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.
For an example of signing a message, refer to handleSignMessage in our sandbox.
Phantom uses Ed25519 signatures for Solana message signatures. To verify a message signature, you can use the tweetnacl npm package.

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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");

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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",
    },
});

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Sign-In with Solana (SIWS)

Developers who use signMessage to authenticate users can now take advantage of Phantom’s new Sign-In with Solana feature. For more information, refer to our specification on GitHub.

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Support for other “Sign-In with” Standards

Phantom supports a range of “Sign-In with” (SIW) message standards. You can read more about them in Sign a message.