Signing Blockchain Messages

📘
This feature is only available for Solana and EVM based blockchains.

Endpoint

POST /api/v1-alpha1/wallets/<chain>:<address>/signMessage

Required Scope

wallets:messages.sign

📘
Alpha API
This API is in alpha. You'll need to contact us via support to get the scope added to your API key.

How to sign a message

🚧
Server Side APIs
All of our APIs should be run from a server and NOT in the browser. Using these APIs in the client exposes your client secret, which WILL result in unauthorized access to your project.

import fetch from 'node-fetch';

const projectId = "";    // your project id (found in API Keys section of dev console)
const clientSecret = ""; // your client secret (found in API Keys section of dev console)

const env = "staging";   // staging, www
const chain = "polygon"; // ethereum, polygon
const address = "_WALLET_ADDRESS_OWNED_BY_YOUR_PROJECT_"; // 0x1234...

const message = "Hello, world!";

fetch(`https://${env}.crossmint.com/api/v1-alpha1/wallets/${chain}:${address}/signMessage`, {
    method: "POST",
    headers: {
        "Content-Type": "application/json",
        "x-project-id": projectId,
        "x-client-secret": clientSecret
    },
    body: JSON.stringify({ chain, address, message })
})
.then(response => response.json())
.then(data => console.log("Signed message:", data))
.catch(error => console.error("Error:", error));

Parameter Details

Parameter	Type	Description
chain	string	The blockchain network you're using (`ethereum`, `polygon`, or `bsc`). For Optimism or Arbitrum support, please reach out to us.
address	string	The wallet address you want to sign the message with. This MUST be a wallet owned by your project.
message	string	The message to be signed.

Response

On successful execution, the API will return a JSON object with the signedMessage property.

Example Response:

{ 
  "signedMessage": "0x7b226d657373616765223a202268656c6c6f2c20776f726c6421222c20227369676e6174757265223a2022307837316237386537333732333430303132303930653130313562323439373335333339656135303737323438333333613833653635373831326438653534373639373333333334227d"
}

Error Handling

The following errors may be returned by the API:

BadRequestException (400 error): If the requested blockchain is not supported.
NotFoundException (404 error): If the specified wallet address is not found.
ForbiddenException (401 error): If the project does not have access to the requested wallet.