> ## Documentation Index
> Fetch the complete documentation index at: https://circle-devdocs-test-ai-codegen-component.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Quickstart: Integrate with CPN as an OFI

This guide walks you through the steps to request, lock, and fulfill your first
quote using CPN.

## Prerequisites

<Note>
  **Note:** This quickstart uses Circle Wallets to demonstrate how to create and
  execute a payment on CPN. To create and manage a Circle Wallet, you also need
  a Circle Developer account. You don't need to use Circle Wallets (or a Circle
  Developer account) in your production implementation, however. You can bring
  your own wallet provider as long as it meets the
  [requirements for CPN](/cpn/references/wallet-provider-compatibility).
</Note>

Before you begin this quickstart, ensure you have:

* Obtained an API key for CPN from Circle

* Created a [Circle Developer](https://console.circle.com/signin) Account

  * [Registered your entity secret](/wallets/dev-controlled/register-entity-secret)
  * [Created a new wallet set](/wallets/dev-controlled/create-your-first-wallet)
    using the API
  * Created at least one EOA wallet on `EVM-TESTNET` in the wallet set (see the
    link in the previous bullet)
  * Have access to the wallet ID for the EOA wallet
  * Funded the wallet with [testnet USDC](https://faucet.circle.com) and
    [testnet ETH](https://cloud.google.com/application/web3/faucet/ethereum).

* Python installed on your development machine
  * The latest `jwcrypto`, `web3`, `eth_utils`, `hexbytes`, and `eth_abi`
    libraries are installed with the `pip` package manager

* cURL installed on your development machine

* (Optional) a
  [configured webhook notification endpoint](/cpn/howtos/setup-webhook-notifications)

This quickstart provides API requests in cURL format, along with example
responses.

<Note>
  **Note:** The base URL for all API endpoints is
  `https://api-staging.circle.com/v1/cpn` for both sandbox and production
  environments. The API determines if a request is for testnet or mainnet based
  on the key used to authenticate the request.
</Note>

## Part 1: Request a quote

Request quotes for a USDC to MX payment with the SPEI payment method. Request
quotes with the [`/quotes`](/api-reference/cpn/cpn-platform/create-quotes)
endpoint, providing the source currency and destination amount. The endpoint
returns a list of quotes from various BFIs with the rate, expiration time, USDC
settlement window, and unique ID.

```shell Shell theme={null}
curl --request POST \
  --url https://api.circle.com/v1/cpn/quotes \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer ${YOUR_API_KEY}' \
  --header 'Content-Type: application/json' \
  --data '
{
    "paymentMethodType": "SPEI",
    "senderCountry": "US",
    "destinationCountry": "MX",
    "sourceAmount": {
        "currency": "USDC"
    },
    "destinationAmount": {
        "amount": "200",
        "currency": "MXN"
    },
    "blockchain": "ETH-SEPOLIA",
    "senderType": "INDIVIDUAL",
    "recipientType": "INDIVIDUAL"
}
'
```

**Response**

```json JSON theme={null}
{
  "data": [
    {
      "id": "922a06cd-ff1e-4ee4-840e-54006893fd1a",
      "paymentMethodType": "SPEI",
      "blockchain": "ETH-SEPOLIA",
      "senderCountry": "US",
      "destinationCountry": "MX",
      "createDate": "2025-03-28T16:21:47.089081899Z",
      "quoteExpireDate": "2025-03-28T16:22:45.713598Z",
      "cryptoFundsSettlementExpireDate": "2025-03-28T18:21:45.713615Z",
      "sourceAmount": {
        "amount": "10.000000",
        "currency": "USDC"
      },
      "destinationAmount": {
        "amount": "200.23",
        "currency": "MXN"
      },
      "fiatSettlementTime": {
        "min": "1",
        "max": "12",
        "unit": "HOURS"
      },
      "exchangeRate": {
        "rate": "20.040000",
        "pair": "USDC/MXN"
      },
      "fees": {
        "totalAmount": {
          "amount": "0.170000",
          "currency": "USDC"
        },
        "breakdown": [
          {
            "type": "TAX_FEE",
            "amount": {
              "amount": "0.070000",
              "currency": "USDC"
            }
          },
          {
            "type": "BFI_TRANSACTION_FEE",
            "amount": {
              "amount": "0.100000",
              "currency": "USDC"
            }
          }
        ]
      },
      "senderType": "INDIVIDUAL",
      "recipientType": "INDIVIDUAL",
      "certificate": {
        "id": "201c52fc-8866-44cf-a2e2-3ceae098381c",
        "certPem": "LS0t...",
        "domain": "api.circle.com",
        "jwk": {
          "kty": "EC",
          "crv": "P-256",
          "kid": "263521881931753643998528753619816524468853605762",
          "x": "YdjOeAmlNfWV0xIryFAivcp9of21s0c-JhyGEOINV2Y",
          "y": "n621ve_OV_p3jdocxtNkAk4uaKcYR2XWYUu1NMzBei8"
        }
      }
    }
  ]
}
```

