EVM

How to generate the proof with EVM?

const generate = async (schemaId: string, appid: string) => {
    try {
      // The appid of the project created in dev center
      const appid = "8fb9d43c-2f24-424e-a98d-7ba34a5532f5"
  
      // Create the connector instance
      const connector = new TransgateConnect(appid)
  
      // Check if the TransGate extension is installed
      // If it returns false, please prompt to install it from chrome web store
      const isAvailable = await connector.isTransgateAvailable()
  
      if (isAvailable) {
        // The schema id of the project
        const schemaId = "516a720e-29a4-4307-ae7b-5aec286e446e"
  
        // Launch the process of verification
        // This method can be invoked in a loop when dealing with multiple schemas
        const res = await connector.launch(schemaId)
        
        // If you want to send the result to the blockchain, please add the wallet address as the second parameter.
        // const res = await connector.launch(schemaId, address)
  
        // verifiy the res onchain/offchain based on the requirement     
        
      } else {
        console.log('Please install TransGate')
      }
    } catch (error) {
      console.log('transgate error', error)
    }
  }

The result includes two signatures: the allocator signature and the validator signature. Developers should verify both signatures based on the other returned fields.

Verify Allocator Signature

Encode the allocator message struct

import Web3 from "web3"

const web3 = new Web3()

const { taskId } = res //return by Transgate

const taskIdHex = Web3.utils.stringToHex(taskId)
const schemaIdHex = Web3.utils.stringToHex(schemaId)

const encodeParams = web3.eth.abi.encodeParameters(
  ["bytes32", "bytes32", "address"],
  [taskIdHex, schemaIdHex, validatorAddress]
)
const paramsHash = Web3.utils.soliditySha3(encodeParams)

Recover the allocator address

const signedAllocatorAddress = web3.eth.accounts.recover(paramsHash, allocatorSignature)

Check if the signed allocator address is registered. The current allocator address is fixed.

return signedAllocatorAddress === "0x19a567b3b212a5b35bA0E3B600FbEd5c2eE9083d"

Verify Validator Signature

Encode the validator message

import Web3 from "web3"

const web3 = new Web3()

const { taskId, uHash, publicFieldsHash, recipient } = res //return by Transgate

const taskIdHex = Web3.utils.stringToHex(taskId)
const schemaIdHex = Web3.utils.stringToHex(schemaId)


const types = ["bytes32", "bytes32", "bytes32", "bytes32"]
const values = [taskIdHex, schemaIdHex, uHash, publicFieldsHash]

//If you add the wallet address as the second parameter when launch the Transgate
if (recipient) {
    types.push("address")
    values.push(recipient)
}

const encodeParams = web3.eth.abi.encodeParameters(types, values)

const paramsHash = Web3.utils.soliditySha3(encodeParams)

Recover the validator address

const signedValidatorAddress = web3.eth.accounts.recover(paramsHash, validatorSignature)

Verify if the signed validator address matches the address assigned by the allocator

return signedValidatorAddress === validatorAddress

Here, we've only given the reference code for off-chain verification. However, the result can also be verified on-chain.