How momo manages encryption keys without a central secret server: a pluggable provider chain (env, then config file), a per-node versioned key registry in local storage, and rotation that promotes a new key without any downtime. Teaches: why a provider chain beats a single source, how key versioning enables online rotation, and when rotation is and is not worth the complexity.
How momo isolates tenants without a central secret server: HKDF-derived per-tenant keys, default-deny ACLs evaluated per request, and a SHA-256 hash-chained audit log that makes tampering detectable. Teaches: key derivation vs. key storage, why ACL evaluation order matters, and how hash chaining turns a log into evidence.
Threshold-OPRF lets E2EE cas blobs dedup without revealing content hashes — plus adaptive failed-auth backoff and lockout.
Envelope encryption with a client-held key: the server stores ciphertext and can’t read it — across S3 and native transports.
A 76-deep audit (authed via Sentinel) surfaced CRLF injection, smuggling, traversal and path leaks — the pattern that forged momo’s security mindset.