@misc{BackesBerrangHanzliketal., author = {Backes, Michael and Berrang, Pascal and Hanzlik, Lucjan and Pryvalov, Ivan}, title = {A Framework for Constructing Single Secret Leader Election from MPC.}, series = {Michael Backes, Pascal Berrang, Lucjan Hanzlik, Ivan Pryvalov. "A Framework for Constructing Single Secret Leader Election from MPC." In Computer Security - ESORICS 2022 - 27th European Symposium on Research in Computer Security, Copenhagen, Denmark, September 26-30, 2022, Proceedings, Part II, pp.672-691, Springer.}, journal = {Michael Backes, Pascal Berrang, Lucjan Hanzlik, Ivan Pryvalov. "A Framework for Constructing Single Secret Leader Election from MPC." In Computer Security - ESORICS 2022 - 27th European Symposium on Research in Computer Security, Copenhagen, Denmark, September 26-30, 2022, Proceedings, Part II, pp.672-691, Springer.}, publisher = {Springer}, doi = {10.1007/978-3-031-17146-8_33}, pages = {672 -- 691}, abstract = {The emergence of distributed digital currencies has raised the need for a reliable consensus mechanism. In proof-of-stake cryptocurrencies, the participants periodically choose a closed set of validators, who can vote and append transactions to the blockchain. Each validator can become a leader with the probability proportional to its stake. Keeping the leader private yet unique until it publishes a new block can significantly reduce the attack vector of an adversary and improve the throughput of the network. The problem of Single Secret Leader Election (SSLE) was first formally defined by Boneh et al. in 2020. In this work, we propose a novel framework for constructing SSLE protocols, which relies on secure multi-party computation (MPC) and satisfies the desired security properties. Our framework does not use any shuffle or sort operations and has a computational cost for N parties as low as O(N) of basic MPC operations per party. We improve the stateof-the-art for SSLE protocols that do not assume a trusted setup. Moreover, our SSLE scheme efficiently handles weighted elections. That is, for a total weight S of N parties, the associated costs are only increased by a factor of log S. When the MPC layer is instantiated with techniques based on Shamir's secret-sharing, our SSLE has a communication cost of O(N2) which is spread over O(logN) rounds, can tolerate up to t < N/2 of faulty nodes without restarting the protocol, and its security relies on DDH in the random oracle model. When the MPC layer is instantiated with more efficient techniques based on garbled circuits, our SSLE requires all parties to participate, up to N -1 of which can be malicious, and its security is based on the random oracle model.}, language = {en} } @misc{BackesHanzlikHerzbergetal., author = {Backes, Michael and Hanzlik, Lucjan and Herzberg, Amir and Kate, Aniket and Pryvalov, Ivan}, title = {Efficient Non-Interactive Zero-Knowledge Proofs in Cross-Domains Without Trusted Setup.}, series = {Public-Key Cryptography - PKC 2019 : 22nd IACR International Conference on Practice and Theory of Public-Key Cryptography, Beijing, China, April 14-17, 2019, Proceedings, Part I}, journal = {Public-Key Cryptography - PKC 2019 : 22nd IACR International Conference on Practice and Theory of Public-Key Cryptography, Beijing, China, April 14-17, 2019, Proceedings, Part I}, editor = {Lin, Dongdai}, publisher = {Springer}, doi = {10.1007/978-3-030-17253-4_10}, pages = {286 -- 313}, abstract = {With the recent emergence of efficient zero-knowledge (ZK) proofs for general circuits, while efficient zero-knowledge proofs of algebraic statements have existed for decades, a natural challenge arose to combine algebraic and non-algebraic statements. Chase et al. (CRYPTO 2016) proposed an interactive ZK proof system for this cross-domain problem. As a use case they show that their system can be used to prove knowledge of a RSA/DSA signature on a message m with respect to a publicly known Pedersen commitment gmhr. One drawback of their system is that it requires interaction between the prover and the verifier. This is due to the interactive nature of garbled circuits, which are used in their construction. Subsequently, Agrawal et al. (CRYPTO 2018) proposed an efficient non-interactive ZK (NIZK) proof system fo cross-domains based on SNARKs, which however require a trusted setup assumption. In this paper, we propose a NIZK proof system for cross domains that requires no trusted setup and is efficient both for the prover and the verifier. Our system constitutes a combination of Schnorr based ZK proofs and ZK proofs for general circuits by Giacomelli et al. (USENIX 2016). The proof size and the running time of our system are comparable to the approach by Chase et al. Compared to Bulletproofs (SP 2018), a recent NIZK proofs system on committed inputs, our techniques achieve asymptotically better performance on prover and verifier, thus presenting a different trade-off between the proof size and the running time.