> For the complete documentation index, see [llms.txt](https://docs.esignet.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.esignet.io/home/esignet/esignet-authentication/develop/integration/key-binder.md).
# Key Binder Plugin
The Key Binder plugin interface provides a method to bind an individual's ID with a public key. On successful binding, it returns a signed certificate called Wallet User ID which uniquely identifies the user and the wallet.
When a new binding request is received, it is expected that the key binder implementation takes care of overriding previously bound certificates with the newly generated signed certificate for a user.
The individual needs to be authenticated before binding the key. The interface is structured to accept any type of authentication challenge, namely OTP or biometrics.
The bound certificate will then be usable to do token-based authentication like **WLA** (Wallet Local Authentication) from any digital wallet app.
Please [refer here](https://github.com/mosip/esignet/blob/master/esignet-integration-api/src/main/java/io/mosip/esignet/api/spi/KeyBinder.java) for the key binder interface refrence implementation
{% hint style="info" %}
Note**:** For the latest version of the interface please check our code base - [KeyBinder.java](https://github.com/mosip/esignet/blob/master/esignet-integration-api/src/main/java/io/mosip/esignet/api/spi/KeyBinder.java)
{% endhint %}
## Who uses this interface?
The APIs exposed by this interface are used by [Digital Wallets](/home/esignet/general/glossary.md#digital-id-wallet) to perform wallet binding while it is implemented by [Identity Systems](/home/esignet/general/glossary.md#identity-systems).
## How to implement this plugin?
The Key Binder implementation class must be annotated with `ConditionalOnProperty` with `mosip.esignet.integration.key-binder` property.
Below is an example of how our [Mock Identity System](https://github.com/mosip/esignet-mock-services/blob/master/mock-esignet-integration-impl/src/main/java/io/mosip/esignet/mock/integration/service/MockKeyBindingWrapperService.java) has implemented the eSignet KeyBinder plugin.
```java
@ConditionalOnProperty(value = "mosip.esignet.integration.key-binder", havingValue = "mock-keybinder-service")
@Component
@Slf4j
public class MockKeyBindingWrapperService implements KeyBinder {
//Implement keybinder methods
}
```
## Appendix - Key Binding
The **Key Binding** functionality is depicted in the diagram below:
{% hint style="info" %}
Here, the Binding Partner is nothing but the wallet backend service.
{% endhint %}
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