layout: default title: x/bridge

x/bridge

Abstract

The main goal of this module is to give the user ability to transfer the RMO native token from the Rarimo chain to another one (EVM, Near, Solana, etc.) and the opposite: transfer the RMO token from the external chain to the Rarimo chain. To achieve this we have added some custom logic to the cosmos-sdk/x/bank module to be able to mint and burn tokens on the selected account.

Concepts

Deposit flow

The user calls the DepositNative RPC method and provides all required arguments for transfer into the parameters. Under the hood, the module handler will create the TransferOperation in the rarimocore module after the successful burn of the specified amount of tokens from the user’s account balance. The transfer operation will be approved from the start because the module doesn’t need to check whether the tokens were deposited cause module burns it by itself.

Withdraw flow

After the call of the related RPC method, the module handler must check if TransferOperation was signed in the rarimocore module. After all, if checks were successful, module stores used origin in the module store and mints required amount of tokens to the recipient account balance.

x/bank updates

To provide the implementation of the bridging feature in our module, the logic of cosmos-sdk/x/bank needs to be extended. The x/bridge module requires the ability to mint and burn system tokens on the selected user account for implementing deposit and withdraw logic.

So we need to add the custom MintTokens bank keeper’s method which accepts arguments that determine who is the target of minting, and the amount of tokens to mint. And also BurnTokens should be implemented.

State

Params

Definition:

message Params {
   option (gogoproto.goproto_stringer) = false;
   string withdrawDenom = 1;
}

Example:

{
   "params": {
      "withdrawDenom": "stake"
   }
}

Hash

Hash - stores the hash of withdrawal operation to prevent double-spending.

Definition:

message Hash {
   // hex-encoded
   string index = 1;
}

Transactions

DepositNative

DepositNative - burns user's tokens and creates transfer operation in rarimocore module (will be already approved).

message MsgDepositNative {
   string creator = 1;
   // Random 32 bytes slice encoded to the hex string
   string seed = 2;
   // Information about deposit
   string receiver = 3;
   cosmos.base.v1beta1.Coin amount = 4;
   string bundleData = 5;// hex-encoded
   string bundleSalt = 6;// hex-encoded
   // Information about target chain
   rarimo.rarimocore.tokenmanager.OnChainItemIndex to = 7;
}

WithdrawNative

WithdrawNative - checks that operation in rarimocore is signed and valid and mints tokens to the receiver account. Operation hash (origin) will be stored in modules hash list.

message MsgWithdrawNative {
   string creator = 1;
   // Evidence information
   string origin = 2;
}