signMessage

How to call the API from an app

Hedera Wallet Snap connects to your currently connected Metamask account by default. To learn how apps can connect to Hedera Wallet Snap using a non-metamask(external) account, refer to this documentation.

Then, depending on whether you're trying to connect to a metamask account or a non-metamask account, you can call the snap API in the following way:

const snapId = `npm:@hashgraph/hedera-wallet-snap`

const signMessageAPI = async () => {
  const externalAccountParams = {
    externalAccount: {
      accountIdOrEvmAddress: '0.0.12345',
      curve: 'ED25519'
    }
  }

  await window.ethereum.request({
    method: 'wallet_invokeSnap',
    params: {
      snapId,
      request: {
        method: 'signMessage',
        params: {
          network: 'testnet',
          message: 'Hello there, this is a sample message. ',
          /* 
            Uncomment the below line if you want to connect 
            to a non-metamask account
          */
          // ...externalAccountParams
        }
      }
    }
  })
}

What the API does

  1. Retrieves the currently connected account the user has selected on Metamask. If it's the first time, a new snap account is created and the account info is saved in snap state.

  2. Displays the MetaMask dialog box for the message to sign.

  3. Signs the given message using the private key of the user.

  4. Returns the signature as response.

Some example responses:

For a hedera account id 0.0.3581604:

{
    "currentAccount": {
        "metamaskEvmAddress": "0x0b3628d1b838993b5fceec8b2a26502e7a8e5241",
        "externalEvmAddress": "",
        "hederaAccountId": "0.0.3581604",
        "hederaEvmAddress": "0xca53f9c93d30e0b7212d67901e5a24fb090d542b",
        "publicKey": "0x0206022cea4c6dd6d2e7263b8802253971de922f5380661d97cba82dee66f57ad6",
        "balance": {
            "hbars": 5.67332072,
            "timestamp": "Wed, 13 Mar 2024 20:37:05 GMT",
            "tokens": {
                "0.0.3590430": {
                    "balance": 1,
                    "decimals": 1,
                    "tokenId": "0.0.3590430",
                    "name": "Token1",
                    "symbol": "KP1",
                    "tokenType": "FUNGIBLE_COMMON",
                    "supplyType": "INFINITE",
                    "totalSupply": "100",
                    "maxSupply": "0"
                }
            }
        },
        "network": "testnet",
        "mirrorNodeUrl": "https://testnet.mirrornode.hedera.com"
    },
    "signature": "0x6ecceeaf7e3b81151893827b123a6409445d625dee9c986f29044aa979cf992f0fc3ef426655bc0a074c7de59bec742c72faf00bc5f594316836d2c64ea81e0f1b"
}

Live Demo on CodePen

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