# How to generate a JSON Web Token (JWT) for the signature generation API endpoint
## Overview
In order to pass the identity of the merchant to the 2Checkout Signature Generation API endpoint, you need to generate a valid JSON Web Token (JWT). This is an Internet standard for creating JSON-based access tokens that assert some number of claims.
The website allows you to decode, verify, and generate JSON Web Tokens.
{% hint style="info" icon="lightbulb" %}
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{% endhint %}
{% hint style="warning" %}
JWTs are credentials, which can grant access to resources. Be careful where you paste them!
{% endhint %}
## Generate a merchant JWT
To generate a merchant JWT, follow the steps below:
1. Before generating a JWT, you need to copy the Buy-link Secret Word from your Merchant Control Panel. Log in to your Control Panel and navigate to *Integrations > Webhooks & API >* [*Secret word*](https://secure.2checkout.com/cpanel/webhooks_api.php) *section*.
2. Copy the string from the Buy-link Secret Word field to the clipboard.
3. Navigate to the [https://jwt.io](https://jwt.io/) website and start generating the JWT token.
* In the **Debugger** section, you need to input data into the sections highlighted in this image.
* The data in the **HEADER** section identifies which algorithm and token type are used to generate the signature. For your JWT token, use **HMAC-SHA-512 (HS512)** and token type **JWT**:
* alg: HS512 (string, required) - encryption algorithm;
* typ: JWT (string, required) - token type;
```java
{
"alg" : "HS512",
"typ" : "JWT"
}
```
* The **PAYLOAD** section contains a set of claims. The JWT specification defines seven Registered Claim Names which are the standard fields commonly included in tokens. For your JWT, use the following claims:
* sub: MERCH\_CODE (string, required) - subject, the merchant code whom the token refers;
* iat: 1580915730 (string, required) - issued at, must be current timestamp since the UNIX epoch;
* exp: 1580915730 (string, optional) - expiration time, must be in UNIX timestamp format from future.\
\
If the expiration time (exp) is not provided, the JWT token expiration time will be calculated from **iat + 30 minutes**.
All the other fields/claims will be ignored.
```java
{
"sub": "MERCH_CODE",
"iat": 1580912768,
"exp": 1580916205
}
```
* In the **VERIFY SIGNATURE** section, you calculate the signature. This is calculated by encoding the **header** and **payload** using **Base64url** encoding and concatenating the two values with a period separator. Then run the resulting string through the cryptographic algorithm specified in the header, which in this case is **HMAC-SHA512**.
* For your JWT token, replace the **\** from the example below with your **Buy-link Secret Word** from step 1.
```java
HMACSHA512(
base64UrlEncode(header) + "." +
base64UrlEncode(payload),
)
```
* You will get the JWT token:
```java
eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJz...z0ZY6L6T1GvlOHiptgOQ
```
4. Use this JWT token in the future to pass your identity as a merchant to the 2Checkout Signature Generation API endpoint.
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