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42pak-generator

A modern, open-source pak file manager for the Metin2 private server community. Replaces the legacy EIX/EPK archive format with the new VPK format featuring AES-256-GCM encryption, LZ4/Zstandard/Brotli compression, BLAKE3 hashing, and HMAC-SHA256 tamper detection.

Screenshots: See PREVIEW.md for a full gallery of the GUI in both dark and light themes.

---

Features

• Create VPK archives - Pack directories into single .vpk files with optional encryption and compression
• Manage existing archives - Browse, search, extract, and validate VPK archives
• Convert EIX/EPK to VPK - One-click migration from legacy EterPack format (supports 40250, FliegeV3, and MartySama 5.8 variants)
• AES-256-GCM encryption - Per-file authenticated encryption with unique nonces
• LZ4 / Zstandard / Brotli compression - Choose the algorithm that fits your needs
• BLAKE3 content hashing - Cryptographic integrity verification for every file
• HMAC-SHA256 - Archive-level tamper detection
• Filename mangling - Optional obfuscation of file paths within archives
• Full CLI - Standalone 42pak-cli with pack, unpack, list, info, verify, diff, migrate, search, check-duplicates, and watch commands
• Metin2 C++ integration - Drop-in client and server loader code for 40250, FliegeV3, and MartySama 5.8 source trees

VPK vs EIX/EPK Comparison

Feature	EIX/EPK (Legacy)	VPK (42pak)
Encryption	TEA / Panama / HybridCrypt	AES-256-GCM
Compression	LZO	LZ4 / Zstandard / Brotli
Integrity	CRC32	BLAKE3 + HMAC-SHA256
File format	Dual file (.eix + .epk)	Single file (.vpk)
Archive count	512 max entries	Unlimited
Filename length	160 bytes	512 bytes (UTF-8)
Key derivation	Hardcoded keys	PBKDF2-SHA512 (200k iterations)
Tamper detection	None	HMAC-SHA256 whole-archive

---

Quick Start

Prerequisites

• .NET 8.0 SDK
• Windows 10 version 1809+ (for WebView2)
• WebView2 Runtime (usually pre-installed)

Build

cd 42pak-generator
dotnet restore
dotnet build --configuration Release

Run the GUI

dotnet run --project src/FortyTwoPak.UI

Run the CLI

dotnet run --project src/FortyTwoPak.CLI -- <command> [options]

Run Tests

dotnet test

Publish (Portable / Installer)

# CLI single-exe (~65 MB)
.\publish.ps1 -Target CLI

# GUI portable folder (~163 MB)
.\publish.ps1 -Target GUI

# Both + Inno Setup installer
.\publish.ps1 -Target All

---

CLI Usage

The standalone CLI (42pak-cli) supports all operations:

42pak-cli pack <SOURCE_DIR> [--output <FILE>] [--compression <lz4|zstd|brotli|none>] [--level <N>] [--passphrase <PASS>] [--threads <N>] [--dry-run]
42pak-cli unpack <ARCHIVE> <OUTPUT_DIR> [--passphrase <PASS>] [--filter <PATTERN>]
42pak-cli list <ARCHIVE> [--passphrase <PASS>] [--filter <PATTERN>] [--json]
42pak-cli info <ARCHIVE> [--passphrase <PASS>] [--json]
42pak-cli verify <ARCHIVE> [--passphrase <PASS>] [--filter <PATTERN>] [--json]
42pak-cli diff <ARCHIVE_A> <ARCHIVE_B> [--passphrase <PASS>] [--json]
42pak-cli migrate <LEGACY_ARCHIVE> [--output <FILE>] [--compression <TYPE>] [--passphrase <PASS>]
42pak-cli search <WORKSPACE_DIR> <FILENAME_OR_PATTERN>
42pak-cli check-duplicates <WORKSPACE_DIR> [--read-index]
42pak-cli watch <SOURCE_DIR> [--output <FILE>] [--debounce <MS>]

Flags: -q / --quiet suppresses all output except errors. --json outputs structured JSON for scriptable pipelines.

Exit codes: 0 = success, 1 = error, 2 = integrity failure, 3 = passphrase incorrect.