## Part 2: Create a payment

Use the API to get the requirements for a payment, accept the quote, and create
a payment.

### 2.1. Get payment requirements

Call the
[`/payments/requirements`](/api-reference/cpn/cpn-platform/get-payment-requirements)
endpoint with the quote ID to get the requirements for a payment. The endpoint
returns an object describing the required fields for the compliance check. The
`optional` field for each parameter defines if the parameter must be included in
the response constructed in the next step.

```shell Shell theme={null}
curl -H "Authorization: Bearer ${YOUR_API_KEY}" \
  -X GET "https://api.circle.com/v1/cpn/payments/requirements?quoteId=${QUOTE_ID}"
```

**Response**

```json JSON theme={null}
{
  "data": {
    "travelRule": [
      {
        "name": "ORIGINATOR_FINANCIAL_INSTITUTION_NAME",
        "type": "TEXT",
        "optional": false
      },
      {
        "name": "ORIGINATOR_FINANCIAL_INSTITUTION_ADDRESS",
        "type": "ADDRESS",
        "optional": false
      },
      {
        "name": "ORIGINATOR_FINANCIAL_INSTITUTION_ID",
        "type": "TEXT",
        "optional": true
      },
      {
        "name": "ORIGINATOR_NAME",
        "type": "TEXT",
        "optional": false
      },
      {
        "name": "ORIGINATOR_ACCOUNT_NUMBER",
        "type": "TEXT",
        "optional": false
      },
      {
        "name": "ORIGINATOR_ADDRESS",
        "type": "ADDRESS",
        "optional": false
      },
      {
        "name": "BENEFICIARY_NAME",
        "type": "TEXT",
        "optional": false
      },
      {
        "name": "BENEFICIARY_ADDRESS",
        "type": "ADDRESS",
        "optional": false
      },
      {
        "name": "ORIGINATOR_DATE_OF_BIRTH",
        "type": "TEXT",
        "optional": true
      },
      {
        "name": "ORIGINATOR_NATIONALITY",
        "type": "TEXT",
        "optional": true
      },
      {
        "name": "ORIGINATOR_NATIONAL_IDENTIFICATION_NUMBER",
        "type": "TEXT",
        "optional": true
      },
      {
        "name": "BENEFICIARY_DATE_OF_BIRTH",
        "type": "TEXT",
        "optional": true
      },
      {
        "name": "BENEFICIARY_NATIONALITY",
        "type": "TEXT",
        "optional": true
      },
      {
        "name": "BENEFICIARY_NATIONAL_IDENTIFICATION_NUMBER",
        "type": "TEXT",
        "optional": false
      },
      {
        "name": "BENEFICIARY_PHONE_NUMBER",
        "type": "TEXT",
        "optional": true
      },
      {
        "name": "BENEFICIARY_EMAIL",
        "type": "TEXT",
        "optional": true
      }
    ],
    "beneficiaryAccount": [
      {
        "name": "CLABE",
        "type": "TEXT",
        "optional": false
      }
    ]
  }
}
```

### 2.2. Encrypt the required fields

Construct a JSON object with the information requested in the previous step. For
each schema, the properties that you must include are outlined by the `optional`
field. Encrypt the object with the `jwk` certificate provided in the quote
response.

