eth_signTypedData_v4

Sign structured data according to EIP-712 v4 rules. Compared with raw hashes or ordinary text signatures, it allows users to see more semantic fields and is more suitable for on-chain verification of data such as authorizations, orders, or permits.

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Inputs

Index	Type	Description
0	string	The account address that initiated the signature
1	string	Typed data JSON string

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return value

string - ​​65-byte signature, hexadecimal string format.

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typed data structure

interface TypedData {
  types: {
    EIP712Domain: Array<{ name: string; type: string }>;
    [typeName: string]: Array<{ name: string; type: string }>;
  };
  primaryType: string;
  domain: {
    name?: string;
    version?: string;
    chainId?: number;
    verifyingContract?: string;
    salt?: string;
  };
  message: Record<string, any>;
}

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Demo

const typedData = {
  types: {
    EIP712Domain: [
      { name: "name", type: "string" },
      { name: "version", type: "string" },
      { name: "chainId", type: "uint256" },
      { name: "verifyingContract", type: "address" },
    ],
    Person: [
      { name: "name", type: "string" },
      { name: "wallet", type: "address" },
    ],
    Mail: [
      { name: "from", type: "Person" },
      { name: "to", type: "Person" },
      { name: "contents", type: "string" },
    ],
  },
  primaryType: "Mail",
  domain: {
    name: "UKey Wallet Sample",
    version: "1",
    chainId: 1,
    verifyingContract: "0x2b4d6f8091a3c5e7f9b1d3f507192b4d6f8091a3",
  },
  message: {
    from: {
      name: "Ava",
      wallet: "0x4b6d8f0123456789abcdef0123456789abcdef01",
    },
    to: {
      name: "Liam",
      wallet: "0xc4d2e1f0a9876543210fedcba9876543210abcde",
    },
    contents: "Payment approval sample",
  },
};

const signature = await window.$ukey.ethereum.request({
  method: "eth_signTypedData_v4",
  requestParams: [accounts[0], JSON.stringify(typedData)],
});

console.log("Generated signature:", signature);

Permit signature (ERC-2612)

const permitData = {
  types: {
    EIP712Domain: [
      { name: "name", type: "string" },
      { name: "version", type: "string" },
      { name: "chainId", type: "uint256" },
      { name: "verifyingContract", type: "address" },
    ],
    Permit: [
      { name: "owner", type: "address" },
      { name: "spender", type: "address" },
      { name: "value", type: "uint256" },
      { name: "nonce", type: "uint256" },
      { name: "deadline", type: "uint256" },
    ],
  },
  primaryType: "Permit",
  domain: {
    name: "USDC.e",
    version: "2",
    chainId: 1,
    verifyingContract: "0x2b4d6f8091a3c5e7f9b1d3f507192b4d6f8091a3",
  },
  message: {
    owner: accounts[0],
    spender: "0x4b6d8f0123456789abcdef0123456789abcdef01",
    value: "3500000000", // sample token amount
    nonce: 0,
    deadline: Math.floor(Date.now() / 1000) + 3600,
  },
};

const signature = await window.$ukey.ethereum.request({
  method: "eth_signTypedData_v4",
  requestParams: [accounts[0], JSON.stringify(permitData)],
});

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error code

Code	Message	Details
4001	User rejected the request	Signature approval was rejected by the user
-32602	Parameters failed validation	Typed data structure is invalid

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illustrate

• Typed data must be parsable as valid JSON.
• domain.chainId should be consistent with the current eth_chainId.
• domain.verifyingContract should point to the contract actually responsible for verification.
• Users will see structured fields in the wallet, please use clear field names and understandable business content.
• Follows EIP-712 specification.