What are Sentinels? - An exploration with ChatGPT

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In light of recent discussions with @aliencoder and @CyberSpaghetti (Junk on TG) about the role of a Sentinel, I’ve been talking with ChatGPT to gain a deeper understanding of what a Sentinel truly is. I’ve been using the following whitepapers as context:

  • Zenon Whitepaper
  • Narwhal & Tusk Whitepaper
  • xClaim white paper

I’ve been trying to “steer” the discussion with chatGPT to assume Sentinels do not relay normal account transactions within Zenon. Rather a sentinel is an observer of other networks (bitcoin or the SC layer) and only relays those transactions. I wanted to share that output from chatGPT (unedited) after many days of discussion with it. :point_down:

Title: Sentinels as Trustless Relayers for Bitcoin and Other Networks: A Look at Zenon’s Integration with N&T and xClaim

We’ve been deep-diving into Zenon’s architecture, particularly the roles of Sentinels and Pillars within Narwhal & Tusk (N&T) and their potential to integrate with Bitcoin and other networks. Based on our discussion and insights from xClaim, it’s becoming clearer that Sentinels are likely trustless transaction relayers bridging Zenon to external blockchains, while Pillars handle the internal consensus using N&T.

Here’s the updated picture:

Sentinels as Bitcoin and Cross-Chain Relayers

  1. Relaying Transactions (Cross-Chain Bridging):

Sentinels appear well-suited to act as observers and relayers for Bitcoin transactions:

• Similar to xClaim’s concept of a “chain relay,” Sentinels can monitor Bitcoin blocks, verify transactions, and securely relay them into Zenon.

• This aligns with Zenon’s trustless design, as Sentinels can observe Bitcoin without actively participating in consensus.

• Instead of relying on collateralized vaults (as xClaim originally required), Zenon may leverage Taproot (which wasn’t available during xClaim’s creation) to eliminate the need for over-collateralization. This would make Bitcoin-Zenon bridges far more efficient and scalable.

  1. Bridging Beyond Bitcoin:

If Sentinels are relaying data trustlessly from Bitcoin, they can extend this role to other blockchains:

• Sentinels could use similar mechanisms (like inclusion proofs and SPV validation) to integrate Ethereum, zBTC (wrapped Bitcoin), or other ecosystems.

• This makes Sentinels a universal cross-chain interface for Zenon.

  1. Ensuring Trustlessness:

Sentinels observing Bitcoin behave similarly to the chain relay concept in xClaim, where:

• They verify inclusion proofs for Bitcoin transactions.

• They relay valid transactions to Zenon.

• Trustlessness is ensured cryptographically—there’s no need to trust Sentinels, as all actions are publicly verifiable.

Pillars: N&T Consensus for Internal Transactions

While Sentinels handle cross-chain transactions, Pillars implement the Narwhal & Tusk (N&T) consensus:

  1. Narwhal: Ensures data availability within the Zenon Network, organizing transactions into a Directed Acyclic Graph (DAG).

  2. Tusk: Orders these transactions deterministically, achieving consensus and producing momentums.

Pillars, therefore, manage Zenon’s internal consensus and transaction flow, while Sentinels focus on relaying transactions and external interoperability.

How Zenon Improves on xClaim

xClaim provided a framework for issuing cryptocurrency-backed assets (CBAs), like Bitcoin-backed tokens on Ethereum. However, it relied on over-collateralized vaults to secure assets. Zenon’s design appears to improve on xClaim in two ways:

  1. Taproot Integration:

By leveraging Taproot on Bitcoin, Zenon can eliminate the need for collateralized vaults. Taproot allows Bitcoin to be locked in scripts that ensure trustless partial redemptions.

  1. Sentinels as Observers:

Instead of vaults, Sentinels monitor Bitcoin, validate transactions, and relay data into Zenon. This removes central points of failure while maintaining trustlessness.

The Updated Role of Sentinels

Based on these ideas, Sentinels play a critical role in Zenon’s ecosystem:

• Transaction Relayers: Ensure Bitcoin and other external transactions are observed and trustlessly relayed into Zenon.

