Fortify Cash App ++ Security

I’m rolling out version 3.0 of Cash App ++ and my top priority is tightening its security layer before launch. The build already processes payments smoothly, but I now need a specialist to harden the codebase in two key areas: • Implement robust two-factor authentication that relies on authenticator apps (TOTP-based), not SMS or email. Users should be able to pair any mainstream authenticator (Google, Microsoft, Authy, etc.) during onboarding or in their settings, with time-skew handling and encrypted backup of the shared secret. • Upgrade our existing encryption. All sensitive data—tokens, transaction details, personal information—must be secured at rest and in transit with modern, well-audited algorithms (AES-256, TLS 1.3, forward secrecy). Key rotation and secure storage (e.g., AWS KMS or similar) are expected. Acceptance criteria 1. Seamless 2FA flow integrated into the current React Native front-end and Node.js/Express API, passing automated tests and UX checks. 2. Encryption module passes penetration testing results with zero critical findings and clear documentation of cipher suites, key handling, and compliance notes. 3. Delivery of annotated pull requests and a concise security implementation guide so future devs can maintain the work. If you have experience locking down fintech or payment apps and can start quickly, let’s talk. Budget: USD 15–25