Security app

I am looking for a developer to create a security app for both iOS and Android platforms. The app should have authentication/authorization features to ensure secure messaging. The primary purpose of the app should be secure messaging. Ideal skills and experience for this job include:
- Experience in developing security apps for both iOS and Android platforms
- Knowledge of authentication/authorization protocols
- Experience in developing messaging apps with encryption features
- Understanding of data encryption methods
- Familiarity with activity monitoring and security best practices.