Guide for adding AOPP support to a wallet

The app needs to register itself as an AOPP URI handler in the OS.

aopp:?v=0&msg=hello&asset=btc&format=p2wpkh&callback=https://api.testing.21analytics.xyz/proofs/vasp-chosen-token

https://developer.android.com/guide/topics/manifest/intent-filter-element

See this example.

See this example.

https://celsiusnotes.com/url-schemes-in-ios/

If more than one app registers to handle the same URI scheme (e.g aopp: or also bitcoin:) there is no way to tell which app will be opened by iOS (see https://stackoverflow.com/a/13130477).

Add the following to your plist file:

<key>CFBundleURLTypes</key>
<array>
	<dict>
		<key>CFBundleURLName</key>
		<string>com.example.wallet</string>
		<key>CFBundleURLSchemes</key>
		<array>
			<string>aopp</string>
		</array>
	</dict>
</array>

Docs on how to handle the URI: https://developer.apple.com/documentation/xcode/defining-a-custom-url-scheme-for-your-app

That only makes sense for mobile wallets.

Generate a new address that follows the format from the AOPP URI format query string. Only addresses from compressed pubkeys are supported.

In the AOPP URI, the msg query string contains the message to be signed using Bitcoin's sign message algorithm, i.e. this one.

Note the omission of a segwit specifier for all address types.

const bitcoinMessage = require('bitcoinjs-message')
bitcoinMessage.sign(message, privateKey, keyPair.compressed)

Send result to the callback obtained from the AOPP URI callback query string. It should be a POST request with the following JSON body.

{
    "version": 0,
    "address": "address generated above",
    "signature": "signature created above"
}

The signature should be base64-encoded.

An end-user-facing webapp is made available for testing here.

You can see when your address has been registered in the 21 Analytics software stack, which features an AOPP-compatible backend: https://testing.21analytics.xyz/aopp

Username: admin

Password: admin

The logs of the docker AOPP backend container running on the server (for debugging) are available here: http://testing.21analytics.xyz:8888

There is a fork of the popular desktop wallet Electrum with built-in support for AOPP available here: https://gitlab.com/aopp/electrum

• BlueWallet
  • Pull Request: https://github.com/BlueWallet/BlueWallet/pull/2915
• Bitbox
  • Pull Requests: https://github.com/digitalbitbox/bitbox-wallet-app/pulls?q=is%3Apr+aopp+is%3Aclosed
  • Code (excluding the URI registration): https://github.com/digitalbitbox/bitbox-wallet-app/blob/master/backend/aopp.go
• Sparrow Wallet
  • Code: https://github.com/sparrowwallet/sparrow/commit/425e476f202273dcc4e721a3aa92defca31196f4