Watcher 👀 — Guardian of the Connext Network
Watchers are one of the main actors that play a critical role in securing the bridging process of the Connext Network. But how do they work, and why do we even need them?
How does Connext works?
Before we begin, let’s recap how Connext bridge works:
Connext serves as an execution layer for bridges, outsourcing the verification method from others. With its modular design, we can customize the verification layer for each connected chain, ensuring maximum security.
Modular Bridge in action: L2<>L2 Communication
Let’s take L2<>L2 communication as an example
When Connext executes a cross-chain transaction from L2 to L2, the transaction goes through the source L2 to the Mainnet before reaching the target L2 using the Arbitrary Message Bridges (AMBs). This ensures the maximum security for L2<>L2 transaction possible
Routers get refunded for the fronted cash on the destination chain via the protocol’s slow path.
Modular Bridge in action: Inter-domain Communication
What about ETH<>BNB path?
Without a trustless AMB link between ETH and BNB, we can use Optimistic Verification with fraud proof and delays. Bridges like wormhole, axelar, or zk-light-client can serve as their transport layers.
The latency issue ⏳
However, securities always comes with a tradeoffs. The most secure verification methods for L2<>L2 communication will face a latency issues. For instance, ETH<>L2 AMBs might take approximately 30 minutes.
Connext addresses this by having a router execute transactions optimistically for users via a fast path⚡.
Off-chain Actors
The entire Connext architecture facilitating this fast/slow path cross-chain execution relies on several off-chain actors:
- Relayers (currently outsourcing Gelato) — Execute smart contracts on the destination chain for users
- Sequencers — Collect bids from all chains, assigning routers to fullfill the transactions
- Routers — Liquidity providers for the ecosystem. Routers execute transaction for user using a local verification on the source chain.
These three actors help facilitating the cross-chain messaging while minimizing the trust assumption with optimistic verification method.
The Cross-Chain Concern
Nevertheless, a concern remains with cross-chain communication. Vitalik Buterin once mentioned on r/ethereum that the security of the cross-chain ecosystem is as strong as the weakest link in the chain.
If one chain in the ecosystem gets compromised, the entire ecosystem is at risk
Why is that? When the bridge connects multiple chains, we depend on ALL verification methods to function correctly. Each connected domain has different verification methods, and not all are equally secure! The maximum security we can achieve is as strong as the weakest verification channel.
Overcoming the Challenge
However, this statement is only accurate if the verification channel remains connected after a fraudulent activity is detected. If we can disconnect the verification channel promptly, we can ensure the damage is minimal.
The key player that continually monitors for fraudulent activity in the verification method is the WATCHERS đź‘€!
Connext deploys watchers to track potential fraudulent activity in the connected paths, severing any compromised verification channels. This process bears similarities to how Fraud Proof operates!
As long as the Watchers perform their duties correctly and there’s no collusion among ALL watchers (unlike ~60% for PoS or MPC), the system can disconnect any malicious chain at any time!
The Watchers will be permissionless to make sure that the system has minimal trust-assumption. The challenge lies in designing proper incentives for multiple off-chain actors, such as Watchers and Routers.
Conclusion
In this article, we’ve explored how Connext operates, particularly focusing on its modular bridging stacks and its capabilities for both intra-domain communication (communication within Layer 2, or L2<>L2) and inter-domain communication (communication between Ethereum and Binance Smart Chain, or ETH<>BNB). While there are concerns surrounding the security of these cross-chain transactions, since the overall security is only as robust as the least secure connected verification method, Connext has a strategy to address this. It introduces a method called optimistic verification, which includes delays in the source chain and Watchers monitoring the system. If a breach happens, this system ensures the compromised verification layer is isolated. For this method to work, the assumption is that not all Watchers are working together in collusion, requiring far less trust than the approximate 60% needed for validators in methods like Multi-party computation (MPC) or Proof of Stake (PoS). This approach helps ensure that the cross-chain ecosystem remains secure, thanks to the Watchers.
References
- An Exploration of Connext’s Architecture Pt.1: High Security and Censorship Resistance
- The Messaging Bridge Stack
- Optimistic Bridges
About Connext
Connext is a trust-minimized interoperability protocol aiming to be a HTTP of Web3, abstracting the concept of chains away from users
