We have found 2 software records in our database eligible for .ppt to .key file format conversion.
You can simply open PowerPoint presentations (.ppt) in Keynote on your Mac and save it as the default Keynote presentation (.key or .keynote depending on your version). The very same is also possible in the iOS versions of Keynote for iPhone and iPad or in the online version of iWorks.
Otherwise there doesn't seem to exist any other program that can otherwise reliably create Keynote Presentations from PowerPoint, aka perform ppt to key conversion.
PPT
A ppt file extension is traditionally used for Microsoft PowerPoint presentations. PowerPoint presentation can contain text, pictures, audio or video data. Sometimes also called slide shows.
KEY
Files with key extension can be often found as presentations saved in latest versions of Apple (iWork) Keynote, a professional presentation tool for Mac OS X, macOS and iOS.