---
layout: storage
description: "Storing user data with Blockstack"
permalink: /:collection/:path.html
---
# Hello hub choice tutorial
{:.no_toc}
In this tutorial, you build on the Hello, Blockstack Tutorial. You'll modify the authentication code so that it prompts users who have not yet created a Blockstack identity, to choose a hub URL.
* TOC
{:toc}
{% include note.html content="This tutorial was written on macOS High Sierra 10.13.4. If you use a Windows or Linux system, you can still follow along. However, you will need to \"translate\" appropriately for your operating system. Additionally, this tutorial assumes you are accessing the Blockstack Browser web application via Chrome. The application you build will also work with a local installation and/or with browsers other than Chrome. " %}
## About this tutorial and the prerequisites you need
This tutorial assumes you already set up your environment and tooling as specified in the Hello, Blockstack Tutorial. You should also review that tutorial for basic information about
## Task 1: Generate an initial Blockstack application
In this section, you build an initial React.js application called `hello-hub-choice`.
1. Create the `hello-hub-choice` directory.
```bash
mkdir hello-hub-choice
```
2. Change into your new directory.
```bash
cd hello-hub-choice
```
3. Use Yeoman and the Blockstack application generator to create your initial `hello-hub-choice` application.
```bash
yo blockstack
```
You should see several interactive prompts.
{% raw %}
```bash
$ yo blockstack
...
? Are you ready to build a Blockstack app in React? (Y/n)
```
{% endraw %}
4. Respond to the prompts to populate the initial app.
After the process completes successfully, you see a prompt similar to the following:
{% raw %}
```bash
...
create public/icon-192x192.png
create public/index.html
create public/robots.txt
create public/manifest.json
Im all done. Running npm install for you to install the required dependencies. If this fails, try running the command yourself.
```
{% endraw %}
5. Verify that you have version `18.3.0` of blockstack.js or higher.
```
$ npm ls blockstack
hello-blockstack@0.0.0 /Users/manthony/sampleapps/hello-blockstack
└── blockstack@18.3.0
```
If you don't have the correct version, install it.
```
npm install blockstack@18.3.0
```
Depending on your environment you may have some problems with the `npm` packages. Go ahead and fix these before continuing to the next section.
## Task 2. Start the server and view the application
When you start the server, it will create a Node.js server, start it locally,
and open your browser `http://localhost:5000`. From the root of your new application directory:
1. Start the application server.
```bash
npm run start
```
2. Choose **Allow**.
3. Open your browser to `http://localhost:5000`.
You should see a simple application:
4. Leave your new application running and move onto the next section.
## Task 3: Enable hub selection
By default, the app generator assumes you want to use the default flow `redirectToSignIn()` method. In this section, you replace that method and use the `makeAuthRequest()` method instead. The `makeAuthRequest()` method takes the following parameters:
-
transitPrivateKey(String = generateAndStoreTransitKey())
- A HEX encoded transit private key.
-
redirectURI(String = `${window.location.origin}/`)
- Location to redirect the user to after sign in approval.
-
manifestURI(String = `${window.location.origin}/manifest.json`)
-
Location of this app's manifest file.
-
scopes (Array = DEFAULT_SCOPE)
- The permissions this app is requesting.
-
appDomain(String = window.location.origin)
- The origin of this app.
-
expiresAt(Number = nextHour().getTime())
- The time at which this request is no longer valid.
-
extraParams(Object = {})
- Any extra parameters to pass to the authenticator. Use this to pass options that aren't part of the Blockstack authentication specification, but might be supported by special authenticators.
To replace the default login, do the following:
1. Using your favorite editor, open the `public/app.js` file.
2. Locate the `redirectToSignIn()` method at line 4.
3. Replace `redirectToSignIn()` method with the `blockstack.UserSession.redirectToSignInWithAuthRequest(authRequest)` method.
```javascript
var userSession = new UserSession()
userSession.redirectToSignInWithAuthRequest(authRequest)
```
The `authRequest` is the authentication request generated by `makeAuthRequest()` method.
4. Immediately above the method you just added and below the `event.preventDefault()` method, construct a String `const` for the `authRequest`:
```
const authRequest = userSession.makeAuthRequest(
userSession.generateAndStoreTransitKey(),
'http://localhost:5000/',
'http://localhost:5000/manifest.json',
['store_write', 'publish_data'],
'http://localhost:5000/',
blockstack.nextHour().getTime(), {
solicitGaiaHubUrl: true
} // new options param
);
```
{% include note.html content="If your app is running a different port than 500, enter that port instead. " %}
The extra `solicitGaiaHubUrl` parameter of `true` will cause the Blockstack Browser to prompt new identity creators for a storage hub URL.
5. Save and close the `public/app.js` file.
6. Make sure your app rebuilds cleanly.
## Task 4: Try the new authentication flow
Try your new authentication code.
1. Refresh the client at `http://localhost:5000/`.
2. Click *Sign in with Blockstack*.
The Blockstack Browser prompts you to sign in. I you are _not already authenticated_ with the browser, you should see the following:
If you are already authenticated with an existing ID, you can choose that ID
or **Deny**. Choosing an existing ID, signs you into the Hello Blockstack
application, without offering a hub choice. Instead, choose **Deny**. This
ends the authentication process. Then, reset the Blockstack Browser.
3. Choose **Create new ID**.
The system prompts you to enter a username.
4. Enter a name and press **Check Availability**.
5. Press **Continue** after you find an available name you like.
6. Enter a password and chose **Register ID**.
The system prompts you for a provider.
The default is to user Blockstacks' Gaia hub.
7. Choose **Use a different provider**.
The system prompts you for a URL.
8. Enter a Gaia hub URL.
If you have one of your own enter it here. You can also just enter the Blockstack URL (`https://hub.blockstack.org`).
9. Press **Continue**.
The system takes a moment to check the hub is responsive and establish it in your new identity profile. Then, the system prompts you for an email.
10. Enter an email and press **Next**.
The system creates your user and prompts you to continue to your application.
11. Choose **Go to Hello, Blockstack**.
The system prompts you to allow Hello Blockstack access.
12. Grant the access to the DApp.
You user should be authenticated.
## How to recommend a Gaia hub URL for new users
If you want to create specific sign-up flows for your DApp, you can pass a preset Gaia storage hub URL also. For example, you might
do this if you have a corporate client whose employees would all like to use
your application with a company-run Gaia hub.
To suggest a Gaia hub URL, provide an additional `recommendedGaiaHubUrl` value
alongside the `solicitGaiaHubUrl`, for example:
```javascript
import {
makeAuthRequest,
redirectToSignInWithAuthRequest
} from 'blockstack';
var userSession = new UserSession()
const authRequest = userSession.makeAuthRequest(undefined, undefined, undefined, undefined, undefined, undefined, {
solicitGaiaHubUrl: true,
recommendedGaiaHubUrl: 'https://mygaiahub.com'
});
const authRequest = userSession.makeAuthRequest(
generateAndStoreTransitKey(),
'http://localhost:5000/',
'http://localhost:5000/manifest.json',
['store_write', 'publish_data'],
'http://localhost:5000/',
nextHour().getTime(), {
solicitGaiaHubUrl: true, //new options param
recommendedGaiaHubUrl: 'https://mygaiahub.com' // new options param
}
);
userSession.redirectToSignInWithAuthRequest(authRequest);
```
Passing these parameters changes the storage hub URL prompt to the following:
## Related information
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[`makeAuthRequest()`](https://blockstack.github.io/blockstack.js/#makeauthrequest) method