About this app
Sigil is an open-source, advanced text encryption utility designed for zero-trust environments. Unlike standard tools that rely on a single algorithm, Sigil employs a multi-layered, randomized chaining architecture to ensure your data remains secure against sophisticated cryptanalysis.

The application operates entirely offline, performing all cryptographic operations locally on your device with a modern Material 3 interface that balances high-level defense with professional usability.

Core Security Features
• Quad-Layer Chaining: In Auto Mode, Sigil randomizes a hybrid cascade of AES-256-GCM + ChaCha20-Poly1305 + Twofish-CBC + Serpent-CBC for every message. This defense-in-depth approach ensures that even if one algorithm is compromised, your data remains protected by multiple independent layers.
• Hardware-Backed Vault: Master keys are generated and stored within the Android Trusted Execution Environment (TEE). Your saved encryption passwords never touch the disk in plaintext, and biometric authentication binds directly to a TEE CryptoObject to resist common bypass techniques.
• Tamper-Proof Design: Sigil uses an Encrypt-then-MAC architecture with Global HMAC-SHA256 signatures applied to the final container. Any tampering or corruption is detected and rejected before decryption is attempted.
• Amnesia Protocol: Sensitive data is instantly wiped from RAM when the app backgrounds (configurable). A grace period setting allows quick app switching without re-authentication for convenience.
• Access Control: Protected by App Lock, supporting device biometrics or custom PIN. PINs are stored as Salted Argon2 Hashes in a Zero-Knowledge architecture, making it mathematically impossible to retrieve your PIN.

Privacy & System Hardening
• Screen Shield: Blocks screenshots and hides content in "Recent Apps" using FLAG_SECURE, protecting against shoulder surfing and malicious screen recording apps.
• Clipboard Security: Auto-wipe timer and Android 13+ sensitive content flags prevent clipboard managers from accessing your encrypted data.
• Zero-Knowledge: Operates offline without internet access, tracks no analytics, and stores no data on external servers. ADB and Cloud backups are explicitly disabled.

Advanced User Toolkit
• Secure Keystore: Save, name, view, rename, and delete encryption keys using the hardware-backed vault. Smart Vault Dropdowns enable one-tap access. Accepts text shared from external apps like WhatsApp and Signal.
• System Console: Real-time logging of the encryption process, providing precise timing metrics and detailed error diagnostics.
• Interactive Onboarding: Guided simulation demonstrating live encryption cycles and safe key management, with an Advanced Mode for power users.
• Custom Encryption Control: Full manual control over encryption chains. Add, remove, and reorder layers from 15+ algorithms with interactive physics-based controls. Optional ZLIB compression available.
• Advanced Theming: Material You Dynamic Colors, Dark/Light modes, and custom HSV color engine.

Technical Specifications
• Engine: CryptoEngine v0.10.0 (Bouncy Castle) with performance-tuned Argon2id configuration.
• Key Derivation: Argon2id (64MB) + SHA-512 pre-hashing + HKDF for layer separation to resist GPU attacks.
• Supported Algorithms: AES (GCM/CBC), ChaCha20-Poly1305, Twofish, Serpent, Camellia, CAST6, RC6, SM4, GOST, SEED, Blowfish, IDEA, CAST5, TEA, and XTEA.

Open Source Transparency
The complete source code is available for public audit on GitHub: https://github.com/Animesh-Varma/Sigil
For the complete release catalog and planned features, please visit:
https://github.com/Animesh-Varma/Sigil/releases

For any queries, please contact: sigil@animeshvarma.dev