The correct format for travel rule data and beneficiary account data is a JSON
array of objects where each object contains two properties: `name` and `value`.
You can review an example of each field in the
[encryption how-to](https://learn.circle.com/cpn/howtos/encrypt-travel-rule-beneficiary-data#step-4-prepare-the-payload).

Create a file called `cpn_encryption.py` and put the following code in it,
replacing the `requirements_response_json` parameter with the contents of the
response from the previous step, and the `certificate_json` parameter with the
`jwk` from the quote response. When you run the script, it outputs the encrypted
beneficiary and travel rule data to the console.

```python Python theme={null}
"""
CPN Requirements V1 Encryption Quickstart

This script demonstrates how to:
1. Parse V1 Requirements response
2. Generate realistic test data matching the fields
3. Encrypt data using JWE for CPN API integration

Usage:
1. Replace certificate_json with your JWK from Quote response
2. Replace requirements_response_json with your Requirements response
3. Run the script to get encrypted data for creating payment API requests
"""

import json
import os
import base64
import random
from typing import Dict, Any, Optional, List
from jwcrypto import jwk, jwe

# ========================================
# Test Data Lists for Realistic Generation
# ========================================

FIRST_NAMES = [
    "James", "John", "Robert", "Michael", "William", "David", "Joseph", "Thomas",
    "Charles", "Mary", "Patricia", "Jennifer", "Linda", "Elizabeth", "Barbara",
    "Susan", "Jessica", "Sarah", "Karen", "Nancy"
]

LAST_NAMES = [
    "Smith", "Johnson", "Williams", "Brown", "Jones", "Garcia", "Miller", "Davis",
    "Rodriguez", "Martinez", "Hernandez", "Lopez", "Gonzalez", "Wilson",
    "Anderson", "Thomas", "Taylor", "Moore", "Jackson", "Martin"
]

STREET_TYPES = ["St", "Ave", "Blvd", "Rd", "Ln", "Dr", "Way", "Circle", "Court"]
STREET_NAMES = [
    "Main", "Oak", "Maple", "Cedar", "Pine", "Elm", "Washington", "Lake", "Hill",
    "River", "Valley", "Park", "Spring", "Market", "Church", "Bridge", "Highland"
]

CITIES = [
    "New York", "Los Angeles", "Chicago", "Houston", "Phoenix", "Philadelphia",
    "San Antonio", "San Diego", "Dallas", "San Jose", "Austin", "Jacksonville",
    "Fort Worth", "Columbus", "San Francisco", "Charlotte", "Indianapolis",
    "Seattle", "Denver", "Washington"
]

# ========================================
# Helper Functions
# ========================================

def generate_random_name() -> str:
    """Generate a random realistic name."""
    return f"{random.choice(FIRST_NAMES)} {random.choice(LAST_NAMES)}"

def generate_random_address() -> Dict[str, str]:
    """Generate a random realistic address."""
    street_number = str(random.randint(1, 9999))
    street_name = random.choice(STREET_NAMES)
    street_type = random.choice(STREET_TYPES)
    return {
        "street": f"{street_number} {street_name} {street_type}",
        "city": random.choice(CITIES),
        "country": "US",
        "postalCode": f"{random.randint(10000, 99999)}"
    }

def random_string(length: int = 12) -> str:
    """Generate a random string of given length."""
    return base64.b64encode(os.urandom(length)).decode()[:length]

def get_originator_name(case: Optional[str] = None) -> str:
    """Get the originator name based on test case."""
    if case == 'rfi-failed':
        return "Failed"
    return "Alice Johnson"  # Default for success case

# ========================================
# Core Data Generation
# ========================================

def generate_group_data(fields: List[Dict[str, Any]], originator_name: str) -> List[Dict[str, Any]]:
    """
    Generate test data matching Requirements fields as an array of {name, value}.

    Args:
        fields: List of field objects from Requirements
        originator_name: Name to use for originator fields

