Paper 2021/1530
Experimenting with Collaborative zk-SNARKs: Zero-Knowledge Proofs for Distributed Secrets
Alex Ozdemir and Dan Boneh
Abstract
A zk-SNARK is a powerful cryptographic primitive that provides a succinct and efficiently checkable argument that the prover has a witness to a public NP statement, without revealing the witness. However, in their native form, zk-SNARKs only apply to a secret witness held by a single party. In practice, a collection of parties often need to a prove a statement where the secret witness is distributed or shared among them. We implement and experiment with *collaborative zk-SNARKs*: proofs over the secrets of multiple, mutually distrusting parties. We construct these by lifting conventional zk-SNARKs into secure protocols among $N$ provers to jointly produce a single proof over the distributed witness. We optimize the proof generation algorithm in pairing-based zk-SNARKs so that algebraic techniques for multiparty computation (MPC) yield efficient proof generation protocols. For some zk-SNARKs, optimization is more challenging. This suggests MPC "friendliness" as an additional criterion for evaluating zk-SNARKs. We implement 3 collaborative proofs and evaluate the concrete cost of proof generation. We find that over a good network, security against a malicious minority of provers can be achieved with *approximately the same runtime* as a single prover. Security against $N-1$ malicious provers requires only a $2\times$ slowdown. This efficiency is unusual: most computations slow down by several orders of magnitude when securely distributed. It is also significant: most server-side applications that can tolerate the cost of a single-prover proof should also be able to tolerate the cost of a collaborative proof.
Note: Provide background on & discuss protocols in the same family as GSZ'20.
Metadata
- Available format(s)
- Category
- Cryptographic protocols
- Publication info
- Preprint. MINOR revision.
- Keywords
- zero knowledgemulti-party computationimplementation
- Contact author(s)
-
aozdemir @ cs stanford edu
dabo @ cs stanford edu - History
- 2022-07-16: last of 7 revisions
- 2021-11-22: received
- See all versions
- Short URL
- https://ia.cr/2021/1530
- License
-
CC BY