# Add Sign

In this tutorial, we assume you have complete the [Key configuration](https://lianlianpay.gitbook.io/docs/development/signature/signature-key-configuration) part.

We use a sample from [card bin query API](https://lianlianpay.gitbook.io/docs/relevant-api/card-bin-query-api) to show how to do the add sign step. Let's say we have following unhandled data:

```javascript
{
    "card_no": "403392******1234",
    "oid_partner": "201408071000001543",  
    "sign_type": "RSA"
}
```

We will do 2 steps:

1. [Generate signature source](#1.-generate-signature-source)
2. [Encrypt and merge](#2.-encrypt-and-merge)

## 1. Generate signature source

Put all needed the parameters with format `{key}={value}` and connect them with `&` character together, note:

* The signature source need to be ascended in order of the first letter.
* Parameters whose value is `null` should be removed.

```markup
card_no=403392******1234&oid_partner=201408071000001543&sign_type=RSA
```

## 2. Encrypt and merge

Use your private key to encrypt the generated signature source, here we use `Java` as an example:

```java
    /**
     * Encrypt function
     * @param prikeyvalue: Your private key
     * @param sign_str: Generated signature source
     * @return
     */
    public static String sign(String prikeyvalue, String sign_str)
    {
        try
        {
            PKCS8EncodedKeySpec priPKCS8 = new PKCS8EncodedKeySpec(
                    Base64Utils.getBytesBASE64(prikeyvalue));
            KeyFactory keyf = KeyFactory.getInstance("RSA");
            PrivateKey myprikey = keyf.generatePrivate(priPKCS8);
            java.security.Signature signet = java.security.Signature
                    .getInstance("MD5withRSA");
            signet.initSign(myprikey);
            signet.update(sign_str.getBytes("UTF-8"));
            byte[] signed = signet.sign(); 
            return new String(org.apache.commons.codec.binary.Base64.encodeBase64(signed));
        } catch (java.lang.Exception e)
        {
            e.printStackTrace();
        }
        return null;
    }
```

Once we have the generated `Sign`, merged it together with the original data to create a new `json`:

```javascript
{
  "card_no": "403392******1234",
  "oid_partner": "201408071000001543",
  "sign": "nOfov/bBLyl0cBTYR5m8pKcn1X5+OUuiNmCR3QlnDWGoMNmVopdJUYUXlr7xBR2FZ+kJGjHYHqg8K3NTXQPHN5UY4brNhuC8Xv6kDaJ8Pc4XsO4os7VUd53cqew+CX9IzBSkQ9u8tldSTfqNyX1Stp3+zBNwD7IC3JBKKtmHdb4=",
  "sign_type": "RSA"
}
```

That's it, we now have a request body for [card bin query API](https://lianlianpay.gitbook.io/docs/relevant-api/card-bin-query-api).


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://lianlianpay.gitbook.io/docs/development/signature/signature-add-sign.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.