TL;DR

Lumina is a secure mobile app designed to manage and share contact information with full control and privacy. Unlike traditional contact apps, Lumina gives users total ownership of their data by keeping everything on-device and only syncing encrypted data through a temporary swap server.

It solves 3 major pain points in personal and professional networking:

1. Data privacy & leaks
2. Outdated contact information
3. Disorganized, duplicated contact storage

My Role

I led every aspect of Lumina’s development from concept to implementation. I designed the mobile architecture and UX, built the backend API and database, implemented robust encryption workflows, and handled DevOps, deployment, and CI/CD pipelines. I also designed the branding, logo, and pixel-perfect frontend interfaces. Essentially, I was responsible for the entire stack, ensuring every layer of the app aligned with the privacy-first vision my customer had in mind.

Tech Stack

Lumina was built using Flutter for a consistent iOS and Android experience, while the backend leveraged Serverpod, a Dart-based framework, to seamlessly integrate with our frontend. PostgreSQL and Redis provided reliable storage and caching, and all sensitive communication was secured with end-to-end encryption fully compliant with Apple and Google policies. The app runs in Dockerized environments with automated CI/CD pipelines, and the UI/UX was crafted from Sketch mockups to ensure a polished, intuitive experience.

Challenges & Breakthroughs

Building Lumina was an exercise in balancing extreme security with an elegant, intuitive user experience. I designed a privacy-first architecture where no sensitive data is ever permanently stored on the server, while crafting a lightweight encryption workflow compliant with mobile platform policies. One of the key breakthroughs was achieving seamless offline-first functionality, automatic revocation, and real-time updates without compromising security or usability. The project pushed me to combine my skills in UX, mobile development, backend engineering, and cryptography in a single cohesive product.

Key Features Built

Serverless Contact Syncing

I designed a system where contact data only ever resides on users’ devices. When sharing contacts, encrypted payloads are temporarily stored on a swap server, never leaving users vulnerable to data leaks. This approach provides a seamless, secure syncing experience without compromising privacy.

Faces System

Lumina allows users to create multiple “Faces”, essentially curated sets of contact data that can include trivial, sensitive, or highly confidential information. Each Face can be selectively shared with different contacts, giving users granular control over exactly who sees what.

Auto-sync & Revocation

Whenever a contact updates their information, all linked users automatically receive the latest version. If a user’s access is revoked, the app ensures that their copy of the data is securely purged from their device. This feature balances convenience and security in real-time.

Encryption Workflow

I developed a lightweight but robust encryption flow, handling secure key exchanges and ensuring that only the intended recipient can decrypt and store shared data. This workflow meets the strict security standards of mobile platforms while remaining invisible to the user.

Outcome

The app is fully developed and is currently pending final approval from French encryption authorities. Once approved, it will be launched on the App Store and Play Store, with a security audit marking the next milestone.

From Concept to Reality. Move the blue handle left and right to explore how the real app (left) brings the mockup (right) to life. Throughout development, I stayed true to the original design while making subtle refinements—like enhancing the logo and polishing visual details—always in close collaboration with the customer to ensure a faithful and functional result.

I built Lumina entirely on my own—from architecture and backend to mobile UX, encryption, and branding. This project proves that privacy and user experience don’t have to be at odds, and that it’s possible to create a secure, intuitive app that users can trust with their most sensitive data.