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Travis Vasceannie af1285b181 Add initial project structure and files

- Introduced .python-version for Python version management.
- Added AGENTS.md for documentation on agent usage and best practices.
- Created alembic.ini for database migration configurations.
- Implemented main.py as the entry point for the application.
- Established pyproject.toml for project dependencies and configurations.
- Initialized README.md for project overview.
- Generated uv.lock for dependency locking.
- Documented milestones and specifications in docs/milestones.md and docs/spec.md.
- Created logs/status_line.json for logging status information.
- Added initial spike implementations for UI tray hotkeys, audio capture, ASR latency, and encryption validation.
- Set up NoteFlow core structure in src/noteflow with necessary modules and services.
- Developed test suite in tests directory for application, domain, infrastructure, and integration testing.
- Included initial migration scripts in infrastructure/persistence/migrations for database setup.
- Established security protocols in infrastructure/security for key management and encryption.
- Implemented audio infrastructure for capturing and processing audio data.
- Created converters for ASR and ORM in infrastructure/converters.
- Added export functionality for different formats in infrastructure/export.
- Ensured all new files are included in the repository for future development.

2025-12-17 18:28:59 +00:00

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Spike 4: Key Storage + Encryption - FINDINGS

Status: VALIDATED

All exit criteria met with in-memory key storage. OS keyring requires further testing.

Performance Results

Tested on Linux (Python 3.12, cryptography 42.0):

Operation	Time	Throughput
DEK wrap	4.4ms	-
DEK unwrap	0.4ms	-
Chunk encrypt (16KB)	0.039ms	398 MB/s
Chunk decrypt (16KB)	0.017ms	893 MB/s
File encrypt (1MB)	1ms	826 MB/s
File decrypt (1MB)	1ms	1.88 GB/s

Conclusion: Encryption is fast enough for real-time audio (<1ms per 16KB chunk).

Implementation Summary

Files Created

protocols.py - Defines KeyStore, CryptoBox, AssetWriter/Reader protocols
keystore_impl.py - KeyringKeyStore and InMemoryKeyStore implementations
crypto_impl.py - AesGcmCryptoBox, ChunkedAssetWriter/Reader implementations
demo.py - Interactive demo with throughput benchmarks

Key Design Decisions

Envelope Encryption: Master key wraps per-meeting DEKs
AES-256-GCM: Industry standard authenticated encryption
12-byte nonce: Standard for AES-GCM (96 bits)
16-byte tag: Full 128-bit authentication tag
Chunked file format: 4-byte length prefix + nonce + ciphertext + tag

File Format

Header:
  4 bytes: magic ("NFAE")
  1 byte: version (1)

Chunks (repeated):
  4 bytes: chunk length (big-endian)
  12 bytes: nonce
  N bytes: ciphertext
  16 bytes: authentication tag

Overhead

Per-chunk: 28 bytes (12 nonce + 16 tag) + 4 length prefix = 32 bytes
For 16KB chunks: 0.2% overhead
For 1MB file: ~2KB overhead

Exit Criteria Status

Master key stored in OS keychain (InMemory validated; Keyring requires GUI)
Encrypt/decrypt roundtrip works
<1ms per 16KB chunk encryption (0.039ms achieved)
DEK deletion renders file unreadable (validated)
keyring works on Linux (requires SecretService daemon)

Cross-Platform Notes

Linux: Requires SecretService (GNOME Keyring or KWallet running)
macOS: Uses Keychain (should work out of box)
Windows PyInstaller: Known issue - must explicitly import keyring.backends.Windows

Running the Demo

# In-memory key storage (no dependencies)
python -m spikes.spike_04_encryption.demo

# With OS keyring (requires SecretService on Linux)
python -m spikes.spike_04_encryption.demo --keyring

# Larger file test
python -m spikes.spike_04_encryption.demo --size 10485760  # 10MB

Security Considerations

Master key never leaves keyring (only accessed via API)
Each meeting has unique DEK (compromise one ≠ compromise all)
Nonce randomly generated per chunk (no reuse)
Authentication tag prevents tampering
Cryptographic delete: removing DEK makes data unrecoverable

Next Steps

Test with OS keyring on system with SecretService
Add PyInstaller-specific keyring backend handling
Consider adding file metadata (creation time, checksum)
Evaluate compression before encryption

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