| 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
-
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)
-
AnonFACES: Anonymizing Faces Adjusted to Constraints on Efficacy and Security
- 2020
-
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
-
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
-
Ingår i: Proceedings of the Thirteenth ACM Conference on Data and Application Security and Privacy. - : ACM Digital Library. - 9798400700675 ; , s. 15-26
-
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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| 26. |
- Le, Minh Ha, et al.
(författare)
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StyleID: Identity Disentanglement for Anonymizing Faces
- 2023
-
Ingår i: Proceedings on Privacy Enhancing Technologies (PoPETs).
-
Tidskriftsartikel (refereegranskat)abstract
- Privacy of machine learning models is one of the remaining challenges that hinder the broad adoption of Artificial Intelligent (AI). This paper considers this problem in the context of image datasets containing faces. Anonymization of such datasets is becoming increasingly important due to their central role in the training of autonomous cars, for example, and the vast amount of data generated by surveillance systems. While most prior work de-identifies facial images by modifying identity features in pixel space, we instead project the image onto the latent space of a Generative Adversarial Network (GAN) model, find the features that provide the biggest identity disentanglement, and then manipulate these features in latent space, pixel space, or both. The main contribution of the paper is the design of a feature-preserving anonymization framework, StyleID, which protects the individuals’ identity, while preserving as many characteristics of the original faces in the image dataset as possible. As part of the contribution, we present a novel disentanglement metric, three complementing disentanglement methods, and new insights into identity disentanglement. StyleID provides tunable privacy, has low computational complexity, and is shown to outperform current state-of-the-art solutions.
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| 27. |
- Lindblom, Martin, et al.
(författare)
-
Third-party Link Shortener Usage on Twitter
- 2021
-
Ingår i: Proc. IFIP Network Traffic Measurement and Analysis Conference (TMA) 2021. - 9783903176409
-
Konferensbidrag (refereegranskat)abstract
- Twitter has proven a powerful tool to shape peoples’ opinions and thoughts. One efficient way to spread information is with the use of links. In this paper, we characterize the link sharing usage on Twitter, placing particular focus on third-party link shortener services that hide the full URL from the user. First, we present a measurement framework that combines two Twitter APIs and the Bitly API, and allows us to collect detailed statistics about tweets, their posters, their link usage, and the retweets and clicks 24 hours after the original tweet. Second, using two one-week-long datasets, collected one year apart (April 2019 and2020), we then characterize and analyze important difference in link usage among users, the domains that different users and shorteners (re)direct users too, and compare the click rates of such links with the corresponding retweet rates. The analysis provides insights into link sharing biases on Twitter, skews, and behavioral differences in usage, as well as reveal interesting observations capturing differences in how a tweet containing a link may be retweeted versus how the embedded link is clicked. Finally, we use click-based results for covid-19 tweets to discuss the importance of controlling the spread of (mis)information.
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| 28. |
- Lindskog, Eric, et al.
(författare)
-
Generalized Playback Bar for Interactive Branched Video
- 2019
-
Ingår i: PROCEEDINGS OF THE 27TH ACM INTERNATIONAL CONFERENCE ON MULTIMEDIA (MM19). - New York, NY, USA : ASSOC COMPUTING MACHINERY. - 9781450368896 ; , s. 2369-2377
-
Konferensbidrag (refereegranskat)abstract
- During viewing of interactive branched video, users are asked to make viewing choices that impact the storyline of the video playback. This type of video puts the users in control of their viewing experiences and provides content creators with great flexibility how to personalize the viewing experience of individual viewers. However, in contrast to with traditional video, where the use of a playback bar is default for most - if not all - players, there currently does not exist any generic playback bar for branched video that helps visualize the upcoming branch choices. Instead, most branched video implementations are typically custom-made on a per-video basis (e.g., see custom-made Netflix and BBC movies) and do not use a playback bar. As an important step towards addressing this void, we present the first branched video player with a generalized playback bar that visualizes the tree-like video structure and the buffer levels of the different branches. The player is implemented in dash.js and is made public with this publication, is the first of its kind, and allows both the playback bar and the presentation of branch choices to be customized with regards to visual appearance, functionality, and the content itself. Furthermore, the design is generic (making it applicable to any video) and allows content creators to easily create large numbers of branched movies using a simple metafile format. Finally, and most importantly, we perform a three-phase user study in which we evaluate the playback bar, compare with alternative designs, and other branch-related features. The user study highlights the value of a branched video playback bar, and provides interesting insights into how it and other design customization features may best be integrated into a player.
