There's an algorithm (or two) that leverages multi-step encryption to facilitate two (seemingly exclusive) properties.
The algorithm, developed by Dr. Andrew Neff, was first implemented by a company called VoteHere.
Now it is available for testing and vetting via an implementation at https://vote.heliosvoting.org....
FWIW I've posted about this system almost a dozen times over the past decade.
"Pay no attention to the man behind the curtain." -- The Wizard Of Oz