-varying request rates, transient behavior as a cache fills following instantiation, and selective cache insertion policies. Within the context of a simple cost model, we then develop bounds and compare policies with optimized parameter selections to obtain insights into key cost/performance tradeoffs. We find that dynamic cache instantiation can provide substantial cost reductions, that potential reductions strongly dependent on the object popularity skew, and that selective cache insertion can be even more beneficial in this context than with conventional edge caches. Finally, our contributions also include accurate and easy-to-compute approximations that are shown applicable to LRU caches under time-varying workloads.
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| 9. |
- de Leng, Daniel, 1988-, et al.
(författare)
-
Second Screen Journey to the Cup: Twitter Dynamics during the Stanley Cup Playoffs
- 2018
-
Ingår i: Proceedings of the 2nd Network Traffic Measurement and Analysis Conference (TMA). - 9783903176096 - 9781538671528 ; , s. 1-8
-
Konferensbidrag (refereegranskat)abstract
- With Twitter and other microblogging services, users can easily express their opinion and ideas in short text messages. A recent trend is that users use the real-time property of these services to share their opinions and thoughts as events unfold on TV or in the real world. In the context of TV broadcasts, Twitter (over a mobile device, for example) is referred to as a second screen. This paper presents the first characterization of the second screen usage over the playoffs of a major sports league. We present both temporal and spatial analysis of the Twitter usage during the end of the National Hockey League (NHL) regular season and the 2015 Stanley Cup playoffs. Our analysis provides insights into the usage patterns over the full 72-day period and with regards to in-game events such as goals, but also with regards to geographic biases. Quantifying these biases and the significance of specific events, we then discuss and provide insights into how the playoff dynamics may impact advertisers and third-party developers that try to provide increased personalization.
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| 10. |
- González Dos Santos, Teno, et al.
(författare)
-
Predicting Season Outcomes for the NBA
- 2022
-
Ingår i: Machine Learning and Data Mining for Sports Analytics. - Cham, Switzerland : Springer. - 9783031020438 - 9783031020445 ; , s. 129-142
-
Konferensbidrag (refereegranskat)abstract
- Predicting game or season outcomes is important for clubs as well as for the betting industry. Understanding the critical factors of winning games and championships gives clubs a competitive advantage when selecting players for the team and implementing winning strategies. In this paper, we work with NBA data from 10 seasons and propose an approach for predicting game outcomes that is then used for predicting which team will be champion and which stages a team will reach in the playoffs. We show that our approach has a similar performance as the odds from betting companies and does better than ELO.
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| 11. |
- Hagberg, Johan, 1973, et al.
(författare)
-
Konsumtionsrapporten 2022
- 2022
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I Konsumtionsrapporten 2022 sammanfattas och analyseras konsumtionen i Sverige under 2021 och merparten av 2022. I den första delen, ”Hushållens konsumtion” ges en översikt över den privata konsumtionen i Sverige, hur den har förändrats i såväl kortare som längre perspektiv samt hushållens framtidstro avseende sin egen och Sveriges ekonomi. I andra delen, ”Detaljhandeln” beskrivs försäljning och utveckling inom detaljhandeln under 2021 och inledningen av 2022 med fokus på olika delbranscher, kanaler och platser, e-handeln respektive den butiksbaserade detaljhandeln. Den andra delen avslutas med handelns framtidsförväntningar. Den tredje delen ”Framtidsutsikter” tar avstamp i konsumenters och handelns framtidsförväntningar från de två första delarna och fördjupar analysen av framtidsutsikter utifrån publicerade prognoser och uttalanden från ekonomiska bedömare. Årets rapport innehåller tre fördjupningsdelar som var en och analyserar aktuella teman inom konsumtion. Under lång tid har det skett en ökad digitalisering av konsumtionen och inte minst under pandemin har många konsumtionsbeteenden förskjutits mot en allt större användning av internet och olika digitala gränssnitt som till exempel webshopar, social media och strömningstjänster. I takt med detta har det också väckts många frågor som berör säkerhet och personlig integritet online. I den första av fördjupningsdelarna analyserar Jeanette Carlsson Hauff konsumenters upplevda fördelar och risker avseende digital integritet vid användning av olika digitala tjänster. I den andra fördjupningsdelen visar Niklas Sörum på konsumenters olika förhållningssätt till datainsamling och datadriven marknadsföring. Andra konsumtionsbeteenden som aktualiserats under de senaste åren är olika typer av reaktioner på eller förberedelser inför kriser i termer av bunkring, hamstring och prepping. I den tredje delen analyserar och diskuterar Elias Mellander olika exempel på kriskonsumtion och hemberedskap.