}, language = {en} } @misc{BackesHerzbergKateetal., author = {Backes, Michael and Herzberg, Amir and Kate, Aniket and Pryvalov, Ivan}, title = {Differentially private data aggregation with optimal utility}, series = {Proceedings of the 30th Annual Computer Security Applications Conference, ACSAC 2014, New Orleans, LA, USA, December 8-12, 2014}, journal = {Proceedings of the 30th Annual Computer Security Applications Conference, ACSAC 2014, New Orleans, LA, USA, December 8-12, 2014}, publisher = {Springer}, doi = {10.1145/2664243.2664263}, pages = {316 -- 325}, abstract = {We define the concept of and present provably secure constructions for Anonymous RAM (AnonRAM), a novel multi-user storage primitive that offers strong privacy and integrity guarantees. AnonRAM combines privacy features of anonymous communication and oblivious RAM (ORAM) schemes, allowing it to protect, simultaneously, the privacy of content, access patterns and user's identity, from curious servers and from other (even adversarial) users. AnonRAM further protects integrity, i.e., it prevents malicious users from corrupting data of other users. We present two secure AnonRAM schemes, differing in design and time complexity. The first scheme has a simpler design; like efficient ORAM schemes, its time complexity is poly-logarithmic in the number of cells (per user); however, it is linear in the number of users. The second AnonRAM scheme reduces the overall complexity to poly-logarithmic in the total number of cells (of all users) at the cost of requiring two (non-colluding) servers.}, language = {en} } @misc{GajekLewandowsky, author = {Gajek, Sebastian and Lewandowsky, Marco}, title = {Trustless, Censorship-Resilient and Scalable Votings in the Permission-Based Blockchain Model}, series = {Euro-Par 2020 International Workshops, Warsaw, Poland, August 24-25, 2020, Revised Selected Papers}, journal = {Euro-Par 2020 International Workshops, Warsaw, Poland, August 24-25, 2020, Revised Selected Papers}, publisher = {Springer}, isbn = {978-3-030-71592-2}, doi = {10.1007/978-3-030-71593-9_5}, pages = {54 -- 65}, abstract = {Voting systems are the tool of choice when it comes to settle an agreement of different opinions. We propose a solution for a trustless, censorship-resilient and scalable electronic voting platform. By leveraging the blockchain together with the functional encryption paradigm, we fully decentralize the system and reduce the risks that a voting provider, like a corrupt government, does censor or manipulate the outcome.}, language = {en} } @misc{KharrufaAlKashoashAlNidawietal., author = {Kharrufa, Harith and Al-Kashoash, Hayder and Al-Nidawi, Yaarob and Quezada Mosquera, Maria Fernanda and Kemp, Andrew H.}, title = {Dynamic RPL for multi-hop routing in IoT applications}, series = {13th Annual Conference on Wireless On-demand Network Systems and Services (WONS)}, journal = {13th Annual Conference on Wireless On-demand Network Systems and Services (WONS)}, publisher = {IEEE}, isbn = {978-3-901882-88-3}, doi = {10.1109/WONS.2017.7888753}, pages = {4}, abstract = {The Routing Protocol for Low Power and Lossy Networks (RPL) has become the standard routing protocol for the Internet of Things (IoT). This paper investigates the use of RPL in dynamic networks and presents an enhanced RPL for different applications with dynamic mobility and diverse network requirements. This implementation of RPL is designed with a new dynamic Objective-Function (D-OF) to improve the Packet Delivery Ratio (PDR), end-to-end delay and energy consumption while maintaining low packet overhead and loop-avoidance. We propose a controlled reverse-trickle timer based on received signal strength identification (RSSI) readings to maintain high responsiveness with minimum overhead and consult the objective function when a movement or an inconsistency is detected to help nodes make an informed decision. Simulations are done using Cooja with random waypoint mobility scenario for healthcare applications considering multi-hop routing. The results show that the proposed dynamic RPL (D-RPL) adapts to the nodes mobility and has a higher PDR, slightly lower end-to-end delay and reasonable energy consumption compared to related existing protocols.