Updatable Zero-Knowledge Sets

Abstract

We build on the work of Micali, Rabin, and Killian [4] to introduce zero-knowledge sets and databases that may be updated in a desirable way. In particular, in order to make an update the owner of the set must publish a commitment to the update, and update the commitment to the set. The update should take time independent of the size of the set. In addition, the update should not leak which key was added (or removed), or what data is associated with that key. Furthermore, our update will be transparent in that those already possessing a proof of a particular key being present or absent should be able to update their proofs to obtain a valid proof relative to the updated set, except if their proof is relative to the element that was changed.