Secure Financial Modeling Backend

I need a secure backend to run my financial modeling algorithms. Users should be able to subscribe and pay fees.

Requirements:
- Algorithm Execution: Run financial modeling algorithms.
- User Authentication: Implement two-factor authentication (2FA).
- Payment Integration: Support credit/debit cards and cryptocurrency for subscriptions.

Ideal Skills:
- Experience in backend development.
- Knowledge of financial modeling.
- Proficient in implementing 2FA.
- Familiarity with payment gateways for cards and crypto.