Stealthnote Mobile

This project is inspired by stealthnote.xyz. Our goal is to build on the core idea of StealthNote while significantly enhancing performance and user experience using Mopro. By leveraging native execution, our implementation achieves at least ~10× faster performance compared to the browser-based version — as demonstrated in our benchmarks.

📺 Demo video

🎯 Features

• Sign in with Google OAuth: When a user signs in with Google on StealthNote, an ephemeral key is generated. The platform then requests a JWT from Google OAuth to prove ownership of the user's email address, using the hash of the ephemeral key as a nonce. A Noir proof is generated to attest to the validity of the JWT and the nonce, and this proof is submitted to the server. Upon verification, the server creates a membership record tied to the user's organizational email.

• Create note: After signing in with Google OAuth and storing the ephemeral key, users can use the key to post content on the platform.

• Toggle likes: Just like creating a note, users can use their ephemeral public key to toggle likes on the platform.

• Verify proofs: Each message box includes a "Verify" button, allowing any user to verify the corresponding Noir proof stored in the database and confirm its authenticity via Google OAuth.

• Internal chat: Internal chats are visible only to members of the same organization who choose to post internally. Stealthnote uses the user's ephemeral public key to authenticate message posting and retrieval.

💻 How it is made?

• Rust: All cryptographic functions are implemented in Rust, as the ecosystem offers a richer set of libraries and better performance compared to Flutter. Below is an overview of our implementation.

  • generate_ephemeral_key(): Stealthnote uses an ephemeral key for performing actions and verifying membership. We implemented Ed25519 signature functionality and hashes in Rust to ensure secure and efficient cryptographic operations.
  • prove_jwt(): The prove_jwt function extracts the necessary data for the Noir circuit and invokes the noir-rs proof generation function to produce a valid Noir proof.
  • verify_jwt_proof(): The verify_jwt_proof function retrieves inputs from the database, formats them for the Noir circuit, and uses noir-rs to verify the corresponding proof.

• Mopro: Mopro generates native bindings for iOS and Android, allowing the Flutter app to call Rust-defined functions simply by replacing the generated bindings.

• Flutter: Flutter is used to build our cross-platform frontend. It handles the Google authentication flow to obtain a JWT, and communicates with the Stealthnote.xyz APIs to interact with the backend.

🔧 Build the Bindings

Mopro simplifies generating native mobile bindings through the mopro CLI. The following example demonstrates how to update the bindings when changes are made to the underlying Rust functions. This allows developers to focus solely on maintaining the Rust functions, while automatically ensuring cross-platform support.

Install Mopro CLI

cargo install [email protected]

iOS

Run

mopro build

and select aarch64-apple-ios

Android

Activate android-compat feature in Cargo.toml.

- noir = { git = "https://github.com/zkmopro/noir-rs", features = ["barretenberg"] }
+ noir = { git = "https://github.com/zkmopro/noir-rs", features = ["barretenberg", "android-compat"] }

Run

mopro build

and select aarch64-linux-android

🔄 Manually Update Bindings

Flutter

Copy the generated files into your Flutter project:

cp -r MoproiOSBindings flutter/mopro_flutter_plugin/ios && \
cp -r MoproAndroidBindings/uniffi flutter/mopro_flutter_plugin/android/src/main/kotlin && \
cp -r MoproAndroidBindings/jniLibs flutter/mopro_flutter_plugin/android/src/main

📂 Open the project

Follow the instructions to open the development tools

Flutter

• Go to flutter directory

  cd flutter

• Check flutter environment

  flutter doctor

• Install Flutter Dependencies

  flutter pub get

• Run the app (Please turn on emulators before running the command)

  flutter run

Markdown Support

Stealthnote Mobile supports a variety of Markdown features for rich text formatting in your notes. You can use common Markdown syntax to create headers, lists, bold and italic text, links, and more.

Below is an example of how Markdown is rendered in the app:

Stealthnote Mobile Support Markdown

📊 Benchmarks

The following benchmarks were conducted on iPhone and Android in release mode:

JWT Operation	Prove	Verify
Browser	37.292 s	0.286 s
Desktop (Mac M1 Pro)	2.02 s	0.007 s
Android emulator (Pixel 8)	4.786 s	3.013 s
iPhone 16 Pro	2.626 s	1.727 s