[Resource Topic] 2020/1084: Fully Collision-Resistant Chameleon-Hashes from Simpler and Post-Quantum Assumptions

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Fully Collision-Resistant Chameleon-Hashes from Simpler and Post-Quantum Assumptions

Authors: David Derler, Stephan Krenn, Kai Samelin, Daniel Slamanig


Chameleon-hashes are collision-resistant hash-functions parametrized by a public key. If the corresponding secret key is known, arbitrary collisions for the hash can be found. Recently, Derler et al. (PKC '20) introduced the notion of fully collision-resistant chameleon-hashes. Full collision-resistance requires the intractability of finding collisions, even with full-adaptive access to a collision-finding oracle. Their construction combines simulation-sound extractable (SSE) NIZKs with perfectly correct IND-CPA secure public-key encryption (PKE) schemes. We show that, instead of perfectly correct PKE, non-interactive commitment schemes are sufficient. For the first time, this gives rise to efficient instantiations from plausible post-quantum assumptions and thus candidates of chameleon-hashes with strong collision-resistance guarantees and long-term security guarantees. On the more theoretical side, our results relax the requirement to not being dependent on public-key encryption.

ePrint: https://eprint.iacr.org/2020/1084

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