[Epic] LR-2 · Encryption Robustness & Key-Backup Lifecycle

[Deniel9204]

Make E2EE trustworthy end to end: guide verification & key backup at login, recover undecryptable history in bulk, and finish the cross-signing/SSSS state machine.

Why it's long-running: Touches onboarding (OOBE), the bootstrap/SSSS state machine, bulk re-decryption, cross-session trust indicators, bridge-bot key sharing, and offline export/import — all interlocking and security-critical.

Tracked issues

• Bulk re-decrypt whole room + batch key re-request #7 — Bulk re-decrypt whole room + batch key re-request
• Add encryption setup to OOBE / post-login #8 — Add encryption setup to OOBE / post-login
• Fix fragile key-backup restoration #9 — Fix fragile key-backup restoration
• Share outbound Megolm keys to bridge-bot devices #10 — Share outbound Megolm keys to bridge-bot devices
• Fix 'Encryption is already enabled!' error on room creation #11 — Fix 'Encryption is already enabled!' error on room creation
• Offline E2E room-key export/import to encrypted file #12 — Offline E2E room-key export/import to encrypted file
• Global + per-room trust indicators (unverified session/devices, backup-missing banners)
• Render numeric/decimal SAS in addition to emoji verification

Related (tracked under other epics)

• Room-version selection at creation + additional_creators (v12) #22 — Room-version selection at creation + additional_creators (v12)
• History-visibility control for authorized users #23 — History-visibility control for authorized users

_{Epic LR-2 · area: encryption · auto-generated from ROADMAP.md §5.}