stegasoo/RELEASE_NOTES.md

Stegasoo v4.2.0

Performance Optimizations

Major performance improvements for Raspberry Pi and resource-constrained deployments.

DCT Vectorization (~14x faster)

• Batch DCT processing using scipy.fft.dctn with axes=(1,2)
• Processes 500 blocks at once instead of one-by-one
• Decode time reduced from ~2.6s to ~0.8s on 1MB images

Memory Optimization (50% reduction)

• Switched from float64 to float32 for all DCT operations
• Peak RAM: 211 MB → 107 MB for encode, 104 MB → 52 MB for decode
• Critical for Pi 3/4 avoiding swap thrashing

Progress Callbacks for Decode

• progress_file parameter added to decode() and extraction functions
• UI can now show decode progress (phases: loading, extracting, decoding, complete)
• JSON format: {"current": 80, "total": 100, "percent": 80.0, "phase": "decoding"}

Async API Endpoints

• Encode/decode operations now run in thread pool via asyncio.to_thread()
• API server can handle concurrent requests without blocking
• Essential for multi-user Pi deployments

Compression

Zstd Default Compression

• zstandard is now a core dependency (always installed)
• Better compression ratio than zlib for QR code RSA keys
• New STEGASOO-ZS: prefix for zstd, backward compatible with STEGASOO-Z: (zlib)

QR Code Generation

CLI Support

• stegasoo generate --rsa --qr key.png - save RSA key as QR image (PNG/JPG)
• stegasoo generate --rsa --qr-ascii - print ASCII QR to terminal

API Support

• POST /generate-key-qr - generate QR from RSA key
• Supports png, jpg, and ascii output formats
• Uses zstd compression by default

Other Changes

• RSA key size capped at 3072 bits (4096 too large for QR codes)
• File auto-expire increased to 10 minutes
• Progress bar "candy cane" animation during Argon2 key derivation
• Optional API service in Pi setup (with security warning)

Summary

Metric	v4.1.7	v4.2.0	Improvement
Decode (1MB)	~2.6s	~0.8s	70% faster
Peak RAM	211 MB	107 MB	50% less
Concurrent API	No	Yes	✓
QR Compression	zlib	zstd	~15% smaller

Raspberry Pi Image

Download stegasoo-rpi-4.2.0_final.img.zst from Releases.

# Flash (auto-detects SD card)
sudo ./rpi/flash-image.sh stegasoo-rpi-4.2.0_final.img.zst

# Or manual
zstdcat stegasoo-rpi-4.2.0_final.img.zst | sudo dd of=/dev/sdX bs=4M status=progress

Default login: admin / stegasoo

Docker

# Build and run
docker build -f docker/Dockerfile.base -t stegasoo-base:latest .
docker-compose -f docker/docker-compose.yml up -d

# Or individual services
docker-compose -f docker/docker-compose.yml up -d web  # Web UI on :5000
docker-compose -f docker/docker-compose.yml up -d api  # REST API on :8000

Full Changelog

See CHANGELOG.md for complete version history.