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| 29. |
- Lindskog, Eric, et al.
(författare)
-
REEFT-360: Real-time Emulation and Evaluation Framework for Tile-based 360 Streaming under Time-varying Conditions
- 2021
-
Ingår i: Proc. ACM Multimedia Systems Conference (ACM MMSys) 2021. - New York, NY, USA : ACM Digital Library. - 9781450384346 ; , s. 307-313
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Konferensbidrag (refereegranskat)abstract
- With 360° video streaming, the user's field of view (a.k.a. viewport) is at all times determined by the user's current viewing direction. Since any two users are unlikely to look in the exact same direction as each other throughout the viewing of a video, the frame-by-frame video sequence displayed during a playback session is typically unique. This complicates the direct comparison of the perceived Quality of Experience (QoE) using popular metrics such as the Multiscale-Structural Similarity (MS-SSIM). Furthermore, there is an absence of light-weight emulation frameworks for tiled-based 360° video streaming that allow easy testing of different algorithm designs and tile sizes. To address these challenges, we present REEFT-360, which consists of (1) a real-time emulation framework that captures tile-quality adaptation under time-varying bandwidth conditions and (2) a multi-step evaluation process that allows the calculation of MS-SSIM scores and other frame-based metrics, while accounting for the user's head movements. Importantly, the framework allows speedy implementation and testing of alternative head-movement prediction and tile-based prefetching solutions, allows testing under a wide range of network conditions, and can be used either with a human user or head-movement traces. The developed software tool is shared with the paper. We also present proof-of-concept evaluation results that highlight the importance of including a human subject in the evaluation.
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| 30. |
- Ljung, Dennis, et al.
(författare)
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Player Pairs Valuation in Ice Hockey
- 2019
-
Ingår i: Proceedings of the 5th Workshop on Machine Learning and Data Mining for Sports Analytics. - Cham : Springer. - 9783030172732 - 9783030172749 ; , s. 82-92
-
Konferensbidrag (refereegranskat)abstract
- To overcome the shortcomings of simple metrics for evaluating player performance, recent works have introduced more advanced metrics that take into account the context of the players’ actions and perform look-ahead. However, as ice hockey is a team sport, knowing about individual ratings is not enough and coaches want to identify players that play particularly well together. In this paper we therefore extend earlier work for evaluating the performance of players to the related problem of evaluating the performance of player pairs. We experiment with data from seven NHL seasons, discuss the top pairs, and present analyses and insights based on both the absolute and relative ice time together.
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| 31. |
- Lundtoft, Christian, et al.