}, language = {en} } @misc{CabezasQuezadaMosqueraBernal, author = {Cabezas, Gissela and Quezada Mosquera, Maria Fernanda and Bernal, Ivan}, title = {Sistema de Generaci{\´o}n de Aplicaciones Interactivas para TV Digital para la evaluaci{\´o}n de servicios masivos}, series = {Revista Polit{\´e}cnica}, volume = {32}, journal = {Revista Polit{\´e}cnica}, number = {2}, pages = {11 -- 22}, abstract = {The development of the prototype of the system SGAi (Generation System for InteractiveApplications) designed to obtain feedback from TV viewers about mass services, is reported; in a particularway, it is applied to evaluate the quality of telecommunication services. SGAi consists of three components: 1)Survey Composer, which lets users create and customize interactive applications for surveys and automaticallygenerate the NCL code (Nested Context Language) that will run on the STB (Set Top Box) of the viewer;2) A manageable web application that provides the survey management system, receives and storages opinionsas well as the display of results; and 3) the return channel, responsible for communications between the STBand the server of the manageable web application. The system is aimed, in particular Survey Composer, tofacilitate the generation of interactive applications that use the return channel, allowing the user to focus onthe content and aesthetics of the surveys rather than learning and using NCL. SGAi has been developed as partof research activities carried out in the digital TV area in the National Polytechnic School, considering theISDB-Tb standard, adopted in Ecuador in March 2010.}, language = {es} } @misc{MorenoPastranaReelfsetal., author = {Moreno, Jos{\´e} Miguel and Pastrana, Sergio and Reelfs, Jens Helge and Vallina, Pelayo and Panchenko, Andriy and Smaragdakis, Georgios and Hohlfeld, Oliver and Vallina-Rodriguez, Narseo and Tapiador, Juan}, title = {Reviewing War: Unconventional User Reviews as a Side Channel to Circumvent Information Controls}, doi = {10.48550/arXiv.2302.00598}, pages = {11}, abstract = {During the first days of the 2022 Russian invasion of Ukraine, Russia's media regulator blocked access to many global social media platforms and news sites, including Twitter, Facebook, and the BBC. To bypass the information controls set by Russian authorities, pro-Ukrainian groups explored unconventional ways to reach out to the Russian population, such as posting war-related content in the user reviews of Russian business available on Google Maps or Tripadvisor. This paper provides a first analysis of this new phenomenon by analyzing the creative strategies to avoid state censorship. Specifically, we analyze reviews posted on these platforms from the beginning of the conflict to September 2022. We measure the channeling of war messages through user reviews in Tripadvisor and Google Maps, as well as in VK, a popular Russian social network. Our analysis of the content posted on these services reveals that users leveraged these platforms to seek and exchange humanitarian and travel advice, but also to disseminate disinformation and polarized messages. Finally, we analyze the response of platforms in terms of content moderation and their impact.}, language = {en} } @misc{BuscemiTurcanuCastignanietal., author = {Buscemi, Alessio and Turcanu, Ion and Castignani, German and Panchenko, Andriy and Engel, Thomas and Shin, Kang G.