Sigil

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Sigil, an app that aims to provide a comprehensive cryptography suite for Android with a modern Material 3 interface.

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# SIGIL
**Open-source zero-trust cryptography & privacy suite with multi-layer encryption**

> [!NOTE]
> **Development Status & v0.5.0 Roadmap Update**
> 
> Following initial dev pushes (~3 months ago on `dev`, stable v0.4.5 on `master`), active development is currently on hold while I focus on my Class 12 Boards & SAT prep. **Active development resumes shortly after August 21, 2026**, targeting the major v0.5.0 release in Fall 2026 (Late September / October).
> 
> **What's Coming:**
> * **v0.5.0 (Android):** Massive Steganography suite, authenticated AEAD cryptography upgrade, custom screen shielding, overhauled onboarding and security, along with quality-of-life improvements. Track progress on the [v0.5.0 Project Roadmap](https://github.com/users/Animesh-Varma/projects/2).
> * **Native iOS Port (`Sigil-iOS`):** The initial `v0.1.0` iOS release will launch shortly after Android `v0.5.0`.
> * **Bleeding-Edge Dev Builds:** Signed development APKs are automatically compiled via GitHub Actions. You can download the latest build anytime from the [Actions Runs Tab](https://github.com/Animesh-Varma/Sigil/actions) under **Artifacts**, or email `sigil@animeshvarma.dev` for testing feedback!

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Sigil is an encryption utility built with a focus on defense-in-depth and memory safety. In a world where privacy policies change overnight and "end-to-end" often has a backdoor, Sigil provides a secure, offline-only toolset for securing sensitive information.

By default, Sigil uses the "Sigil Chain" profile, a quad-layer encryption cascade that exceeds almost any threat model. But flexibility is key: you can choose Standard AES (Raw Mode) for compatibility, or build custom profiles tailored to your exact requirements. :)

Sigil aims to be much more than just an encryption app; it aims to be a complete security suite to address all your cryptography needs. Check out the [Roadmap](#roadmap) for planned features—any suggestions are highly appreciated!

---

## Downloads

### Release Status

| Platform            | Current Version | Build Channel |
|:--------------------|:----------------|:--------------|
| **IzzyOnDroid**     | **v0.4.5**      | Pre-release   |
| **Google Play**     | **v0.4.5**      | Pre-release   |
| **GitHub Releases** | **v0.4.5**      | Pre-release   |

---

<h3 align="center">Contents</h2>

<a href="#features">Features</a> •
 <a href="#how-it-works">How It Works</a> •
 <a href="#implemented-modules">Modules</a> •
 <a href="#screenshots">Screenshots</a> •
 <a href="#algorithm-registry">Algorithms</a>
 
 <a href="#roadmap">Roadmap</a> •
 <a href="#technical-stack">Tech Stack</a> •
 <a href="#privacy">Privacy</a> •
 <a href="#build-instructions">Build</a> •
 <a href="#contact">Contact</a>

---

## Features

- **Encryption Profiles (New):** Switch between **Standard AES** (a built‑in profile that uses Raw Mode), the classic **Sigil Chain**, or create your own chain.
- **Multi-Layer Cascade:** By default, Sigil encrypts your data with the "Sigil Chain" profile (`XChaCha20-Poly1305` → `Serpent` → `Twofish` → `AES-256`). For typical text inputs, the KDF dominates execution time, making the multi-layer overhead negligible; however, larger data [>2 MB] will show linear scaling with layer count.
- **Zero-Knowledge Auth:** Support for both **PINs** and **Passwords**. Authentication is handled via salted Argon2id hashes. Credentials are never stored in a reversible format.
- **Hardware-Backed Keystore:** Master seeds are generated and stored inside your phone's **Trusted Execution Environment (TEE)**. They never touch the app layer in plaintext.
- **Access Control:** Includes TEE-verified Biometrics and **Screen Shield** (just fancy talk for `flag_secure`).
- **Memory Hygiene:** Sigil zeros out (wipes) byte arrays from RAM the moment they aren't needed to prevent RAM dumps.
- **Material 3 UI:** Just because it's a security tool doesn't mean it has to look like an app from the 90s. ;)

---

## How It Works

### **Key Derivation (Argon2id)**

Sigil uses Argon2id as the primary KDF. It's memory-hard, which means it forces the device to use a chunk of RAM (up to 256MB) to unlock. This makes it incredibly annoying/expensive for attackers with GPUs to try and brute-force your password.

