Reference : UC Updatable Databases and Applications
 Document type : Scientific congresses, symposiums and conference proceedings : Paper published in a book Discipline(s) : Engineering, computing & technology : Computer science Focus Areas : Security, Reliability and Trust To cite this reference: http://hdl.handle.net/10993/42984
 Title : UC Updatable Databases and Applications Language : English Author, co-author : Damodaran, Aditya Shyam Shankar [University of Luxembourg > Interdisciplinary Centre for Security, Reliability and Trust (SNT) > >] Rial, Alfredo [University of Luxembourg > Interdisciplinary Centre for Security, Reliability and Trust (SNT) > >] Publication date : 2020 Main document title : 12th International Conference on Cryptology Peer reviewed : Yes Audience : International Event name : AFRICACRYPT 2020 Event date : From 20-07-2020 to 22-07-2020 Keywords : [en] Vector commitments ; ZK proofs ; universal composability Abstract : [en] We define an ideal functionality $\Functionality_{\UD}$ and a construction $\mathrm{\Pi_{\UD}}$ for an updatable database ($\UD$). $\UD$ is a two-party protocol between an updater and a reader. The updater sets the database and updates it at any time throughout the protocol execution. The reader computes zero-knowledge (ZK) proofs of knowledge of database entries. These proofs prove that a value is stored at a certain position in the database, without revealing the position or the value. (Non-)updatable databases are implicitly used as building block in priced oblivious transfer, privacy-preserving billing and other privacy-preserving protocols. Typically, in those protocols the updater signs each database entry, and the reader proves knowledge of a signature on a database entry. Updating the database requires a revocation mechanism to revoke signatures on outdated database entries. Our construction $\mathrm{\Pi_{\UD}}$ uses a non-hiding vector commitment (NHVC) scheme. The updater maps the database to a vector and commits to the database. This commitment can be updated efficiently at any time without needing a revocation mechanism. ZK proofs for reading a database entry have communication and amortized computation cost independent of the database size. Therefore, $\mathrm{\Pi_{\UD}}$ is suitable for large databases. We implement $\mathrm{\Pi_{\UD}}$ and our timings show that it is practical. In existing privacy-preserving protocols, a ZK proof of a database entry is intertwined with other tasks, e.g., proving further statements about the value read from the database or the position where it is stored. $\Functionality_{\UD}$ allows us to improve modularity in protocol design by separating those tasks. We show how to use $\Functionality_{\UD}$ as building block of a hybrid protocol along with other functionalities. Research centres : Interdisciplinary Centre for Security, Reliability and Trust (SnT) > Applied Security and Information Assurance Group (APSIA) Funders : Fonds National de la Recherche - FnR Name of the research project : SZK Permalink : http://hdl.handle.net/10993/42984 FnR project : FnR ; FNR11650748 > Alfredo Rial > SZK > Stateful Zero-Knowledge > 01/03/2018 > 28/02/2021 > 2017

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