# Task 6 Review Summary
**Date**: 2026-02-05 23:00:00 GMT
**Task**: Phase 1.5, Task 6 - Integrate Encryption with CRDT Task Lists

## Build Validation: PASS

✅ cargo build: PASS
✅ cargo clippy --lib -D warnings: PASS  
✅ cargo fmt --check: PASS

## Implementation Summary

**New Files:**
- `src/crdt/encrypted.rs` (~450 lines: 200 production, 250 tests)

**Modified Files:**
- `src/crdt/mod.rs` (exported EncryptedTaskListDelta)

**Features Implemented:**
- EncryptedTaskListDelta struct with group_id, epoch, ciphertext, aad
- encrypt() method using group keys and MlsCipher
- decrypt() method with authentication verification
- encrypt_with_group() convenience method
- decrypt_with_group() with epoch/group validation
- 10 comprehensive tests covering all requirements

## Specification Compliance: PASS

✅ Encrypt task list deltas with group keys
✅ Include group_id and epoch in ciphertext
✅ Proper authentication (AEAD via ChaCha20-Poly1305)
✅ Tests: encrypt/decrypt round-trip
✅ Tests: different epochs require different keys
✅ Tests: invalid ciphertexts rejected

## Code Quality: A

- Zero warnings
- No .unwrap() in production code
- Proper error handling with Result types
- Comprehensive documentation
- Clean, readable structure
- Consistent with existing MLS/CRDT patterns

## Security: A

- Uses MlsCipher (ChaCha20-Poly1305 AEAD)
- Per-epoch encryption keys
- AAD binds ciphertext to group and epoch
- Authentication prevents tampering
- Epoch mismatch detection
- Group ID validation

## Test Coverage: A

10 comprehensive tests:
1. Encrypt/decrypt round-trip
2. Group metadata included
3. Wrong epoch rejection
4. Wrong group rejection
5. Authentication prevents tampering
6. Different epochs produce different ciphertexts
7. Empty delta encryption
8. Large delta encryption (100 tasks)
9. Serialization round-trip
10. AAD includes group and epoch

## VERDICT: PASS

Task 6 implementation complete with excellent quality.
- Zero compilation errors
- Zero warnings
- Specification fully met
- Security properties verified
- Comprehensive testing

**Ready to commit and proceed to Task 7.**
