Contract source code verification

Verifying contracts on EtherScan

ICO package has a semi-automated process to verify deployed contracts on EtherScan verification service.

Benefits of verification

• You can see the state of your contract variables real time on EtherScan block explorer
• You prove that there are deterministic and verifiable builds for your deployed smart contracts

Prerequisites

• You need to have Chrome and chromedriver installed for the browser automation
• You need to have Splinter Python package installed:

pip install Splinter

How automatic verification works

You need to specify the verification settings in your YAML deployment script for deploy-contracts command.

You need to make sure that you have your Solidity version and optimization parameters correctly.

Example how to get Solidity version:

solc --version

Here is an example YAML section:

# Use automated Chrome to verify all contracts on etherscan.io
verify_on_etherscan: yes
browser_driver: chrome

solc:

    # This is the Solidity version tag we verify on EtherScan.
    # For available versions see
    # https://kovan.etherscan.io/verifyContract2
    #
    # See values in Compiler drop down.
    # You can also get the local compiler version with:
    #
    #     solc --version
    #
    # Note that for EtherScan you need to add letter "v" at the front of the version
    #
    # Note: You need to have correct optmization settings for the compiler
    # in populus.json that matches what EtherScan is expecting.
    #
    version: v0.4.14+commit.c2215d46

    #
    # We supply these to EtherScan as the solc settings we used to compile the contract.
    # They must match values in populus.json compilication / backends section.
    # These are the defaults supplied with the default populus.json.
    #
    optimizations:
        optimizer: true
        runs: 500

When you run deploy-contracts and verify_on_etherscan is turned on, a Chrome browser will automatically open after a contract has been deployed. It goes to Verify page on EtherScan and automatically submits all verification information, including libraries.

In the case there is a problem with the verification, deploy-contracts will stop and ask you to continue. During this time, you can check what is the actual error from EtherScan on the opened Chrome browser.