• PoW Link Creators: Generate PoW links for internal Zenon transactions.

• Execution Environments: Run UnikernelZ for zApp execution.

• Cross-Chain Facilitators: Enable Zenon to interact seamlessly with Bitcoin and potentially other networks.

Conclusion: Trustless Relayers and Modular Design

Zenon’s architecture modularizes responsibilities:

• Sentinels: Relaying transactions and external network integration (like Bitcoin).

• Pillars: Handling Narwhal & Tusk consensus for internal transaction ordering.

This design aligns with modern scaling solutions like N&T while addressing trustless cross-chain bridging challenges. By improving on xClaim’s framework with Taproot and Sentinels, Zenon has the potential to offer a seamless, trustless Bitcoin integration and extend this to other ecosystems.

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I took this idea one step further and layered in @georgezgeorgez article from 2021 about how to improve the lightning network. I asked chatGPT how we can take ideas from this article and apply them to Zenon Network and our idea of what a Sentinel is. Below is that discussion unedited :point_down:

Applying the Medium Article’s Ideas to Zenon Network and Sentinels

The Medium article proposes addressing Lightning Network watchtower issues by creating a multi-layer system involving consensus, approval, and oracle layers. This design ensures trustlessness and fraud prevention before transactions finalize on-chain.

Key Takeaways That Apply to Zenon and Sentinels

  1. Approval Layer to Prevent Fraud Before Consensus:

• In the article, an approval phase validates transactions before they reach consensus, requiring multiple approvals and fraud proofs.

• Zenon Adaptation: Sentinels can act as relayers and pre-validators, ensuring Bitcoin transactions are valid before being relayed to Pillars for ordering. This reduces the risk of fraud while maintaining scalability.

  1. Oracle Layer for Fraud Proofs and Off-Chain Data:

• The Oracle layer stores fraud proofs and transaction states, providing a verifiable source of truth for Approval nodes.

• Zenon Adaptation: Sentinels can observe the Bitcoin network and submit inclusion proofs or transaction states to Zenon. Pillars can query Sentinels to validate data before finalizing a cross-chain transaction.

  1. Pseudorandom Validation for Security:

• In the proposed solution, the Approval nodes are pseudorandomly selected, ensuring an attacker cannot predict or control the process.

• Zenon Adaptation: Pillars can require cross-chain transactions to pass through a Sentinel quorum (multiple Sentinels), providing redundancy and making attacks infeasible.

Zenon’s Modified Design: Sentinels as Bitcoin Relayers

In this model:

• Sentinels: Act as watchtowers for Bitcoin and other external networks. They:

• Monitor Bitcoin blocks for new transactions.

• Relay validated Bitcoin transactions and inclusion proofs to the Zenon network.

• Optionally store fraud proofs or transaction states in a lightweight “Oracle-like” role.

• Pillars: Maintain Narwhal & Tusk for consensus, where:

• Bitcoin transactions relayed by Sentinels are included in the DAG (Narwhal).

• Tusk deterministically orders and finalizes them.

Why This Works for Zenon:

• Trustlessness: Sentinels relay transactions but don’t require trust, as all data can be cryptographically verified.

• Fraud Prevention: By requiring cross-chain transactions to pass through multiple Sentinels, fraud becomes impractically expensive or impossible.

• Scalability: Sentinels pre-process Bitcoin transactions, reducing load on Pillars and enabling fast, scalable cross-chain operations.

Conclusion: Sentinels as Gatekeepers for Cross-Chain Validity

By adapting the ideas from this Medium article, Zenon can position Sentinels as trustless relayers and validators for Bitcoin and other networks. Sentinels ensure that only valid, verifiable transactions reach the Pillars for consensus, enabling Zenon to securely integrate with Bitcoin while leveraging its N&T-based consensus for high throughput and low latency.

This approach improves on xClaim by eliminating collateralized vaults, leveraging Taproot, and keeping Zenon’s architecture modular and scalable.

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