Title

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

Authors

Jan Camenisch (IBM Research - Zurich), David Derler (TU GRAZ), Stephan Krenn (AIT), Henrich C. Pöhls (UNI PASSAU), Kai Samelin (IBM Research - Zurich), and Daniel Slamanig (TU GRAZ)

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 that 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.

Venue

20th International Conference on Practice and Theory of Public-Key Cryptography - PKC 2017

Place and Date

Amsterdam, The Netherlands, March 28-31, 2017

Publication Reference

Jan Camenisch, David Derler, Stephan Krenn, Henrich C. Pöhls, Kai Samelin, and Daniel Slamanig. "Chameleon-Hashes with Ephemeral Trapdoors And Applications to Invisible Sanitizable Signatures". In: PKC 2017, LNCS, Springer. (to appear)

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Bibtex:

@inproceedings{cdkpss17,
 author = {Jan Camenisch  and David Derler and Stephan Krenn and Henrich C. Pöhls and Kai Samelin and Daniel Slamanig},
 title = {{Chameleon-Hashes with Ephemeral Trapdoors And Applications to Invisible Sanitizable Signatures}},
 booktitle = {20th International Conference on Practice and Theory of Public-Key Cryptography - PKC 2017},
 year = {2017},
 note = {(to appear)},
 series = {LNCS},
 publisher = {Springer},
 }