(författare)
-
Function of multiple sclerosis-protective HLA class I alleles revealed by genome-wide protein-quantitative trait loci mapping of interferon signalling
- 2020
-
Ingår i: PLOS Genetics. - : Public Library of Science (PLoS). - 1553-7390 .- 1553-7404. ; 16:10
-
Tidskriftsartikel (refereegranskat)abstract
- Interferons (IFNs) are cytokines that are central to the host defence against viruses and other microorganisms. If not properly regulated, IFNs may contribute to the pathogenesis of inflammatory autoimmune, or infectious diseases. To identify genetic polymorphisms regulating the IFN system we performed an unbiased genome-wide protein-quantitative trait loci (pQTL) mapping of cell-type specific type I and type II IFN receptor levels and their responses in immune cells from 303 healthy individuals. Seven genome-wide significant (p < 5.0E-8) pQTLs were identified. Two independent SNPs that tagged the multiple sclerosis (MS)-protective HLA class I alleles A*02/A*68 and B*44, respectively, were associated with increased levels of IFNAR2 in B and T cells, with the most prominent effect in IgD–CD27+ memory B cells. The increased IFNAR2 levels in B cells were replicated in cells from an independent set of healthy individuals and in MS patients. Despite increased IFNAR2 levels, B and T cells carrying the MS-protective alleles displayed a reduced response to type I IFN stimulation. Expression and methylation-QTL analysis demonstrated increased mRNA expression of the pseudogene HLA-J in B cells carrying the MS-protective class I alleles, possibly driven via methylation-dependent transcriptional regulation. Together these data suggest that the MS-protective effects of HLA class I alleles are unrelated to their antigen-presenting function, and propose a previously unappreciated function of type I IFN signalling in B and T cells in MS immune-pathogenesis.Author summaryGenetic association studies have been very successful in identifying disease-associated single nucleotide polymorphisms (SNPs), but it has been challenging to define the molecular mechanisms underlying these associations. As interferons (IFNs) have a central role in the immune system, we hypothesized that some of the SNPs associated to immune-mediated diseases would affect the IFN system. By combining genetic data with characterization of interferon receptor levels and their responses on the protein level in immune cells from 303 genotyped healthy individuals, we show that two SNPs tagging the HLA class I alleles A*02/A*68 and B*44 are associated with a decreased response to type I IFN stimulation in B cells and T cells. Notably, both HLA-A*02 and HLA-B*44 confer protection from developing multiple sclerosis (MS), which is a chronic inflammatory neurologic disease. In addition to suggesting a pathogenic role of enhanced type I interferon signalling in B cells and T cells in MS, our data emphasize the fact that genetic associations in the HLA locus can affect functions not directly associated to antigen presentation, which conceptually may be important for other diseases genetically associated to the HLA locus.
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| 32. |
- Minh-Ha, Le, 1989-
(författare)
-
Beyond Recognition : Privacy Protections in a Surveilled World
- 2024
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis addresses the need to balance the use of facial recognition systems with the need to protect personal privacy in machine learning and biometric identification. As advances in deep learning accelerate their evolution, facial recognition systems enhance security capabilities, but also risk invading personal privacy. Our research identifies and addresses critical vulnerabilities inherent in facial recognition systems, and proposes innovative privacy-enhancing technologies that anonymize facial data while maintaining its utility for legitimate applications.Our investigation centers on the development of methodologies and frameworks that achieve k-anonymity in facial datasets; leverage identity disentanglement to facilitate anonymization; exploit the vulnerabilities of facial recognition systems to underscore their limitations; and implement practical defenses against unauthorized recognition systems. We introduce novel contributions such as AnonFACES, StyleID, IdDecoder, StyleAdv, and DiffPrivate, each designed to protect facial privacy through advanced adversarial machine learning techniques and generative models. These solutions not only demonstrate the feasibility of protecting facial privacy in an increasingly surveilled world, but also highlight the ongoing need for robust countermeasures against the ever-evolving capabilities of facial recognition technology.Continuous innovation in privacy-enhancing technologies is required to safeguard individuals from the pervasive reach of digital surveillance and protect their fundamental right to privacy. By providing open-source, publicly available tools, and frameworks, this thesis contributes to the collective effort to ensure that advancements in facial recognition serve the public good without compromising individual rights. Our multi-disciplinary approach bridges the gap between biometric systems, adversarial machine learning, and generative modeling to pave the way for future research in the domain and support AI innovation where technological advancement and privacy are balanced.
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| 33. |
- Minh-Ha, Le, 1989-, et al.