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| 12. |
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| 13. |
- Hasselquist, David, et al.
(författare)
-
Hypothesis-based Comparison of IPv6 and IPv4 Path Distances
- 2020
-
Ingår i: Symposium on Modelling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS). - Cham : Springer. - 9783030681098 - 9783030681104
-
Konferensbidrag (refereegranskat)abstract
- Short end-to-end path lengths and faster round-trip times (RTTs) are important for good client performance. While prior measurement studies related to IPv6 primarily focus on various adoption aspects, much less work have focused on performance metrics such as these. In this paper, we compare the relative end-to-end path distances and RTTs when using IPv6 and IPv4 between PlanetLab nodes in Europe and different subsets of popular domains. In addition to providing access to multiple measurement nodes, the use of PlanetLab also provides a use-case driven report of running IPv6 experiments on this previously prosperous experimental platform for academic research. In particular, the study provides a first report on performing IPv6 experiments on PlanetLab, highlights the lack of IP support among PlanetLab nodes and limitations of state-of-the-art traceroute tools used for IPv6 measurements, and provides a statistical methodology that uses hypothesis testing to derive insights while accounting for such testbed and traceroute shortcomings. Our performance analysis shows (among other things) that the relative RTTs of the IPv6 paths are currently faster than the corresponding IPv4 paths, and that the fraction of pairings for which this is the case is quickly increasing across a wide range of domain popularities and domain categories. These findings suggest that there is incentive to use IPv6, which may impact the rate of further IPv6 deployment.
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| 14. |
- Hasselquist, David, et al.
(författare)
-
Lightweight Fingerprint Attack and Encrypted Traffic Analysis on News Articles
- 2022
-
Ingår i: <em></em>2022 IFIP Networking Conference (IFIP Networking). - : IEEE. - 9783903176485
-
Konferensbidrag (refereegranskat)abstract
- The news articles we read online can reveal a lot about us. Privacy aware groups have therefore long pushed for the use of HTTPS (encrypted end-to-end communication). In this paper, we present the design and evaluation of a lightweight framework that can (1) successfully identify individual news articles even when the articles are delivered over encrypted connections, and (2) separate between articles associated with different news websites even when the websites are delivered over the same infrastructure. Our results demonstrate that naive use of HTTPS is not enough to prevent attackers monitoring a user's connections from identifying articles that the user reads on the most popular news website. We also provide insights into what makes some websites more/less resilient to our attack, and we use Twitter data to evaluate the effectiveness of an example attack that in addition incorporates the popularity of individual news articles. We are the first to demonstrate and evaluate the practical effectiveness of this type of attack when applied on modern news websites, and our multi-website-based evaluation provides valuable insights into how websites can best protect themselves against this type of attacks. These insights are important for websites that want to help protect the privacy of their users.
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| 15. |
- Hasselquist, David, et al.
(författare)
-
Phishing in Style: Characterizing Phishing Websites in the Wild
- 2023
-
Ingår i: Proc. Network Traffic Measurement and Analysis Conference (TMA). - : Institute of Electrical and Electronics Engineers (IEEE). - 9783903176584 - 9798350325676
-
Konferensbidrag (refereegranskat)abstract
- The prevalence of phishing domains is steadily rising as attackers exploit toolkits to create phishing websites. As web development expertise is no longer a prerequisite, phishing attacks have become more widespread, outpacing many existing detection methods. Developing novel techniques to identify malicious domains is crucial to safeguard potential victims online. While most current methods emphasize the visual aspects of phishing websites, in this paper, we investigate the underlying structure by collecting data on style sheets and certificates from both verified phishing domains and benign domains. Using a token-based similarity algorithm, we group the phishing domains into three categories and identify shared characteristics of these domains. Our work demonstrates the feasibility of using structural similarities to identify a website created using a phishing kit. By employing such detection, users would be able to browse the web with a reduced risk of falling victim to malicious activities.
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| 16. |
- Hasselquist, David, et al.
(författare)
-
QUIC Throughput and Fairness over Dual Connectivity
- 2020
-
Ingår i: Symposium on Modelling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS). - Cham : Springer. - 9783030681098 - 9783030681104
-
Konferensbidrag (refereegranskat)abstract
- Dual Connectivity (DC) is an important lower-layer feature accelerating the transition from 4G to 5G that also is expected to play an important role in standalone 5G. However, even though the packet reordering introduced by DC can significantly impact the performance of upper-layer protocols, no prior work has studied the impact of DC on QUIC. In this paper, we present the first such performance study. Using a series of throughput and fairness experiments, we show how QUIC is affected by different DC parameters, network conditions, and whether the DC implementation aims to improve throughput or reliability. Our findings provide insights into the impacts of splitting QUIC traffic in a DC environment. With reasonably selected DC parameters and increased UDP receive buffers, QUIC over DC performs similarly to TCP over DC and achieves optimal fairness under symmetric link conditions when DC is not used for packet duplication.
