SecureNotes is a military-grade encrypted note-taking application built for Android that prioritizes user privacy and data security above all else. Unlike traditional note apps that sync to the cloud, SecureNotes keeps everything local, encrypted, and under your control.

• 100% Offline - No internet permissions, no data transmission
• Military-Grade Encryption - AES-256-GCM encryption for all data
• Zero-Knowledge Architecture - Your data, your keys, your control
• Per-Note Lock - Lock individual notes with separate passwords for maximum security
• No Cloud Sync - All notes stored locally on your device
• Open Source - Transparent and auditable security implementation

Note Security Highlight: SecureNotes offers dual-layer protection. Every note is encrypted with your master PIN, and you can add an additional password lock to specific notes for ultra-sensitive information. This means even if someone gains access to your device with the master PIN, your most private notes remain protected.

• Rich Text Support - Format your notes with style
• To-Do Lists - Built-in task management with checkboxes
• File Attachments - Images, voice recordings, documents
• Category Organization - Organize notes into custom categories (General, Work, Study, Personal, Goals, Travel, Journal)
• Per-Note Lock - Additional password protection for individual sensitive notes
• Fast Search - Quick search across all notes with on-device indexing
• Favorites & Pinning - Keep important notes at the top
• Trash Management - Recover accidentally deleted notes
• Note Colors - Visual organization with color-coded notes

• Material Design 3 - Clean, modern interface with gradient backgrounds
• User Profile - Personalized profile with avatar support
• Custom Themes - Personalize your note-taking experience
• Responsive UI - Optimized for all screen sizes
• Performance - Smooth, fast, and lightweight
• No Ads - Distraction-free note-taking
• Drawer Navigation - Easy access to all app features
• Help & FAQ - Built-in help system and feedback options

SecureNotes implements multiple layers of security to ensure your data remains private and secure.

┌─────────────────────────────────────────┐
│         User Authentication             │
│    (PIN + Biometric Support)            │
└──────────────┬──────────────────────────┘
               │
               ▼
┌─────────────────────────────────────────┐
│      Android KeyStore (AES-256)         │
│   Hardware-Backed Key Generation        │
└──────────────┬──────────────────────────┘
               │
               ▼
┌─────────────────────────────────────────┐
│         AES-256-GCM Encryption          │
│  • Note Content                         │
│  • Attachments                          │
│  • Metadata                             │
└──────────────┬──────────────────────────┘
               │
               ▼
┌─────────────────────────────────────────┐
│       Room Database (Encrypted)         │
│     Local SQLite Storage                │
└─────────────────────────────────────────┘

public class EncryptionUtil {
    private static final String ANDROID_KEY_STORE = "AndroidKeyStore";
    
    public static String encrypt(String plainText) {
        SecretKey key = getSecretKey();
        Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
        cipher.init(Cipher.ENCRYPT_MODE, key);
        
        byte[] iv = cipher.getIV();
        byte[] cipherBytes = cipher.doFinal(plainText.getBytes());
        
        // IV + encrypted data for secure decryption
        return encodeWithIV(iv, cipherBytes);
    }
}

Main Interface

Lock Screen Secure PIN authentication

Notes List Clean, organized interface

Note Editor Rich text editing

Advanced Features

Categories Organize your notes

Attachments Images, voice, documents

Settings Customization options

• Android Studio Hedgehog (2023.1.1) or later
• JDK 17 or higher
• Android SDK API Level 24+ (Android 7.0+)
• Gradle 8.0+

1. Clone the repository

   git clone https://github.com/yourusername/SecureNotes.git
   cd SecureNotes

2. Open in Android Studio

   • Launch Android Studio
   • Select "Open an Existing Project"
   • Navigate to the cloned directory

3. Sync Gradle

   • Android Studio will automatically sync Gradle
   • If not, click File > Sync Project with Gradle Files

4. Build the project

   ./gradlew build

5. Run on device/emulator

   ./gradlew installDebug

SecureNotes/
├── app/
│   ├── src/
│   │   ├── main/
│   │   │   ├── java/com/example/securenote/
│   │   │   │   ├── data/              # Database & Repository layer
│   │   │   │   │   ├── AppDatabase.java
│   │   │   │   │   ├── NoteDao.java
│   │   │   │   │   ├── NoteRepository.java
│   │   │   │   │   └── AuthRepository.java
│   │   │   │   ├── model/             # Data models
│   │   │   │   │   ├── Note.java
│   │   │   │   │   ├── Attachment.java
│   │   │   │   │   └── UserProfile.java
│   │   │   │   ├── ui/                # Activities & Adapters
│   │   │   │   │   ├── MainActivity.java
│   │   │   │   │   ├── AddEditNoteActivity.java
│   │   │   │   │   ├── LockActivity.java
│   │   │   │   │   └── NoteAdapter.java
│   │   │   │   ├── util/              # Utility classes
│   │   │   │   │   ├── EncryptionUtil.java
│   │   │   │   │   ├── PasswordUtil.java
│   │   │   │   │   └── BackupUtils.java
│   │   │   │   └── viewmodel/         # ViewModels
│   │   │   │       └── NoteViewModel.java
│   │   │   ├── res/                   # Resources
│   │   │   │   ├── layout/            # XML layouts
│   │   │   │   ├── drawable/          # Icons & graphics
│   │   │   │   └── values/            # Strings, colors, themes
│   │   │   └── AndroidManifest.xml
│   │   └── test/                      # Unit tests
│   └── build.gradle.kts
└── README.md

• Android SDK - API Level 24+ (Android 7.0 Nougat and above)
• Java - JDK 17 with modern language features
• Gradle - 8.0+ build automation
• Material Design 3 - Latest Android design system

The application uses several key data models:

• Note - Main note entity with title, content, category, timestamp, and encryption metadata
• TodoItem - Task items within notes with completion status
• Attachment - File attachments linked to notes (images, voice recordings, documents)
• UserProfile - User settings and profile information

MVVM (Model-View-ViewModel) with Repository Pattern

• Clean separation of concerns
• Reactive data flow with LiveData
• Testable architecture
• Scalable and maintainable

Unit Tests

./gradlew test

Instrumentation Tests

./gradlew connectedAndroidTest

• Encryption/Decryption unit tests
• Database operations testing
• PIN verification logic
• Backup/Restore functionality
• UI component tests

SecureNotes is designed with privacy at its core:

• No data collection - We don't collect any user data
• No analytics - No tracking or telemetry
• No internet access - App has no network permissions
• No third-party services - No external dependencies
• Open source - Fully auditable codebase
• Local storage only - All data stays on your device

• Biometric authentication support
• Dark mode themes
• Note templates
• Export to PDF
• Advanced search filters
• Note sharing (encrypted)
• Markdown support
• Voice-to-text notes
• Widget support

This project is licensed under the MIT License.

Praisilia Anastasya Pandoh

• GitHub: @praisi-tech
• LinkedIn: Praisilia Pandoh
• Email: [email protected]

• Android KeyStore documentation and security best practices
• Material Design 3 guidelines
• Open source community for inspiration and support
• Security researchers for encryption implementation guidance

SecureNotes - Your Privacy, Our Priority

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