---

Project Structure

42pak-generator/
├── 42pak-generator.sln
├── src/
│   ├── FortyTwoPak.Core/            # Core library: VPK read/write, crypto, compression, legacy import
│   │   ├── VpkFormat/               # VPK header, entry, archive classes
│   │   ├── Crypto/                  # AES-GCM, PBKDF2, BLAKE3, HMAC
│   │   ├── Compression/             # LZ4 / Zstandard / Brotli compressors
│   │   ├── Legacy/                  # EIX/EPK reader and converter (40250 + FliegeV3 + MartySama 5.8)
│   │   ├── Cli/                     # Shared CLI handler (12 commands)
│   │   └── Utils/                   # Filename mangling, progress reporting
│   ├── FortyTwoPak.CLI/             # Standalone CLI tool (42pak-cli)
│   ├── FortyTwoPak.UI/              # WebView2 desktop application
│   │   ├── MainWindow.cs            # WinForms host with WebView2 control
│   │   ├── BridgeService.cs         # JavaScript <-> C# interop bridge
│   │   └── wwwroot/                 # HTML/CSS/JS frontend (6 tabs, dark/light theme)
│   └── FortyTwoPak.Tests/           # xUnit test suite (22 tests)
├── Metin2Integration/
│   ├── Client/
│   │   ├── 40250/                   # C++ integration for 40250/ClientVS22 (HybridCrypt)
│   │   ├── MartySama58/             # C++ integration for MartySama 5.8 (Boost + HybridCrypt)
│   │   └── FliegeV3/                # C++ integration for FliegeV3 (XTEA/LZ4)
│   └── Server/                      # Shared server-side VPK handler
├── docs/
│   └── FORMAT_SPEC.md               # VPK binary format specification
├── publish.ps1                      # Publish script (CLI/GUI/Installer/All)
├── installer.iss                    # Inno Setup 6 installer script
├── assets/                          # Screenshots and banner images
└── build/                           # Build output

---

VPK File Format

Single-file archive with this binary layout:

+-------------------------------------+
| VpkHeader (512 bytes, fixed)        |  Magic "42PK", version, entry count,
|                                     |  encryption flag, salt, author, etc.
+-------------------------------------+
| Data Block 0 (aligned to 4096)      |  File content (compressed + encrypted)
+-------------------------------------+
| Data Block 1 (aligned to 4096)      |
+-------------------------------------+
| ...                                 |
+-------------------------------------+
| Entry Table (variable size)         |  Array of VpkEntry records. If encrypted,
|                                     |  wrapped in AES-GCM (nonce + tag + data).
+-------------------------------------+
| HMAC-SHA256 (32 bytes)              |  Covers everything above. Zero if unsigned.
+-------------------------------------+

Encryption Pipeline

For each file: Original -> LZ4 Compress -> AES-256-GCM Encrypt -> Store

On extraction: Read -> AES-256-GCM Decrypt -> LZ4 Decompress -> BLAKE3 Verify

Key derivation: PBKDF2-SHA512("42PK-v1:" + passphrase, salt, 100000 iterations) -> 64 bytes

• First 32 bytes: AES-256 key
• Last 32 bytes: HMAC-SHA256 key

For the full binary specification, see docs/FORMAT_SPEC.md.

---

Usage

Creating a VPK Archive (GUI)

1. Open 42pak-generator
2. Go to Create Pak tab
3. Select source directory containing files to pack
4. Choose output .vpk file path
5. Configure options:
   • Encryption: Toggle on and enter a passphrase
   • Compression Level: 0 (none) to 12 (maximum)
   • Filename Mangling: Obfuscate paths within the archive
   • Author / Comment: Optional metadata
6. Click Build

Converting EIX/EPK to VPK

1. Go to Convert tab
2. Select the .eix file (the .epk must be in the same directory)
3. Choose output .vpk path
4. Optionally set encryption passphrase
5. Click Convert

Metin2 Client Integration

Three integration profiles are provided for different source trees:

• 40250 / ClientVS22 (HybridCrypt, LZO): Metin2Integration/Client/40250/INTEGRATION_GUIDE.md
• MartySama 5.8 (Boost, HybridCrypt, LZO): Metin2Integration/Client/MartySama58/INTEGRATION_GUIDE.md
• FliegeV3 (XTEA, LZ4): Metin2Integration/Client/FliegeV3/INTEGRATION_GUIDE.md

Metin2 Server Integration

See Metin2Integration/Server/INTEGRATION_GUIDE.md for server-side VPK reading.

---

Technologies

Component	Technology
Runtime	.NET 8.0 (C#)
UI	WebView2 (WinForms host)
Frontend	HTML5, CSS3, Vanilla JavaScript
Encryption	AES-256-GCM via System.Security.Cryptography
Key Derivation	PBKDF2-SHA512 (200,000 iterations)
Hashing	BLAKE3 via blake3 NuGet
Compression	LZ4 via K4os.Compression.LZ4, Zstandard via ZstdSharp, Brotli (built-in)
Tamper Detection	HMAC-SHA256
C++ Crypto	OpenSSL 1.1+
Testing	xUnit

---

License

This project is licensed under the MIT License - see the LICENSE file for details.

Contributing

Contributions are welcome! See CONTRIBUTING.md for guidelines.

Acknowledgments

• The Metin2 private server community for keeping the game alive
• The original YMIR Entertainment EterPack format for providing the foundation
• BLAKE3 team for the fast hash function
• K4os for the .NET LZ4 binding
• MartySama - for his excellent tutorials and clean codebase
• Fliege - for the inspiring server files and systems
• TMP4 - for the high-quality reference files and tools

Without their work, this project wouldn't have been possible. 🙏