}, title = {A Survey on Controller Area Network Reverse Engineering}, series = {IEEE Communications Surveys \& Tutorials}, volume = {25}, journal = {IEEE Communications Surveys \& Tutorials}, number = {3,3}, publisher = {IEEE}, issn = {1553-877X}, doi = {10.1109/COMST.2023.3264928}, pages = {1445 -- 1481}, abstract = {Controller Area Network (CAN) is a masterless serial bus designed and widely used for the exchange of mission and time-critical information within commercial vehicles. In-vehicle communication is based on messages sent and received by Electronic Control Units (ECUs) connected to this serial bus network. Although unencrypted, CAN messages are not easy to interpret. In fact, Original Equipment Manufacturers (OEMs) attempt to achieve security through obscurity by encoding the data in their proprietary format, which is kept secret from the general public. As a result, the only way to obtain clear data is to reverse engineer CAN messages. Driven by the need for in-vehicle message interpretation, which is highly valuable in the automotive industry, researchers and companies have been working to make this process automated, fast, and standardized. In this paper, we provide a comprehensive review of the state of the art and summarize the major advances in CAN bus reverse engineering. We are the first to provide a taxonomy of CAN tokenization and translation techniques. Based on the reviewed literature, we highlight an important issue: the lack of a public and standardized dataset for the quantitative evaluation of translation algorithms. In response, we define a complete set of requirements for standardizing the data collection process. We also investigate the risks associated with the automation of CAN reverse engineering, in particular with respect to the security network and the safety and privacy of drivers and passengers. Finally, we discuss future research directions in CAN reverse engineering.}, language = {en} } @misc{MuellerPejoPryvalov, author = {M{\"u}ller, Johannes and Pej{\´o}, Bal{\´a}zs and Pryvalov, Ivan}, title = {DeVoS: Deniable Yet Verifiable Vote Updating}, series = {Proceedings on Privacy Enhancing Technologies}, journal = {Proceedings on Privacy Enhancing Technologies}, number = {1}, issn = {2299-0984}, doi = {10.56553/popets-2024-0021}, pages = {357 -- 378}, abstract = {Internet voting systems are supposed to meet the same high stan- dards as traditional paper-based systems when used in real political elections: freedom of choice, universal and equal suffrage, secrecy of the ballot, and independent verifiability of the election result. Although numerous Internet voting systems have been proposed to achieve these challenging goals simultaneously, few come close in reality. We propose a novel publicly verifiable and practically efficient Internet voting system, DeVoS, that advances the state of the art. The main feature of DeVoS is its ability to protect voters' freedom of choice in several dimensions. First, voters in DeVoS can intu- itively update their votes in a way that is deniable to observers but verifiable by the voters; in this way voters can secretly overwrite potentially coerced votes. Second, in addition to (basic) vote privacy, DeVoS also guarantees strong participation privacy by end-to-end hiding which voters have submitted ballots and which have not. Finally, DeVoS is fully compatible with Perfectly Private Audit Trail, a state-of-the-art Internet voting protocol with practical everlasting privacy. In combination, DeVoS offers a new way to secure free Internet elections with strong and long-term privacy properties.}, language = {en} } @misc{MitsevaAlexandrovaPanchenko, author = {Mitseva, Asya and Alexandrova, Marharyta and Panchenko, Andriy}, title = {Security and Performance Implications of BGP Rerouting-resistant Guard Selection Algorithms for Tor}, series = {Computers and Security}, volume = {132}, journal = {Computers and Security}, issn = {1872-6208}, doi = {10.1016/j.cose.2023.103374}, abstract = {Tor is the most popular anonymization network with millions of daily users. This makes it an attractive target for attacks, e.g., by malicious autonomous systems (ASs) performing active routing attacks to become man in the middle and deanonymize users. It was shown that the number of such malicious ASs is significantly larger than previously expected due to the lack of security guarantees in the Border Gateway Protocol (BGP). In response, recent works suggest alternative Tor path selection methods preferring Tor nodes with higher resilience to active BGP attacks. In this work, we analyze the implications of such proposals and demonstrate that two state-of-the-art path selection methods, namely Counter-RAPTOR and DPSelect, are not as secure as thought before. First, we show that DPSelect achieves only one third of its originally claimed resilience and, thus, is not as resilient as widely accepted. Second, we reveal that the resilience to active BGP attacks on the way back, i.e., from the first anonymization node to a given Tor