This file was created by the TYPO3 extension bib --- Timezone: CEST Creation date: 2024-07-03 Creation time: 13-27-05 --- Number of references 3 article 2021_matzutt_coinprune_v2 IEEE Transactions on Network and Service Management 2021 9 10 18 3 3064-3078 Popular cryptocurrencies continue to face serious scalability issues due to their ever-growing blockchains. Thus, modern blockchain designs began to prune old blocks and rely on recent snapshots for their bootstrapping processes instead. Unfortunately, established systems are often considered incapable of adopting these improvements. In this work, we present CoinPrune, our block-pruning scheme with full Bitcoin compatibility, to revise this popular belief. CoinPrune bootstraps joining nodes via snapshots that are periodically created from Bitcoin's set of unspent transaction outputs (UTXO set). Our scheme establishes trust in these snapshots by relying on CoinPrune-supporting miners to mutually reaffirm a snapshot's correctness on the blockchain. This way, snapshots remain trustworthy even if adversaries attempt to tamper with them. Our scheme maintains its retrospective deployability by relying on positive feedback only, i.e., blocks containing invalid reaffirmations are not rejected, but invalid reaffirmations are outpaced by the benign ones created by an honest majority among CoinPrune-supporting miners. Already today, CoinPrune reduces the storage requirements for Bitcoin nodes by two orders of magnitude, as joining nodes need to fetch and process only 6 GiB instead of 271 GiB of data in our evaluation, reducing the synchronization time of powerful devices from currently 7 h to 51 min, with even larger potential drops for less powerful devices. CoinPrune is further aware of higher-level application data, i.e., it conserves otherwise pruned application data and allows nodes to obfuscate objectionable and potentially illegal blockchain content from their UTXO set and the snapshots they distribute. blockchain; block pruning; synchronization; bootstrapping; scalability; velvet fork; Bitcoin mynedata; impact_digital; digital_campus https://www.comsys.rwth-aachen.de/fileadmin/papers/2021/2021-matzutt-coinprune-v2.pdf English 1932-4537 10.1109/TNSM.2021.3073270 1 RomanMatzutt BenediktKalde JanPennekamp ArthurDrichel MartinHenze KlausWehrle inproceedings 2020_matzutt_coinprune 2020 6 24 298-306 Bitcoin was the first successful decentralized cryptocurrency and remains the most popular of its kind to this day. Despite the benefits of its blockchain, Bitcoin still faces serious scalability issues, most importantly its ever-increasing blockchain size. While alternative designs introduced schemes to periodically create snapshots and thereafter prune older blocks, already-deployed systems such as Bitcoin are often considered incapable of adopting corresponding approaches. In this work, we revise this popular belief and present CoinPrune, a snapshot-based pruning scheme that is fully compatible with Bitcoin. CoinPrune can be deployed through an opt-in velvet fork, i.e., without impeding the established Bitcoin network. By requiring miners to publicly announce and jointly reaffirm recent snapshots on the blockchain, CoinPrune establishes trust into the snapshots' correctness even in the presence of powerful adversaries. Our evaluation shows that CoinPrune reduces the storage requirements of Bitcoin already by two orders of magnitude today, with further relative savings as the blockchain grows. In our experiments, nodes only have to fetch and process 5 GiB instead of 230 GiB of data when joining the network, reducing the synchronization time on powerful devices from currently 5 h to 46 min, with even more savings for less powerful devices. blockchain; block pruning; synchronization; bootstrapping; scalability; velvet fork; Bitcoin mynedata; impact_digital; digital_campus https://comsys.rwth-aachen.de/fileadmin/papers/2020/2020-matzutt-coinprune.pdf https://coinprune.comsys.rwth-aachen.de IEEE Proceedings of the 19th IFIP Networking 2020 Conference (NETWORKING '20), June 22-26, 2020, Paris, France Paris, France NETWORKING 2020 June 22-26, 2020 978-3-903176-28-7 1 RomanMatzutt BenediktKalde JanPennekamp ArthurDrichel MartinHenze KlausWehrle inproceedings 2017-henze-mobiquitous-cloudanalyzer 2017 11 7 262-271 Developers of smartphone apps increasingly rely on cloud services for ready-made functionalities, e.g., to track app usage, to store data, or to integrate social networks. At the same time, mobile apps have access to various private information, ranging from users' contact lists to their precise locations. As a result, app deployment models and data flows have become too complex and entangled for users to understand. We present CloudAnalyzer, a transparency technology that reveals the cloud usage of smartphone apps and hence provides users with the means to reclaim informational self-determination. We apply CloudAnalyzer to study the cloud exposure of 29 volunteers over the course of 19 days. In addition, we analyze the cloud usage of the 5000 most accessed mobile websites as well as 500 popular apps from five different countries. Our results reveal an excessive exposure to cloud services: 90 % of apps use cloud services and 36 % of apps used by volunteers solely communicate with cloud services. Given the information provided by CloudAnalyzer, users can critically review the cloud usage of their apps. Privacy; Smartphones; Cloud Computing; Traffic Analysis trinics https://www.comsys.rwth-aachen.de/fileadmin/papers/2017/2017-henze-mobiquitous-cloudanalyzer.pdf Online ACM Proceedings of the 14th EAI International Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services (MobiQuitous '17), November 7-10, 2017, Melbourne, VIC, Australia Melbourne, VIC, Australia November 7-10, 2017 en 978-1-4503-5368-7 10.1145/3144457.3144471 1 MartinHenze JanPennekamp DavidHellmanns ErikMühmer Jan HenrikZiegeldorf ArthurDrichel KlausWehrle