Bridge2

The hyperliquid bridge native USDC and is secured by the L1 validator set: https://arbiscan.io/address/0x2df1c51e09aecf9cacb7bc98cb1742757f163df7

The deposit flow is for the bridge is simple. The user sends native USDC to the bridge and it is credited to the account that sent it in less than 1 minute. The minimum deposit amount is $5. If you send an amount less than this it will not be credited and be lost forever.

The withdrawal flow requires a user wallet signature on the L1 only, and no Arbitrum transaction. The withdrawal from Arbitrum is handled entirely the validators, and the funds arrive in the user wallet in 3-4 minutes. This payload for signTypedData is

#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
#[serde(deny_unknown_fields)]
pub(crate) struct WithdrawAction3 {
    pub(crate) signature_chain_id: U256,
    pub(crate) hyperliquid_chain: Chain,
    pub(crate) destination: String,
    pub(crate) amount: String,
    pub(crate) time: u64,
}

impl Eip712 for WithdrawAction3 {
    type Error = Eip712Error;

    fn domain(&self) -> StdResult<EIP712Domain, Self::Error> {
        Ok(eip_712_domain(self.signature_chain_id))
    }

    fn type_hash() -> StdResult<[u8; 32], Self::Error> {
        Ok(eip712::make_type_hash(
            format!("{HYPERLIQUID_EIP_PREFIX}Withdraw"),
            &[
                ("hyperliquidChain".to_string(), ParamType::String),
                ("destination".to_string(), ParamType::String),
                ("amount".to_string(), ParamType::String),
                ("time".to_string(), ParamType::Uint(64)),
            ],
        ))
    }

    fn struct_hash(&self) -> StdResult<[u8; 32], Self::Error> {
        let Self { signature_chain_id: _, hyperliquid_chain, destination, amount, time } = self;
        let items = vec![
            ethers::abi::Token::Uint(Self::type_hash()?.into()),
            encode_eip712_type(hyperliquid_chain.to_string().into_token()),
            encode_eip712_type(destination.clone().into_token()),
            encode_eip712_type(amount.clone().into_token()),
            encode_eip712_type(time.into_token()),
        ];
        Ok(keccak256(encode(&items)))
    }
}

Example signed L1 action:

{
    "action": {
        "type": "withdraw3",
        "signatureChainId": "0xa4b1",
        "hyperliquidChain": "Mainnet" or "Testnet" 
        "destination": "0x000....0",
        "amount": "12.3",
        "time": 1698693262
    },
    "nonce": 1698693262 // IMPORTANT: this must match "time",
    "signature": {"r": ..., "s": ..., "v": ... } // signedTypedData output based on Eip712 implementation above. See python sdk for equivalent python code
}