user, provided by both methods is significantly lower than on the forward path. Beside their lower resilience in specific cases, we show that for particular users the usage of Counter-RAPTOR and DPSelect also leads to leakage of user's location. Furthermore, we uncover the performance implications of both methods and identify scenarios where their usage leads to significant performance bottlenecks. Finally, we propose a new metric to quantify the user's location leakage by path selection. Using this metric and performing large-scale analysis, we show to which extent a malicious Tor middle node can fingerprint the user's location and the confidence it can achieve. Our findings shed light on the implications of path selection methods on the users' anonymity and the need for further research.}, language = {en} } @misc{BartschGopeKavunetal., author = {Bartsch, Witali and Gope, Prosanta and Kavun, Elif and Millwood, Owen and Panchenko, Andriy and Pasikhani, Aryan and Polian, Ilia}, title = {Design Rationale for Symbiotically Secure Key Management Systems in IoT and Beyond}, series = {Proceedings of the 9th International Conference on Information Systems Security and Privacy ICISSP - Volume 1}, journal = {Proceedings of the 9th International Conference on Information Systems Security and Privacy ICISSP - Volume 1}, publisher = {SciTePress}, isbn = {978-989-758-624-8}, issn = {2184-4356}, doi = {10.5220/0011726900003405}, pages = {583 -- 591}, abstract = {The overwhelmingly widespread use of Internet of Things (IoT) in different application domains brought not only benefits, but, alas, security concerns as a result of the increased attack surface and vectors. One of the most critical mechanisms in IoT infrastructure is key management. This paper reflects on the problems and challenges of existing key management systems, starting with the discussion of a recent real-world attack. We identify and elaborate on the drawbacks of security primitives based purely on physical variations and - after highlighting the problems of such systems - continue on to deduce an effective and cost-efficient key management solution for IoT systems extending the symbiotic security approach in a previous work. The symbiotic architecture combines software, firmware, and hardware resources for secure IoT while avoiding the traditional scheme of static key storage and generating entropy for key material on-the-fly via a combination of a Physical Unclonable Func tion (PUF) and pseudo-random bits pre-populated in firmware.}, language = {en} } @misc{MitsevaThierseHoffmannetal., author = {Mitseva, Asya and Thierse, Paul and Hoffmann, Harald and Er, Devran and Panchenko, Andriy}, title = {Challenges and Pitfalls in Generating Representative ICS Datasets in Cyber Security Research}, series = {Computer Security, ESORICS 2022 International Workshops CyberICPS 2022, SECPRE 2022, SPOSE 2022, CPS4CIP 2022, CDT\&SECOMANE 2022, EIS 2022, and SecAssure 2022 Copenhagen, Denmark, September 26-30, 2022, Revised Selected Papers}, journal = {Computer Security, ESORICS 2022 International Workshops CyberICPS 2022, SECPRE 2022, SPOSE 2022, CPS4CIP 2022, CDT\&SECOMANE 2022, EIS 2022, and SecAssure 2022 Copenhagen, Denmark, September 26-30, 2022, Revised Selected Papers}, editor = {Katsikas, Sokratis}, publisher = {Springer International Publishing}, address = {Cham}, isbn = {978-3-031-25459-8}, doi = {10.1007/978-3-031-25460-4_22}, pages = {379 -- 397}, language = {en} } @misc{GaoZhangChenetal., author = {Gao, Yunlong and Zhang, Yisong and Chen, Baihua and Xiong, Yuhui}, title = {Local Neighborhood Reliability Weighted Support Vector Machine}, series = {2020 2nd International Conference on Industrial Artificial Intelligence (IAI)}, journal = {2020 2nd International Conference on Industrial Artificial Intelligence (IAI)}, publisher = {IEEE}, isbn = {978-1-7281-8216-2}, doi = {10.1109/IAI50351.2020.9262215}, pages = {1 -- 6}, abstract = {Support vector machine (SVM) is a classification model, which learns the decision surface that maximizes the margin in the feature space. Such a decision surface has a good classification ability for unknown new samples. In real-world applications, the data set usually contains many noises and outliers, which will affect the learning of the decision surface, thus the maximum margin cannot be obtained, and the generalization ability of SVM will be reduced. In this paper, we introduce an adjacency factor to each input point to characterize the local neighbor relationship between each point. Weighting each sample point by the adjacency factor can let different sample points make different contributions to the learning of the decision surface. Thus, we can filter out the influence of noises and outliers on the decision surface by this weighting method. We propose this new method namely local neighborhood reliability weighted support vector machine (LN-SVM).