Attacking the Diebold Signature Variant -- RSA Signatures with Unverified High-order Padding

TL;DR

An very mathematically simple attack is presented that enables an adversary to forge signatures on arbitrary messages in a negligible amount of time.

Abstract

We examine a natural but improper implementation of RSA signature verification deployed on the widely used Diebold Touch Screen and Optical Scan voting machines. In the implemented scheme, the verifier fails to examine a large number of the high-order bits of signature padding and the public exponent is three. We present an very mathematically simple attack that enables an adversary to forge signatures on arbitrary messages in a negligible amount of time.