Use Microsoft’s XapSignTool (from the old Windows Phone SDK) to verify digital signatures.
xapsign verify -file app.xap
A valid output means the XAP hasn’t been repacked corruptly. Extra quality archives keep signatures intact even if expired. windows phone xap archive extra quality
Downloading a 20GB folder of XAPs is step one. “Extra quality” requires validation. Here’s your forensic toolkit: Use Microsoft’s XapSignTool (from the old Windows Phone
For Windows 10 Mobile devices (Lumia 950), you may need to enable “Sideload apps” in Settings > Update & Security > For developers. A valid output means the XAP hasn’t been
Pro tip: Some high-quality XAPs require interop-unlock (registry editing). Tools like WP Internals can unlock bootloaders on old Lumias, allowing full access.