    Returns:
        List[{"name": str, "value": Any}] for required fields
    """
    items: List[Dict[str, Any]] = []

    for field in fields:
        name = field["name"]
        field_type = field["type"].upper()
        optional = field.get("optional", False)

        if optional:
            continue  # only include required fields

        # Address fields
        if field_type == "ADDRESS" or "ADDRESS" in name.upper():
            items.append({"name": name, "value": generate_random_address()})

        # Text fields
        elif field_type == "TEXT":
            if "NAME" in name.upper():
                if "ORIGINATOR" in name.upper():
                    items.append({"name": name, "value": originator_name})
                else:
                    items.append({"name": name, "value": generate_random_name()})
            elif "CLABE" in name.upper():
                items.append({"name": name, "value": ''.join(str(random.randint(0, 9)) for _ in range(18))})
            elif "ACCOUNT" in name.upper():
                items.append({"name": name, "value": ''.join(str(random.randint(0, 9)) for _ in range(12))})
            elif "DATE" in name.upper() or "BIRTH" in name.upper():
                year = random.randint(1970, 2000)
                month = random.randint(1, 12)
                day = random.randint(1, 28)
                items.append({"name": name, "value": f"{year:04d}-{month:02d}-{day:02d}"})
            elif "EMAIL" in name.upper():
                items.append({"name": name, "value": f"{random_string(8)}@example.com"})
            else:
                items.append({"name": name, "value": random_string(12)})

    return items

# ========================================
# Encryption
# ========================================

def encrypt_data(data: Any, jwk_data: Dict[str, Any]) -> str:
    """
    Encrypt data using JWE with provided JWK.

    Args:
        data: Data to encrypt (will be JSON serialized)
        jwk_data: JWK from certificate

    Returns:
        Encrypted JWE string
    """
    recipient_key = jwk.JWK(**jwk_data)
    jwe_obj = jwe.JWE(
        plaintext=json.dumps(data).encode(),
        protected=json.dumps({"alg": "ECDH-ES+A128KW", "enc": "A128GCM"})
    )
    jwe_obj.add_recipient(recipient_key)
    return jwe_obj.serialize(True)

# ========================================
# Configuration - Replace with your data
# ========================================

# Certificate JWK - copy from Quote response
# e.g. {"kty":"EC","crv":"P-256","kid":"263...5762","x":"Ydj...2Y","y":"n621...i8"}
certificate_json = '''certificate_json'''

# Requirements response - copy from Requirements API
# e.g. {"data": {"travelRule": [...], "beneficiaryAccount": [...]}}
requirements_response_json = '''requirements_response_json'''

# ========================================
# Main Execution
# ========================================

if __name__ == "__main__":
    # Parse configuration
    certificate = json.loads(certificate_json)
    required_fields = json.loads(requirements_response_json)

    # Extract field arrays
    travel_rule_fields = required_fields['data']['travelRule']
    beneficiary_account_fields = required_fields['data']['beneficiaryAccount']

    # Generate test data (array of {name, value})
    test_data = {
        "travelRuleData": generate_group_data(travel_rule_fields, get_originator_name()),
        "beneficiaryAccountData": generate_group_data(beneficiary_account_fields, get_originator_name())
    }

    # Create encrypted data (encrypt arrays directly)
    travel_rule_encrypted = encrypt_data(test_data["travelRuleData"], certificate)
    beneficiary_account_encrypted = encrypt_data(test_data["beneficiaryAccountData"], certificate)

    # Output encrypted data ready for API
    print(f"Travel Rule encryptedData: {travel_rule_encrypted}\n")
    print(f"Beneficiary Account encryptedData: {beneficiary_account_encrypted}")
```

