loran

Loran

Loran is a Go implementation of the Gravity Bridge Orchestrator originally implemented by Injective Labs. Loran itself is a fork of the original Gravity Bridge Orchestrator implemented by Althea.

Table of Contents

• Dependencies
• Installation
• How to run
• How it works

Dependencies

• Go 1.17+

Installation

To install the loran binary:

$ make install

How to run

Setup

First we must register the validator's Ethereum key. This key will be used to sign claims going from Ethereum to Hilo and to sign any transactions sent to Ethereum (batches or validator set updates).

$ hilod tx gravity set-orchestrator-address \
  {validatorAddress} \
  {validatorAddress} \
  {ethAddress} \
  --eth-priv-key="..." \
  --chain-id="..." \
  --fees="..." \
  --keyring-backend=... \
  --keyring-dir=... \
  --from=...

Run the orchestrator

$ loran orchestrator {gravityAddress} \
  --eth-pk=$ETH_PK \
  --eth-rpc=$ETH_RPC \
  --relay-batches=true \
  --relay-valsets=true \
  --cosmos-chain-id=... \
  --cosmos-grpc="tcp://..." \
  --tendermint-rpc="http://..." \
  --cosmos-keyring=... \
  --cosmos-keyring-dir=... \
  --cosmos-from=...

Send a transfer from Hilo to Ethereum

This is done using the command hilod tx gravity send-to-eth, use the --help flag for more information.

If the coin doesn't have a corresponding ERC20 equivalent on the Ethereum network, the transaction will fail. This is only required for Cosmos originated coins and anyone can call the deployERC20 function on the Gravity Bridge contract to fix this (Loran has a helper command for this, see loran bridge deploy-erc20 --help for more details).

This process takes longer than transfers the other way around because they get relayed in batches rather than individually. It primarily depends on the amount of transfers of the same token and the fees the senders are paying.

Important notice: if an "unlisted" (with no monetary value) ERC20 token gets sent into Hilo it won't be possible to transfer it back to Ethereum, unless a validator is configured to batch and relay transactions of this token.

Send a transfer from Ethereum to Hilo

Any ERC20 token can be sent to Hilo and it's done using the command loran bridge send-to-cosmos, use the --help flag for more information. It can also be done by calling the sendToCosmos method on the Gravity Bridge contract.

The ERC20 tokens will be locked in the Gravity Bridge contract and new coins will be minted on Hilo with the denomination gravity{token_address}. This process takes around 3 minutes or 12 Ethereum blocks.

How it works

Loran allows transfers of assets back and forth between Ethereum and Hilo. It supports both assets originating on Hilo and assets originating on Ethereum (any ERC20 token).

It works by scanning the events of the contract deployed on Ethereum (Gravity) and relaying them as messages to the Hilo chain; and relaying transaction batches and validator sets from Hilo to Ethereum.

Events and messages observed/relayed

Ethereum

Deposits (SendToCosmosEvent): emitted when sending tokens from Ethereum to Hilo using the sendToCosmos function on Gravity.

Withdraw (TransactionBatchExecutedEvent): emitted when a batch of transactions is sent from Hilo to Ethereum using the submitBatch function on the Gravity Bridge contract by a validator. This serves as a confirmation to Hilo that the batch was sent successfully.

Valset update (ValsetUpdatedEvent): emitted on init of the Gravity Bridge contract and on every execution of the updateValset function.

Deployed ERC 20 (ERC20DeployedEvent): emitted when executing the function deployERC20. This event signals Hilo that there's a new ERC20 deployed from Gravity, so Hilo can map the token contract address to the corresponding native coin. This enables transfers from Hilo to Ethereum.

Hilo

Validator sets: Hilo informs the Gravity Bridge contract who are the current validators and their power. This results in an execution of the updateValset function.

Request batch: Loran will check for new transactions in the Outgoing TX Pool and if the transactions' fees are greater than the set minimum batch fee, it will send a message to Hilo requesting a new batch.

Batches: Loran queries Hilo for any batches ready to be relayed and relays them over to Ethereum using the submitBatch function on the Gravity Bridge contract.