Beyond Token Bridges: How Connext and Hop are Evolving into AMBs

The term ‘bridges’ has become synonymous with protocols enabling tokens to move from one chain to another. This is fair, given that the most used ‘bridges’ are, in fact, token bridges (like Multichain, Across, and Stargate, to name a few).

However, there’s now a consensus that cross-chain token transfers are just scratching the surface of what’s possible with bridges. A new breed of bridges is coming out on top: arbitrary messaging bridges (AMBs).

AMBs expand the scope of cross-chain transfers from fungible tokens to more complex data like messages, contract calls, NFTs, etc. This functionality unlocks the ability to develop cross-chain dApps. For now, the most popular dApps built on top of AMBs are some of your favorite token bridges:

• Portal built on Wormhole

• Stargate built on LayerZero

• Satellite and Squid built on Axelar

• cBridge by Celer Network

As mentioned above, this is just scratching the surface of what can be built on top of AMBs. For example, Fuji is building a cross-chain money market experience on Connext (more on why Connext is an AMB will be explained below), and Pudgy Penguins went cross-chain via LayerZero.

Being able to transfer tokens across chains is helpful, but it only fulfills some of the requirements of users and dApps in a multi-chain ecosystem. The ability to pass messages between chains is paramount to build cross-chain dApps that enable more complex use cases with superior UX.

The power of AMBs and the need for cross-chain communication is evident. This brings us to today’s topic: how Connext and Hop are evolving into AMBs.

Background

Hop and Connext are two of the most widely used token bridges. Both teams started out as token bridges but with different mechanisms.

In their most recent or upcoming upgrades, both teams announced that they are adding the ability to send cross-chain messages into their stacks, and, this time, they’re also aligned on the best approach for message passing.

Arjun | xcall me maybe 🏴 @arjunbhuptani

Connext (post-Amarok) and @HopProtocol v2 have almost the exact same mechanism for message passing. I find this really encouraging! 😄 If two strong, experienced teams independently iterate to the same solution, chances are higher it's objectively the right solution.

The endgame is the same for both projects — enabling the development of cross-chain dApps on top of their messaging layer. However, the journey behind how they reached there and the plans for the future are different. Let’s take a look.

Hop v2 and the Hop Core Messenger

In June 2022, Chris Whinfrey (founder of Hop) kickstarted an important discussion on Hop’s mission and future plans. While one aspect of the discussion was related to using volume as a way to measure Hop’s success, we’ll focus on the discussion around Hop’s mission statement in this article:

Hop DAO’s mission is to drive the adoption of secure, trustless, and community-owned bridge infrastructure within Ethereum’s scaling ecosystem and to connect Ethereum to the broader multi-chain world.

Since the beginning, Hop’s values have been aligned on bringing more value to the Ethereum ecosystem. The team has repeatedly emphasized their focus on making the bridging experience between different Ethereum Layer-2s seamless, trustless, and inexpensive. And the next phase of Hop’s development will be no different.

While Hop’s token bridge offers users a quick and easy way to move tokens between different L2s, the next phase of the protocol’s development is believed to be crucial infra required for the next era of Ethereum’s development. This phase will be marked by the launch of Hop V2 per HIP-14, which includes the development of a V2 Core Messenger.

HopProtocol @HopProtocol

3/ Probably the most pivotal proposal in Hop’s existence has passed governance and will shape the year ahead for the DAO. Let’s look at it in detail 🔍 HIP-14 lays out the roadmap for the DAO and turns Hop from a simple asset bridge into a generalised interoperability protocol.

Hop’s Core Messenger is a trust-minimized messaging protocol that leverages native bridges of different L2s for generalized message passing. This will support an ecosystem of cross-chain dApps built on top of Hop V2, enabling cross-chain functionality including but not limited to, messaging, token transfers, NFT transfers, and omnichain tokens.

The Core Messenger uses a Hub (Ethereum) and spoke (L2s) model to send messages across L2s. Messages are aggregated into bundles which are then hashed and sent to the destination chain using native bridges of L2s and through Ethereum as the Hub. The bundle can then be unpacked and messages can be executed on the destination chain.

While Core Messenger’s best features are its ability to send messages across Ethereum's ecosystem in a trust-minimized manner, it will also benefit from economies of scale given its mechanism of bundling messages. As it sees more adoption, it will become cheaper for dApps to send messages since the number of messages that can be added to Bundles will increase. This will decrease the costs to transfer message Bundles and make Hop’s token bridge more capital efficient.

Connext Amarok

Connext’s vision, just like Hop’s, is aligned with adding more value to Ethereum. In their quest to scale Ethereum to a billion users, the Connext team launched two versions of its token bridge — xPollinate and NXTP.

However, like Hop, the team realized the importance and need for cross-chain messaging to build applications that abstract away the complexities of interacting with different chains.

With that in mind, Connext announced the Amarok upgrade in April 2022, partnering closely with Nomad to offer fully generalized communication between chains. However, on August 2, 2022, Nomad was exploited due to an implementation bug, and $190M in liquidity was drained from the protocol. The team had to find an alternative approach to build Amarok — an approach that would enable message passing but, at the same time, also align with the team’s vision of building decentralized and trust-minimized infrastructure for the Ethereum ecosystem.

The new approach leverages native bridges of L2s (similar to Hop V2’s mechanism) and follows a hub and spoke model to send messages across chains. The team believes that the most secure mechanism to interact with any chain is through its canonical or native bridge since these bridges are already the basis for trust for any chain. They call this thesis canonical bridge maximalism.

Arjun | xcall me maybe 🏴 @arjunbhuptani

The Connext thesis is actually pretty simple: Canonical bridge maximalism. There is no more secure mechanism to interact with a rollup/chain than through that rollup/chain's canonical bridge.

Thus, similar to Hop V2, it uses the native bridges of different chains for message passing. This means Connext (and Hop V2) uses:

• Rollup bridges for Optimism and Arbitrum,

• Polygon PoS Bridge, and 

• GnosisChain Arbitrary Messaging Bridge.

Additionally, for chains that don’t have native bridges, the team plans on using the most secure third-party bridge on that chain for message passing. For instance, for communication between Ethereum and Cosmos, Connext might use something like zkIBC.

Closing Thoughts

The evolution of Connext and Hop from token bridges to AMBs marks a significant milestone in the development of cross-chain dApps. This shift from token bridges to AMBs will ultimately pave the way for a more connected and interoperable ecosystem.

Soon we can expect a new wave of innovative and sophisticated dApps that leverage AMBs as the messaging layer and token bridge aggregators (like LI.FI) as the liquidity layer to offer superior user experiences in the multi-chain ecosystem.

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