Coffer: Offline Journal

Secure Path

About this app

Coffer is a private, fully offline digital journal built from the ground up for maximum security, encryption, and peace of mind. Every entry, photo attachment, and backup is encrypted locally on your device — nothing ever leaves your phone.

ZERO NETWORK ACCESS
Coffer requires no internet permissions. Your personal thoughts, photos, and memories cannot leak or be transmitted to external servers because the app has no network access at all.

HARDWARE-BACKED ENCRYPTION
Built around a 256-bit Journal Master Key (JMK), your data is secured at rest:
• Database Security: All journal entries and tags are stored in a SQLCipher-encrypted Room database (AES-256).
• Argon2id Key Derivation: Passphrase protection uses memory-hard Argon2id key derivation to prevent brute-force attacks.
• Biometric Unlock: Optionally enable fingerprint or face unlock backed by Android Keystore hardware security.
• Photo Encryption: Photos attached to entries are stripped of sensitive EXIF metadata and encrypted individually with AES-256-GCM.

FEATURE HIGHLIGHTS
• Timeline & Search: Browse entries grouped by day with instant full-text search and tag filtering.
• Rich Markdown Support: Write naturally with full markdown rendering, titles, bullet lists, and tags.
• Custom Paper Themes: Choose between Coffer (Light Blue), Sage (Green), and Charcoal (Dark) paper aesthetics.
• Portable Encrypted Backups: Export your entire journal or individual entries into passphrase-protected encrypted files to restore seamlessly on another device.
• Writing Streaks & Security Tips: Stay consistent with daily writing statistics and on-device privacy advice.

PRIVACY HARDENING BY DESIGN
• Automatic Screenshots Blocking: Built-in protection (FLAG_SECURE) prevents accidental screen captures or recent-app previews.
• Auto-Lock: Automatically locks when sent to the background or after 5 minutes of inactivity.
• Account-Free: No registration, no sign-in, no subscriptions, and zero analytics tracking.

Your memories belong to you alone. Start journaling with total privacy today with Coffer.