# Integrate an existing project using VATs with Unity Authentication

> Integrate Unity Authentication to an existing Vivox project that's already using Vivox Access Token.

If you already have a Vivox integration that's using VATs for players to join channels and interact with Vivox, you can use this guide
to integrate with [UAS](/authentication.md) to access the full suite of services Unity provides.

You will have to make some changes to the player sign-in flow and the VAT creation flow.

Overall, the two flows will work like this:

![A flow diagram showing the player sign in process between the game client, game back end, and Unity Authentication services. The second flow shows the token process of requesting a VAT from the game back end, token validation done by UAS and being sent back to the game back end before being returned to the game client.](/api/media?file=/vivox-unity/media/images/sign-in-with-vivox-access-token.png)

## Sign In

1. Register all users with the UAS [custom ID provider](/authentication/platform-signin/custom-id.md) on sign-in and retrieve `accessToken` and `sessionTokens` for players.
2. Set up the AuthenticationService in the client using the `accessToken` and `sessionToken`

> **Important:**
>
> You might not need to use VATs at all. VATs are only needed if you have custom logic in your backend to determine if a player is allowed to access a specific channel.
> If this is not the case, you can simply remove the VAT generation flow and let the Unity Authentication SDK handle it.
> Simply use the default initialization for Vivox: `await VivoxService.Instance.InitializeAsync();` and skip the Creating VATs step.

## Creating VATs

1. The Vivox SDK will request a VAT from the backend whenever one is needed using a custom token provider implementation.
2. Add the `accessToken` to the request to the backend when requesting VATs within the `GetTokenAsync` method.
3. Validate and extract the needed information from the token in the backend and create the Vivox Access Token to send it back to the client.

## Steps

Follow these tutorials to update your sign-in and VAT creation flows.

### 1. Update sign-In flow

To set up the custom ID sign-in, follow the steps in [Sign-in with Custom IDs](../../unity/developer-guide/vivox-unity-sdk-basics/sign-in-with-custom-id).

### 2. Update VAT creation flow

To adapt your VAT creation flow to integrate with UAS, follow the steps in [Using Vivox Access Tokens together with UAS](../vivox-unity-sdk-basics/using-vivox-access-tokens-together-with-uas).

With all of this done, you are now ready to use any of the [Unity Gaming Services](/services.md), including the [Vivox Moderation Platform](/safe-text/overview.md).