(författare)
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StyleAdv: A Usable Privacy Framework Against Facial Recognition with Adversarial Image Editing
- 2024
-
Ingår i: Proceedings on Privacy Enhancing Technologies. ; , s. 106-123
-
Konferensbidrag (refereegranskat)abstract
- In this era of ubiquitous surveillance and online presence, protecting facial privacy has become a critical concern for individuals and society as a whole. Adversarial attacks have emerged as a promising solution to this problem, but current methods are limited in quality or are impractical for sensitive domains such as facial editing. This paper presents a novel adversarial image editing framework called StyleAdv, which leverages StyleGAN's latent spaces to generate powerful adversarial images, providing an effective tool against facial recognition systems. StyleAdv achieves high success rates by employing meaningful facial editing with StyleGAN while maintaining image quality, addressing a challenge faced by existing methods. To do so, the comprehensive framework integrates semantic editing, adversarial attacks, and face recognition systems, providing a cohesive and robust tool for privacy protection. We also introduce the ``residual attack`` strategy, using residual information to enhance attack success rates. Our evaluation offers insights into effective editing, discussing tradeoffs in latent spaces, optimal edits for our optimizer, and the impact of utilizing residual information. Our approach is transferable to state-of-the-art facial recognition systems, making it a versatile tool for privacy protection. In addition, we provide a user-friendly interface with multiple editing options to help users create effective adversarial images. Extensive experiments are used to provide insights and demonstrate that StyleAdv outperforms state-of-the-art methods in terms of both attack success rate and image quality. By providing a versatile tool for generating high-quality adversarial samples, StyleAdv can be used both to enhance individual users' privacy and to stimulate advances in adversarial attack and defense research.
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| 34. |
- Mohammadinodooshan, Alireza, 1983-
(författare)
-
Data-driven Contributions to Understanding User Engagement Dynamics on Social Media
- 2024
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Social media platforms have fundamentally transformed the way information is produced, distributed, and consumed. News digestion and dissemination are not an exception. A recent study by the Pew Research Center highlights that 53% of Twitter (renamed X) users, alongside notable percentages on Facebook (43%), Reddit (38%), and Instagram (34%), rely on these platforms for their daily news. Unfortunately, not all news is reliable and unbiased, which poses a significant societal challenge. Beyond news, content posted by influencers can also play an important role in shaping opinions and behaviors.Indeed, how users engage with different classes of content (including unreliable content) on social media can amplify their visibility and shape public perceptions and debates. Recognizing this, prior research has studied different aspects of user engagement dynamics with varying classes of content. However, several unexplored dimensions remain. To better understand these dynamics, this thesis addresses part of this research gap through eight comprehensive studies across four key dimensions, where we place particular focus on news content.The first dimension of this thesis presents a large-scale analysis of users' interactions with news publishers on Twitter. This analysis provides a fine-grained understanding of engagement patterns with various classes of publishers, with key findings indicating elevated engagement rates among unreliable news publishers. The second dimension examines the dynamics of interaction patterns between public and private (less public) sharing of news articles on Facebook. This dimension highlights deeper user engagement in private contexts compared to the public sphere, with both spheres showing the highest interaction levels with highly unreliable content. The third dimension investigates the drivers of popularity among news tweets to understand what makes some tweets more/less successful in gaining user engagement. For instance, this analysis reveals the negative impact of analytic language on user engagement, with the biggest engagement declines observed among unreliable publishers. Finally, the thesis emphasizes the importance of temporal dynamics in user engagement. For example, exploring the temporal user engagement with different news classes over time, we observe a positive correlation between the reliability of a post and the early interactions it receives on Facebook. While the thesis quantitatively assesses the effects of reliability across all dimensions, it also places additional focus on the role of bias in the observed patterns.These and other insights presented in the thesis offer actionable insights that can benefit multiple stakeholders, providing policymakers and content moderators with a comprehensive perspective for addressing the spread of problematic content. Moreover, platform designers can leverage the insights to build features that promote healthy online communities, while news outlets can use them to tailor content strategies based on target audiences, and individual users can use them to make informed decisions. Although the thesis has inherent limitations, it deepens our current understanding of engagement dynamics to foster a more secure and trustworthy social media experience that remains engaging.
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| 35. |
- Mohammadinodooshan, Alireza, 1983-, et al.
