Kyu Archiver (QQX5)

A lightweight, secure-capable archiver utilizing LZ77 compression and modern authenticated encryption (AEAD). Now featuring WebAssembly support for secure, in-browser video streaming.

Features

• Algorithm: Tunable LZ77 (Greedy/Lazy matching) + Huffman-style coding.
• Format: QQX5 (Streaming-friendly, chunk-based).
• Web-Ready: Compiles to WASM for high-performance (500MB/s+) in-browser decryption.
• Security:
  • Cipher: XChaCha20-Poly1305 (via Monocypher).
  • KDF: Argon2id (Memory-hard key derivation).
  • Model: Insecure by default (for convenience) with Smart Decryption.
• Integrity: Full cryptographic authentication of headers and data.

Build

Kyu uses a simple Makefile and requires a C99 compiler. It relies on monocypher for cryptography, which is automatically fetched via scripts/vendor.sh.

# 1. Build optimized release binary (CLI tool)
make

# 2. Build WebAssembly Library & Demo
make wasm

# 3. Generate Documentation (Doxygen)
make docs

Usage

CLI Tool

Basic (Insecure Mode) By default, Kyu uses a hardcoded default password. This is convenient for non-sensitive data.

# Compress
./kyu -c -o video.kyu ./my_video.mp4

# Decompress
./kyu -d video.kyu

Secure Mode To encrypt your data securely, use -p.

# Encrypt
./kyu -c -p -o secret.kyu ./sensitive.data

# Decrypt (Auto-detects encryption)
./kyu -d secret.kyu

Web Demo (WASM)

Kyu includes a high-performance browser demo that can decrypt and stream 4K video in real-time using WebAssembly and the Streams API.

1. Build the WASM target:

   make wasm

2. Launch the Live Server:

   ./scripts/rebuild_live.sh go

3. Test: Open http://localhost:8080 and drag-and-drop a .kyu encrypted video file. It will decrypt and play instantly without downloading the full file to memory.

Technical Details

QQX5 Format

The archive consists of a sequence of chunks. Each chunk is individually encrypted and authenticated, allowing for random access and streaming.

1. Header: KYU5 + Salt (16 bytes).
2. Packet (V2):
   • Header: Sequence ID (8 bytes) + Length/Flags (8 bytes).
   • MAC: 16 bytes (Poly1305).
   • Payload: Encrypted/Compressed data (XChaCha20).
3. Manifest: Encrypted metadata (filename, permissions, mtime) at the end of the stream.

Directory Structure

• src/: Core C implementation and TypeScript wrappers.
• include/: Public API headers.
• scripts/: Build helpers, benchmarks, and test runners.

License

BSD-2-Clause / CC0 (Dual Licensed).