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Easy mode

If you don't want users having to deal with the hassle of using Rollbridge 7 days later to finalize their withdrawals, Easy Mode is for you. For a small fee (to cover gas costs) when initiating your withdrawal we'll handle relaying your users withdrawal to Ethereum mainnet.

So we can understand more in depth the how and why of Easy mode withdrawals, we’ll quickly cover the standard withdrawal flow its complexity.

Withdrawals

Withdrawals are cross domain transactions initiated on the rollup (ie. Arbitrum One, Arbitrum Nitro or an Orbit L3), and finalized by a transaction executed on the base chain (ie. Ethereum Mainnet, Arbitrum One or Arbitrum Nitro).

Ether withdrawals are initiated by a withdrawETH call to the ArbSys precompile.

ERC20 token withdrawals are initiated via calls to outboundTransfer on the GatewayRouter.

Once assertions are posted to the base chain (usually within ~ 1 hour) and the assertion is confirmed (usually about ~ 1 week) the withdrawal can be finalized by posting a proof to the Outbox's executeTransaction function.

On Arbitrum Nitro powered rollups, withdrawals require two transactions (one on the rollup and one on the basechain) and a seven day waiting period.

After initiating the withdrawal, a 7 day challenge period needs to be observed. This 7 day period allows for other network participants to challenge the integrity of the corresponding output root. Once the challenge period has passed, the withdrawal can be finalized with a second finalizing transaction.

For more information, please refer to L2 to L1 messaging in the Arbitrum Nitro documentation.

Easy mode withdrawals

With that context on normal withdrawals, we can dive into how easy mode withdrawals work.

The Rollbridge indexing layer is constantly listening to new bridge events and scanning for the status of deposits and withdrawals. When a withdrawal is marked as Ready to finalize, we check to see if there is a relaying fee associated with this withdrawal.

The relaying fee, currently denominated in ETH, is added to your withdrawal when you toggle on easy mode withdrawals in the settings page of Rollbridge. The fee is set to the cost of one transaction, using 400,000 units of gas priced at 40 gwei. In the depths of the current bear market we recognise 40 gwei is potentially too high, so we’re looking to either implement a slightly smarter gas pricing strategy, taking into account historical peaks and valleys in gas pricing, or let users specify the maximum gas price they’d like to pay for these transactions. We just won’t relay them until gas prices dip below the specified amount.

If there is a relaying fee and it’s enough to cover the gas cost of finalizing, the indexing layer will send the necessary transaction on your behalf. This is a major improvement over the standard withdrawal flow for a few reasons,

  • Sending one transaction is better than two
  • You don’t need to set calendar reminders or alarms to finish your withdrawals