Digital Stamp Card App Development

I'm looking for a skilled app developer to create a digital stamp card application for both iOS and Android platforms. The app's core functionality will be QR code scanning for stamping.

Key Requirements:
- QR Code Scanning: Users can scan codes to earn stamps.
- User Authentication: Secure login with email/password.

Ideal Skills:
- Experience in cross-platform app development.
- Proficiency in QR code integration.
- Strong background in implementing secure authentication systems.

Please provide examples of similar work.