Activation Key Generator for Multi-platforms

I want a digital key generator that can generate activation keys for multiple platforms. It doesn't need to have a payment gateway or complex user management system.

Key Features:
- Multi-platform: Compatible with Windows, Mac, and Android
- Key Type: Activation keys

User Management:
- Basic tracking system for key distribution

Ideal Skills:
- Proficiency in programming for various platforms
- Experience in key generation algorithms
- Basic understanding of user management systems