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| 17. |
- Holmstrom, Jesper, et al.
(författare)
-
Do we Read what we Share? Analyzing the Click Dynamic of News Articles Shared on Twitter
- 2019
-
Ingår i: PROCEEDINGS OF THE 2019 IEEE/ACM INTERNATIONAL CONFERENCE ON ADVANCES IN SOCIAL NETWORKS ANALYSIS AND MINING (ASONAM 2019). - New York, NY, USA : Institute of Electrical and Electronics Engineers (IEEE). - 9781450368681 ; , s. 420-425
-
Konferensbidrag (refereegranskat)abstract
- News and information spread over social media can have big impact on thoughts, beliefs, and opinions. It is therefore important to understand the sharing dynamics on these forums. However, most studies trying to capture these dynamics rely only on Twitters open APIs to measure how frequently articles are shared/retweeted, and therefore do not capture how many users actually read the articles linked in these tweets. To address this problem, in this paper, we first develop a novel measurement methodology, which combines the Twitter steaming API, the Bitly API, and careful sample rate selection to simultaneously collect and analyze the timeline of both the number of retweets and clicks generated by news article links. Second, we present a temporal analysis of the news cycle based on five-day-long traces (containing both clicks and retweet over time) for the news article links discovered during a seven-day period. Among other things, our analysis highlights differences in the relative timelines observed for clicks and retweets (e.g., retweet data often lags and underestimates the bias towards reading popular links/articles), and helps answer important questions regarding differences in how age-based biases and churn affect how frequently news articles shared on Twitter are accessed over time.
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| 18. |
- Jarpehult, Oscar, et al.
(författare)
-
A Longitudinal Characterization of the Third-Party Authentication Landscape
- 2022
-
Ingår i: <em></em>2022 IFIP Networking Conference (IFIP Networking). - : IEEE. - 9783903176485
-
Konferensbidrag (refereegranskat)abstract
- Many websites offer users to authenticate using third-party identity providers (IDPs) such as Facebook or Google. As part of the signup process, these websites often ask the user to give them additional permissions with the IDP (e.g., some data sharing or authorize some actions) that can have significant privacy implications. Motivated by the increased scrutiny of Facebook and other popular IDPs (e.g., due to the 2018 Cambridge Analytica scandal), we present a longitudinal analysis of the IDP usage and permissions changes over the past nine years (2012–2021) as well as a large-scale characterization of the current state. Our longitudinal analysis identifies trends and characterizes changes in both the IDP usage and permission agreements of different subsets of websites. For our large-scale analysis, we develop and share a Selenium-based measurement framework that we use to collect datasets. Using this data, we study the IDP usage across popularity ranges, the permissions used in the wild, and highlight differences between websites using different IDPs and those that do not. Our analysis shows increased IDP usage, especially among the most popular websites, and that the permission requests on average are becoming more modest but also brings forward significant exceptions that may need further scrutiny.
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| 19. |
- Keskisärkkä, Robin, 1987-, et al.
(författare)
-
An Ontology for Ice Hockey
- 2019
-
Ingår i: ISWC 2019 Satellites. ; , s. 13-16
-
Konferensbidrag (refereegranskat)abstract
- Ice hockey is a highly popular sport that has seen significant increase in the use of sport analytics. To aid in such analytics, most major leagues collect and share increasing amounts of play-by-play data and other statistics. Additionally, some websites specialize in making such data available to the public in user-friendly forms. However, these sites fail to capture the semantic information of the data, and cannot be used to support more complex data requirements. In this paper, we present the design and development of an ice hockey ontology that provides improved knowledge representation, enables intelligent search and information acquisition, and helps when using information from multiple databases. Our ontology is substantially larger than previous ice hockey ontologies (that cover only a small part of the domain) and provides a formal and explicit representation of the ice hockey domain, supports information retrieval, data reuse, and complex performance metrics.
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| 20. |
- Korzhitskii, Nikita, et al.
