principle-security

Designing secure authentication and authorization separation requires enforcing default-deny policies and preventing confused-deputy privilege escalation at the trust boundary. You should split identity verification from access control decisions and apply least-privilege scope to every request.

Trust-boundary-driven input validation enforces defensive checks wherever data crosses trust levels, requiring re-validation on every hop. You need it when handling untrusted input to mitigate common injection patterns and ensure data integrity across system layers.

Handling secrets management securely means keeping secrets out of source code and logs, designing rotation from day one, and using placeholder-only examples. You should implement rotation-aware secret handling with minimal permissions and fail-closed defaults.

Applying defense in depth with least privilege involves layering security controls, enforcing fail-closed defaults, and minimizing the attack surface. You should design systems with multiple independent validation checks and grant only the smallest permissions necessary.

Choosing misuse-resistant cryptography means preferring safe constructions, using constant-time comparisons, and applying secure defaults for key management. You should avoid custom crypto implementations and ensure your design specifies safe algorithm choices explicitly.