mirror of
https://github.com/0glabs/0g-chain.git
synced 2024-11-14 03:55:19 +00:00
f4b8bf8f07
* first pass at convert cosmos coin -> evm msg * test ConvertCosmosCoinFromERC20 method * test message server for MsgConvertCosmosCoinFromERC20 * update spec to include MsgConvertCosmosCoinFromERC20 * update changelog * add CLI command for convert-cosmos-coin-from-erc20 * add test of removed/re-enable denom for convert
72 lines
4.9 KiB
Markdown
72 lines
4.9 KiB
Markdown
<!--
|
|
order: 1
|
|
-->
|
|
|
|
# Concepts
|
|
|
|
## EVM Gas Denom
|
|
|
|
In order to use the EVM and be compatible with existing clients, the gas denom used by the EVM must be in 18 decimals. Since `ukava` has 6 decimals of precision, it cannot be used as the EVM gas denom directly.
|
|
|
|
To use the Kava token on the EVM, the evmutil module provides an `EvmBankKeeper` that is responsible for the conversion of `ukava` and `akava`. A user's excess `akava` balance is stored in the `x/evmutil` store, while its `ukava` balance remains in the cosmos-sdk `x/bank` module.
|
|
|
|
## `EvmBankKeeper` Overview
|
|
|
|
The `EvmBankKeeper` provides access to an account's total `akava` balance and the ability to transfer, mint, and burn `akava`. If anything other than the `akava` denom is requested, the `EvmBankKeeper` will panic.
|
|
|
|
This keeper implements the `x/evm` module's `BankKeeper` interface to enable the usage of `akava` denom on the EVM.
|
|
|
|
### `x/evm` Parameter Requirements
|
|
|
|
Since the EVM denom `akava` is required to use the `EvmBankKeeper`, it is necessary to set the `EVMDenom` param of the `x/evm` module to `akava`.
|
|
|
|
### Balance Calculation of `akava`
|
|
|
|
The `akava` balance of an account is derived from an account's **spendable** `ukava` balance times 10^12 (to derive its `akava` equivalent), plus the account's excess `akava` balance that can be accessed via the module `Keeper`.
|
|
|
|
### `akava` <> `ukava` Conversion
|
|
|
|
When an account does not have sufficient `akava` to cover a transfer or burn, the `EvmBankKeeper` will try to swap 1 `ukava` to its equivalent `akava` amount. It does this by transferring 1 `ukava` from the sender to the `x/evmutil` module account, then adding the equivalent `akava` amount to the sender's balance in the module state.
|
|
|
|
In reverse, if an account has enough `akava` balance for one or more `ukava`, the excess `akava` balance will be converted to `ukava`. This is done by removing the excess `akava` balance in the module store, then transferring the equivalent `ukava` coins from the `x/evmutil` module account to the target account.
|
|
|
|
The swap logic ensures that all `akava` is backed by the equivalent `ukava` balance stored in the module account.
|
|
|
|
## ERC20 token <> sdk.Coin Conversion
|
|
|
|
`x/evmutil` facilitates moving assets between Kava's EVM and Cosmos co-chains. This must be handled differently depending on which co-chain to which the asset it native. The messages controlling these flows involve two accounts:
|
|
1. The _initiator_ who sends coins from their co-chain
|
|
2. The _receiver_ who receives coins on the other co-chain
|
|
|
|
When converting assets from the EVM to the Cosmos co-chain, the initiator is an 0x EVM address and the receiver is a `kava1` Bech32 address.
|
|
|
|
When converting assets from the Cosmos co-chain to the EVM, the initiator is a `kava1` Bech32 address and the receiver is an 0x EVM address.
|
|
|
|
### Cosmos-Native Assets
|
|
|
|
`sdk.Coin`s native to the Cosmos co-chain can be converted to an ERC-20 representing the coin in the EVM. This works by transferring the coin from the initiator to `x/evmutil`'s module account and then minting an ERC-20 token to the receiver. Converting back, the initiator's ERC-20 representation of the coin is burned and the original Cosmos-native asset is transferred to the receiver.
|
|
|
|
Cosmos-native asset converstion is done through the use of the `MsgConvertCosmosCoinToERC20` & `MsgConvertCosmosCoinFromERC20` messages (see **[Messages](03_messages.md)**).
|
|
|
|
Only Cosmos co-chain denominations that are in the `AllowedCosmosDenoms` param (see **[Params](05_params.md)**) can be converted via these messages.
|
|
|
|
`AllowedCosmosDenoms` can be altered through governance.
|
|
|
|
The ERC20 contracts are deployed and managed by x/evmutil. The contract is deployed on first convert of the coin. Once deployed, the addresses of the contracts can be queried via the `DeployedCosmosCoinContracts` query (`deployed_cosmos_coin_contracts` endpoint).
|
|
|
|
If a denom is removed from the `AllowedCosmosDenoms` param, existing ERC20 tokens can be converted back to the underlying sdk.Coin via `MsgConvertCosmosCoinFromERC20`, but no conversions from sdk.Coin -> ERC via `MsgConvertCosmosCoinToERC20` are allowed.
|
|
|
|
### EVM-Native Assets
|
|
|
|
ERC-20 tokens native to the EVM can be converted into an `sdk.Coin` in the Cosmos ecosystem. This works by transferring the tokens to `x/evmutil`'s module account and then minting an `sdk.Coin` to the receiver. Converting back is the inverse: the `sdk.Coin` of the initiator is burned and the original ERC-20 tokens that were locked into the module account are transferred back to the receiver.
|
|
|
|
EVM-native asset conversion is done through the use of the `MsgConvertERC20ToCoin` & `MsgConvertCoinToERC20` messages (see **[Messages](03_messages.md)**).
|
|
|
|
Only ERC20 contract address that are in the `EnabledConversionPairs` param (see **[Params](05_params.md)**) can be converted via these messages.
|
|
|
|
`EnabledConversionPairs` can be altered through governance.
|
|
|
|
## Module Keeper
|
|
|
|
The module Keeper provides access to an account's excess `akava` balance and the ability to update the balance.
|