Prerequisites
- Ensure you have a wallet created.
- API Key: Ensure you have an API key with the scopes:
wallets:signatures.create.
If you are signing with a delegated signer, the wallet must have executed at least one transaction before signatures will work. This is because the wallet needs to be deployed on-chain first.
Signing a Message
- React
- Node.js
- React Native
- Swift
- REST
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import { useWallet, EVMWallet } from '@crossmint/client-sdk-react-ui';
const { wallet } = useWallet();
const evmWallet = EVMWallet.from(wallet);
const signedMessage = await evmWallet.signMessage({ message: "Hello, world!" });
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import { CrossmintWallets, createCrossmint, EVMWallet } from "@crossmint/wallets-sdk";
const crossmint = createCrossmint({
apiKey: "<your-server-api-key>",
});
const crossmintWallets = CrossmintWallets.from(crossmint);
const wallet = await crossmintWallets.getWallet(
"email:user@example.com:evm",
{ chain: "base-sepolia", signer: { type: "email" } }
);
const evmWallet = EVMWallet.from(wallet);
const signedMessage = await evmWallet.signMessage({ message: "Hello, world!" });
Parameters
The message to sign.
Returns
The signature of the message.
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import { useWallet, EVMWallet } from '@crossmint/client-sdk-react-native-ui';
const { wallet } = useWallet();
const evmWallet = EVMWallet.from(wallet);
const signedMessage = await evmWallet.signMessage({ message: "Hello, world!" });
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import CrossmintClient
import Wallet
let sdk = CrossmintSDK.shared
let wallet = try await sdk.crossmintWallets.getOrCreateWallet(
chain: .baseSepolia,
signer: .email("user@example.com")
)
let evmWallet = try EVMWallet.from(wallet: wallet)
let signature = try await evmWallet.signMessage("Hello, world!")
Parameters
The message to sign.
Returns
The signature of the message.
Signatures must be approved by one of the wallet’s signers.
The SDK handles this automatically, but with the REST API you must approve the signature to complete it.Sign the approval message field returned in the response inside
Create the signature
Call the create signature endpoint.See the API reference for more details.
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curl --request POST \
--url https://staging.crossmint.com/api/2025-06-09/wallets/email:user@example.com:evm/signatures \
--header 'Content-Type: application/json' \
--header 'X-API-KEY: <x-api-key>' \
--data '{
"type": "message",
"params": {
"message": "Hello, world!",
"signer": "email:user@example.com",
"chain": "base-sepolia"
}
}'
Sign the approval returned in the response
If you are using an
api-key as the admin signer you can skip the following steps.signature.approvals using the signer.Approve the signature
Call the approve signature endpoint using the signature from the previous step and the signature id returned in the call from Step 1.See the API reference for more details.
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curl --request POST \
--url https://staging.crossmint.com/api/2025-06-09/wallets/email:user@example.com:evm/signatures/91e90094-9fe0-43a7-bab6-e5725767a3ad/approvals \
--header 'Content-Type: application/json' \
--header 'X-API-KEY: <x-api-key>' \
--data '{
"approvals": [{
"signer": "email:user@example.com",
"signature": "0x1234567890abcdef..."
}]
}'
Signing Typed Data
- React
- Node.js
- React Native
- Swift
- REST
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import { useWallet, EVMWallet } from '@crossmint/client-sdk-react-ui';
const { wallet } = useWallet();
const evmWallet = EVMWallet.from(wallet);
const typedData = {
"types": {
"EIP712Domain": [{
"name": "name",
"type": "string"
}],
},
"primaryType": "Mail",
"domain": {
"name": "example.com",
"version": "1"
},
"message": {
"from": {
"name": "John Doe"
},
"to": {
"name": "Jane Doe"
},
"contents": "Hello, world!"
}
};
const signedMessage = await evmWallet.signTypedData(typedData);
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import { CrossmintWallets, createCrossmint, EVMWallet } from "@crossmint/wallets-sdk";
const crossmint = createCrossmint({
apiKey: "<your-server-api-key>",
});
const crossmintWallets = CrossmintWallets.from(crossmint);
const wallet = await crossmintWallets.getWallet(
"email:user@example.com:evm",
{ chain: "base-sepolia", signer: { type: "email" } }
);
const evmWallet = EVMWallet.from(wallet);
const typedData = {
"types": {
"EIP712Domain": [{
"name": "name",
"type": "string"
}],
},
"primaryType": "Mail",
"domain": {
"name": "example.com",
"version": "1"
},
"message": {
"from": {
"name": "John Doe"
},
"to": {
"name": "Jane Doe"
},
"contents": "Hello, world!"
}
};
const signedMessage = await evmWallet.signTypedData(typedData);
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import { useWallet, EVMWallet } from '@crossmint/client-sdk-react-native-ui';
const { wallet } = useWallet();
const evmWallet = EVMWallet.from(wallet);
const typedData = {
"types": {
"EIP712Domain": [{
"name": "name",
"type": "string"
}],
},
"primaryType": "Mail",
"domain": {
"name": "example.com",
"version": "1"
},
"message": {
"from": {
"name": "John Doe"
},
"to": {
"name": "Jane Doe"
},
"contents": "Hello, world!"
}
};
const signedMessage = await evmWallet.signTypedData(typedData);
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import CrossmintClient
import Wallet
let sdk = CrossmintSDK.shared
let wallet = try await sdk.crossmintWallets.getOrCreateWallet(
chain: .baseSepolia,
signer: .email("user@example.com")
)
let evmWallet = try EVMWallet.from(wallet: wallet)
let signature = try await evmWallet.signTypedData(typedData)
Parameters
The typed data to sign.
Returns
The signature of the message.
Signatures must be approved by one of the wallet’s signers.
The SDK handles this automatically, but with the REST API you must approve the signature to complete it.Sign the approval message field returned in the response inside
Create the signature
Call the create signature endpoint.See the API reference for more details.
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curl --request POST \
--url https://staging.crossmint.com/api/2025-06-09/wallets/email:user@example.com:evm/signatures \
--header 'Content-Type: application/json' \
--header 'X-API-KEY: <x-api-key>' \
--data '{
"type": "typed-data",
"params": {
"typedData": {
"types": {
"EIP712Domain": [{
"name": "name",
"type": "string"
}],
},
"primaryType": "Mail",
"domain": {
"name": "example.com",
"version": "1"
},
"message": {
"from": {
"name": "John Doe"
},
"to": {
"name": "Jane Doe"
},
"contents": "Hello, world!"
}
},
"signer": "email:user@example.com",
"chain": "base-sepolia"
}
}'
Sign the approval returned in the response
If you are using an
api-key as the admin signer you can skip the following steps.signature.approvals using the signer.Approve the signature
Call the approve signature endpoint using the signature from the previous step and the signature id returned in the call from Step 1.See the API reference for more details.
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curl --request POST \
--url https://staging.crossmint.com/api/2025-06-09/wallets/email:user@example.com:evm/signatures/91e90094-9fe0-43a7-bab6-e5725767a3ad/approvals \
--header 'Content-Type: application/json' \
--header 'X-API-KEY: <x-api-key>' \
--data '{
"approvals": [{
"signer": "email:user@example.com",
"signature": "0x1234567890abcdef..."
}]
}'