Why Intents are the Answer to Interoperability

Introduction

The arrival of rollups and L2s scaled Ethereum but made end user UX worse in every way except gas costs. Devs building on L2s have to ask themselves which silo they want to build in. Users have had to become experts in the interoperability tooling landscape simply to use dapps. This fragmentation will continue as more rollups and app-chains come online

The Across thesis is that an intents-based design paradigm is the right one to tackle these problems because it can deliver assets to users immediately and use slower, secure settlement, which is a lot cheaper to pay for.

Interoperability by Passing Messages

The first question of interop 101 is token bridging: How can we send assets from Chain A to Chain B quickly? The naive answer is to “send a message” between the chains. This approach has had years of R&D but it faces a problem: it is nearly impossible to send messages cheaply, quickly, and securely.

Finality risk puts the brakes on bridging with messages because the message needs time to be confirmed before it can be executed.

What if there was another way than this naive approach that could get assets nearly instantly?

Interoperability with Intents

Intents introduce a third party, a relayer (alternatively named filler, or solver) that does the job of delivering assets / executing user transactions quickly.

An intent is a type of order where a user specifies an outcome instead of an execution path. Relayers compete on cost and speed to fill user intents, which can include onchain actions as well as assets. Relayers deliver very quickly, without any messages.

From the user’s perspective, interoperability is solved. Now we need to think about how to repay the relayer.

Closing the Loop: Settlement

The intents architecture can fill user orders really quickly, but what happens to relayers? User funds are escrowed in the protocol, and are only released to the relayer once the protocol has verified that the user intent was “fulfilled.”

The innovation with this model is that it pushes the tricky “verification” part until after the user is already filled, so we can take our time to do this. Across does this optimistically using assumption that there is one honest disputer. Using slow settlement is less costly than running a verification node network or dedicated blockchain for fast verification.

This is the key innovation that intents unlock for interop: we can decouple the urgent part (filling user orders) from the complicated part (message verification). The trade-off is just that the relayer must loan funds for the duration, and it turns out that is a worthwhile tradeoff.

The Across architecture takes this cost-savings a step further by bundling 1000’s of settlements into a single message.

The Future of Interoperability is Intents

In summary:

• Message-passing is nearly impossible to do cheaply, quickly, and securely.
• Intents-based solutions get relayers to fill users instantly.
• We can repay the relayer slowly now.
• Slower verification allows for cheap and secure settlement, which we can do in bundles.

After two years in live competition, Across’ intents-based bridging solution consistently outperforms on the basis of these points. Intents allow us to solve the interoperability challenge by taking advantage of this “third party” that can help deliver incredible UX, and balancing the rest of the system is actually a lot cheaper to do, too.