[Resource Topic] 2017/011: Chameleon-Hashes with Ephemeral Trapdoors And Applications to Invisible Sanitizable Signatures

Welcome to the resource topic for 2017/011

Title:
Chameleon-Hashes with Ephemeral Trapdoors And Applications to Invisible Sanitizable Signatures

Authors: Jan Camenisch, David Derler, Stephan Krenn, Henrich C. Pöhls, Kai Samelin, Daniel Slamanig

Abstract:

A chameleon-hash function is a hash function that involves a trapdoor the knowledge of which allows one to find arbitrary collisions in the domain of the function. In this paper, we introduce the notion of chameleon-hash functions with ephemeral trapdoors. Such hash functions feature additional, i.e., ephemeral, trapdoors which are chosen by the party computing a hash value. The holder of the main trapdoor is then unable to find a second pre-image of a hash value unless also provided with the ephemeral trapdoor used to compute the hash value. We present a formal security model for this new primitive as well as provably secure instantiations. The first instantiation is a generic black-box construction from any secure chameleon-hash function. We further provide three direct constructions based on standard assumptions. Our new primitive has some appealing use-cases, including a solution to the long-standing open problem of invisible sanitizable signatures, which we also present.

ePrint: https://eprint.iacr.org/2017/011

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