# 4. Architecture & Security

- [4.1 Where Things Live](/4.-architecture-and-security/4.1-where-things-live.md)
- [4.2 Authentication Flow](/4.-architecture-and-security/4.2-authentication-flow.md)
- [4.3 Key Custody & Biometrics](/4.-architecture-and-security/4.3-key-custody-and-biometrics.md)