}, language = {en} } @misc{Sheikhi‐GarjanGiustolisiSchuermann, author = {Sheikhi-Garjan, Maryam and Giustolisi, Rosario and Schuermann, Carsten}, title = {Receipt-Free Electronic Voting from zk-SNARK}, series = {Proceedings of the 20th International Conference on Security and Cryptography}, journal = {Proceedings of the 20th International Conference on Security and Cryptography}, publisher = {SCITEPRESS - Science and Technology Publications}, isbn = {978-989-758-666-8}, doi = {10.5220/0012140000003555}, pages = {254 -- 266}, language = {en} } @phdthesis{Mitseva, author = {Mitseva, Asya}, title = {State of affairs in online user privacy : assessing real-world user information leakages and designing effective and practical countermeasures}, publisher = {Brandenburgische Technische Universit{\"a}t}, address = {Cottbus-Senftenberg}, doi = {10.26127/BTUOpen-7214}, pages = {xxvii, 194}, abstract = {The Tor network ensures confidentiality of user data over the Internet and hides the IP addresses and relationships between communication partners to avoid user profiling and censorship. However, Tor cannot hide the number, direction, and timing of transmitted packets. Two types of attackers - autonomous systems (AS) and malicious Tor nodes - can exploit this for sophisticated attacks, such as website fingerprinting (WFP) and end-to-end traffic correlation, or fingerprinting attacks revealing the Tor users' location. On the other hand, in case of a malicious first Tor node or a malicious AS on the path between the user and the Tor network, the scalability of prior WFP attacks remains questionable due to impractical assumptions. This dissertation aims to provide a more realistic assessment of the exposure of Tor users to passive deanonymization attacks from different perspectives. First, we conduct a comprehensive review of fundamental Border Gateway Protocol (BGP) threats. We present a methodology for evaluating existing BGP security proposals and provide an extensive and up-to-date survey of proposals intended to make BGP secure and methods for detecting and mitigating routing instabilities. Based on the identified research gaps and unresolved challenges, we analyze the current level of resilience of Tor and two alternative Tor path selection methods against malicious ASs. While we detect a notable increase in the Tor's resilience to BGP attacks over the years, when measured from a Tor user to its first Tor node, the resilience provided by the alternative path selection methods on the way back, i.e., from the first Tor node to a Tor user, has decreased notably compared to the resilience measured on the forward path for these methods. Moreover, these methods tend to select first Tor nodes in a predictable manner, resulting in the exposure of users' locations to Tor middle nodes. We also show novel attacks against a state-of-the-art method for measuring bandwidth capabilities of Tor nodes, allowing a low-bandwidth attacker to gain notably higher bandwidth estimates than theoretically defined. We propose a novel lightweight defense against malicious Tor nodes, performing WFP or end-to-end traffic correlation, that splits user traffic over multiple Tor paths. Our defense is fully implemented on the user side, reducing deployment costs and making it independent of the underlying anonymization network. We also propose a metric that is capable of quantifying the user's location leakage considering a malicious Tor middle node. This metric enables Tor users to avoid specific first Tor nodes by strategically selecting those from which their location cannot be revealed. Finally, we examine the real-world scalability of WFP, especially against Tor users who visit several pages of a single website consecutively. We propose both a novel WFP attack and efficient strategies for adapting existing methods to account for sequential visits of pages within a website.}, language = {en} }