Kaihua Qin, Henryk Hadass, Arthur Gervais, Joel Reardon
{"title":"Applying Private Information Retrieval to Lightweight Bitcoin Clients","authors":"Kaihua Qin, Henryk Hadass, Arthur Gervais, Joel Reardon","doi":"10.1109/CVCBT.2019.00012","DOIUrl":"https://doi.org/10.1109/CVCBT.2019.00012","url":null,"abstract":"Lightweight Bitcoin clients execute a Simple Payment Verification (SPV) protocol to verify the validity of transactions related to a particular user. Currently, lightweight clients use Bloom filters to significantly reduce the amount of bandwidth required to validate a particular transaction. This is despite the fact that research has shown that Bloom filters are insufficient at preserving the privacy of clients' queries. In this paper we describe our design of an SPV protocol that leverages Private Information Retrieval (PIR) to create fully private and performant queries. We show that our protocol has a low bandwidth and latency cost; properties that make our protocol a viable alternative for lightweight Bitcoin clients and other cryptocurrencies with a similar SPV model. In contract to Bloom filters, our PIR-based approach offers deterministic privacy to the user. Among our results, we show that in the worst case, clients who would like to verify 100 transactions occurring in the past week incurs a bandwidth cost of 33.54 MB with an associated latency of approximately 4.8 minutes, when using our protocol. The same query executed using the Bloom-filter-based SPV protocol incurs a bandwidth cost of 12.85 MB; this is a modest overhead considering the privacy guarantees it provides.","PeriodicalId":289955,"journal":{"name":"2019 Crypto Valley Conference on Blockchain Technology (CVCBT)","volume":"74 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116253611","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Pernice, Sebastian A. Henningsen, Roman Proskalovich, Martin Florian, Hermann W. Elendner, B. Scheuermann
{"title":"Monetary Stabilization in Cryptocurrencies – Design Approaches and Open Questions","authors":"I. Pernice, Sebastian A. Henningsen, Roman Proskalovich, Martin Florian, Hermann W. Elendner, B. Scheuermann","doi":"10.1109/CVCBT.2019.00011","DOIUrl":"https://doi.org/10.1109/CVCBT.2019.00011","url":null,"abstract":"The price volatility of cryptocurrencies is often cited as a major hindrance to their wide-scale adoption. Consequently, during the last two years, multiple so called stablecoins have surfaced – cryptocurrencies focused on maintaining stable exchange rates. In this paper, we systematically explore and analyze the stablecoin landscape. Based on a survey of 24 specific stablecoin projects, we go beyond individual coins for extracting general concepts and approaches. We combine our findings with learnings from classical monetary policy, resulting in a comprehensive taxonomy of cryptocurrency stabilization. We use our taxonomy to highlight the current state of development from different perspectives and show blank spots. For instance, while over 91% of projects promote 1-to-1 stabilization targets to external assets, monetary policy literature suggests that the smoothing of short term volatility is often a more sustainable alternative. Our taxonomy bridges computer science and economics, fostering the transfer of expertise. For example, we find that 38% of the reviewed projects use a combination of exchange rate targeting and specific stabilization techniques that can render them vulnerable to speculative economic attacks – an avoidable design flaw.","PeriodicalId":289955,"journal":{"name":"2019 Crypto Valley Conference on Blockchain Technology (CVCBT)","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121550708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. França, Marvin Wissfeld, Pascal Berrang, Philipp von Styp-Rekowsky, Reto Trinkler
{"title":"Albatross – An optimistic consensus algorithm","authors":"B. França, Marvin Wissfeld, Pascal Berrang, Philipp von Styp-Rekowsky, Reto Trinkler","doi":"10.1109/CVCBT.2019.000-1","DOIUrl":"https://doi.org/10.1109/CVCBT.2019.000-1","url":null,"abstract":"Distributed ledgers have the potential to revolutionize the financial landscape by removing trusted third parties. At the heart of most distributed ledgers is their consensus protocol. The consensus protocol describes the way participants in a distributed network interact with each other to obtain and agree on a shared state. While classical Byzantine fault tolerant (BFT) algorithms are designed to work in closed, size-limited networks only, modern distributed ledgers - and blockchains in particular - often focus on open, permissionless networks. In this paper, we present a novel blockchain consensus algorithm for open, permissionless networks, called Albatross, inspired by speculative BFT algorithms. We argue that the protocol is secure under regular PBFT security assumptions and has a theoretical performance close to the maximum for single-chain Proof-of-Stake consensus algorithms. We conclude by describing our future work related to Albatross.","PeriodicalId":289955,"journal":{"name":"2019 Crypto Valley Conference on Blockchain Technology (CVCBT)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129122914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}