> For the complete documentation index, see [llms.txt](https://l1x-sdk.gitbook.io/l1x-developer-interface/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://l1x-sdk.gitbook.io/l1x-developer-interface/multi-chain-with-x-talk/start-building-with-x-talk/cross-chain-data-and-message-passing-xcdp/v1.1-latest.md). # v1.1 (Latest) ## XTalk Protocol: High-Level System Overview ### Introduction The L1X XTalk Protocol enables secure and reliable communication between different blockchains, initially supporting EVM-compatible chains and the L1X mainnet. It uses a combination of off-chain **XTalk Nodes** and on-chain **XTalk Smart Contracts** to validate, achieve consensus on, and execute cross-chain messages. ### Core Components #### 1. XTalk Node An off-chain application that monitors, validates, and relays messages. It has three key validator roles: * **Listener Validator:** Detects new cross-chain message requests initiated on a source EVM chain. * **Signer Validator:** Cryptographically signs validated message details, contributing to a multi-signature consensus. * **Relayer Validator:** Delivers the consensus-approved message and signatures to the destination EVM chain for execution. #### 2. XTalk Smart Contracts **a. XTalkBeacon Contract (EVM Chains)** Deployed on participating EVM chains: * **Source Chain Role:** Allows users to register outgoing cross-chain messages and emits an event (`XTalkMessageBroadcasted`) to alert XTalk Nodes. * **Destination Chain Role:** Receives messages from Relayer Validators. It verifies the aggregated signatures from Signer Validators and, if valid, executes the message by calling a predefined function on the target contract, delivering the payload. **b. L1X Chain Contracts** These contracts manage consensus and routing on the L1X mainnet: * **Source Registry (`SourceRegistry`):** A directory that maps source chain IDs to specific L1X `FlowContract` addresses. This allows XTalk Nodes to determine the correct L1X contract for processing messages from a particular source chain. * **XTalk Consensus Contract (`XTalkConsensusContract`):** The central hub for message validation and consensus: * **Listener Consensus:** Collects votes from Listener Validators about new messages. When enough listeners agree, the message is considered `ListenerFinalized`. * **Signer Consensus:** After listener consensus, it collects cryptographic signatures from Signer Validators for a specific message hash. When enough signers agree, the message is `SignerFinalized`, and their signatures are stored. * **Flow Contract (`FlowContract`):** An intermediary processing contract on L1X: * **Stores Event Data:** After listener consensus, it receives and stores the validated event details from the source chain. * **Provides Data for Signing:** Generates a unique, deterministic hash for each message (based on its content and destination details) that Signer Validators must sign. * **Prepares Execution Payload:** Constructs the complete transaction data (including the original message and collected signer signatures) that Relayer Validators use to execute the message on the destination chain. ### High-Level Message Lifecycle 1. **Initiation (Source EVM Chain):** A user initiates a cross-chain message via the `XTalkBeacon` contract, which emits an `XTalkMessageBroadcasted` event. 2. **Listener Validation (L1X Chain):** * Listener Validators detect the event. * They consult the `SourceRegistry` to find the appropriate L1X `FlowContract` for this message. * They submit their observations as votes to the `XTalkConsensusContract`. Once consensus is reached, the message is `ListenerFinalized`. * The `XTalkConsensusContract` then instructs the designated `FlowContract` to store the validated event data. 3. **Signer Validation (L1X Chain):** * Signer Validators fetch a specific hash for the message from the `FlowContract`. * They sign this hash and submit their signatures to the `XTalkConsensusContract`. * Once sufficient signatures are collected and verified, the message is `SignerFinalized`. 4. **Relaying & Execution (Destination EVM Chain):** * A Relayer Validator retrieves the message details and the collected Signer signatures. * It uses the `FlowContract` to prepare the final transaction payload for the destination chain. * The Relayer submits this payload to the `XTalkBeacon` contract on the destination chain. * The destination `XTalkBeacon` verifies the multi-signature bundle against the message. If valid, it executes the message by calling the specified target contract with the original message payload. This multi-stage process, involving off-chain nodes and on-chain smart contracts with distinct consensus phases, ensures the secure and reliable transfer and execution of cross-chain messages. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. 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