(författare)
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Temporal Dynamics of User Engagement with U.S. News Sources on Facebook
- 2022
-
Ingår i: Proc. International Conference on Social Networks Analysis, Management and Security (SNAMS). - : Institute of Electrical and Electronics Engineers (IEEE). - 9798350320480 - 9798350320497
-
Konferensbidrag (refereegranskat)abstract
- Recently, researchers have modeled how reliability and political bias of news may affect Facebook users' engagement, as measured using interaction metrics such as the number of shares, likes, etc. However, the temporal dynamics of Facebook users' engagement with news of varying degrees of bias and reliability is less studied. In light of the COVID-19 pandemic, it is also important to quantify how the pandemic changed user engagement with various news. This paper presents the first temporal study of Facebook users' interaction dynamics, accounting for both the bias and reliability of the publishers. We consider a dataset of 992 U.S. publishers, and the study spans the period from Jan. 2018 to July 2022. This allows us to accurately assess the effect of the covid outbreak on the temporal dynamics of Facebook users' interactions with different classes of news. Our study examines these two parameters' effect on Facebook user engagement using both per-publisher and aggregated statistics. Several findings are revealed by our analysis, including that publishers in different bias and reliability classes experienced significantly different levels of engagement dynamics during and following the covid outbreak. For example, we show that the least reliable news exhibited the most considerable growth of followers during the covid period and the most reliable news sources exhibited the greatest growth rate of followers during the post-covid period. We also show that the interaction rate (number of interactions normalized over the number of followers) with Facebook news posts during the post-covid period is smaller than it was even before the outbreak. Furthermore, we demonstrate how the COVID-19 outbreak caused statistically significant structural breaks in the temporal dynamics of engagement with several types of news, and quantify this effect. With social media becoming a popular news source during crises, the observed temporal dynamics provide important insights into how information was consumed over the recent years, benefiting both researchers and public sectors.
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| 36. |
- Nsolo, Edward, 1988-, et al.
(författare)
-
Player Valuation in European Football
- 2019
-
Ingår i: Proceedings of the 5th Workshop on Machine Learning and Data Mining for Sports Analytics. - Cham : Springer. - 9783030172732 - 9783030172749 ; , s. 42-54
-
Konferensbidrag (refereegranskat)abstract
- As the success of a team depends on the performance of individual players, the valuation of player performance has become an important research topic. In this paper, we compare and contrast which attributes and skills best predict the success of individual players in their positions in five European top football leagues. Further, we evaluate different machine learning algorithms regarding prediction performance. Our results highlight features distinguishing top-tier players and show that prediction performance is higher for forwards than for other positions, suggesting that equally good prediction of defensive players may require more advanced metrics.
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| 37. |
- Nykvist, Carl, et al.
(författare)
-
Server-Side Adoption of Certificate Transparency
- 2018
-
Ingår i: Passive and Active Measurement. - Cham : Springer. - 9783319764801 - 9783319764818 ; , s. 186-199
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Konferensbidrag (refereegranskat)abstract
- Certificate Transparency (CT) was developed to mitigate shortcomings in the TLS/SSL landscape and to assess the trustworthiness of Certificate Authorities (CAs) and the certificates they create. With CT, certificates should be logged in public, audible, append-only CT logs and servers should provide clients (browsers) evidence, in the form of Signed Certificate Timestamps (SCTs), that the certificates that they present have been logged in credible CT logs. These SCTs can be delivered using three different methods: (i) X.509v3 extension, (ii) TLS extension, and (iii) OSCP stapling. In this paper, we develop a client-side measurement tool that implements all three methods and use the tool to analyze the SCT adoption among the one-million most popular web domains. Using two snapshots (from May and Oct. 2017), we answer a wide range of questions related to the delivery choices made by different domains, identify differences in the certificates used by these domains, the CT logs they use, and characterize the overheads and potential performance impact of the SCT delivery methods. By highlighting some of the tradeoffs between the methods and differences in the websites selecting them, we provide insights into the current SCT adoption status and differences in how domains have gone upon adopting this new technology.
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| 38. |
- Sans Fuentes, Carles, et al.
(författare)
-
Player impact measures for scoring in ice hockey
- 2019
-
Ingår i: Proceedings of MathSport International 2019 Conference. - Athen : Athens University of Economics and Business. ; , s. 307-317
-
Konferensbidrag (refereegranskat)abstract
- A commonly used method to evaluate player performance is to attribute values to the different actions that players perform and sum up these values every time a player performs these actions. In ice hockey, such metrics include the number of goals, assists, points, plus-minus statistics and recently Corsi and Fenwick. However, these metrics do not capture the context of player actions and the impact they have on the outcome of later actions. Therefore, recent works have introduced more advanced metrics that take into account the context of the actions and perform look-ahead. The use of look-ahead is particularly valuable in low-scoring sports such as ice hockey. In this paper, we first extend a recent approach based on reinforcement learning for measuring a player's impact on a team's scoring. Second, using NHL play-by-play data for several regular seasons, we analyze and compare these and other traditional measures of player impact. Third, we introduce notions of streaks and show that these may provide information about good players, but do not provide a good predictor for the impact that a player will have the next game. Finally, streaks are compared for different player categories, highlighting differences between player positions and correlations with player salaries.
