Printing Secure Automatic Receipts with Activating Ink

The Scantegrity voting systems requires a printer to create hidden codes that can be revealed by a ballot marking pen only.The codes are used as confirmation numbers to create an automatic privacy preserving receipt for each voter.We discuss the techniques used to make the marks irreversible, and make the codes unrecoverable in any other way on the printed ballot.This documents current progress in our work, which is ongoing.This document is subject to change.