Commerceblock has launched a brand new atomic swap protocol to be used with statechains on their Mercury Layer protocol. The HSM server has launched performance to help atomically swapping two statechains, in addition to implementing an atomic change of a statechain for a Lightning cost. That is the primary instance of concretely outlined and constructed interactions between statechains and the Lightning Community. Synergy between each protocols has been postulated for the reason that idea of a statechain was initially proposed by Ruben Somsen, particularly as a solution to clear up the limitation of getting to switch a complete statechain UTXO directly.
Fundamental Statechain Swaps
With a purpose to help the brand new swap protocols, the HSM server wants so as to add some new fields to its database entries monitoring every statechain it’s facilitating. To facilitate the statechain to statechain swap, the server wants to trace:
- Batch_id: a price to affiliate statechains being swapped in a bunch.
- Batch-time: a time that begins a counter after which the statechains might be “reclaimed” if the swap fails.
- Locked: a price indicating whether or not or not the statechain is locked and restricted from common transfers.
This permits the HSM server to trace and implement all of the variables crucial to make sure a secure atomic swap. When initiating a swap, customers have to speak with one another instantly with the intention to set up a shared batch_id between them. From this level they commerce all the mandatory info required to facilitate a traditional statechain switch, and ship that info plus the batch_id and batch-time to the server. They primarily begin the common switch course of, but additionally connect the variables to attach the person statechains as taking part in a swap collectively and the way lengthy the timeout interval is for that.
The server at this level will apply a lock to each statechain utilizing the identical batch_id within the switch course of. Till the timeout expires, or all the statechains in its database utilizing the identical batch_id have been unlocked by the present house owners, the server won’t approve any transfers. A neat factor about the best way the HSM enforces the swap logic is that it doesn’t matter who contacts the server first. When the server will get a message utilizing a batch_id, it checks each statechain in its database and if there’s a pre-existing batch-time for that batch_id it units it as the identical. This ensures that irrespective of who registers the swap first all of them use the identical time worth for the timeout perform.
Every shopper concerned within the swap at this level checks for and downloads the messages that initiated the switch protocol, and upon verifying they’re appropriate sends a message to the server to unlock their statechain, eradicating the switch restrictions. Each time anybody makes an attempt to finalize a switch on the receiver aspect of any of the statechains concerned within the swap, the server checks to verify all the statechains with the identical batch_id are unlocked. If even a single one with the associated batch_id remains to be locked the server will finalize a switch for none of them. If a swap doesn’t succeed earlier than the timeout, the server will proceed proscribing the finalization of the swap switch, however will let the present house owners initialize a brand new switch to themselves to successfully cancel the swap.
Lightning Latch
The Lightning Latch performance, swapping a statechain for a Lightning cost, works very equally to the statechain to statechain swap. Listed below are the brand new fields the server should observe for the Lightning swap:
- Batch_id: a price to affiliate statechains being swapped in a bunch.
- Batch-time: a time that begins a counter after which the statechains might be “reclaimed” if the swap fails.
- Pre-image: the preimage of the Lightning cost, which is generated by the HSM server.
- Locked_1 and locked_2: there are two lock fields for the Lightning swap, one licensed by every person concerned.
Identical to with the statechain to statechain swap, the customers set up and share a random batch_id. The present statechain proprietor then messages the server with the batch_id and statechain concerned and requests it generates a hashlock preimage for a Lightning cost. This person then generates a Lightning bill utilizing this preimage, and the second person contacts the server to substantiate it generated the preimage. The present statechain proprietor then begins the statechain switch course of and uploads the switch message to the server.
After affirmation of that, the second person making an attempt to swap for the statechain initiates the Lightning cost. Right now the server is the one one with the preimage, so the statechain proprietor can not finalize the cost but. The present proprietor after verifying the pending Lighting cost sends the server an unlock message to take away the primary lock on the statechain. The receiver lastly verifies the switch message, and if legitimate messages the server to take away their lock as nicely.
Now with each locks eliminated, the HSM server will launch the preimage to the present statechain proprietor to finalize the Lightning cost, and can finalize the statechain switch to the receiver.
This scheme does require trusting the statechain operator to perform truthfully, however that’s essentially not a change to the pre-existing belief mannequin of utilizing a statechain typically. At no time does the operator have management over customers’ funds, nor do they study something in regards to the Lightning cost particulars.
What Is This Good For?
This scheme is a far cry from the initially posited interplay between statechains and Lightning channels, stacking one on high of the opposite, however whilst a easy place to begin this presents useful utility for present Lightning customers. Rebalancing channels is a crucial factor for a lot of nodes, if the capability is solely pushed to at least one aspect or the opposite the utility of that channel is restricted for routing funds. Many companies and customers have began experimenting with utilizing Liquid as a mechanism for this because of on-chain charges rising and making swaps into and out of the Lightning Community costlier.
Statechains provide an alternate mechanism to a federated sidechain to alleviate a few of the price bills related to channel stability administration. As an alternative of getting to swap out to the mainchain instantly, or use a sidechain, funds might be swapped to a statechain and held there till they’re wanted for swapping funds again right into a channel. Related financial savings in charges might be had whereas nonetheless sustaining the power to unilaterally declare your funds on the mainchain.
One other potential use case (TRIGGER WARNING) can be the opportunity of extra environment friendly marketplaces for buying and selling ordinals. Since ordinals are merely an index scheme monitoring paths backwards within the transaction historical past to particular satoshis, they’ll simply be lifted off-chain onto a statechain. That dynamic together with Lightning Latch may permit cheaper and quicker off-chain purchases of ordinals. Somebody may construct a market the place they are often bought immediately off-chain over the Lightning Community.
It’s even attainable sooner or later if Lightning shoppers may turn into conscious by some means of which statechain operators particular Lightning nodes belief that Latch may very well be used to assist route funds by passing statechains round between completely different nodes as an alternative of utilizing standard Lightning channels.
On the entrance of pure statechain to statechain transfers, this affords the potential for a message passing layer to recreate coinjoin like system mixing cash off-chain, just like the unique mixing performance in Commerceblock’s first statechain implementation.
Whereas it’s a quite simple place to begin, Lightning Latch and the statechain swap performance crack open the primary door of statechains integrating into the prevailing Lightning Community – and different comparable layers to come back sooner or later – in a manner that lets all of them combine seamlessly and performance as a singular community by way of cost routing and liquidity administration. Even whereas we debate the necessity for and usefulness of covenants, there’s nonetheless various room to proceed constructing with what we have already got.
You’ll be able to take heed to the Commerceblock staff clarify the logic past the protocol right here:
Chatting with the Dr @TTrevethan about why to construct lightning latch on @mercurylayer #bitcoin #layer2 pic.twitter.com/CKVG9aHTQ6
— Nicholas Gregory (@gregory_nico) March 15, 2024
And for a extra technical rationalization, right here:
Going via the technicals of how lightning latch will work with @TTrevethan on @mercurylayer #bitcoin #layer2 pic.twitter.com/aQIcjh2ukq
— Nicholas Gregory (@gregory_nico) March 16, 2024
