signmessage.md

SignMessage

Once it's connected to Phantom, an app can request that the user signs a given message. Applications are free to write their own messages which will be displayed to users from within Phantom's signature prompt. Message signatures do not involve network fees and are a convenient way for apps to verify ownership of an address.

In order to send a message for the user to sign, an application must:

1. Provide a hex or UTF-8 encoded string as a Uint8Array and then base58-encoded it.
2. Request that the encoded message is signed via the user's Phantom wallet.

The deeplinking demo app provides an example of signing a message.

{% hint style="info" %} For more information on how to verify the signature of a message, please refer to Encryption Resources. {% endhint %}

Base URL

https://phantom.app/ul/v1/signMessage

Query String Parameters

• dapp_encryption_public_key (required): The original encryption public key used from the app side for an existing Connect session.

• nonce (required): A nonce used for encrypting the request, encoded in base58.

• redirect_link (required): The URI where Phantom should redirect the user upon completion. Please review Specifying Redirects for more details. URL-encoded.

• payload (required): An encrypted JSON string with the following fields:

  {
    "message": "...", // the message, base58 encoded
    "session": "...", // token received from connect-method
    "display": "utf8" | "hex", // the encoding to use when displaying the message 
  }

  • message (required): The message that should be signed by the user, encoded in base58. Phantom will display this message to the user when they are prompted to sign.
  • session (required): The session token received from the Connect method. Please see Handling Sessions for more details.
  • display (optional): How you want us to display the string to the user. Defaults to utf8

Returns

✅ Approve

• nonce: A nonce used for encrypting the response, encoded in base58.

• data: An encrypted JSON string. Refer to Encryption to learn how apps can decrypt data using a shared secret. Encrypted bytes are encoded in base58.

  // content of decrypted `data`-parameter
  {
      signature: "...", // message-signature
  }

  • signature: The message signature, encoded in base58. For more information on how to verify the signature of a message, please refer to Encryption Resources.

❌Reject

An errorCode and errorMessage as query parameters. Please refer to Errors for a full list of possible error codes.

{
  "errorCode": "...",
  "errorMessage": "..."
}

Example

Please refer to the signMessage method implemented in our React Native demo application.