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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.
The message to be signed must be passed as a base58-encoded string. For more information on how to verify the signature of a message, please refer to Encryption resources.

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Base URL

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

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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. For more details, see Specify redirects. 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. For more details, see Handle sessions.
    • display (optional): How you want us to display the string to the user. Defaults to utf8.

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Returns

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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, see Encryption resources.

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Reject

An errorCode and errorMessage as query parameters. For a full list of possible error codes, see Errors. 
{
  "errorCode": "...",
  "errorMessage": "..."
}

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Example

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