### 2.3. Create a payment

After the quote is accepted, create a payment by calling the
[`/payments`](/api-reference/cpn/cpn-platform/create-payment) endpoint. You need
to provide the quote ID and encrypted sender and receiver information. The
endpoint returns a unique payment ID and the initial status of the payment.

<Note>
  **Note:** You must create the payment before the quote expires, otherwise
  you'll need to request a new quote.
</Note>

```shell Shell theme={null}
curl --request POST \
  --url https://api.circle.com/v1/cpn/payments \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer ${YOUR_API_KEY}' \
  --header 'Content-type: application/json' \
  --data '
{
  "idempotencyKey" : "${randomUUID}",
  "quoteId" : "${cpn_ofi_quote_id}",
  "beneficiaryAccountData" : "${encrypted_beneficiary_data}",
  "travelRuleData" : "${encrypted_travel_rule_data}",
  "senderAddress" : "${YOUR_WALLET_ADDRESS}",
  "blockchain" : "ETH-SEPOLIA",
  "reasonForPayment" : "PMT001",
  "customerRefId" : "123c7442-e843-4afa-bfad-35f50636d35b",
  "refCode" : "7b479c5a-3684-4423-9fc6-f7c890c0e816",
  "useCase" : "B2B"
}
'
```

**Response**

```json JSON theme={null}
{
  "data": {
    "id": "07dbe320-6bcb-475b-8d21-17b57263cd3e",
    "quoteId": "922a06cd-ff1e-4ee4-840e-54006893fd1a",
    "blockchain": "ETH-SEPOLIA",
    "paymentMethodType": "SPEI",
    "sourceAmount": {
      "amount": "10.000000",
      "currency": "USDC"
    },
    "destinationAmount": {
      "amount": "200.23",
      "currency": "MXN"
    },
    "status": "CRYPTO_FUNDS_PENDING",
    "refCode": "7b479c5a-3684-4423-9fc6-f7c890c0e816",
    "customerRefId": "123c7442-e843-4afa-bfad-35f50636d35b",
    "useCase": "B2B_INVOICE_PAYMENT",
    "expireDate": "2025-03-31T20:59:21.211547Z",
    "createDate": "2025-03-31T18:59:30.183044Z",
    "fees": {
      "totalAmount": {
        "amount": "0.170000",
        "currency": "USDC"
      },
      "breakdown": [
        {
          "type": "TAX_FEE",
          "amount": {
            "amount": "0.070000",
            "currency": "USDC"
          }
        },
        {
          "type": "BFI_TRANSACTION_FEE",
          "amount": {
            "amount": "0.100000",
            "currency": "USDC"
          }
        }
      ]
    },
    "fiatSettlementTime": {
      "min": "1",
      "max": "12",
      "unit": "HOURS"
    },
    "rfis": [],
    "onChainTransactions": []
  }
}
```

## Part 3: Create a transaction

Use the API to create a blockchain transaction to transfer USDC. Sign the
transaction locally, and use the API to broadcast it to the blockchain.

<Note>
  **Note:** This quickstart uses Circle Wallets to act as the originator wallet
  for the onchain payment. This section uses the wallet ID from the EOA wallet
  mentioned in the [prerequisites](#prerequisites) section.
</Note>

### 3.1. Initiate the onchain transaction

Initiate the onchain funds transfer by calling the
[`/payments/{paymentId}/transactions`](/api-reference/cpn/cpn-platform/create-transaction)
endpoint with the payment ID from the previous step, and other
transaction-related parameters. The endpoint returns an unsigned onchain
transaction object and a transaction ID.

```shell Shell theme={null}
curl --request POST \
  --url https://api.circle.com/v1/cpn/payments/:paymentId/transactions \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer ${YOUR_API_KEY}' \
  --header 'Content-Type: application/json' \
  --data '
{
  "idempotencyKey" : "${RANDOM_UUID}",
  "senderAccountType": "EOA",
}
'
```

