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ZKCross Architecture

ZKCross Architecture Overview

ZKCross provides a full-stack solution for building fully stateful, on-chain provable decentralized applications (dApps). This holistic framework sits between dApps and Layer 1 (L1) chains, offering a comprehensive set of tools and services for efficient and secure development.

Core Components​

Sequencer​

  • Function: Handles the sequencing of requests (transactions) from dApps
  • Role: Acts as the entry point for dApp interactions, ensuring ordered processing of transactions

ZKC Executor​

The core component of the ZKCross architecture, consisting of two main parts:

  • App WASM: Contains the compiled application logic
  • Host SDK: A comprehensive hub of APIs and toolsets that:
    • Facilitates compiling and loading WASM images
    • Establishes links to other components and services
    • Provides standard API functions (e.g., Jubjub signature, Poseidon hash, random number generation)

Prover (zkWASM)​

  • Type: A specialized zero-knowledge virtual machine supporting WebAssembly
  • Function: Generates zero-knowledge proofs for execution traces
  • Process:
    • Accepts execution tracing logs and witnesses from the ZKC executor
    • Produces zkProofs
    • Automatically batches proofs for maximum scalability

Settlement Module​

  • Function: Manages the interaction between ZKCross and the L1 chain
  • Process:
    • Retrieves transaction data and execution results (pre and post Merkle roots)
    • Acquires corresponding zk-proofs
    • Submits data to the on-chain settlement smart contract
    • The smart contract verifies the zk-proof and updates the final state Merkle root on-chain

Supporting Services​

DA (Data Availability) Service​

  • Function: Saves user transactions and execution proofs
  • Partnership: ZKCross has partnered with Avail, a leading data availability solution provider
  • Benefit: Enables developers to access advanced DA features while building ZK dApps

State Service​

  • Provided by: ZKCross
  • Features:
    • Key-value pair database service
    • MongoDB service
  • Communicates with the ZKC executor to update and maintain dApp states based on processed transactions

Host Service​

  • Component: Part of the WASM software development kit (SDK)
  • Offerings:
    • Essential tools for interacting with WASM modules
    • Interfaces for communication with other components (e.g., State service)
    • Library functions for cryptographic operations (signing, hashing, etc.)

Workflow​

ZKCross Workflow Overview
The ZKCross workflow enables efficient and secure deployment of dApps with robust state management and verifiable computations across multiple blockchain layers:

Application to Sequencer​

Requests and transactions flow from the Application's UI to the Sequencer

Sequencer to ZKC Executor​

The Sequencer forwards transactions to the ZKC executor for processing

ZKC Executor Operations​

  • Execute dApp logic compiled into WASM
  • Interacts with the Prover to generate zero-knowledge proofs
  • Communicates with the State Service for state management
  • Connects with the DA Service for data availability

Settlement​

  • Engages with L1 Chains for final settlement and state updates

This architecture ensures a seamless flow of data and computations, from the initial dApp interaction to the final on-chain settlement, while maintaining security, scalability, and verifiability throughout the process.