Sigil

About this app
Sigil is an open-source, offline zero-trust encryption utility designed to secure your sensitive data against modern threats. Unlike standard tools that rely on a single algorithm, Sigil offers a flexible "Encryption Profiles" system, allowing you to choose between maximum defense-in-depth or standard compatibility.

The application operates entirely offline, performing all cryptographic operations locally on your device with a modern Material 3 interface.

New in v0.4.5: Encryption Profiles
• Sigil Chain (Default): A pre-configured, multi-layer cascade (XChaCha20 + Serpent + Twofish + AES-256) designed for extreme resistance against cryptanalysis.
• Raw Mode: Standard, single-layer encryption (e.g., AES-256-GCM only) for maximum compatibility with external tools and faster processing.
• Custom Profiles: Build your own encryption chain! Select from 18 algorithms, reorder layers, and save your custom configuration for repeated use.

Core Security Features
• 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.
• Zero-Knowledge Auth: Support for PINs and Passwords, hashed using Argon2id. Credentials are never stored in a reversible format.
• Tamper-Proof Design: Sigil uses an Encrypt-then-MAC architecture. Any data corruption or tampering is detected and rejected before decryption is attempted.
• Memory Hygiene: Sensitive data is wiped from RAM immediately after use. A configurable grace period allows for convenient multitasking without compromising security.

Privacy & System Hardening
• Screen Shield: Utilizes FLAG_SECURE to block screenshots and hide content in the "Recent Apps" overview, protecting against shoulder surfing and spyware.
• Clipboard Auto-Wipe: Prevents clipboard managers from retaining your decrypted text.
• Truly Offline: No internet permission requested. No analytics, no telemetry, and no cloud backups. Your data never leaves your device.

Advanced User Toolkit
• Algorithm Registry: Support for 18 ciphers including AES-GCM, XChaCha20-Poly1305, ARIA, Serpent, Twofish, Camellia, and more.
• Secure Keystore: Save and manage your encryption keys securely. Includes an Entropy Meter to gauge password strength.
• App Lock: Biometric unlock verified by the hardware TEE or a custom high-security PIN.
• System Console: View real-time logs of the encryption process, including timing metrics and cryptographic parameters.
• Modern UI: Built with Jetpack Compose, featuring Material You dynamic colors and dark/light themes.

Technical Specifications
• Cryptography Library: Bouncy Castle (v1.83).
• Key Derivation: Argon2id (Memory-hard KDF) + SHA-512 pre-hashing to resist GPU brute-force attacks.
• Supported Algorithms: AES (GCM/CBC), ChaCha20-Poly1305, XChaCha20-Poly1305, ARIA-256-GCM, Serpent, Twofish, Camellia, SM4, CAST-256, RC6, SEED.
• Legacy Support: Blowfish, IDEA, CAST-128, GOST, TEA, XTEA (included for educational purposes).

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