**Response**

```json JSON theme={null}
{
  "data": {
    "id": "8e0cc03f-799c-4971-ba41-6b790b4f9548",
    "status": "CREATED",
    "paymentId": "0a6973af-3089-4265-812b-0f68a426a4d8",
    "expireDate": "2025-04-01T17:28:25.198159Z",
    "senderAddress": "0x140f52a9D27764a51032ebDff7E6352D1640cbfd",
    "senderAccountType": "EOA",
    "blockchain": "ETH-SEPOLIA",
    "amount": {
      "amount": "10.000000",
      "currency": "USDC"
    },
    "destinationAddress": "0x6e87cdf0b9d2d96232f5c605526cb0e89db7387a",
    "estimatedFee": {
      "type": "EIP1559",
      "payload": {
        "gasLimit": "150000",
        "maxFeePerGas": "4829089726",
        "maxPriorityFeePerGas": "2000000000"
      }
    },
    "messageType": "EIP3009",
    "messageToBeSigned": {
      "domain": {
        "chainId": "11155111",
        "name": "USDC",
        "verifyingContract": "0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238",
        "version": "2"
      },
      "message": {
        "from": "0x140f52a9D27764a51032ebDff7E6352D1640cbfd",
        "nonce": "0x75cc053bfcdedd359bfdaaa560fc0c7d3899097dcf6396e65b029df3b1e05a0e",
        "to": "0x6e87cdf0b9d2d96232f5c605526cb0e89db7387a",
        "validAfter": "1743519573",
        "validBefore": "1743527605",
        "value": "10000000"
      },
      "primaryType": "TransferWithAuthorization",
      "types": {
        "EIP712Domain": [
          {
            "name": "name",
            "type": "string"
          },
          {
            "name": "version",
            "type": "string"
          },
          {
            "name": "chainId",
            "type": "uint256"
          },
          {
            "name": "verifyingContract",
            "type": "address"
          }
        ],
        "TransferWithAuthorization": [
          {
            "name": "from",
            "type": "address"
          },
          {
            "name": "to",
            "type": "address"
          },
          {
            "name": "value",
            "type": "uint256"
          },
          {
            "name": "validAfter",
            "type": "uint256"
          },
          {
            "name": "validBefore",
            "type": "uint256"
          },
          {
            "name": "nonce",
            "type": "bytes32"
          }
        ]
      }
    }
  }
}
```

### 3.2. Sign the call data

Using the
[`/sign/typedData`](/api-reference/wallets/developer-controlled-wallets/sign-typed-data)
endpoint, input the `messageToBeSigned` object from the previous step along with
your entity secret and wallet ID. The transaction parameter should be
[stringified](https://jsonformatter.org/json-stringify-online) from the
`messageToBeSigned` field from the transaction response.

```shell Shell theme={null}
curl --request POST \
  --url https://api.circle.com/v1/w3s/developer/sign/typedData \
  --header 'Accept: application/json' \
  --header 'authorization: Bearer ${YOUR_API_KEY}' \
  --header 'Content-Type: application/json' \
  --data '
{
  "entitySecretCiphertext": "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",
  "data": "{\"domain\":{\"chainId\":\"11155111\",\"name\":\"USDC\",\"verifyingContract\":\"0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238\",\"version\":\"2\"},\"message\":{\"from\":\"0x39fd73b03a01c6230b5e0d946e1960d79db44fd8\",\"nonce\":\"0x854f1f66cb7cb0e266e17a3715c24c8dae1eb540c4eb00a7a1b39f4bfa9bcf09\",\"to\":\"0x6734b39043f1029f8d5f1b6948d5417b75a72cf8\",\"validAfter\":\"1743522751\",\"validBefore\":\"1743530842\",\"value\":\"10000000\"},\"primaryType\":\"TransferWithAuthorization\",\"types\":{\"EIP712Domain\":[{\"name\":\"name\",\"type\":\"string\"},{\"name\":\"version\",\"type\":\"string\"},{\"name\":\"chainId\",\"type\":\"uint256\"},{\"name\":\"verifyingContract\",\"type\":\"address\"}],\"TransferWithAuthorization\":[{\"name\":\"from\",\"type\":\"address\"},{\"name\":\"to\",\"type\":\"address\"},{\"name\":\"value\",\"type\":\"uint256\"},{\"name\":\"validAfter\",\"type\":\"uint256\"},{\"name\":\"validBefore\",\"type\":\"uint256\"},{\"name\":\"nonce\",\"type\":\"bytes32\"}]}}",
  "walletId": "${YOUR_CIRCLE_WALLET_ID}"
}
'
```

**Response**

```json JSON theme={null}
{
  "signature": "0x905d70de3f1d9e86b982f6aee2755807fcd50a11cd9035bf47845c856be920fc3b7af8d06bf953bfdecdcea4cc9250aeaeb178b50116774d6bfab37bcc3757621c"
}
```

