Smart Cards in Hostile Environments

摘要

This paper argues that many proposed smart card systems still lack effectivesecurity for point-of-sale applications. We discuss several types of modifications that can be made to smart cards to improve their security and address this problem. We prove a set of equivalences among a number of these modifications: (1) private input = private output; (2) trusted input + one-bit trusted output = trusted output + one-bit trusted input; and (3) secure input = secure output.