(författare)
-
Characterizing the Root Landscape of Certificate Transparency Logs
- 2020
-
Ingår i: Proceedings of the 19th International IFIP TC6 Networking Conference, IFIP Networking 2020, Paris, France, June 22-25. - : IEEE. - 9783903176287 - 9781728167107 ; , s. 190-198
-
Konferensbidrag (refereegranskat)abstract
- Internet security and privacy stand on the trustworthiness of public certificates signed by Certificate Authorities (CAs). However, software products do not trust the same CAs and therefore maintain different root stores, each typically containing hundreds of trusted roots capable of issuing “trusted” certificates for any domain. Incidents with misissued certificates motivated Google to implement and enforce Certificate Transparency (CT). CT logs archive certificates in a public, auditable and append-only manner. The adoption of CT changed the trust landscape. As a part of this change, CT logs started to maintain their own root lists and log certificates that chain back to one of the trusted roots. In this paper, we present a first characterization of this emerging CT root store landscape, as well as the tool that we developed for data collection, visualization, and analysis of the root stores. As part of our characterization, we compare the logs’ root stores and quantify their changes with respect to both each other and the root stores of major software vendors, look at evolving vendor CT policies, and show that root store mismanagement may be linked to log misbehavior. Finally, we present and discuss the results of a survey that we have sent to the log operators participating in Apple’s and Google’s CT log programs.
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| 21. |
- Krishnamoorthi, Vengatanathan, 1987-
(författare)
-
Efficient HTTP-based Adaptive Streaming of Linear and Interactive Videos
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Online video streaming has gained tremendous popularity over recent years and currently constitutes the majority of Internet traffic. As large-scale on-demand streaming continues to gain popularity, several important questions and challenges remain unanswered. This thesis addresses open questions in the areas of efficient content delivery for HTTP-based Adaptive Streaming (HAS) from different perspectives (client, network and content provider) and in the design, implementation, and evaluation of interactive streaming applications over HAS.As streaming usage scales and new streaming services emerge, continuous improvements are required to both the infrastructure and the techniques used to deliver high-quality streams. In the context of Content Delivery Network (CDN) nodes or proxies, this thesis investigates the interaction between HAS clients and proxy caches. In particular, we propose and evaluate classes of content-aware and collaborative policies that take advantage of information that is already available, or share information among elements in the delivery chain, where all involved parties can benefit. Asides from the users’ playback experience, it is also important for content providers to minimize users’ startup times. We have designed and evaluated different classes of client-side policies that can prefetch data from the videos that the users are most likely to watch next, without negatively affecting the currently watched video. To help network providers to monitor and ensure that their customers enjoy good playback experiences, we have proposed and evaluated techniques that can be used to estimate clients’ current buffer conditions. Since several services today stream over HTTPS, our solution is adapted to predict client buffer conditions by only observing encrypted network-level traffic. Our solution allows the operator to identify clients with low-buffer conditions and implement policies that help avoid playback stalls.The emergence of HAS as the de facto standard for delivering streaming content also opens the door to use it to deliver the next generation of streaming services, such as various forms of interactive services. This class of services is gaining popularity and is expected to be the next big thing in entertainment. For the area of interactive streaming, this thesis proposes, models, designs, and evaluates novel streaming applications such as interactive branched videos and multi-video stream bundles. For these applications, we design and evaluate careful prefetching policies that provides seamless playback (without stalls or switching delay) even when interactive branched video viewers defer their choices to the last possible moment and when users switches between alternative streams within multi-video stream bundles. Using optimization frameworks, we design and implement effective buffer management techniques for seamless playback experiences and evaluate several tradeoffs using our policies.
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| 22. |
- Krishnamoorthi, Vengatanathan, 1987-, et al.
(författare)
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Empowering the Creative User : Personalized HTTP-based Adaptive Streaming of Multi-path Nonlinear Video
- 2013
-
Ingår i: Computer communication review. - New York : Association for Computing Machinery (ACM). - 0146-4833 .- 1943-5819. ; 43:4, s. 591-596
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents the design, implementation, and validation of a novel system that supports streaming and playout of personalized, multi-path, nonlinear video. In contrast to regular video, in which the file content is played sequentially, our design allows multiple nonlinear video sequences of the underlying (linear) video to be stitched together and played in any personalized order, and clients can be provided multiple path choices. The design combines the ideas of HTTP-based adaptive streaming (HAS) and multi-path nonlinear video. Personalization of the content is achieved with the use of a customized metafile, which is downloaded separately from the underlying media and the manifest file that defines the HAS structure. An extension to the user interface allows path choices to be presented to and made by the user. Novel buffer management and prefetching policies are used to ensure seamless uninterrupted playback regardless of client path choices, even under scenarios in which clients defer their choices until the last possible moment. Our solution allows creative home users to easily create their own multi-path nonlinear video, opening the door to an endless possibility of new opportunities and media forms.
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| 23. |
- Lambrix, Patrick, Professor, 1965-, et al.
