Cross-Platform Mobile ZKPs

Flutter is a popular cross-platform mobile app development framework. Mopro Flutter shows an example of integrating ZK-proving into a Flutter app, allowing for streamlined creation of ZK-enabled mobile apps.

Important

Please refer to the latest mopro documentation for the most up-to-date information.

Running The Example App

Prerequisites

1. Install Flutter

   If Flutter is not already installed, you can follow the official Flutter installation guide for your operating system.

2. Check Flutter Environment

   After installing Flutter, verify that your development environment is properly set up by running the following command in your terminal:

   flutter doctor

   This command will identify any missing dependencies or required configurations.

3. Install Flutter Dependencies

   Navigate to the root directory of the project in your terminal and run:

   flutter pub get

   This will install the necessary dependencies for the project.

Running the App via VS Code

1. Open the project in VS Code.
2. Open the "Run and Debug" panel.
3. Start an emulator (iOS/Android) or connect your physical device.
4. Select "example" in the run menu and press "Run".

Running the App via Console

If you prefer using the terminal to run the app, use the following steps:

1. For Android:

   Ensure you have an Android emulator running or a device connected. Then run:

   flutter run

2. For iOS:

   Make sure you have an iOS simulator running or a device connected. Then run:

   flutter run

Integrating Your ZKP

The example app comes with a simple prover generated from a Circom circuit. To integrate your own prover, follow the steps below.

Warning

In the frb branch, the example app uses flutter_rust_bridge to generate bindings. If you need to work with mopro-ffi or mopro-cli versions earlier than 0.3.0, please switch to the main branch or the v0.2.0 tag.

Setup

• Install the latest mopro CLI on GitHub

git clone https://github.com/zkmopro/mopro
cd mopro/cli
cargo install --path .

• Follow the Getting Started guide to run

  mopro init

  (select your preferred adapter) and then

  mopro build

  to generate the mopro_flutter_bindings.

Copying The Generated Libraries

After running mopro build, copy the generated mopro_flutter_bindings. If you add new functions with flutter_rust_bridge and want to use them in Flutter, run mopro build again to regenerate and update the bindings.

zKey

1. Place your .zkey file in your app's assets folder. For example, to run the included example app, you need to replace the .zkey at assets/multiplier2_final.zkey with your file. If you change the .zkey file name, don't forget to update the asset definition in your app's pubspec.yaml:

   assets:
       - assets/your_new_zkey_file.zkey

2. Load the new .zkey file properly in your Dart code. For example, update the file path in lib/main.dart:

   var inputs = "{\"a\":[\"3\"],\"b\":[\"5\"]}";
   proofResult = await generateCircomProof(
                       zkeyPath: zkeyPath,
                       circuitInputs: inputs,
                       proofLib: ProofLib.arkworks);

Don't forget to modify the input values for your specific case!

Developing The Plugin

Android

Open the ./android directory in Android Studio. You will be able to browse to the plugin code in Android and Project view.

E2E Tests

End-to-End (E2E) / Integration Tests

1. Start an emulator or simulator

   • iOS: Open the iOS simulator via Xcode or open -a Simulator.

   • Android: Launch an emulator using Android Studio or emulator -avd <your_avd_name>.

     [!NOTE]
     If you encounter the error command not found: emulator, ensure the emulator binary is present in one of the following locations:

     • ~/Library/Android/sdk/emulator/emulator
     • ~/Android/Sdk/emulator/emulator

     To resolve this issue, update your shell configuration file (likely ~/.zshrc) by adding the following lines:

     export ANDROID_SDK_ROOT=~/Library/Android/sdk
     export PATH=$PATH:$ANDROID_SDK_ROOT/emulator

     After making these changes, verify that the issue is resolved by running:

     emulator -list-avds

2. Run the integration test

flutter test integration_test/plugin_integration_test.dart

Make sure you're using a real or virtual device (not just a Dart VM), as integration tests require it.

Widget & Unit Tests

To run unit and widget tests (headless, using Dart VM):

flutter test

These are ideal for testing individual widgets, business logic, and pure Dart code.