Pause and Unpause the Bridge
# Why do it?
OptimismPortal is a bridge contract that makes it possible to send messages between your L1 and your L2 OP Stack chain.
OptimismPortal is pausable as a backup safety mechanism that allows a specific
GUARDIAN address to temporarily halt deposits and withdrawals to mitigate security issues if necessary.
An OP Stack chain does not have to specify a usable
GUARDIAN address if it does not want to make the
OptimismPortal contract pausable, it can specify an address such as zero.
# Who can do it?
OptimismPortal (opens new window) has an immutable
That address can call
pause (opens new window) and
unpause (opens new window).
# Changing the guardian
The guardian created by the setup script is the admin account. This is sufficient for testing, but for a production system you would want the guardian to be a multisig with trusted security council.
GUARDIAN variable is immutable, but the
OptimismPortal contract sits behind a proxy, so the
GUARDIAN can be modified by changing the
OptimismPortal proxy to point to a new implementation contract.
You do this using the L1
ProxyAdmin (opens new window) contract.