Create a file called `cpn_signature.py` and add the following code to it,
replacing `circle_signature` with the signature returned from the endpoint, and
replacing the message object values with the corresponding values from the
response in
[step 3.1](/cpn/quickstarts/integrate-with-cpn-ofi#31-initiate-the-onchain-transaction).

```python Python theme={null}
from web3 import Web3
from eth_utils import keccak, to_hex
from hexbytes import HexBytes
from eth_abi import encode

def get_function_selector(signature: str) -> str:
    """Return 4-byte function selector from signature."""
    hash_bytes = keccak(text=signature)
    return to_hex(hash_bytes[:4])

def encode_transfer_with_authorization(
    from_address: str,
    to_address: str,
    value: int,
    valid_after: int,
    valid_before: int,
    nonce: str,
    v: int,
    r: str,
    s: str
) -> str:
    """Encode callData for transferWithAuthorization (EIP-3009 USDC)."""
    types = [
        "address", "address", "uint256", "uint256", "uint256",
        "bytes32", "uint8", "bytes32", "bytes32"
    ]
    args = [
        Web3.to_checksum_address(from_address),
        Web3.to_checksum_address(to_address),
        value,
        valid_after,
        valid_before,
        HexBytes(nonce),
        v,
        HexBytes(r),
        HexBytes(s)
    ]
    encoded_args = encode(types, args)
    selector = get_function_selector(f"transferWithAuthorization({','.join(types)})")
    return selector + encoded_args.hex()

# === INPUT DATA ===

circle_signature = your_signature
message = {
    "from": your_from_address,
    "to": your_to_address,
    "value": 10_000_000,  # 10 USDC (6 decimals)
    "validAfter": your_valid_after,
    "validBefore": your_valid_before,
    "nonce": your_nonce
}

# === SPLIT SIGNATURE ===

sig_bytes = Web3.to_bytes(hexstr=circle_signature)
r = Web3.to_hex(sig_bytes[0:32])
s = Web3.to_hex(sig_bytes[32:64])
v = sig_bytes[64]
if v < 27:
    v += 27  # Normalize v for Ethereum

# === ENCODE CALL DATA ===

call_data = encode_transfer_with_authorization(
    from_address=message["from"],
    to_address=message["to"],
    value=message["value"],
    valid_after=message["validAfter"],
    valid_before=message["validBefore"],
    nonce=message["nonce"],
    v=v,
    r=r,
    s=s
)

print(f"✅ Final Call Data:\n{call_data}")
```

When run, the script outputs the final call data.

### 3.3. Sign the transaction

In the previous step, you signed the call data to authorize the transaction.
Next, you must create and sign the raw transaction using the
[`/sign-transaction`](/api-reference/wallets/developer-controlled-wallets/sign-transaction)
endpoint. Include the call data from the script as the `data` field and the
wallet ID from your Circle Wallet.

The raw transaction to be signed can be composed like the following example:

```json JSON theme={null}
{
  "nonce": 1,                                          // The nonce of the sender address, obtained via eth_getTransactionCount RPC call
  "to": "0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238",  // The target contract address, in this case, the USDC contract address
  "gas": "150000",                                     // The gas limit for the transaction, from `data.estimatedFee.payload.gasLimit` in the step 3.1 response.
  "maxFeePerGas": "70000000000",                       // The max fee per gas, from `data.estimatedFee.payload.maxFeePerGas` in the step 3.1 response.
  "maxPriorityFeePerGas": "3000000000",                // The max priority fee per gas, from `data.estimatedFee.payload.maxPriorityFeePerGas` in the step 3.1 response.
  "chainId": 11155111,                                 // The chain ID, for Ethereum Sepolia testnet, the chain ID is 11155111
  // The call data, obtained from the script in step 3.2
  "data": "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"
}
```

Use the following endpoint to sign the transaction:

```shell Shell theme={null}
curl --request POST \
  --url https://api.circle.com/v1/w3s/developer/sign/transaction \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer ${YOUR_API_KEY}' \
  --header 'Content-Type: application/json' \
  --data '
{
  "entitySecretCiphertext": "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",
  "transaction": "{\"nonce\":1,\"to\":\"0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238\",\"gas\":\"150000\",\"maxFeePerGas\":\"70000000000\",\"maxPriorityFeePerGas\":\"3000000000\",\"chainId\":11155111,\"data\":\"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\"}",
  "walletId": "${YOUR_CIRCLE_WALLET_ID}"
}
'
```

