Alloy Book

Example: sign_permit_hash

Example

To run this example:

• Clone the examples repository: git clone git@github.com:alloy-rs/examples.git
• Run: cargo run --example sign_permit_hash

//! Example of signing a permit hash using a wallet.

use alloy::{
    primitives::{address, keccak256, U256},
    signers::{local::PrivateKeySigner, Signer},
    sol,
    sol_types::{eip712_domain, SolStruct},
};
use eyre::Result;
use serde::Serialize;

sol! {
    #[allow(missing_docs)]
    #[derive(Serialize)]
    struct Permit {
        address owner;
        address spender;
        uint256 value;
        uint256 nonce;
        uint256 deadline;
    }
}

#[tokio::main]
async fn main() -> Result<()> {
    // Set up a random signer.
    let signer = PrivateKeySigner::random();

    let domain = eip712_domain! {
        name: "Uniswap V2",
        version: "1",
        chain_id: 1,
        verifying_contract: address!("B4e16d0168e52d35CaCD2c6185b44281Ec28C9Dc"),
        salt: keccak256("test"),
    };

    let permit = Permit {
        owner: signer.address(),
        spender: address!("B4e16d0168e52d35CaCD2c6185b44281Ec28C9Dc"),
        value: U256::from(100),
        nonce: U256::from(0),
        deadline: U256::from(0),
    };

    // Derive the EIP-712 signing hash.
    let hash = permit.eip712_signing_hash(&domain);

    // Sign the hash asynchronously with the wallet.
    let signature = signer.sign_hash(&hash).await?;

    println!(
        "Recovered address matches wallet address: {}",
        signature.recover_address_from_prehash(&hash)? == signer.address()
    );

    println!("Wallet signature matches: {}", signer.sign_hash(&hash).await? == signature);

    Ok(())
}

Find the source code on Github here.