OpenCrypt

Small Windows tool to encrypt files. Right-click a file, get a key, done. Rust does the crypto, PyQt6 is just a wrapper around it. No accounts, no cloud, no telemetry.

Why I made this

I wanted a one-click file encryptor that doesn't require installing something big, doesn't phone home, and doesn't lock me into a format I don't understand. So I wrote the format myself, kept it simple, and put everything in one directory.

How it works

1. Right-click a file → Encrypt with OpenCrypt.
2. OpenCrypt generates a random key and shows it to you once. Save it (a .key file or just copy it somewhere).
3. The file becomes name.ocrypt. Without the key it's noise.

Decryption is the same menu item on the .ocrypt file — paste the key, get your file back.

The key is everything

AES-256-GCM with an Argon2id-derived key. There is no backdoor, no "forgot your key" button, no recovery service. Losing the key loses the data. Save the key before you encrypt anything you care about.

Install

Portable — grab OpenCrypt.exe, run it once (splash screen, context menu registers itself), done. One file, works from a USB stick.

Installer — run OpenCrypt_Setup_v0.2.1.exe. No admin needed, installs to %LOCALAPPDATA%\Programs\OpenCrypt, uninstalls through Settings → Apps. Also installs the opc CLI (see below).

Both versions speak Russian or English depending on your system language.

CLI

GUI (also usable from the command line):

OpenCrypt.exe --encrypt "C:\Docs\report.docx"
OpenCrypt.exe --decrypt "C:\Docs\report.docx.ocrypt"
OpenCrypt.exe --unregister

Headless CLI — opc ships with the installer and is added to PATH if you keep the "Add OpenCrypt to PATH" checkbox (checked by default). Encryption is the default action; the key is printed to the console and saved next to the file:

opc "C:\Docs\report.docx"
:: Encrypted: C:\Docs\report.docx.ocrypt
:: Key: e9Jc2Llh6h_DvzjaxrHbOdY5j9XB7Ne98W1H4OBadHw
:: Saved key to: C:\Docs\report_key.key

opc -d "C:\Docs\report.docx.ocrypt"      :: key auto-detected
opc -d -k "C:\Docs\report_key.key" "C:\Docs\report.docx.ocrypt"

opc never overwrites an existing file, and removes the .ocrypt file after a successful decrypt. Exit codes: 0 success, 1 error, 2 usage. While developing, the same entry point lives in python_gui\.venv\Scripts\opc.exe.

Building from source

You need Rust, Python 3.11+, and optionally Inno Setup 6.

git clone https://github.com/Arean-Max/OpenCrypt.git
cd OpenCrypt

:: 1. Rust core
cd rust_core
cargo build --release
cargo test        :: optional
cd ..

:: 2. Python environment
cd python_gui
python -m venv .venv
.venv\Scripts\pip install -e .
cd ..

:: 3. Portable EXE
python_gui\.venv\Scripts\pyinstaller --onefile --windowed ^
    --icon assets\shield.ico ^
    --add-data "rust_core\target\release\rust_core.dll;open_crypt\core" ^
    --hidden-import PyQt6 --hidden-import PyQt6.QtWidgets ^
    --hidden-import PyQt6.QtCore --hidden-import PyQt6.QtGui ^
    --hidden-import PyQt6.sip ^
    --collect-submodules PyQt6 ^
    --distpath Release --workpath build_tmp ^
    python_gui\src\open_crypt\__main__.py

:: (Optional) 4. Installer
"%LOCALAPPDATA%\Programs\Inno Setup 6\ISCC.exe" installer\installer.iss

Or just run build.bat once the venv exists.

Design notes

• Memory-safe Rust core — no buffer overflows or use-after-free in the crypto path, and every C export catches panics at the boundary.
• Truncated files are detected, never silently decrypted as garbage.
• Per-file random nonces — the same key never produces the same key stream twice.
• 54 automated tests: unit + integration, plus FFI-boundary tests that load the real DLL (wrong password, null pointers, buffer sizes, truncation, nonce uniqueness, empty files).
• cargo fmt --check and clippy -D warnings are clean.
• The .ocrypt format is documented in docs/FILE_FORMAT.md.

Limitations / known issues

• No third-party security audit. The core has been reviewed internally only. Use it knowing that.
• Binaries are not code-signed. Windows SmartScreen will warn on first run.
• Whole-folder encryption is not implemented yet — only single files. (tracked in the issues)
• No key import UI — you can save a key to a .key file, but there's no import dialog; paste it manually when decrypting.
• The .ocrypt format is still young. It is documented and versioned, but treat it as subject to change before 1.0.

Layout

OpenCrypt/
├── assets/              # Icons
├── docs/
│   └── FILE_FORMAT.md   # .ocrypt format specification
├── installer/
│   └── installer.iss    # Inno Setup script
├── python_gui/          # PyQt6 frontend (FFI bridge, dialogs, context menu)
├── rust_core/           # Encryption engine (crypto.rs, ffi.rs, error.rs)
├── build.bat            # One-command build
├── LICENSE.md
└── README.md

License

MIT — see LICENSE.md.