### **Encryption Profiles & Raw Mode**

Sigil v0.4.5 introduces **Encryption Profiles**, allowing users to define the complexity of their encryption once and reuse it:

1.  **Sigil Chain (Default):** The classic hybrid cascade designed for maximum defense depth. It wraps data in a custom container with metadata headers, compression, and KDF salts.
    *   *Layers:* `XChaCha20-Poly1305` → `Serpent-CBC` → `Twofish-CBC` → `AES-256-GCM`.
2.  **Standard AES:** A pre-configured profile using **Raw Mode** with AES-GCM. Raw Mode bypasses the multi-cipher chain and metadata headers, outputting pure ciphertext/IV/tag. This is ideal for users who prefer a minimal attack surface or require compatibility with external tools.  
    *   *Flexibility:* You may use **any** algorithm from the registry (AES-GCM, XChaCha20, etc.) in Raw Mode by creating a new profile in Custom Mode and checking the RAW mode box (only available if a single algorithm is selected).
3.  **Custom Profiles:** Define your own cryptographic chain. Select from the registry of 18 algorithms to create a bespoke encryption pipeline suited to your specific threat model. You can also override global KDF settings per profile if required (even though global settings are tweakable in the settings tab).

---

## Implemented Modules

### **Encryption (Auto & Custom)**

- **Auto Tab:** Quickly encrypt your text using Saved Profiles (Custom Chains) and Built-in ones.
- **Custom Tab:** A layer manager allowing users to select specific algorithms from the registry, reorder the cascade, and toggle ZLib compression among other things. This is also where you save new profiles.

### **Keystore**

- A manager for your saved keys. Sigil only decrypts these from the hardware vault when you successfully authenticate.
- Includes an **Entropy Meter** to show you how strong your key actually is.

### **Settings**

- **Cryptography Tuning:** Tweak the Argon2id parameters (Iterations, Memory, Parallelism).
- **App Lock:** A new wizard to set up your PIN or Password safely.
- **Privacy:** Controls for Screen Security, Grace Periods, and clipboard auto-wipe.
- **Appearance:** Dynamic colors and themes.

---

## Screenshots

<details>
<summary>Click here to view App Screenshots</summary>

| | | |
|:----------------------------------------------------------------------------------------------------------------------------------------------:|:------------------------------------------------------------------------------------------------------------------------------------:|:----------------------------------------------------------------------------------------------------------------------------:|
| <img src="fastlane/metadata/android/en-US/images/phoneScreenshots/01.jpg" alt="Onboarding" width="200"> Onboarding | <img src="fastlane/metadata/android/en-US/images/phoneScreenshots/02.jpg" alt="App Lock" width="200"> App Lock | <img src="fastlane/metadata/android/en-US/images/phoneScreenshots/03.jpg" alt="Navigation" width="200"> Navigation |
| <img src="fastlane/metadata/android/en-US/images/phoneScreenshots/04.jpg" alt="Encryption Profiles" width="200"> Encryption Profiles | <img src="fastlane/metadata/android/en-US/images/phoneScreenshots/05.jpg" alt="Custom Mode" width="200"> Custom Mode | <img src="fastlane/metadata/android/en-US/images/phoneScreenshots/06.jpg" alt="Algorithms" width="200"> Algorithms |
| <img src="fastlane/metadata/android/en-US/images/phoneScreenshots/07.jpg" alt="Save Profile" width="200"> Save Profile | <img src="fastlane/metadata/android/en-US/images/phoneScreenshots/08.jpg" alt="Logs" width="200"> Logs | <img src="fastlane/metadata/android/en-US/images/phoneScreenshots/09.jpg" alt="Settings" width="200"> Settings |
| <img src="fastlane/metadata/android/en-US/images/phoneScreenshots/10.jpg" alt="Keystore" width="200"> Keystore | <img src="fastlane/metadata/android/en-US/images/phoneScreenshots/11.jpg" alt="Keystore Usage" width="200"> Keystore Usage | <img src="fastlane/metadata/android/en-US/images/phoneScreenshots/12.jpg" alt="Releases" width="200"> Releases |

