Add encrypted local storage for MLS group state so groups survive app
restarts, plus key lifecycle management:
- MlsGroupState: TLS-encoded serializable snapshot of complete group state
(group context, ratchet tree, epoch secrets, private keys, transcript hash)
- MlsGroupStateStore: interface for encrypted per-group storage (platform
implementations provide EncryptedSharedPreferences / encrypted file)
- MlsGroupManager: high-level coordinator managing group lifecycle, epoch
secret retention window (N-1 for late messages), state persistence,
and key export
- RetainedEpochSecrets: bounded window of past epoch decryption secrets
for out-of-order message handling
- MlsGroup.saveState()/restore(): roundtrip serialization via TLS codec
- MlsGroup.proposeSigningKeyRotation(): Update proposal with fresh Ed25519
signing key and X25519 encryption key for forward secrecy
- KeyPackageRotationManager: tracks consumed KeyPackages after Welcome
processing, handles slot rotation and proactive age-based rotation
- Tests: 16 tests covering state serialization roundtrips, manager lifecycle,
multi-group independence, and signing key rotation persistence
https://claude.ai/code/session_01MuRS2zSVm6A36HNFwG7M5p
Claude
40eb128cb8