Why is the exported verification contract random?

[doubiliu]

I used the MPC procedure to generate the corresponding Phase1 and Phase2 files. Why do I export a solidity verification contract through these files is random?
example:
groth16.Setup(css.(*cs.R1CS), &pk, &vk)； vk.ExportSolidity(contract, solidity.WithHashToFieldFunction(sha256.New()))

Is there any way to avoid this randomness? This causes the contract I posted to fail to match the proof of my local calculation

[ivokub]

Do you run the setup every time you generate the contract? MPC setup is a non-deterministic step and uses randomness internally for ensuring soundness.

Or is the contract random even if you re-use existing setup?

[doubiliu]

Do you run the setup every time you generate the contract? MPC setup is a non-deterministic step and uses randomness internally for ensuring soundness.

Or is the contract random even if you re-use existing setup?

I coded based on the release version of 0.12.0.
I first generated the corresponding phae1 and phase2 files through MPC. After that, I calculated the proof and exported the contract by reading the files of the existing files. But I found that the contract exported using an existing file will be different every time. Through testing, I found that after execution of groth16.Setup(css.(*cs.R1CS), &pk, &vk), it will bring randomness to vk, resulting in different contracts generated. However, the code groth16.Setup(css.(*cs.R1CS), &pk, &vk) cannot be removed, otherwise the content of CommitmentsPok will be missing in vk.
I saw you merged the new PR and said that it was fixed the bug that lacked CommitmentsPok. I am trying to use that PR version

[ivokub]

Could you also try with the latest gnark? go get github.com/consensys/gnark@master. We recently just merged #1372 which significantly refactored the MPC key generation. But it is not included in any tagged release yet, so you should try out the rolling release. We try to keep the rolling release stable in general.

[ivokub]

Could you also try with the latest gnark? go get github.com/consensys/gnark@master. We recently just merged #1372 which significantly refactored the MPC key generation. But it is not included in any tagged release yet, so you should try out the rolling release. We try to keep the rolling release stable in general.

@doubiliu - could you confirm if master version fixed the issue? Would look into it otherwise.

[doubiliu]

Could you also try with the latest gnark? go get github.com/consensys/gnark@master. We recently just merged #1372 which significantly refactored the MPC key generation. But it is not included in any tagged release yet, so you should try out the rolling release. We try to keep the rolling release stable in general.

@doubiliu - could you confirm if master version fixed the issue? Would look into it otherwise.

Thanks, it has been resolved

[ivokub]

Thanks!