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Backing up a wallet
This guide will walk you through how backups of a user's wallet are set up with Portal.
MPC backups allow your users to recover their MPC wallets in the event that their device is lost, stolen, or is bricked.
At the time of recovery, these two backups are used together to generate new shares to be stored on-device, allowing the user to migrate their wallet with a new device.
Storing a user MPC backup is done by storing an encryption key with the user's cloud storage provider and the encrypted share within your infrastructure.
In order to support user MPC backups, three main dependencies must be met:
- 1.You must have cloud storage configured for storing the user's share of the MPC backup
- 2.Your server must be able to store the encrypted share
- 3.Your mobile app must send the encrypted share to your server for storage
With our kotlin implementation, we support Google Drive.
On your server, create an endpoint to accept the encrypted share and store it.
server.js
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/*
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* This endpoint can be defined by you however you want
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*/
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app.post('/portal/clients/:clientId/backup', async (req, res) => {
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const { clientId } = req.params
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const { backupShare } = req.body
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// Example db function updating a "users" table with the backupShare
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await db.users.update({
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where: {
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clientId,
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},
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data: {
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backupShare,
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},
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})
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res.status(200).send()
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})
In order to add support for user MPC backups to your mobile app, you must perform two steps:
- 1.Generate an encrypted client backup share using
portal.mpc.backup
. - 2.Send the resulting backup share to your API and store it.
- 3.Call
portal.api.storedClientBackupShare
to notify Portal that the encrypted client backup share was saved successfully. (Alternatively you can make an HTTP request to our API directly.)
In the example below, we back up a wallet with a
Backup Wallet
button that utilizes Google Drive storage:package io.portal.android.app
// Imports...
class MainActivity : AppCompatActivity() {
lateinit var portal: Portal
lateinit var backupButton: Button
// Your API instance.
private val exchangeApi: Api = Api()
// The user from your API instance.
lateinit var user: User
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
backupButton = findViewById(R.id.backupButton)
backupButton.setOnClickListener { handleBackup() }
}
override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
super.onActivityResult(requestCode, resultCode, data)
if (portal.backup.drive.auth.onActivityResult != null) {
portal.backup.drive.auth.onActivityResult!!(requestCode, resultCode, data)
}
}
private fun handleBackup() {
CoroutineScope(Dispatchers.IO).launch {
try {
// Get an encryped client backup share.
val backupShare = portal.mpc.backup() { status ->
// Do something with the status, such as update a progress bar
// or log the progress
Log.println(Log.INFO, "[PortalEx]", "Backup status: ${status.status} is done: ${status.done}")
}
// Send the backup share to your API and store it.
exchangeApi.storeCipherText(user.id, backupShare)
// ✅ Notify Portal that the backup share was stored! 🙌
portal.api.storedClientBackupShare(true)
} catch (err: Throwable) {
// ❌ Notify Portal that the backup share was not stored.
portal.api.storedClientBackupShare(false)
}
}
}
}
ReadingShare("Reading share")
GeneratingShare("Generating share")
ParsingShare("Parsing share")
EncryptingShare("Encrypting share")
StoringShare("Storing share")
Done("Done")
Storing a custodian MPC backup is done by Portal generating a custodian backup share and sending the share – via
webhook
– to be stored within your infrastructure.In order to support custodian MPC backups, two main dependencies must be met:
- 1.Register a
webhooks_root
with Portal - 2.Implement the
/{webhooks_root}/backup
route in your server to store your backup share
Portal will send the custodian MPC backup share to
/{webhooks_root}/backup
via a POST
request. The body of this POST
request will contain two fields:clientId
- The PortalclientId
for the usershare
- aJSON.stringified
version of the backup share
server.js
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import express from 'express'
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const app = express()
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app.post('/webhook/backup', async (req, res) => {
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// Destructure the provided fields from the request body
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const {
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clientId, // The Portal clientId for the user
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share, // a JSON.strinfigied version of the backup share
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} = req.body
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// TODO: Store the backup share within your infrastructure
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res.status(200).send()
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})
When Portal makes a request to your
/backup
webhook, another immediate request is made to /backup/fetch
in order to validate the backup share was stored successfully.Now that you've successfully implemented MPC backups, your app can support MPC recovery. In the next section, we will walk through the recovery process.
Last modified 4mo ago