EVM Signing | Crossmint Wallet APIs

This page has been updated for Wallets SDK V1. If you are using the previous version, see the previous version of this page or the V1 migration guide.

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 an operational signer, the wallet must have executed at least one transaction before signatures will work. This is because the wallet needs to be deployed onchain first.

Signing a Message

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!" });

See the React SDK reference for more details.

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" }
);

await wallet.useSigner({ type: "email", email: "user@example.com" });

const evmWallet = EVMWallet.from(wallet);

const signedMessage = await evmWallet.signMessage({ message: "Hello, world!" });

Parameters

message

string

required

The message to sign.

Returns

signature

string

The signature of the message.

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!" });

See the React Native SDK reference for more details.

import com.crossmint.kotlin.sdk.Crossmint
import com.crossmint.kotlin.types.EVMChain

val sdk = Crossmint.instance
val wallet = sdk.crossmintWallets.getWallet(chain = EVMChain.BaseSepolia).getOrThrow()

val signature = wallet.signMessage("Hello, world!").getOrThrow()
println("Signature: $signature")

import CrossmintClient
import Wallet

let sdk = CrossmintSDK.shared

let wallet = try await sdk.crossmintWallets.getWallet(
    chain: .baseSepolia
)

let evmWallet = try EVMWallet.from(wallet: wallet)

let signature = try await evmWallet.signMessage("Hello, world!")

Parameters

message

string

required

The message to sign.

Returns

signature

string

The signature of the message.

import 'package:crossmint_flutter/crossmint_flutter_ui.dart';

final controller = CrossmintWalletContext.of(context).requireWalletController;
final evmWallet = controller.createEvmWallet();

final signature = await evmWallet.signMessage('Hello, world!');

See the Flutter SDK reference for more details.

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.

Create the signature

Call the create signature endpoint.

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"
        }
    }'

See the API reference for more details.

Sign the approval returned in the response

If you are using an api-key as the recovery signer (admin signer) you can skip the following steps.

Sign the approval message field returned in the response inside 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.

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..."
        }]
    }'

See the API reference for more details.

Signing Typed Data

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);

See the React SDK reference for more details.

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" }
);

await wallet.useSigner({ type: "email", email: "user@example.com" });

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);

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);

See the React Native SDK reference for more details.

import com.crossmint.kotlin.sdk.Crossmint
import com.crossmint.kotlin.types.EVMChain

val sdk = Crossmint.instance
val wallet = sdk.crossmintWallets.getWallet(chain = EVMChain.BaseSepolia).getOrThrow()

val typedDataJson = """
    {
        "types": {
            "EIP712Domain": [{ "name": "name", "type": "string" }],
            "Person": [
                { "name": "name", "type": "string" }
            ],
            "Mail": [
                { "name": "from", "type": "Person" },
                { "name": "to", "type": "Person" },
                { "name": "contents", "type": "string" }
            ]
        },
        "primaryType": "Mail",
        "domain": { "name": "example.com", "version": "1" },
        "message": {
            "from": { "name": "John Doe" },
            "to": { "name": "Jane Doe" },
            "contents": "Hello, world!"
        }
    }
""".trimIndent()

val signature = wallet.signTypedData(typedDataJson).getOrThrow()
println("Signature: $signature")

import CrossmintClient
import Wallet

let sdk = CrossmintSDK.shared

let wallet = try await sdk.crossmintWallets.getWallet(
    chain: .baseSepolia
)

let evmWallet = try EVMWallet.from(wallet: wallet)

let typedData = EIP712.Builder()
    .withDomain(name: "example.com")
    .defineEIP712Domain(includeName: true, includeVersion: false, includeChainId: false, includeVerifyingContract: false)
    .defineType("Person") { fields in
        fields.string("name")
    }
    .defineType("Mail") { fields in
        fields
            .structType("from", typeName: "Person")
            .structType("to", typeName: "Person")
            .string("contents")
    }
    .withPrimaryType("Mail")
    .withMessage([
        "from": ["name": "John Doe"],
        "to": ["name": "Jane Doe"],
        "contents": "Hello, world!"
    ])
    .build()
guard let typedData else { return }
let signature = try await evmWallet.signTypedData(typedData)

Parameters

typedData

EIP712.TypedData

required

The typed data to sign, constructed using EIP712.Builder.

Returns

signature

string

The signature of the message.

import 'package:crossmint_flutter/crossmint_flutter_ui.dart';

final controller = CrossmintWalletContext.of(context).requireWalletController;
final evmWallet = controller.createEvmWallet();

final typedData = CrossmintTypedData(
  raw: const <String, Object?>{
    'types': <String, Object?>{
      'EIP712Domain': <Map<String, Object?>>[
        <String, Object?>{'name': 'name', 'type': 'string'},
      ],
    },
    'primaryType': 'Mail',
    'domain': <String, Object?>{
      'name': 'example.com',
      'version': '1',
      'chainId': 84532,
      'verifyingContract': '0x...',
    },
    'message': <String, Object?>{
      'from': <String, Object?>{'name': 'John Doe'},
      'to': <String, Object?>{'name': 'Jane Doe'},
      'contents': 'Hello, world!',
    },
  },
);
final signature = await evmWallet.signTypedData(typedData);

See the Flutter SDK reference for more details.

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.

Create the signature

Call the create signature endpoint.

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"
        }
    }'

See the API reference for more details.

Sign the approval returned in the response

If you are using an api-key as the recovery signer (admin signer) you can skip the following steps.

Sign the approval message field returned in the response inside 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.

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..."
        }]
    }'

See the API reference for more details.

Introduction

Quickstarts ⚡️

Concepts

Guides

API Reference

EVM

Prerequisites

Signing a Message

Parameters

Returns

Parameters

Returns

Signing Typed Data

Parameters

Returns

Introduction

Quickstarts ⚡️

Concepts

Guides

API Reference

Documentation Index

​Prerequisites

​Signing a Message

​Parameters

​Returns

​Parameters

​Returns

​Signing Typed Data

​Parameters

​Returns

Prerequisites

Signing a Message

Parameters

Returns

Parameters

Returns

Signing Typed Data

Parameters

Returns