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Applications that rely on signMessage for authenticating users can choose to opt-in to one of the various Sign-In with (SIW) standards. If a message follows one of the supported standards, Phantom will verify required fields at the time of signing. At the time of this writing, Phantom supports: The serialized format of SIW messages is as follows: 
${domain} wants you to sign in with your ${blockchain} account:
${address}

${statement}

URI: ${uri}
Version: ${version}
Chain ID: ${chain-id}
Nonce: ${nonce}
Issued At: ${issued-at}
Expiration Time: ${expiration-time}
Not Before: ${not-before}
Request ID: ${request-id}
Resources:
- ${resources[0]}
- ${resources[1]}
...
- ${resources[n]}
NameTypeRequired?Description
domainstringtrueThe authority that is requesting the signing.
addressstringtrueThe blockchain address that is performing the signing.
statementstringfalseA human-readable ASCII assertion that the user will sign. It MUST NOT contain \\n.
uristringtrueA URI referring to the resource that is the subject of the signing—that is, the subject of the claim.
versionstringtrueThe current version of the message.
chain-idstringtrueThe Chain ID to which the session is bound, and the network where Contract Accounts MUST be resolved.
noncestringtrueA randomized token to prevent signature replay attacks.
issued-atstringtrueThe issuance time.
expiration-timestringfalseThe time at which the signed authentication message is no longer valid.
not-beforestringfalseThe time at which the signed authentication message starts being valid.
request-idstringfalseA system-specific identifier used to uniquely refer to the authentication request.
resourcesstring[]falseA list of URIs the user wishes to have resolved as part of the authentication by the relying party.

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Sign-In with Solana

See our specification and integration guide on GitHub.

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Sign-In with Ethereum

The Sign-In with Ethereum standard is defined by EIP-4361.

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Examples

signMessage() 
const provider = getProvider(); // see "Detecting the Provider"
const message = `magiceden.io wants you to sign in with your Ethereum account:
0xb9c5714089478a327f09197987f16f9e5d936e8a

Click Sign or Approve only means you have proved this wallet is owned by you.

URI: https://magiceden.io
Version: 1
Chain ID: 1
Nonce: bZQJ0SL6gJ
Issued At: 2022-10-25T16:52:02.748Z
Resources:
- https://foo.com
- https://bar.com`;
const encodedMessage = new TextEncoder().encode(message);
const signedMessage = await provider.signMessage(encodedMessage, "utf8");
request() 
const provider = getProvider(); // see "Detecting the Provider"
const message = `magiceden.io wants you to sign in with your Ethereum account:
0xb9c5714089478a327f09197987f16f9e5d936e8a

Click Sign or Approve only means you have proved this wallet is owned by you.

URI: https://magiceden.io
Version: 1
Chain ID: 1
Nonce: bZQJ0SL6gJ
Issued At: 2022-10-25T16:52:02.748Z
Resources:
- https://foo.com
- https://bar.com`;
const encodedMessage = new TextEncoder().encode(message);
const signedMessage = await provider.request({
    method: "signMessage",
    params: {
         message: encodedMessage,
         display: "utf8",
    }
});

​
Sign-In with X

The Sign-In with X standard is defined by CAIP-122. It uses CAIP-10 identifiers for the address field and CAIP-2 for chain-id.
While CAIP-122 is technically chain-agnostic, only Ethereum and Solana parsing are supported at this time.

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Ethereum example

signMessage() 
const provider = getProvider(); // see "Detecting the Provider"
const message = `magiceden.io wants you to sign in with your Ethereum account:
eip155:1:0xb9c5714089478a327f09197987f16f9e5d936e8a

Click Sign or Approve only means you have proved this wallet is owned by you.

URI: https://magiceden.io
Version: 1
Chain ID: eip155:1
Nonce: bZQJ0SL6gJ
Issued At: 2022-10-25T16:52:02.748Z
Resources:
- https://foo.com
- https://bar.com`;
const encodedMessage = new TextEncoder().encode(message);
const signedMessage = await provider.signMessage(encodedMessage, "utf8");
request() 
const provider = getProvider(); // see "Detecting the Provider"
const message = `magiceden.io wants you to sign in with your Ethereum account:
eip155:1:0xb9c5714089478a327f09197987f16f9e5d936e8a

Click Sign or Approve only means you have proved this wallet is owned by you.

URI: https://magiceden.io
Version: 1
Chain ID: eip155:1
Nonce: bZQJ0SL6gJ
Issued At: 2022-10-25T16:52:02.748Z
Resources:
- https://foo.com
- https://bar.com`;
const encodedMessage = new TextEncoder().encode(message);
const signedMessage = await provider.request({
    method: "signMessage",
    params: {
         message: encodedMessage,
         display: "utf8",
    }
});

​
Solana example

signMessage() 
const provider = getProvider(); // see "Detecting the Provider"
const message = `magiceden.io wants you to sign in with your Solana account:
solana:mainnet:FYpB58cLw5cwiN763ayB2sFT8HLF2MRUBbbyRgHYiRpK

Click Sign or Approve only means you have proved this wallet is owned by you.

URI: https://magiceden.io
Version: 1
Chain ID: solana:mainnet
Nonce: bZQJ0SL6gJ
Issued At: 2022-10-25T16:52:02.748Z
Resources:
- https://foo.com
- https://bar.com`;
const encodedMessage = new TextEncoder().encode(message);
const signedMessage = await provider.signMessage(encodedMessage, "utf8");
request() 
const provider = getProvider(); // see "Detecting the Provider"
const message = `magiceden.io wants you to sign in with your Solana account:
solana:mainnet:FYpB58cLw5cwiN763ayB2sFT8HLF2MRUBbbyRgHYiRpK

Click Sign or Approve only means you have proved this wallet is owned by you.

URI: https://magiceden.io
Version: 1
Chain ID: solana:mainnet
Nonce: bZQJ0SL6gJ
Issued At: 2022-10-25T16:52:02.748Z
Resources:
- https://foo.com
- https://bar.com`;
const encodedMessage = new TextEncoder().encode(message);
const signedMessage = await provider.request({
    method: "signMessage",
    params: {
         message: encodedMessage,
         display: "utf8",
    }
});
Phantom uses Ed25519 signatures for Solana message signatures. To verify a message signature, you can use the tweetnacl npm package.
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