Bridge Throttling

Zircuit goes live with bridge throttling on the canonical bridge in order to maximize user security. Bridge throttling means we intentionally limit the rate at which assets move across different networks. Controlling this rate is a critical security measure for bridges, as large withdrawals can be a result of potential exploits or hacks. This limitation will eventually be removed to allow unlimited bridging.

Bridge Throttling of ETH

We have enabled bridge throttling for ETH deposits and withdrawals on the canonical L1 and L2 bridge. It does not apply for any other third party bridges.

Throttling Mechanism

The throttles for each asset can be set to unlimited, adapted, or removed, when appropriate. That is, eventually the network will not have any limitations.

Throttling is implemented in a streaming fashion. It limits the throughput of an asset over time. The mechanism is best explained by the following scenario.

Consider a scenario with a limit of 100 ETH per hour for withdrawals. Here’s how it works:

1. Initially, you can withdraw up to 100 ETH at once. After this withdrawal, no more funds can be withdrawn immediately.

2. Every 10 minutes, 1/6th of the limit (approximately 16.67 ETH) becomes available.

3. After 30 minutes, 50 ETH is available. If you withdraw 25 ETH when 50 ETH is available, 25 ETH will be left.

4. The limit gradually refills until the full 100 ETH is restored after an hour.

This system controls and spreads out withdrawals over time. The limit of deposits and withdrawals is tracked separately.

In addition to limiting the throughput of an asset over time, there also exists a total cap for value locked in the L1 contracts, which specifies the maximum amount of an asset that can be locked into Zircuit using the canonical bridge.

Per-Account Throttling

We have enabled per-account throttling on deposits as well to encourage a secure bridge during the test phase. Per-account throttling ensures that each address can only deposit a limited amount of assets within a specified time period.

Throttling Overview

During the first phase of mainnet, the following assets will be throttled with the respective limits.

Asset	Throttle Limit per Address	Maximum Cap
ETH	50 ETH	3000 ETH