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| 39. |
- Säfvenberg, Rasmus, 1998-, et al.
(författare)
-
Identifying Player Roles in Ice Hockey
- 2024
-
Ingår i: Machine Learning and Data Mining for Sports Analytics. - : Springer Nature Switzerland. - 9783031538322 - 9783031538339 ; , s. 131-143
-
Konferensbidrag (refereegranskat)abstract
- Understanding the role of a particular player, or set of players, in a team is an important tool for players, scouts, and managers, as it can improve training, game adjustments and team construction. In this paper, we propose a probabilistic method for quantifying player roles in ice hockey that allows for a player to belong to different roles with some probability. Using data from the 2021–2022 NHL season, we analyze and group players into clusters. We show the use of the clusters by an examination of the relationship between player role and contract, as well as between role distribution in a team and team success in terms of reaching the playoffs.
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| 40. |
- Säfvenberg, Rasmus, 1998-, et al.
(författare)
-
Simple and Practical Goal Importance Metrics for Ice Hockey
- 2023
-
Ingår i: Proceedings of the Linköping Hockey Analytics Conference LINHAC 2023 Research Track. - Linköping, Sweden : Linköping University Electronic Press. ; , s. 40-52
-
Konferensbidrag (refereegranskat)abstract
- To capture that not all goals are of the same importance, a new performance metric called the Game Points Importance Value (GPIV) was recently proposed. While this metric takes into account the expected impact that a goal has on the outcome of a game based on the context when the goal was scored, it relies on a relatively fine-grained state space. To address this problem, this paper presents simplified and more practical variations of the GPIV metric. Motivated by our analysis of the relative importance of different dimensions of the state space, we present two metrics that capture the most important component(s) of GPIV. Our evaluation shows that the metrics are relatively stable and capture most of the relative differences between GPIV and traditional metrics (e.g., goals, assist, points, and +/-). These results suggest that these simple and practical metrics are intuitive, capture most of the desirable variations that GPIV captures, and that the value of a goal can be well estimated using GPIV data based on historic data.
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| 41. |
- Säfvenberg, Rasmus, 1998-, et al.
(författare)
-
The Importance of Special Teams in Ice Hockey
- 2023
-
Ingår i: Proceedings of the Linköping Hockey Analytics Conference LINHAC 2023 Research Track. - Linköping, Sweden : Linköping University Electronic Press. ; , s. 53-65
-
Konferensbidrag (refereegranskat)abstract
- This paper explores the significance of special teams, particularlypowerplay, in ice hockey. Despite the commonly held perception oftheir importance, little research has examined the impact of powerplayand penalty kill performance on overall team success. The paper usesseveral seasons of NHL data to characterize goal-scoring and manpoweropportunities, and perform analysis from several perspectives. The resultsindicate that individual even strength goals and powerplay goalshave similar value, but the larger share of even strength goals scoredover a season makes even strength play a more important contributorto team success. The paper also finds a high correlation between teamsthat perform above/below average during even strength and powerplay.This study provides valuable insights into the dynamics of ice hockeygameplay and the role of special teams in determining team success.
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| 42. |
- Terve, Carl, et al.
