sign-message.md

Sign Message

{% hint style="warning" %} Make sure you initialize Blocto SDK first {% endhint %}

Once your app is connected to Blocto wallet, it can sign message on behalf of the user, with the user's permission.

To sign a message, the app must specify the sign type. All available types are listed below.

Sign Type	Type	Message
ETH Sign	EvmSignType.ETH_SIGN	hex string (0x prefix)
Personal Sign	EvmSignType.PERSONAL_SIGN	plain string
Sign Typed Data v3	EvmSignType.TYPED_DATA_V3	json string
Sign Typed Data v4	EvmSignType.TYPED_DATA_V4	json string
Sign Typed Data (currently identical to Sign Typed Data v4)	EvmSignType.TYPED_DATA	json string

// Sign message based on specific chain

BloctoSDK.evm.signMessage(
    context = context,
    blockchain = Blockchain.ETHEREUM,
    fromAddress = address,
    signType = [EvmSignType.ETH_SIGN/EvmSignType.PERSONAL_SIGN/...],
    message = message,
    onSuccess = { signature ->
        // get signature
    },
    onError = { error ->
        // handle error
    }
)

For dApps relying on signMessage for off-chain authentication, Blocto follows EIP-1654. To verify the signature, you need to call a method on the wallet contract to check if the signature came from a rightful owner of the wallet contract.

// Example code by using web3j

// hash: hash of data (message) to be signed
// signature: signature byte array associated with hash

fun verifySignature(hash: ByteArray, signature: ByteArray): Boolean {
    val web3j = Web3j.build(HttpService(rpcUrl))
    val function = Function(
        "isValidSignature",
        listOf(Bytes32(hash), DynamicBytes(signature)),
        listOf<TypeReference<Bytes4>>()
    )
    val encodedFunction = FunctionEncoder.encode(function)
    return web3j.ethCall(
        Transaction.createEthCallTransaction(
            address,
            address,
            encodedFunction
        ),
        DefaultBlockParameterName.LATEST
    ).send().value.orEmpty() == ERC1271_MAGIC_VALUE
}