MSL Mobile Bridge

React Native library providing JavaScript bindings for Emurgo's Message Signing Library with native Rust components.

📦 Installation

Requirements

• Rust — Install rustup
• Python 3 — Required for Android builds
• Rust targets — Cross-compilation targets for iOS/Android

# Install Rust
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
source ~/.zshrc

# Install Rust targets
rustup target add aarch64-apple-ios aarch64-apple-ios-sim x86_64-apple-ios \
    aarch64-linux-android armv7-linux-androideabi i686-linux-android x86_64-linux-android

# Verify Python 3
python3 --version

Install Package

npm install @emurgo/msl-mobile-bridge --save

Usage

import { COSESign1Builder } from '@emurgo/msl-mobile-bridge';

See more examples in example/app/examples.

🛠 Development Setup

For contributors and library developers.

Quick Start

Ensure Requirements are installed first.

# 1. Setup Rust targets (or install manually as shown in Requirements)
./setup-rust-environment.sh

# 2. Install dependencies
yarn install && yarn prepare

# 3. Run example app
yarn example ios    # or: yarn example android

Prerequisites

| Tool | Version | Check Command | |------|---------|---------------| | Node.js | ≥ 18.0.0 | node --version | | Yarn | ≥ 3.6.1 | yarn --version | | Rust | ≥ 1.70.0 | rustc --version | | Xcode | Latest | xcodebuild -version | | Java JDK | 17 | java -version | | Android NDK | 27.0.12077973 | ls $ANDROID_HOME/ndk/ |

Environment Variables

Add to ~/.zshrc (or ~/.bash_profile):

# Java
export JAVA_HOME=/Library/Java/JavaVirtualMachines/zulu-17.jdk/Contents/Home

# Android
export ANDROID_HOME="$HOME/Library/Android/sdk"
export ANDROID_SDK_ROOT="$ANDROID_HOME"
export ANDROID_NDK_HOME="$ANDROID_HOME/ndk/27.0.12077973"
export PATH="$PATH:$ANDROID_HOME/emulator:$ANDROID_HOME/platform-tools"

# Rust Android Gradle
export RUST_ANDROID_GRADLE_PYTHON_COMMAND="python3"

Then run source ~/.zshrc to apply.

Android NDK Installation

⚠️ NDK version 27.0.12077973 is required. Other versions will cause build failures.

1. Open Android Studio → Settings → Android SDK → SDK Tools
2. Check Show Package Details
3. Expand NDK (Side by side) → Select 27.0.12077973
4. Click Apply

Java JDK 17

brew install --cask zulu@17

Rust Targets

Use the setup script or install manually (see Requirements):

./setup-rust-environment.sh

Running the Example App

# iOS
yarn example ios

# Android (start emulator first)
yarn example android

# Metro bundler only
yarn example start

Troubleshooting

Quick Diagnostics

echo "JAVA_HOME: $JAVA_HOME"
echo "ANDROID_HOME: $ANDROID_HOME"
echo "ANDROID_NDK_HOME: $ANDROID_NDK_HOME"
rustup target list --installed | grep -E "(ios|android)"

Common Issues

NDK version mismatch

ls "$ANDROID_HOME/ndk/"
# Must have 27.0.12077973 - install via Android Studio SDK Tools

Rust build failures

./setup-rust-environment.sh
rustup update
cargo clean

iOS build failures

cd example
rm -rf ios/build
pod install --repo-update
cd ..
yarn example ios

Android Gradle failures

cd example/android && ./gradlew clean && cd ../..
yarn example android

Metro cache issues

yarn example start --reset-cache

Port 8081 in use

lsof -ti:8081 | xargs kill -9

Clean Reinstall

rm -rf node_modules example/node_modules
yarn install
yarn prepare

Resources

• Message Signing Library
• GitHub Issues
• React Native Docs