Comparison with EVM

Godwoken targets 100% EVM compatibility, the plan is to back every smart contract that the latest Ethereum hard fork version supports. But there are certain things that are incompatible with EVM in the current version.

pETH

Godwoken introduced a new concept called pETH.

In Ethereum, the gas for each smart contract is derived by calculation, then calculating the transaction fee by multiplying the gas with a specified gas price. In Godwoken, however, pETH comes in as the unit for calculating transaction fees. In other words, the price of gas in Ethereum is ETH/gas ( denominated in wei, i. e. 1e-18 ether), while that of Godwoken is measured in pETH/gas. When executing a transaction, Godwoken deducts the transaction fee by using tokens with the layer 2 sUDT type denoted by pETH.

Account Abstraction

Godwoken only provides contract accounts, and the user accounts of Godwoken serve as EoAs.

Different Address Types

• All eth_address(EoA/contract) format are short_godwoken_account_script_hash, which is the 20 bytes prefix of Godwoken account script hash.
• Creating a contract account returns short_godwoken_account_script_hash

When passing some parameters of address-type to call smart-contract, the address conversion has to be done beforehand, and vice versa to return the address value. Polyjuice-Provider is designed to handle these conversion tasks. It conducts address type conversions based on the ABI of the contract.

Unfortunately, we are not yet able to display assets directly on metamask or other Ethereum wallets. We currently use a single web app to display users' assets. This wallet display issue will be resolved in future updates.

Transaction Structure

A Polyjuice transaction is essentially a Godwoken transaction.

When sending an Ethereum transaction, the transaction gets converted to a Godwoken RawL2Transaction type, which is automatically processed by Polyjuice-Provider.

Behavioral Differences of Some Opcodes

EVM Opcode	Solidity Usage	Behavior in Polyjuice	Behavior in EVM
COINBASE	block.coinbase	address of the block_producer	address of the current block's miner
CHAINID	chain_id()	creator_account_id	Istanbul hardfork, EIP-1344: current network's chain id
GASLIMIT	block.gaslimit	12,500,000	current block's gas limit
DIFFICULTY	block.difficulty	2,500,000,000,000,000	current block's difficulty

Addition Features

• pre-compiled contract
  • Add recover_account for recover any supported signature
  • Add balance_of_any_sudt for query the balance of any sudt_id account
  • Add transfer_to_any_sudt for transfer value by sudt_id (Must collaborate with SudtErc20Proxy.sol contract)
  • Add eth_to_godwoken_addr for convert ETH address to polyjuice contract address (godwoken short address)

recover_account Spec

  Recover an EoA account script hash by signature

  input: (the input data is from abi.encode(mesage, signature, code_hash))
  ======
    input[ 0..32]  => message
    input[32..64]  => offset of signature part
    input[64..96]  => code_hash (EoA lock hash)
    input[96..128] => length of signature data
    input[128..]   => signature data

  output (32 bytes):
  =======
    output[0..32] => account script hash

See: Example

balance_of_any_sudt Spec

  Query the balance of `account_id` of `sudt_id` token.

   input:
   ======
     input[ 0..32] => sudt_id (big endian)
     input[32..64] => address (short_address)

   output:
   =======
     output[0..32] => amount

See: Example

transfer_to_any_sudt Spec

  Transfer `sudt_id` token from `from_id` to `to_id` with `amount` balance.

  NOTE: This pre-compiled contract need caller to check permission of `from_id`,
  currently only `solidity/erc20/SudtERC20Proxy.sol` is allowed to call this contract.

   input:
   ======
     input[ 0..32 ] => sudt_id (big endian)
     input[32..64 ] => from_addr (short address)
     input[64..96 ] => to_addr (short address)
     input[96..128] => amount (big endian)

   output: []

See: Example

eth_to_godwoken_addr Spec

 Calculate godwoken short address of an contract account by it's corresponding ETH address

 input:
 ======
   input[12..32] => ETH address

 output:
   output[12..32] => godwoken short address

See: Example

Others

• transaction context
  • chain_id is creator_account_id
  • block gas limit is 12500000, and is not block level limit, every transaction can reach the limit
  • block difficulty is always 2500000000000000
• The transfer value can not exceed uint128:MAX
• pre-compiled contract
  • bn256_pairing is not supported yet，due to too high cycle cost (WIP)
  • addition pre-compiled contracts