Introduction

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Overview

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Architecture

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Components

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Permit-Based System

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How It Works

1. User requests an action through Fishnet (e.g., swap tokens on Uniswap)
2. Fishnet evaluates the request against policy rules (spending limits, allowed protocols, etc.)
3. Backend signs a permit using EIP-712 structured data signing
4. Permit is submitted on-chain by a relayer (user or third-party)
5. Contract validates the permit and executes the approved action

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Benefits

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EIP-712 Permit Structure

struct FishnetPermit {
    address wallet;          // The FishnetWallet contract address
    uint64  chainId;         // Chain ID (prevents replay attacks across chains)
    uint256 nonce;           // Unique nonce (prevents replay attacks)
    uint48  expiry;          // Expiration timestamp (prevents stale permits)
    address target;          // Target contract to call (e.g., Uniswap Router)
    uint256 value;           // ETH value to send
    bytes32 calldataHash;    // Hash of the exact calldata
    bytes32 policyHash;      // Hash of the policy that authorized this action
}

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Security Features

• Nonce-based replay protection: Each permit can only be used once
• Chain ID binding: Permits are valid only on the intended network
• Expiration timestamps: Permits automatically expire after a set time
• Calldata commitment: The exact transaction data is cryptographically bound to the permit
• Policy tracking: Every action is linked to the policy that approved it

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Smart Contract Features

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Core Functions

function execute(
    address target,
    uint256 value,
    bytes calldata data,
    FishnetPermit calldata permit,
    bytes calldata signature
) external whenNotPaused;

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Access Control

• Owner: Can update the signer address, pause/unpause the wallet, and withdraw funds
• Signer: Backend service that signs permits (can be rotated by owner)
• Anyone: Can submit valid signed permits (relayer model)

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Deployment Networks

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Compatibility Testing

• Typehash matching: Raw keccak256 of type strings match
• Domain separator: Field-by-field EIP-712 domain construction is identical
• Struct hash encoding: abi.encode padding matches Rust’s manual big-endian padding
• End-to-end flow: Full sign → verify → execute cycle works correctly
• Signature format: r || s || v (65 bytes) unpacking is compatible

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Next Steps