(författare)
-
Social Media Dynamics of Shorted Companies
- 2022
-
Ingår i: Proc. International Conference on Social Networks Analysis, Management and Security (SNAMS). - : Institute of Electrical and Electronics Engineers (IEEE). - 9798350320480 - 9798350320497
-
Konferensbidrag (refereegranskat)abstract
- The discussions on social-media forums can impact the sentiment of a company, and consequently also its stock price. As we show here, some of the most shorted companies have provided some of the clearest examples of this relationship. In light of these observations, this paper presents a longitudinal study of the cross-forum dynamics of ten highly shorted stocks that saw significant discussions on the popular forums Reddit, Twitter, and Seeking Alpha. Using the posts from these forums, their sentiments, and the daily snapshots of the stock price of each company, we use a combination of qualitative case studies and quantitative hypothesis testing to derive new insights. Through a combination of time-series analysis, clustering, and domain-optimized sentiment analysis, we study the relationship between the times that discussions peak on the different forums, the changes in sentiment, and the stock price movements. We find that all three forums are likely to experience peaks in their activity close to each other, that Reddit is most likely to peak first, and that the sentiment of Twitter discussions were more sensitive to the current derivative of the stock price than the sentiment observed on the other forums.
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| 43. |
- Thorgren, Elin, et al.
(författare)
-
Temporal Dynamics of User Engagement on Instagram : A Comparative Analysis of Album, Photo, and Video Interactions
- 2024
-
Ingår i: Proceedings of the 16th ACM Web Science Conference. - New York : Association for Computing Machinery (ACM). - 9798400703348 ; , s. 224-234
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Konferensbidrag (refereegranskat)abstract
- Despite Instagram being an integral part of many people's lives, it is relatively less studied than many other platforms (e.g., Twitter and Facebook). Furthermore, despite offering diverse content formats for user expression and interaction, prior works have not studied the temporal dynamics of user engagement across albums, photos, and videos. To address this gap, we present a pioneering temporal comparative analysis that unveils nuanced patterns in user interactions across content types. Our analysis sheds light on interaction longevity and disparities among album, photo, and video engagement. Additionally, it offers empirical comparisons through statistical tests, examines contributing factors such as post and uploader characteristics, and analyzes content composition’s impact on user engagement. The findings reveal distinct temporal engagement patterns. Despite initial spikes in interactions post-upload, albums exhibit somewhat more sustained interest, while photos and videos have shorter engagement lifespans. Moreover, a consistent trend between shallow (likes) and deep (comments) interactions persists across content types. Notably, concise content, characterized by shorter descriptions and minimal hashtags/mentions, consistently drives higher engagement, emphasizing its relevance across all content formats. These insights deepen comprehension of temporal nuances in user engagement on Instagram, offering valuable guidance for content creators and marketers to tailor strategies that evoke immediate and sustained user interest.
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| 44. |
- Vik, Jon, et al.
(författare)
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Not all goals are equally important : a study for the NHL
- 2021
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Ingår i: Mathsport International 8 2021 Proceedings. ; , s. 26-31
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Konferensbidrag (refereegranskat)abstract
- The evaluation of player performance is an important topic in sport 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 take into consideration the context in which the value for the metric was assigned. For instance, when a player scores a goal, then the value of the goals metric for that player is raised by one, regardless of the importance of the goal. In this paper, we introduce new variants of classical metrics based on the importance of the goals regarding their contribution to team wins and ties. Further, we investigate using play-by-play data from the 2013-2014 NHL season how these new metrics relate to the classical metrics and which players stand out with respect to important goals.
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| 45. |
- Vogel, Albin, et al.
(författare)
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Fast-forwarding, Rewinding, and Path Exploration in Interactive Branched Video Streaming
- 2021
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Ingår i: Proc. ACM International Conference on Multimedia (ACM Multimedia) 2021. - New York, NY, USA : ACM Digital Library. - 9781450386517 ; , s. 1664-1672
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Konferensbidrag (refereegranskat)abstract
- With interactive branched video, the storyline is typically determined by branch choices made by the user during playback. Despite putting users in control of their viewing experiences, prior work has not considered how to best help users that may want to quickly navigate, explore, or skip parts of the branched video. Such functionalities are important for both impatient users and those rewatching the video. To address this void, we present the design, implementation and evaluation of interface solutions that help users effectively navigate the video, and to identify and explore previously unviewed storylines. Our solutions work with large, general video structures and allow users to effectively forward/rewind the branched structures. Our user study demonstrates the added value of our novel designs, presents promising tradeoffs, provides insights into the pros/cons of different design alternatives, and highlights the features that best address specific tasks and design aspects.
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