Your private ecash wallet on Bitcoin
elcaju.me • Installation • Features • Technologies
ElCaju is a Cashu wallet (ecash on Bitcoin) with Cuban identity, brother of LaChispa (Lightning). Designed to offer privacy, offline transactions, and a warm tropical experience.
Cashu is an ecash protocol that enables Bitcoin transactions with maximum privacy. Cashu tokens are:
- Private: Fungible and untraceable
- Offline: Store and send tokens without internet connection
- Instant: No waiting for blockchain confirmations
| Feature | Description |
|---|---|
| Total Privacy | Fungible ecash tokens, no traceable history |
| Works Offline | Store, create, and share tokens without internet |
| Lightning Bridge | Deposit and withdraw sats via Lightning Network |
| Multi-Mint | Connect to unlimited Cashu mints simultaneously |
| Multi-Unit | Support for sat, USD, EUR, and any unit offered by mints |
| P2PK (NUT-10) | Lock tokens to a Nostr public key — only the recipient can claim |
| Token Recovery (NUT-13) | Restore tokens from any mint using your seed phrase |
| NFC Transfers | Share tokens via NFC — includes Host Card Emulation (HCE) |
| Animated QR | UR-format multi-frame QR codes for large tokens |
| Peanut Emoji | Encode tokens as emoji (compatible with cashu.me) |
| Transaction History | Full history with filters: Ecash, Lightning, Pending |
| Pending Tokens | Save tokens to claim later (up to 50, 30-day expiry) |
| BTC Price | Live price via Yadio API with fiat conversion |
| Your Seed, Your Money | Backup with 12 words (BIP39) |
| Optional PIN | 4-digit PIN to protect wallet access |
| 11 Languages | ES, EN, PT, FR, RU, DE, IT, KO, ZH, JA, SW |
| Friendly UX | Confetti celebrations when receiving funds |
- Flutter 3.27+: Cross-platform framework
- Dart 3.11+: Programming language
- Provider: State management
- QR Flutter + Mobile Scanner: QR generation and scanning
- elcaju_core: Internal Rust library via flutter_rust_bridge v2.11.1 (FFI)
- CDK 0.15.1: Cashu Development Kit (wallet, SQLite, HTTP client, signatory)
- SQLite: Local persistence via cdk-sqlite
- Flutter Secure Storage: Encrypted storage for seed and PIN
- Cashu: NUT-00, 04, 05, 06, 07, 09, 10 (P2PK), 13 (restore)
- Lightning Network: Deposits and withdrawals via BOLT11
- BIP39 / BIP32: Seed phrase generation and key derivation
- NIP-06: Nostr key derivation from mnemonic for P2PK
- NFC Manager + HCE: Phone-to-phone token transfers
- Android NDK 27.0: Multi-architecture native compilation
- Cargokit: Automated Rust build integration
- Flutter SDK (>=3.27.0)
- Dart SDK (>=3.11.0)
- Android Studio with Android SDK
- Android NDK 27.0+ (install via Android Studio > SDK Manager > SDK Tools)
- Rust toolchain (edition 2024; rustc >= 1.85.0)
git clone https://github.com/Forte11Cuba/elcaju.git
cd elcajuflutter pub get# Install Rust if not already installed
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
# Update to latest stable
rustup update stable
# Install Android targets
rustup target add aarch64-linux-android # arm64-v8a (modern devices)
rustup target add armv7-linux-androideabi # armeabi-v7a (older devices)
rustup target add x86_64-linux-android # x86_64 (emulators)Create or edit ~/.cargo/config.toml with your NDK path:
[target.x86_64-unknown-linux-gnu]
linker = "gcc"
rustflags = ["-C", "link-arg=-fuse-ld=bfd"]
[target.aarch64-linux-android]
linker = "/path/to/Android/Sdk/ndk/27.0.12077973/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android24-clang"
[target.armv7-linux-androideabi]
linker = "/path/to/Android/Sdk/ndk/27.0.12077973/toolchains/llvm/prebuilt/linux-x86_64/bin/armv7a-linux-androideabi24-clang"
[target.x86_64-linux-android]
linker = "/path/to/Android/Sdk/ndk/27.0.12077973/toolchains/llvm/prebuilt/linux-x86_64/bin/x86_64-linux-android24-clang"
[env]
CC_armv7-linux-androideabi = "/path/to/Android/Sdk/ndk/27.0.12077973/toolchains/llvm/prebuilt/linux-x86_64/bin/armv7a-linux-androideabi24-clang"
AR_armv7-linux-androideabi = "/path/to/Android/Sdk/ndk/27.0.12077973/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ar"
CC_x86_64-linux-android = "/path/to/Android/Sdk/ndk/27.0.12077973/toolchains/llvm/prebuilt/linux-x86_64/bin/x86_64-linux-android24-clang"
AR_x86_64-linux-android = "/path/to/Android/Sdk/ndk/27.0.12077973/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ar"
CC_aarch64-linux-android = "/path/to/Android/Sdk/ndk/27.0.12077973/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android24-clang"
AR_aarch64-linux-android = "/path/to/Android/Sdk/ndk/27.0.12077973/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ar"Note: Replace
/path/to/Android/Sdkwith your actual Android SDK path (usually~/Android/Sdkon Linux or~/Library/Android/sdkon macOS).
The Rust library compiles automatically via Cargokit during flutter run:
flutter runNote: The first build will take several minutes while Rust compiles. Subsequent builds are incremental.
