schnee 2026.5.5.4

NFC/RFID tag authentication and encryption library

schnee

schnee is a Python package and CLI for working with NFC/RFID tags through a PC/SC reader, with a current focus on NTAG profile inspection and NDEF URL writes.

Installation

Install the package from PyPI:

pip install schnee

Requirements

schnee talks to tags through PC/SC via pyscard, so practical use requires:

• a compatible NFC or smart card reader
• a working system PC/SC library/service
• access to the target tag

Platform-specific PC/SC prerequisites:

• Linux: install a PC/SC implementation such as pcsc-lite and ensure the pcscd daemon/service is installed and running. Depending on your distribution, you may also need your reader's driver package.
• Windows: pyscard uses the built-in WinSCard PC/SC subsystem that ships with Windows; make sure the smart card service and your reader driver are available.
• macOS: pyscard uses the system PCSC.framework, which is included with macOS; make sure the reader is connected and recognized by the system.

If the PC/SC stack, service, or reader is not available, pyscard may fail to import, no readers may be discovered, or CLI commands that access hardware will fail during reader discovery or card communication.

CLI Usage

After installation, the schnee command is available on your PATH.

Show the top-level help:

schnee --help

List selectable backends and detected PC/SC readers:

schnee backends

Read the current NTAG profile as JSON:

schnee ntag read --backend pcsc

Use a specific reader by name:

schnee ntag read --backend "pcsc:ACS ACR1252 1S CL Reader PICC 0"

Write a URL as a single NDEF URI record:

schnee ntag write-url --backend pcsc --url "https://example.com"

For NTAG 424 DNA tags that require application authentication before writing, provide the current 16-byte AES key as 32 hex characters:

schnee ntag write-url \
  --backend pcsc \
  --url "https://example.com" \
  --ntag424-master-key-hex 00112233445566778899aabbccddeeff

Warning: passing a secret key on the command line can expose it through shell history, terminal logging, or process listings visible to other local users. Avoid using real production keys this way; prefer a safer secret input mechanism if one is available in your environment.

Python API

The stable Python entry points currently exposed by the package are the service classes re-exported from schnee.services. For example, you can list the selectable backends from Python:

from schnee.services import ListBackendNamesService

backends = ListBackendNamesService.call(ListBackendNamesService.Request())
print(backends)

This call uses the same backend discovery as schnee backends, so it also depends on a working PC/SC environment when the PC/SC backend is enabled.

Trademarks and Disclaimer

• Trademarks: NTAG, MIFARE, and NXP are registered trademarks of NXP B.V. This project is an independent open-source implementation and is not affiliated with, endorsed by, or sponsored by NXP B.V.
• Accuracy of Information: This SDK is developed based on publicly available datasheets. While every effort has been made to ensure the accuracy of the implementation, the author makes no guarantees regarding its suitability for any specific purpose.
• Limitation of Liability: In no event shall the author be liable for any damages arising from the use of this software, including but not limited to hardware damage (NFC tags, readers, etc.), data loss, or "bricking" of tags due to incorrect AES key configuration or authentication failures. Use this software at your own risk.