Digital signatures of PROFINET GSD files - References - SIMATIC AX - AX Hardware Engineering documentation - Hardware Engineering,

The manufacturer provides a general station description file (GSD file) for each PROFINET device. The GSD file describes the properties of the device in a machine readable XML format and contains all properties of a PROFINET‑device that are needed for configuring.

With the introduction of PROFINET Security Class 1, GSD files together with other related files, such as images or text files, are provided in a GSDX file with a verified manufacturer signature. A GSDX file can also contain multiple GSD files, such as all GSD files of a device family. The included signature confirms the integrity and authenticity of the contained files. This ensures that the files contained in the GSDX file originate from the expected manufacturer and have not been altered.

If your engineering system does not support the import of GSDX files, continue using GSD files as up to now.