sixcy — .6cy Container Format

A Rust implementation of the .6cy archive format featuring:

• Self-describing blocks: Every block carries its own magic, version, codec UUID, sizes, and integrity checksums
• Mandatory integrity verification: CRC32 header checks + BLAKE3 content hashes on every block
• Multiple codecs: Zstd (default), LZ4, Brotli, LZMA, and passthrough (none)
• AES-256-GCM encryption with Argon2id key derivation
• Content-defined chunking (Gear64 CDC) for improved deduplication
• Reed-Solomon FEC for recovery from missing/corrupt blocks
• Merkle proofs for efficient integrity verification
• Shamir Secret Sharing for key fragmentation
• Basic steganography utilities for hiding data in image LSBs

Quick Start

# Pack files into an archive
6cy pack -o archive.6cy -i file1.txt file2.txt

# List archive contents
6cy list archive.6cy

# Extract files
6cy unpack archive.6cy -C ./output_dir

# View archive info
6cy info archive.6cy

# Create encrypted archive
6cy pack -o secure.6cy -i sensitive.dat --password "mypassword"

# Use FEC for error recovery (10 data shards, 4 parity shards)
6cy pack -o resilient.6cy -i data/ --fec 10/4

# Use content-defined chunking for deduplication
6cy pack -o dedup.6cy -i data/ --cdc --merkle

# Recover from damaged archive
6cy recover damaged.6cy -o recovered.6cy

# Merge archives
6cy merge archive1.6cy archive2.6cy -o merged.6cy

CLI Commands

Command	Description
pack	Create archive from files/directories
unpack	Extract files from archive
list	List archive contents
info	Show archive metadata
scan	Scan blocks without index
recover	Extract recoverable data from damaged archive
optimize	Re-compress at different level
merge	Combine multiple archives
bench	Benchmark RLE pre-filter
vanta	Steganography subcommands

Library Usage

use sixcy::Archive;

let opts = sixcy::PackOptions {
    default_codec: sixcy::CodecId::Zstd,
    level: 3,
    use_cdc: true,
    build_merkle: true,
    ..Default::default()
};

let mut ar = Archive::create("data.6cy", opts)?;
ar.add_file("readme.txt", b"Hello, world!")?;
ar.finalize()?;

Architecture

src/
├── archive.rs      # High-level Archive API
├── block.rs        # Block format (84-byte headers)
├── superblock.rs   # Archive header (512 bytes)
├── codec/          # Compression codec registry
├── crypto/         # AES-256-GCM + Argon2id
├── cdc.rs          # Gear64 content-defined chunking
├── fec.rs          # Reed-Solomon forward error correction
├── merkle.rs       # Binary Merkle tree + proofs
├── sharding.rs     # Shamir's Secret Sharing
├── stego.rs        # LSB steganography
├── chaos.rs        # Block scrambling utilities
├── io_stream/      # Archive reader/writer
├── index/          # File index management
├── recovery/       # Index-bypass recovery scanner
├── perf.rs        # Performance utilities
└── plugin.rs      # C ABI for codec plugins

Format Version

Current: v2.0.0 (format_version = 2)

The .6cy format is documented in spec.md.

License

• Code: Apache-2.0
• Specification: CC BY 4.0