# Sentry Node Utility

## Sentry Node Operations: Pre and Post V2 BOLD Update on Xai Blockchain

Xai blockchain's infrastructure, currently leveraging Arbitrum’s Nitro Rollup Contracts, is poised for a significant evolution with the upcoming V2 BOLD update from Arbitrum. This transition marks a pivotal shift in the functionality of the Sentry Nodes within the Xai ecosystem, especially in terms of security and proactive error detection.

{% hint style="info" %}
* The code and specification for Offchain Labs' BOLD (Bounded Liquidity Delay) is available on [**Github**](https://github.com/OffchainLabs/bold).
* Read more about BOLD protocol and roadmap [**here**](https://medium.com/offchainlabs/bold-permissionless-validation-for-arbitrum-chains-9934eb5328cc).
* Details regarding v2 BOLD will be available in the near future.&#x20;
{% endhint %}

### Pre-V2 BOLD Update Scenario:

In the current state, the Challenger, a critical component in our system, retrieves the State Root from the Rollup Protocol. Simultaneously, the Nitro Nodes, responsible for supplying this State Root, also receive the same data. The primary function of the Sentry Nodes, in this setup, is to ensure the integrity of the State Root as submitted to the Rollup Protocol.

A crucial limitation, however, is the Sentry's inability to foresee the State Root. This reactive approach means that Sentry Nodes act more like traditional digital detectives, verifying the State Root only after it has been committed. Think of this as the conventional crime-fighting approach in a digital realm – the Sentry Nodes investigate and flag an error (akin to a crime) only after it has occurred. They are effectively working post-event, detecting and raising an alarm when issues make their way into the system.

### Post-V2 BOLD Update Scenario:

The V2 BOLD update introduces a paradigm shift. While the Challenger continues to receive the State Root from the Rollup Protocol, the Nitro Nodes gain a significant enhancement – the ability to predict the next State Root before the completion of the current challenge. This prediction is synchronized with the closure of the Challenger's current challenge and the submission of the new State Root.

This advanced capability dramatically elevates the security posture of Xai blockchain. We transition from reactive to proactive error detection. The Sentry Nodes, equipped with this foresight, can now identify and address improper State Roots before they are even submitted to the Rollup Protocol. It’s akin to having a 'precognitive' ability, reminiscent of the 'precogs' in the science fiction classic, "Minority Report".

To elaborate, in the movie, 'precogs' are individuals with the gift to foresee crimes before they happen, allowing law enforcement to prevent them proactively. Analogously, in our Post V2 BOLD update scenario, our Sentry Nodes assume the role of these 'precogs', gaining the ability to 'see' potential issues (improper State Roots) before they materialize in the Rollup Protocol. This is a monumental leap from the traditional 'after-the-fact' approach to a more advanced, predictive security measure, ensuring a robust and preemptively secure blockchain environment.
