signing-a-message.md

Signing a Message

When a web application is connected to Phantom, it can also 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, a web application must:

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

The handleSignMessage section of our developer sandbox 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 tweetnacl-js. {% endhint %}

{% tabs %} {% tab title="signMessage()" %}

const provider = getProvider(); // see "Detecting the Provider"
const message = `To avoid digital dognappers, sign below to authenticate with CryptoCorgis`;
const encodedMessage = new TextEncoder().encode(message);
const signedMessage = await provider.signMessage(encodedMessage, "utf8");

{% endtab %}

{% tab title="request()" %}

const provider = getProvider(); // see "Detecting the Provider"
const message = `To avoid digital dognappers, sign below to authenticate with CryptoCorgis`;
const encodedMessage = new TextEncoder().encode(message);
const signedMessage = await provider.request({
    method: "signMessage",
    params: {
         message: encodedMessage,
         display: "hex",
    },
});

{% endtab %} {% endtabs %}

Support for "Sign In With" Standards

Applications that rely on signMessage for authenticating users can choose to opt-in to one of the various Sign In With (SIW) standards. You can read more about them here.