</div>

</details>

---

## Algorithm Registry

Sigil currently supports **18 cryptographic algorithms**, including modern standards, AES finalists, and some legacy ones (for educational/testing purposes, trigger a UI warning when selected).

| Algorithm              | Type          | Block Size | Origin/Standard             | Status           |
|:-----------------------|:--------------|:-----------|:----------------------------|:-----------------|
| **AES-GCM**            | Block (AEAD)  | 128-bit    | NIST Standard (USA)         | **Primary**      |
| **ChaCha20-Poly1305**  | Stream (AEAD) | N/A        | IETF Standard               | **Primary**      |
| **XChaCha20-Poly1305** | Stream (AEAD) | N/A        | Extended Nonce Variant      | **SOTA**         |
| **ARIA-256-GCM**       | Block (AEAD)  | 128-bit    | IETF RFC 5794 (South Korea) | **Very Strong**  |
| **Serpent**            | Block (CBC)   | 128-bit    | AES Finalist                | **Strong**       |
| **Twofish**            | Block (CBC)   | 128-bit    | AES Finalist                | **Strong**       |
| **Camellia**           | Block (CBC)   | 128-bit    | NESSIE/CRYPTREC (EU/Japan)  | **Strong**       |
| **SM4**                | Block (CBC)   | 128-bit    | GB/T 32907 (China)          | **Strong**       |
| **SEED**               | Block (CBC)   | 128-bit    | KISA (South Korea)          | **Strong**       |
| **CAST-256**           | Block (CBC)   | 128-bit    | AES Finalist                | **Strong**       |
| **RC6**                | Block (CBC)   | 128-bit    | AES Finalist                | **Strong**       |
| **AES-CBC**            | Block (CBC)   | 128-bit    | NIST Standard               | Legacy Support   |
| **Blowfish**           | Block (CBC)   | 64-bit     | Legacy Schneier Design      | *Weak (Flagged)* |
| **IDEA**               | Block (CBC)   | 64-bit     | PGP Standard                | *Weak (Flagged)* |
| **CAST-128**           | Block (CBC)   | 64-bit     | GPG Legacy                  | *Weak (Flagged)* |
| **GOST 28147**         | Block (CBC)   | 64-bit     | GOST (USSR/Russia)          | *Weak (Flagged)* |
| **TEA**                | Block (CBC)   | 64-bit     | Cambridge                   | *Weak (Flagged)* |
| **XTEA**               | Block (CBC)   | 64-bit     | Extended TEA                | *Weak (Flagged)* |

---

## Roadmap

Development is active. To view the current status, planned features, and release milestones, please visit the official Project Board.

[**View Project Roadmap**](https://github.com/users/Animesh-Varma/projects/2)

---

## Technical Stack

- **Language:** Kotlin
- **UI:** Jetpack Compose (Material 3 Expressive APIs)
- **Cryptography:** Bouncy Castle (bcprov-jdk18on v1.83)
- **Persistence:** Hardware Keystore (TEE) + Encrypted SharedPreferences
- **Architecture:** MVVM + UDF with Clean Architecture

---

## Privacy

Sigil is strictly **Offline-Only**. 
1. **No Internet:** The `INTERNET` permission is absent from the manifest. Data cannot leave the device.
2. **No Analytics:** No trackers, telemetry, or crash reporters included.
3. **No Backups:** `android:allowBackup` is disabled to prevent encrypted vault data from being synced to cloud providers accidentally.

---

## Build Instructions

Ensure you have the latest Android Studio and JDK 17+.

```bash
git clone https://github.com/Animesh-Varma/Sigil.git
cd Sigil
./gradlew assembleDebug
```

---

## Security Disclaimer

Sigil is an open-learning project. While I try my hardest to adhere to best practices, it hasn't been audited by a professional firm yet. I encourage you to read the code!

**Permanent Data Loss:** If you lose your Master PIN or Password, your data is gone forever. I can't help you recover it.

---

## Contact

If you have questions or security findings:
Email: `sigil@animeshvarma.dev`

**Note:** This is my first foray into Android development and cryptography. I’m a high school student building this project in any spare time I can find, so contributors and general advice are always more than welcomed!

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