**Response**

```json JSON theme={null}
{
  "signature": "0xe59d32312a920b6c63ad4c7344bb76d8e7cae2615f79f707649e325abea00a247cddec90138bb6790e68e01998fdf77efc9496a91b3b4b42e59fd0e8ad89d0bc00",
  "signedTransaction": "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",
  "txHash": "0xc1d5963f87e4a9035eae4e31fe7842a8bc1cd0ebf941d541c0b7ff37b4d1f5df"
}
```

### 3.4. Submit the signed transaction

Use the
[`/payments/{paymentId}/transactions/{transactionId}/submit`](/api-reference/cpn/cpn-platform/submit-transaction)
endpoint to submit the transaction to be broadcast to the appropriate
blockchain. You should use the signed transaction and `transactionId` from the
previous steps to populate the endpoint call.

```shell Shell theme={null}
curl --request POST \
  --url https://api.circle.com/v1/cpn/payments/:paymentId/transactions/:transactionId/submit \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer ${YOUR_API_KEY}' \
  --header 'Content-type: application/json' \
  --data '
{
  "signedTransaction": "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"
}
'
```

**Response**

```json JSON theme={null}
{
  "data": {
    "id": "1f3ccc13-69e3-4811-9648-755bc9aa26f4",
    "status": "PENDING",
    "paymentId": "fed8687a-d911-3682-a6f2-b2474a1016ba",
    "expireDate": "2025-04-25T19:54:46.230217Z",
    "senderAddress": "0x39fd73b03a01c6230b5e0d946e1960d79db44fd8",
    "senderAccountType": "EOA",
    "blockchain": "ETH-SEPOLIA",
    "amount": {
      "amount": "10.000000",
      "currency": "USDC"
    },
    "destinationAddress": "0x3eebc158f254838e2f6275b892e6a0621e3ea321",
    "estimatedFee": {
      "type": "EIP1559",
      "payload": {
        "gasLimit": "150000",
        "maxFeePerGas": "27514930294",
        "maxPriorityFeePerGas": "2000000000"
      }
    },
    "messageType": "EIP3009",
    "messageToBeSigned": {
      "domain": {
        "chainId": "11155111",
        "name": "USDC",
        "verifyingContract": "0x1c7D4B196Cb0C7B01d743Fbc6116a902379C7238",
        "version": "2"
      },
      "message": {
        "from": "0x39fd73b03a01c6230b5e0d946e1960d79db44fd8",
        "nonce": "0x3a30a084fe9ef623cf95ea778067b98b69accf602b8f240f55073339f4c2f2b2",
        "to": "0x3eebc158f254838e2f6275b892e6a0621e3ea321",
        "validAfter": "1745603040",
        "validBefore": "1745610886",
        "value": "10000000"
      },
      "primaryType": "TransferWithAuthorization",
      "types": {
        "EIP712Domain": [
          {
            "name": "name",
            "type": "string"
          },
          {
            "name": "version",
            "type": "string"
          },
          {
            "name": "chainId",
            "type": "uint256"
          },
          {
            "name": "verifyingContract",
            "type": "address"
          }
        ],
        "TransferWithAuthorization": [
          {
            "name": "from",
            "type": "address"
          },
          {
            "name": "to",
            "type": "address"
          },
          {
            "name": "value",
            "type": "uint256"
          },
          {
            "name": "validAfter",
            "type": "uint256"
          },
          {
            "name": "validBefore",
            "type": "uint256"
          },
          {
            "name": "nonce",
            "type": "bytes32"
          }
        ]
      }
    },
    "signedTransaction": "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",
    "transactionHash": "0xc1d5963f87e4a9035eae4e31fe7842a8bc1cd0ebf941d541c0b7ff37b4d1f5df"
  }
}
```

Once the onchain transaction is confirmed by the BFI, the BFI initiates a fiat
payout to the recipient. As the fiat payout progresses, the OFI is notified by
[webhook notifications](/cpn/howtos/setup-webhook-notifications).