The first result of this submission consists in defining ``secure'' database commitment and in observing that previous constructions do not satisfy this definition. This leaves open the question of whether there is any way this functionality can be achieved.
We then provide an affirmative answer to this question by using new techniques that combined together achieve ``secure'' database commitment. Our construction is in particular optimized to require only a constant number of rounds, to provide non-interactive proofs on the content of the database, and to rely only on the existence of a family of CRHFs. This is the first result where input-size hiding secure computation is achieved for an interesting functionality and moreover we obtain this result with standard security (i.e., simulation in expected polynomial time against fully malicious adversaries, without random oracles, non-black-box extraction assumptions, hardness assumptions against super-polynomial time adversaries, or other controversial/strong assumptions).
A key building block in our construction is a universal argument enjoying an improved proof of knowledge property, that we call quasi-knowledge. This property is significantly closer to the standard proof of knowledge property than the weak proof of knowledge property satisfied by previous constructions.
Category / Keywords: foundations / ZK sets, universal arguments, input-size hiding computation. Publication Info: This is the full version of a paper that will appear at Crypto '12 Date: received 1 Aug 2012 Contact author: melissac at microsoft com Available format(s): PDF | BibTeX Citation Version: 20120805:174944 (All versions of this report) Discussion forum: Show discussion | Start new discussion