Bridging

Bridging in protokit is supported out of the box and we offer an intuitive UI to extend your appchain with bridging functionality very easily.

Bridging builds up from Settlement, so make sure you read that first.

Bridging basics

Bridging in protokit is fully trustless, that means that the sequencer cannot interfere or use his position to do something malicious.

Protokit supports both directions of travel, L1 -> L2 (often referred to as deposits) and L2 -> L1 (withdrawals). Most projects will use this mechanism for token bridging, meaning trustless deposits and withdrawals of tokens from the L1 to the appchain. Therefore, this docs page will focus on token bridging.

The mechanism however is general enough to support arbitrary messages, which could be used for a bunch of things. Interop between appchains, self-upgrading appchains, force-inclusion in case of sequencer censorship and automatic staking delegation & rewards distribution being among the most exciting.

Token bridging

Token bridging has two main parts, depositing and withdrawing.

The default implementation allow bridging Mina as well as custom tokens following the fungible token standard. They follow different mechanisms and can be configured separately if needed.

Finality considerations

L2s like protokit generally have to consider safety with regards to a concept called finality of their L1. Finality is the time it takes for a blockchain to consider some block “irreversable”. For some chains that is instant, for others, this can take a while.

For mina, most exchanges consider block final after 20 subsequent blocks have added to the chain. This translates to approximately 30-60 minutes in most cases (after the mesa hardfork).

Now, deposits have to respect that finality time before they can safely be processed by the L2, so this is the reason why it may take a while until new deposits arrive on your appchain. This is of course only the case for remote networks like devnet and mainnet.

For withdrawals, this is less the case since the sequencer can safely handle all eventualities that can occur.

Deploying L1 contracts

Deploying currently works the exact same way as described in Settlement

Testing bridging

See an example of how to test bridging in Settlement.test.ts