# Android APK (includes all architectures)
flutter build apk --release
# Android App Bundle (recommended for Play Store)
flutter build appbundle --releaseFor faster builds targeting only modern devices:
flutter build apk --release --target-platform android-arm64┌─────────────────────────────────────────┐
│ Flutter UI (Dart 3.11+) │
│ Provider + Streams + Intl (11 langs) │
├─────────────────────────────────────────┤
│ 4 Providers: Wallet, Settings, │
│ Price (Yadio), P2PK (NIP-06) │
├─────────────────────────────────────────┤
│ flutter_rust_bridge v2.11.1 (FFI) │
├─────────────────────────────────────────┤
│ elcaju_core (Rust interno) │
│ CDK 0.16.0 + SQLite + BIP39 + Tokio │
└─────────────────────────────────────────┘
elcaju/
├── lib/
│ ├── main.dart # Entry point (RustLib.init + Providers)
│ ├── core/
│ │ ├── constants/ # Colors, dimensions
│ │ ├── models/ # Proof model
│ │ ├── services/ # LNURL, NFC, price, proofs
│ │ ├── theme/ # Material 3 dark theme
│ │ └── utils/ # Formatters, parsers, nostr, p2pk, peanut codec
│ ├── data/ # Pending tokens, transaction metadata storage
│ ├── models/ # P2PK key model (npub/nsec)
│ ├── providers/
│ │ ├── wallet_provider.dart # Multi-mint, multi-unit wallet logic
│ │ ├── settings_provider.dart # Preferences, PIN, seed
│ │ ├── price_provider.dart # BTC price cache (Yadio API)
│ │ └── p2pk_provider.dart # Nostr key management (NIP-06)
│ ├── screens/
│ │ ├── 1_splash/ # Loading & initialization
│ │ ├── 2_onboarding/ # Create / restore / backup seed
│ │ ├── 3_home/ # Main dashboard
│ │ ├── 4_receive/ # Receive tokens (paste, QR, NFC)
│ │ ├── 5_send/ # Send tokens + offline mode + share
│ │ ├── 6_mint/ # Lightning deposit
│ │ ├── 7_melt/ # Lightning withdrawal
│ │ ├── 8_settings/ # Settings, mints, P2PK keys, language
│ │ ├── 9_history/ # Transaction history with filters
│ │ └── 10_scanner/ # QR code scanner
│ ├── src/rust/ # FFI bridge (auto-generated + API bindings)
│ ├── widgets/
│ │ ├── common/ # Buttons, cards, numpad, backgrounds
│ │ ├── effects/ # Confetti animation
│ │ ├── proof/ # Proof selector (offline send)
│ │ └── scanner/ # QR scanner widget
│ └── l10n/ # 11 languages (354 translation keys)
├── rust/
│ ├── Cargo.toml # elcaju_core: CDK 0.16.0, flutter_rust_bridge 2.11.1
│ └── src/api/ # wallet, token, keys, mint_info, error
├── rust_builder/ # Cargokit integration (auto Rust compilation)
├── android/ # Android config (NDK 27.0, NFC HCE service)
└── assets/img/ # Logo and screenshots
| NUT | Name | Status |
|---|---|---|
| NUT-00 | Cashu Protocol | Supported |
| NUT-04 | Mint (Lightning deposit) | Supported |
| NUT-05 | Melt (Lightning withdrawal) | Supported |
| NUT-06 | Token swap | Supported |
| NUT-07 | Spend conditions (witness) | Supported |
| NUT-09 | Token restore | Supported |
| NUT-10 | P2PK (locked tokens) | Supported |
| NUT-13 | Deterministic secrets (recovery) | Supported |
| Feature | Implementation |
|---|---|
| Seed Phrase | BIP39 12 words, stored with Flutter Secure Storage (native encryption) |
| Key Derivation | BIP32 + NIP-06 (m/44'/1237'/0'/0/0) for P2PK keys |
| PIN | 4-digit PIN with secure hash, local verification |
| Local Data | SQLite with proofs managed by CDK |
| P2PK Keys | Primary (from seed) + up to 10 imported keys, all encrypted |
| No Tracking | We don't collect user data |
| Open Source | 100% auditable |
Backup your seed phrase (12 words). Without it, you won't be able to recover your funds if you lose your device.
| Platform | Status | Minimum Version |
|---|---|---|
| Android | Supported | API 24 (Android 7.0) |
| iOS | Coming soon | iOS 11.0+ |
| Web | Coming soon | - |
ElCaju comes preconfigured with the Cuba Bitcoin mint:
https://mint.cubabitcoin.org
You can add other Cashu mints from the settings.
Automated releases via GitHub Actions (.github/workflows/release.yml):
- Triggers on Git tags (
v*) - Builds multi-architecture APKs (arm64, armv7, x86_64) + universal APK
- Creates GitHub releases automatically
Contributions are welcome!
- Fork the repository
- Create a branch for your feature (
git checkout -b feature/new-feature) - Commit your changes (
git commit -m 'Add new feature') - Push to the branch (
git push origin feature/new-feature) - Open a Pull Request
Open an issue with:
- Problem description
- Steps to reproduce
- Android version/device
- Relevant logs
This project is under the MIT License - see the LICENSE file for more details.
- Cashu - Ecash protocol
- CDK - Cashu Development Kit
- flutter_rust_bridge - Rust-Dart FFI
- Cashu4Community - Global Cashu community
- Cuba Bitcoin - Cuban Bitcoin community
Made with 🧡 by Forte11