How to verify ink! smart-contracts

ink! smart contract is using Rust so its verification is done by ensuring a certain Rust code + metadata == the code_hash of the wasm binariy deployed on chain.

The wasm binariy is deployed on-chain and is identified by its code_hash (the blake2b hash of the wasm binary). You can query the code_hash of a contract address by querying chain state contractsInfoOf(contractAdress)

Now we need to ensure that the code_hash of this account address is equal to a certain Rust code (ink!) and metadata.

metadata structure

ink!4.0 will integrate this new metadata type: https://github.com/paritytech/cargo-contract/pull/680è

"source": {
  "hash": "0xccb6f8277de7a9d2c8161c2f9d7f86446819222b7f15807ea33958d7b5c170a7",
  "language": "ink! 4.0.0",
  "compiler": "rustc 1.64.0-nightly",
  "build_info": {
    "build_mode": "Debug",
    "cargo_contract_version": "1.4.0",
    "rustc_version": "nightly-2022-07-25",
    "wasm_opt_settings": {
      "optimization_passes": "Z",
      "version": 109
    }
  }
}

This metadata file provides all information to ensure a certain Rust code as input will all time compile the same wasm binaries with the same code hash. As contracts are written in Rust rust compiler version is important "compiler": "rustc 1.64.0-nightly"

To compile smart contracts cargo-contract is used: https://github.com/paritytech/cargo-contract

cargo-contracts first builds the ink! contract as a Rust binary then compile it to wasm then optimize the wasm file (so it has the smallest size possible)

So different versions of cargo-contract can produce different wasm binaries (that’s why the version is mandatory).

Also, the wasm optimizer version is important (but it should be integrated to the next version of cargo-contract).

You can also build contracts using "build_mode": "Debug" or "build_mode": "Release"

OUTDATED (but explain what is done under the hood)

Info needed by the user (who wants to verify a contract)

1. user upload the Rust code (ink! smart contracts requires several files to be uploaded). or git hub link of the code.
2. user upload the metadata
3. user Specify the address of the contract & the network (Shibuya, Shiden, Astar,..)