Cross-Platform Trading App Development

I'm looking to develop a trading app for both iOS and Android platforms. The app should include:

Core Functionalities:
- Real-time stock prices
- Trading execution
- Portfolio management

Security is a top priority; I'm open to suggestions on essential security features like two-factor authentication, biometric login, or encryption.

Ideal skills and experience:
- Proven experience in developing secure trading apps
- Expertise in mobile app development for both iOS and Android
- Strong knowledge of financial markets and trading functionalities
- Experience with implementing robust security measures