This tool allows you to extract nas_plugin.sprx from a 3.55 (now, only 3.55...) pup sony update.
After extract this module, you can decrypt the module using fail0verflow's unself tool.

To extract the module just run my app and browse the 3.55 pup file.
You will find the file in C:\depkg after the extraction.

KUDOS TO GEOHOT (This tool uses depkg.exe).