# API Co-Signer

## Why do we need API Co-Signer?

API Co-Signer automates MPC Sign. You need to deploy the API Co-Signer on your server and call Safeheron API. Then, API Co-Signer can automatically have 3 parties perform MPC Sign.

Remember, you are the only owner of your server that Safeheron cannot and won't intervene.

## What can API Co-Signer do?

1. Send transaction requests via API to Safeheron
2. Safeheron generates a to-sign transaction list
3. Co-Signer on your end will regularly call Safeheron API to get the to-sign list
4. Co-Signer on your end, with the to-sign list, executes the callback for the authorization  interface of your business system
5. Your business system returns the authorization result
6. Your Co-Signer call Safeheron API and submit the approval result
7. Safeheron reviews the approval result and initiates MPC Sign
8. Your Co-Signer will receive the message on MPC Sign and identify the authorization is approved. And then, the 3 parties will perform MPC Sign.

<figure><img src="https://content.gitbook.com/content/RN8kRfl2uPxOwStzznzu/blobs/HpSWS8Oj4G4T6qpVsbGm/%E5%AE%A2%E6%88%B7%E7%AD%BE%E5%90%8D%E6%9C%BA%E6%B5%81%E7%A8%8B(%E8%8B%B1).jpg" alt=""><figcaption></figcaption></figure>

{% hint style="success" %}
🪄 <mark style="color:green;">**Tips**</mark>: How to call API please refer to [**API Co-Signer**](https://docs.safeheron.com/api/en.html#API%20Co-Signer).
{% endhint %}