Distributed Systems Security and Trust Questions

Security problems that exist because a system is distributed: keeping trust state correct while it propagates across many services, clusters and regions. Covers credential, token and certificate revocation under eventual consistency and network partitions; fleet-wide rotation of signing keys, secrets and trust anchors without outages (key rollover and grace windows, canary rotation, recovery from a compromised root); distributed authorization (replicated policy decision points, cached decisions, fail-open versus fail-closed when an auth dependency degrades); propagating caller identity and permissions through service call chains; tamper-evident audit trails across services and regions (hash chains, Merkle proofs, ordering events with imperfect clocks); Byzantine and partially trusted participants; cross-cluster and cross-organization trust federation; securing shared distributed components such as caches and message brokers against injection, replay and cross-tenant access; protecting data in transit across region boundaries; and tenant isolation as a security blast-radius boundary. Steady-state mTLS, service-mesh identity and network segmentation mechanics are covered by zero-trust service-to-service security; single-system cryptography and KMS basics by applied cryptography.