Sealr is an end-to-end encrypted messenger built on React Native and Firebase. It gives senders absolute post-send control by attaching cryptographic rules (views, expiry, geo-fencing) to each message. We use AES-256-GCM and RSA-OAEP-2048, enforcing permissions via Firestore rules without the server ever reading the content and without any plain-text and media ever being stored on the local device. Screen capture and mirroring is blocked at the OS level.