Cryptology ePrint Archive: Report 2013/662

Fine-Tuning Groth-Sahai Proofs

Alex Escala and Jens Groth

Abstract: Groth-Sahai proofs are efficient non-interactive zero-knowledge proofs that have found widespread use in pairing-based cryptography. We propose efficiency improvements of Groth-Sahai proofs in the SXDH setting, which is the one that yields the most efficient non-interactive zero-knowledge proofs.

- We replace some of the commitments with ElGamal encryptions, which reduces the prover's computation and for some types of equations reduces the proof size.

- Groth-Sahai proofs are zero-knowledge when no public elements are paired to each other. We observe that they are also zero-knowledge when base elements for the groups are paired to public constants.

- The prover's computation can be reduced by letting her pick her own common reference string. By giving a proof she has picked a valid common reference string this does not compromise soundness.

- We define a type-based commit-and-prove scheme, which allows commitments to be reused in many different proofs.

Category / Keywords: cryptographic protocols / Non-interactive zero-knowledge proofs, commit-and-prove schemes, Groth-Sahai proofs, type-based commitments

Date: received 15 Oct 2013

Contact author: Alexandre Escala at uab cat

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Version: 20131024:075552 (All versions of this report)

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