Tuvali API Documentation

Tuvali module is based on the OpenID for Verifiable Presentations over BLE implementation to support sending vc/vp using Bluetooth Low Energy local channel. The below sections explains the APIs of the library in detail.

Firstly, for establishing the secured connection over BLE the connection params which include name and key needs to be exchanged between the two devices. This exchange of parameters can be accomplished but is not limited to by using a QR code.

For example, use a QR code generator to visually display params and a QR code scanner to get params. A mobile app that displays a QR code can act as an Verifier by including its connection params as data in the QR code and another device can act as Wallet which scans the QR code, it can extract the connection parameters and initiate a BLE connection with the advertising device.

URI Exchange and Establishing Connection

Verifier

The Verifier device generates a URI using the startAdvertisement() method and displays it as a QR code. Once the advertisement starts, the Verifier continuously advertises with a payload derived from the URI.

URI contains:

OPENID4VP://connect?name=STADONENTRY&key=8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4e6a

URI structure can be found in the spec. Currently, the library doesn't support iOS as a verifier.But it can act as a wallet for android verifier.

var verifier = Verifier()
var uri = verifier.startAdvertisement()
println(uri)

Wallet

Start Connection

The device that scans the QR code will extract the connection parameters from the QR code and set its connection parameters using the startConnection() method :

var wallet = Wallet()
wallet.startConnection(uri)

The connection param is a URI with a name & a key. The name is the client's name & the key is the verfier's public key.

OPENID4VP://connect:?name=OVPMOSIP&key=69dc92a2cc91f02258aa8094d6e2b62877f5b6498924fbaedaaa46af30abb364

• The key part of the data is the same data that will be advertised by the verifier device but in hex-encoded form.

E.g: OVPMOSIP://connect:?name=<>&key=<verifier public key>

Share data

Once the connection is established, wallet app can send the data in a secured way to the Verifier. Note: At this moment, we currently support data transfer from Wallet to Verifier only.

wallet.sendData(payload);

and verifier app can acknowledge it.

verifier.sendVerificationStatus(status);

The following sequence of actions should be performed to transfer data over BLE:

1. Verifier must start advertising by calling verifier.startAdvertisement(name) method
2. Subscribe to events using wallet.handleDataEvents
3. Initiate the secure connection using wallet.startConnection(uri). The Wallet public keys are exchanged with verifier on successful connection.
4. Wallet calls wallet.sendData(payload) to transfer requisite data over BLE.
5. Send VC response - Verifier can exchange "Accept/Reject" status to Wallet with the following message type for verifier.sendVerificationStatus method

Subscribe to events

Data received from other apps via BLE can be subscribed to using: Tuvali sends multiple events to propagate connection status, received data etc. These events can be subscribed to by calling:

on Wallet:

wallet.subscribe {
  event  ->
  // Add the code that needs to run once event is received
}

on Verifier:

verifier.subscribe {
  event  ->
  // Add the code that needs to run once data is received
}

Here are the different types of events that can be received

Common Events

Events which are emitted by both Wallet and Verifier

1. ConnectedEvent

   • on BLE connection getting established between Wallet and Verifier
2. SecureChannelEstablishedEvent

   • on completion of key exchange between Wallet and Verifier
3. ErrorEvent

   • on any error in Wallet or Verifier
4. DisconnectedEvent

   • on BLE disconnection between Wallet and Verifier

Wallet Specific Events

1. DataSentEvent

   • on completion of Data transfer from the Wallet Side
2. VerificationStatusReceivedEvent

   • on received verification status from Verifier

Verifier Specific Events

1. DataReceivedEvent

• on receiving data from the Wallet Side

Connection closure

The device on which app is running can destroy the connection by calling disconnect() method:

wallet.disconnect();
verifier.disconnect();

Tuvali & Inji Integration

The below diagram explains the series of handshakes between the Verifier and the Wallet device.