Finally got communication with a locked chip working on MacOS today. Had encryption, detection of 1.07 & public key hash, parsing ehex and pretty much everything else working for the last couple days, but got stuck on this one last piece.
If I manage to make progress today or tomorrow on the remaining code security UI bugs, might package up 1.55-beta2 before Arduino 1.8.16 drops, since we also have the recent redesign of the File base class. There's no guarantee Arduino really will publish 1.8.16 on Monday, Sept 6 - it's just a github commit to their changelog at this point.
Hopefully we can wrap up 1.55 quickly and with a little luck Arduino will remain on 1.8.16 for a while, allowing time for adding ambitious features in 1.56.