{"id":164034,"date":"2012-01-01T00:00:00","date_gmt":"2012-01-01T00:00:00","guid":{"rendered":"https:\/\/www.microsoft.com\/en-us\/research\/msr-research-item\/secure-database-commitments-and-universal-arguments-of-quasi-knowledge\/"},"modified":"2018-10-16T20:05:14","modified_gmt":"2018-10-17T03:05:14","slug":"secure-database-commitments-and-universal-arguments-of-quasi-knowledge","status":"publish","type":"msr-research-item","link":"https:\/\/www.microsoft.com\/en-us\/research\/publication\/secure-database-commitments-and-universal-arguments-of-quasi-knowledge\/","title":{"rendered":"Secure Database Commitments and Universal Arguments of Quasi Knowledge"},"content":{"rendered":"<div class=\"asset-content\">\n<p>In this work we focus on a simple database commitment functionality where besides<br \/>\nthe standard security properties, one would like to hide the size of the input of the<br \/>\nsender. Hiding the size of the input of a player is a critical requirement in some applica-<br \/>\ntions, and relatively few works have considered it. Notable exceptions are the work on<br \/>\nzero-knowledge sets introduced in [MRK03], and recent work on size-hiding private set<br \/>\nintersection [ADCT11]. However, neither of these achieves a secure computation (i.e., a<br \/>\nreduction of a real-world attack of a malicious adversary into an ideal-world attack) of<br \/>\nthe proposed functionality.<br \/>\nThe first result of this submission consists in defining &#8220;secure&#8221; database commitment<br \/>\nand in observing that previous constructions do not satisfy this definition. This leaves<br \/>\nopen the question of whether there is any way this functionality can be achieved.<br \/>\nWe then provide an affirmative answer to this question by using new techniques<br \/>\nthat combined together achieve &#8220;secure&#8221; database commitment. Our construction is<br \/>\nin particular optimized to require only a constant number of rounds, to provide non-<br \/>\ninteractive proofs on the content of the database, and to rely only on the existence of<br \/>\na family of CRHFs. This is the first result where input-size hiding secure computation<br \/>\nis achieved for an interesting functionality and moreover we obtain this result with<br \/>\nstandard security (i.e., simulation in expected polynomial time against fully malicious<br \/>\nadversaries, without random oracles, non-black-box extraction assumptions, hardness<br \/>\nassumptions against super-polynomial time adversaries, or other controversial\/strong<br \/>\nassumptions).<br \/>\nA key building block in our construction is a universal argument enjoying an improved<br \/>\nproof of knowledge property, that we call quasi-knowledge. This property is significantly<br \/>\ncloser to the standard proof of knowledge property than the weak proof of knowledge<br \/>\nproperty satisfied by previous constructions.<\/p>\n<\/div>\n<p><!-- .asset-content --><\/p>\n","protected":false},"excerpt":{"rendered":"<p>In this work we focus on a simple database commitment functionality where besides the standard security properties, one would like to hide the size of the input of the sender. Hiding the size of the input of a player is a critical requirement in some applica- tions, and relatively few works have considered it. Notable [&hellip;]<\/p>\n","protected":false},"featured_media":0,"template":"","meta":{"msr-url-field":"","msr-podcast-episode":"","msrModifiedDate":"","msrModifiedDateEnabled":false,"ep_exclude_from_search":false,"_classifai_error":"","msr-author-ordering":null,"msr_publishername":"","msr_publisher_other":"","msr_booktitle":"","msr_chapter":"","msr_edition":"Crypto 2012","msr_editors":"","msr_how_published":"","msr_isbn":"","msr_issue":"","msr_journal":"","msr_number":"","msr_organization":"","msr_pages_string":"","msr_page_range_start":"","msr_page_range_end":"","msr_series":"","msr_volume":"","msr_copyright":"","msr_conference_name":"Crypto 2012","msr_doi":"","msr_arxiv_id":"","msr_s2_paper_id":"","msr_mag_id":"","msr_pubmed_id":"","msr_other_authors":"Ivan 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