(författare)
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Performance Metrics for Ice Hockey Accounting for Goal Importance
- 2022
-
Ingår i: Linköping Hockey Analytics Conference LINHAC 2022 June 6-8, 2022, Linköping, Sweden. - Linköping, Sweden : LiU Electronic Press. ; , s. 11-25
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Konferensbidrag (refereegranskat)abstract
- The evaluation of player performance is an important topic in sports analytics and is used by coaches for team management, in scouting and in sports broadcasts. When evaluating the performance of ice hockey players, many metrics are used, including traditional metrics such as goals, assists, points and modern metrics such as Corsi. One weakness of such metrics is that they do not consider the context in which the value for the metric was assigned. Other advanced metrics have been introduced, but as they are not easily explainable to practitioners, they may not make it into the hockey discourse. In this paper we introduce new goal-based metrics that (i) are based on traditional and well-known metrics, and thus easily understandable, (ii) take context into account in the form of time, manpower differential and goal differential and (iii) add a new aspect by taking into account the importance of the goals regarding their contribution to team wins and ties. We describe the intuitions behind the metrics, give formal definitions, evaluate the metrics using the eye test and show correlations to the traditional metrics. We have used data from the NHL seasons 2007-2008 to 2013-2014 and show which players stand out with respect to the number of goals and the importance of goals.
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| 24. |
- Le, Minh Ha, et al.
(författare)
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AnonFACES: Anonymizing Faces Adjusted to Constraints on Efficacy and Security
- 2020
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Ingår i: WPES 2020 - Proceedings of the 19th Workshop on Privacy in the Electronic Society. - New York, NY, USA : ACM. ; , s. 87-100, s. 87-100
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Konferensbidrag (refereegranskat)abstract
- Image data analysis techniques such as facial recognition can threaten individuals’ privacy. Whereas privacy risks often can be reduced by adding noise to the data, this approach reduces the utility of the images. For this reason, image de-identification techniques typically replace directly identifying features (e.g., faces, car number plates) present in the data with synthesized features, while still preserving other non-identifying features. As of today, existing techniques mostly focus on improving the naturalness of the generated synthesized images, without quantifying their impact on privacy. In this paper, we propose the first methodology and system design to quantify, improve, and tune the privacy-utility trade-off, while simultaneously also improving the naturalness of the generated images. The system design is broken down into three components that address separate but complementing challenges. This includes a two-step cluster analysis component to extract low-dimensional feature vectors representing the images (embedding) and to cluster the images into fixed-sized clusters. While the importance of good clustering mostly has been neglected in previous work, we find that our novel approach of using low-dimensional feature vectors can improve the privacy-utility trade-off by better clustering similar images. The use of these embeddings has been found particularly useful when wanting to ensure high naturalness and utility of the synthetically generated images. By combining improved clustering and incorporating StyleGAN, a state-of-the-art Generative Neural Network, into our solution, we produce more realistic synthesized faces than prior works, while also better preserving properties such as age, gender, skin tone, or even emotional expressions. Finally, our iterative tuning method exploits non-linear relations between privacy and utility to identify good privacy-utility trade-offs. We note that an example benefit of these improvements is that our solution allows car manufacturers to train their autonomous vehicles while complying with privacy laws.
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| 25. |
- Le, Minh Ha, et al.
(författare)
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IdDecoder: A Face Embedding Inversion Tool and its Privacy and Security Implications on Facial Recognition Systems
- 2023
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Ingår i: Proceedings of the Thirteenth ACM Conference on Data and Application Security and Privacy. - : ACM Digital Library. - 9798400700675 ; , s. 15-26
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Konferensbidrag (refereegranskat)abstract
- Most state-of-the-art facial recognition systems (FRS:s) use face embeddings. In this paper, we present the IdDecoder framework, capable of effectively synthesizing realistic-neutralized face images from face embeddings, and two effective attacks on state-of-the-art facial recognition models using embeddings. The first attack is a black-box version of a model inversion attack that allows the attacker to reconstruct a realistic face image that is both visually and numerically (as determined by the FRS:s) recognized as the same identity as the original face used to create a given face embedding. This attack raises significant privacy concerns regarding the membership of the gallery dataset of these systems and highlights the importance of both the people designing and deploying FRS:s paying greater attention to the protection of the face embeddings than currently done. The second attack is a novel attack that performs the model inversion, so to instead create the face of an alternative identity that is visually different from the original identity but has close identity distance (ensuring that it is recognized as being of the same identity). This attack increases the attacked system's false acceptance rate and raises significant security concerns. Finally, we use IdDecoder to visualize, evaluate, and provide insights into differences between three state-of-the-art facial embedding models.
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