sidneys/dp3t-sdk-ios

The DP3T-SDK for iOS

DP3T-SDK for iOS

DP3T

The Decentralised Privacy-Preserving Proximity Tracing (DP-3T) project is an open protocol for COVID-19 proximity tracing using Bluetooth Low Energy functionality on mobile devices that ensures personal data and computation stays entirely on an individual's phone. It was produced by a core team of over 25 scientists and academic researchers from across Europe. It has also been scrutinized and improved by the wider community.

DP-3T is a free-standing effort started at EPFL and ETHZ that produced this protocol and that is implementing it in an open-sourced app and server.

Introduction

This is the first implementation of the DP-3T "low bandwidth" protocol. The current implementation does not use the as yet unreleased "Contact Tracing" API of Apple/Google--and has limitations as a result. Our "hybrid approach" uses Bluetooth Low Energy (BLE) to exchange EphIDs. It uses advertisements whenever possible and falls back to GATT Server connections if not possible to transmit/collect an EphID this way (e.g., on iOS devices when the app is in background). This approach can result in higher energy consumption and scalability issues and will be replaced by the Apple/Google API.

Our immediate roadmap is: to support the Apple/Google wire protocol, to be forward-compatible, and to support the actual Apple/Google API as soon as it is released to iOS and Android devices.

Repositories

• Android SDK & Calibration app: dp3t-sdk-android
• iOS SDK & Calibration app: dp3t-sdk-ios
• Android Demo App: dp3t-app-android
• iOS Demo App: dp3t-app-ios
• Backend SDK: dp3t-sdk-backend

Work in Progress

The DP3T-SDK for iOS contains alpha-quality code only and is not yet complete. It has not yet been reviewed or audited for security and compatibility. We are both continuing the development and have started a security review. This project is truly open-source and we welcome any feedback on the code regarding both the implementation and security aspects. This repository contains the open prototype SDK, so please focus your feedback for this repository on implementation issues.

Further Documentation

The full set of documents for DP3T is at https://github.com/DP-3T/documents. Please refer to the technical documents and whitepapers for a description of the implementation.

Architecture

A central discovery service is hosted on Github. This server provides the necessary information for the SDK to initialize itself. After the SDK loads the base url for its own backend, it will load the infected list from there, as well as post if a user is infected. This will also allow apps to fetch lists from other backend systems participating in this scheme and can handle roaming of users.

Calibration App

Included in this repository is a Calibration App that can run, debug and test the SDK directly without implementing it in a new app first. It collects additional data and stores it locally into a database to allow for tests with phones from different vendors. Various parameters of the SDK are exposed and can be changed at runtime. Additionally it provides an overview of how to use the SDK.

Function overview

Initialization

Name	Description	Function Name
init	Initializes the SDK and configures it	func initialize(with appId: String, enviroment: Enviroment

Methods

Name	Description	Function Name
startTracing	Starts Bluetooth tracing	func startTracing() throws
stopTracing	Stops Bluetooth tracing	func stopTracing()
sync	Pro-actively triggers sync with backend to refresh exposed list	func sync(callback: ((Result<Void, DP3TTracingErrors>) -> Void)?)
status	Returns a TracingState-Object describing the current state. This contains: - numberOfHandshakes : Int - trackingState : TrackingState - lastSync : Date - infectionStatus:InfectionStatus	func status(callback: (Result<TracingState, DP3TTracingErrors>) -> Void)
iWasExposed	This method must be called upon positive test.	func iWasExposed(onset: Date, authString: String, callback: @escaping (Result<Void, DP3TTracingErrors>) -> Void)
reset	Removes all SDK related data (key and database) and de-initializes SDK	func reset() throws

Installation

Swift Package Manager

DP3T-SDK is available through Swift Package Manager

1. Add the following to your Package.swift file:

dependencies: [
    .package(url: "https://github.com/DP-3T/dp3t-sdk-ios.git", branch: "develop")
]

Using the SDK

Initialization

In your AppDelegate in the didFinishLaunchingWithOptions function you have to initialize the SDK with

try DP3TTracing.initialize(with: "com.example.your.app", enviroment: .prod)

The provided app name has to be registered in the discovery service on Github

Certificate pinning

The SDK accepts a URLSession as an optional argument to the initializer. This can be used to enable certificate pinning. If no session is provided URLSession.shared will be used.

Start / Stop tracing

To start and stop tracing use

try DP3TTracing.startTracing()
DP3TTracing.stopTracing()

Make sure that the app includes in the Info.plist the bluetooth keys NSBluetoothAlwaysUsageDescription and NSBluetoothPeripheralUsageDescription and that the user has granted the app permission to use the Bluetooth periferals. Also the app as to support BackgroundMode capability for bluetooth-central and bluetooth-peripheral.

Info.plist sample:

<key>UIBackgroundModes</key>
  <array>
    <string>bluetooth-central</string>
    <string>bluetooth-peripheral</string>
  </array>
<key>NSBluetoothAlwaysUsageDescription</key>
  <string>User facing text justifying bluetooth usage</string>
<key>NSBluetoothPeripheralUsageDescription</key>
  <string>User facing text justifying bluetooth usage</string>

Checking the current tracing status

DP3TTracing.status(callback: (Result<TracingState, DP3TTracingErrors>) -> Void)

The TracingState object contains all information regarding the current tracing status.

To receive callbacks and notifications when the state changes, you should assign a delegate object conforming to DP3TTracingDelegate:

DP3TTracing.delegate = yourDelegateObject // weak retained by the SDK

// Delegate method
func DP3TTracingStateChanged(_ state: TracingState) {

}

The SDK will call your delegate on every state change, this includes: Handshake detection, start/stop of tracing, change in exposure, errors...

Report user exposed

DP3TTracing.iWasExposed(onset: Date(), authString: "") { result in
	// Handle result here
}

Sync with backend for exposed user

The SDK does not automatically sync with the backend for new exposed users. The app is responsible for fetching the new exposed users as it sees fit (periodically or via user input):

DP3TTracing.sync() { result in
	// Handle result here
}

License

This project is licensed under the terms of the MPL 2 license. See the LICENSE file.