> ## Documentation Index
> Fetch the complete documentation index at: https://docs.m4psp.com/llms.txt
> Use this file to discover all available pages before exploring further.

# M4 Payment Gateway API (1.0.0)

## Description

Using this API, you can interact with M4 payment platform: accept payments, make payments and perform other operations supported by the platform.

API runs over HTTP(S) protocol and uses JSON format to exchange data.

All API requests must use `UTF-8` encoding and specify the `Content-Type: application/json` header. Each request must be signed, the signature generation process is described below, in the **Request signature** section.

We use the [ISO 8601](https://en.wikipedia.org/wiki/ISO_8601) standard as the date and time formats, if the time zone is not specified, then [UTC+03:00](https://en.wikipedia.org/wiki/Time_zone) is assumed.

## Request signature

### Request signature

Every API request must be signed so that we can identify your account.

The signature is transferred in the request body through the `sign` parameter, for example:

```json theme={null}
{
"shop_id": 1520,
"shop_order_id": "5b0efa8a-153b-4421-abac-2aba4d772a86",
"amount": "6320.91",
"currency": 840,
"payway": "card_invoice_usd",
"description": "My test invoice #1",
"sign": "77a6f7a30876d480d4e771d08cb83800dd5cb874664c77e515ffc052b20293c6"
}
```

> All further request examples do not include the `"sign"` parameter, nevertheless your real requests **must** include it in the request body where required. Signature line is generated according to the following algorithm: all request parameters involved in signature generation are ordered in the alphabetical order of keys, the values are concatenated with a colon (":") and the account secret key is added at the end (without the colon), a sha256 hash is generated from the resulting line and its hex representation is passed in the sign request parameter.

Signature line is generated according to the following algorithm: all request parameters involved in signature generation are ordered in the alphabetical order of keys, the values are concatenated with a colon (":") and the account secret key is added at the end (without the: `sign`), a sha256 hash is generated from the resulting line and its hex representation is passed in the sign request parameter.

### Example of signature generation for a method [invoice/create](/api-reference/invoice-create/invoice-issue):

1. Determining the list of parameters. It looks as follows for the method in consideration:

* shop\_id
* shop\_order\_id
* amount
* currency
* payway

2. Let's sort keys in alphabetical sequence: `"amount", "currency", "payway", "shop_id", "shop_order_id"`
3. The line for generating the SHA256 hash will be as follows: `6320.91:840:card_invoice_usd:1520:5b0efa8a-153b-4421-abac-2aba4d772a86account-secret-key"` Where account-secret-key is the secret identification key for your account. You can request a key from the support service.
4. Let's get a hash expression of the generated line using Python code:

`string\_to\_sign = '6320.91:840:card\_invoice\_usd:1520:5b0efa8a-153b-4421-abac-2aba4d772a86account-secret-key'`

`import hashlib`

`sign = hashlib.sha256(string\_to\_sign.encode()).hexdigest()`

`print(sign) '77a6f7a30876d480d4e771d08cb83800dd5cb874664c77e515ffc052b20293c6'`