Deploy the Semaphore protocol on zkSync

[vplasencia]

Which compiler are you using?

• zksolc
• zkvyper

Which version of Solidity or Vyper?

0.8.4 / 0.8.23

zksolc/zkvyper version?

v1.3.23

Explain the issue

Hello 👋

I'm trying to deploy the Semaphore protocol on zkSync. I'm trying with Semaphore v3 which is the latest stable version and also Semaphore v4 which is the new version.

I have some questions:

1. How can I deploy bytecode?

To deploy Semaphore v3, it is necessary to get the Poseidon code from a JavaScript library: https://github.com/semaphore-protocol/semaphore/blob/main/packages/hardhat/src/tasks/deploy-semaphore.ts#L59-L73

I'm trying to deploy Poseidon and I get the following error: Error: The bytecode length in bytes must be divisible by 32!

Here is the code of the script: https://github.com/vplasencia/semaphore-zksync/blob/main/semaphorev3/deploy/poseidon/deploy-poseidon.ts

More info:

This is the Hardhat task to deploy Semaphore v3: https://github.com/semaphore-protocol/semaphore/blob/main/packages/hardhat/src/tasks/deploy-semaphore.ts

2. How can I link libraries?

After deploying the Poseidon bytecode, it is necessary to link the library, how can I recreate this code: https://github.com/semaphore-protocol/semaphore/blob/main/packages/hardhat/src/tasks/deploy-semaphore.ts#L76-L80

If the code of the library is already there in the .sol file, I can deploy the library using yarn hardhat deploy-zksync:libraries --private-key <PRIVATE_KEY> and everything should be fine when I want to compile. But what would be the flow when not all the code is in the .sol file?

3. When I try to deploy this Poseidon contract, it does not finish the deployment. Any idea why this is happening?

https://github.com/vimwitch/poseidon-solidity/blob/main/contracts/PoseidonT3.sol

Link to your repo?

https://github.com/vplasencia/semaphore-zksync

[uF4No]

Hi @vplasencia

How can I deploy bytecode?

zkSync is not EVM bytecode compatible, but source-code compatible. This means that you can have the same source code that you'd use in other EVM protocols, but zkSync has its own compilers (zksolc and zkvyper), that generate a different bytecode compatible with zkSync's ZKEVM. You'd need to get the source code of the contract, compile it with zksolc to generate the bytecode (which is done automatically if the hardhat-zksync-solc plugin is installed and added in the hardhat.config.ts file), and then deploy it.

How can I link libraries?

Not sure if I understand this correctly. You could deploy the library first and then reference it by its address in a separate contract.

When I try to deploy this Poseidon contract, it does not finish the deployment. Any idea why this is happening?

Are you getting any errors?

[vplasencia]

Hey @uF4No! Thank you so much for the answers.

1. Makes sense.

2. It was related to deploying the bytecode and then linking the library. For libraries in general I saw that I can deploy them first and in the hardhat.config.ts file, in the settings property inside the zksolc property it will add the library addresses.

3. It's like it's frozen. I tried again, it takes about 1 or 2 hours compiling, and then it throws the following error:

vivian@mbp-de-vivian my-zksync-project % npm run compile

> compile
> hardhat compile

Compiling contracts for zkSync Era with zksolc v1.4.0 and solc v0.8.17
Compiling 1 Solidity file
An unexpected error occurred:

Error: Command failed: /Users/vivian/Library/Caches/hardhat-nodejs/compilers-v2/zksolc/zksolc-v1.4.0 --standard-json   --solc /Users/vivian/Library/Caches/hardhat-nodejs/compilers-v2/macosx-amd64/solc-macosx-amd64-v0.8.17+commit.8df45f5f --detect-missing-libraries
/Users/vivian/Library/Caches/hardhat-nodejs/compilers-v2/macosx-amd64/solc-macosx-amd64-v0.8.17+commit.8df45f5f error: 

    at ChildProcess.exithandler (node:child_process:421:12)
    at ChildProcess.emit (node:events:514:28)
    at ChildProcess.emit (node:domain:489:12)
    at maybeClose (node:internal/child_process:1105:16)
    at Socket.<anonymous> (node:internal/child_process:457:11)
    at Socket.emit (node:events:514:28)
    at Socket.emit (node:domain:489:12)
    at Pipe.<anonymous> (node:net:337:12) {
  code: 1,
  killed: false,
  signal: null,
  cmd: '/Users/vivian/Library/Caches/hardhat-nodejs/compilers-v2/zksolc/zksolc-v1.4.0 --standard-json   --solc /Users/vivian/Library/Caches/hardhat-nodejs/compilers-v2/macosx-amd64/solc-macosx-amd64-v0.8.17+commit.8df45f5f --detect-missing-libraries'
}

[uF4No]

@vplasencia let us know if you managed to compile the contract with forceEvmla: true

[vplasencia]

Hey @uF4No!

Thank you for reporting the issue. I compiled the PoseidonT3.sol contract with forceEvmla: true in the zksolc settings and it works fine.

One question, when I compile this contract Feedback.sol, I think that it should generate the artifacts for all the contracts it's using so that when I want to deploy that contract, all the artifacts are there, but it does not generate all the artifacts. Should I add another config for that?

I think if I copy/paste all the contracts that the Feedback.solcontract uses, everything should work fine.

[uF4No]

Glad you were able to compile PoseidonT3.sol with forceEvmla: true 🎉

Regarding the Feedback.sol contract, I don't think you need any other config. I don't see that Feedback.sol imports any other contracts, just the ISemaphore interface so it it would not generate any other artifacts. Try to deploy it locally or to the zkSync Sepolia testnet to confirm it works as expected.

[vplasencia]

Hey! Regarding the artifacts, I get what you mean, but when I compile that contract in the Hardhat environment without zksolc, it generates all the artifacts that are needed to deploy. If I compile this contract with zksolc, it only generates the ISemaphore.sol artifacts and we need more artifacts to deploy that contract.

If I copy/paste manually all the contracts that Semaphore is using and compile them all together, it works. I was able to deploy all of them successfully using forceEvmla: true. However, developers would need to copy/paste all the contracts that Semaphore is using to make a contract work.

I was able to interact with the contract on zkSync Era Sepolia Testnet, but the transactions to verify Semaphore proofs (the zk part in contracts) were reverting with this error: shortMessage: 'execution reverted (unknown custom error)'. I will try other ideas to check if the error is related to something in the code or if the Verifier is not working properly on zkSync and will let you know.

Thank you for all the help.

[uF4No]

hey @vplasencia sorry, I'm not familiar with Semaphore so I'm don't really understand what other artifacts are required for the Feedback.sol contract to work as it does not import any contracts, just the ISemaphore.sol interface. Can you put all the contracts needed inside the same project and compile them with zksolc? that should generate all the artifacts you need.

Regarding the workaround you've done and the failed transactions, you can debug them by replaying them locally using era-test-node.

[duongnd-183902]

Hi @vplasencia
Have you deployed Poseidon hash yet?

[duongnd-183902]

I would like to emphasize that I am able to deploy the PoseidonT3 contract by configuring forceEvmla: true. However, I've come across a cautionary note indicating that enabling the forceEvmla field may lead to the following adverse effects:

Lack of support for recursion.
Lack of support for internal function pointers.
Potential impact on contract size and performance.
For Solidity versions older than 0.8, only this compilation mode is available, and it is used by default.
Are there any other documents that provide further clarification on this issue? Additionally, should I consider using this configuration forceEvmla: true for other contracts?

[bxpana]

@duongnd-183902 if you haven't already, let's go ahead and open a separate discussion post for this.