Communications of the ACM
Volume 50, Number 11 (2007), Pages 120-120
Matt Bishop, David Wagner
Electronic voting has spread throughout the U.S. and the
world without sufficient attention to reliability, security, or transparency.
Today's e-voting systems use proprietary code, and vendors have often asserted
the confidentiality of this code when independent reviews of certified systems
were requested. This confidentiality conflicts with the transparency required
for public elections.
In order to provide an independent assessment of the voting
systems certified for use in California, Secretary of State Debra Bowen
initiated a top-to-bottom review of those e-voting systems. She asked us to
recruit a team of experts and gave us access to all the equipment, source code,
and technical information that the Secretary of State's office had.
The results showed that the systems appeared not to be
designed or implemented with security in mind. The design and implementation
ignored basic security principles, and we found serious security
vulnerabilities in all three vendors' systems. The security flaws were systemic
and surprisingly similar across the three systems.
For example, malicious code could exploit vulnerabilities in
the voting software to spread virally from machine to machine. As a result,
when the voting machines return results to election central to count the votes,
a virus could infect the county's election management systems. At the next
election, the infected election management systems could then infect every
voting machine in the county.
This virus could be introduced at several points in the
process. An attacker could tamper with an e-voting machine while it is stored
unattended over-night in a polling place. For some of the systems, a voter
could introduce malicious code in under a minute, while voting.
Many flaws resulted from elementary mistakes such as
straightforward buffer overrun vulnerabilities and flawed cryptography. One
piece of voting software appends a three-letter suffix to a password and sends
this "encrypted'' result over the network. Another has encryption keys
hard-coded in the source code, meaning the keys are the same for all machines
using that software—an obvious security flaw. One of the manufacturers used its
own name as a hard-wired password. Our public reports had to be written
carefully to convey the depth of the problem without providing a "road
map" for attackers.
We drew several lessons from this exercise.
First, the national regulatory system has not worked well.
Federal testing repeatedly failed to detect flaws in voting systems. Election
officials relied in good faith upon these certifications when they purchased,
deployed, and used these voting systems. They, and voters, deserve better.
This should provide a strong impetus to reform the oversight
system so that states do not have to bear the cost of securing voting systems
one state at a time. Vendors will build whatever the regulatory system allows
and the marketplace demands. So far these forces have failed to weed out flawed
Fortunately, the results of the top-to-bottom review give us
an opportunity to change the regulatory process to make it effective. Federal
officials are currently preparing a major revision of the federal voting
standards, and we encourage the computing community to become more involved in
Secondly, applying technology to solve one problem may
introduce other problems. E-voting systems were introduced to eliminate paper
and problems such as hanging chads. However, without paper, voters cannot check
that their vote is correctly recorded and cannot independently validate vote
totals. Thus the solution to one problem introduced another: the violation of a
fundamental tenet, that there must be an independent means for verifying
This problem can be mitigated with voter-verified paper
records that election officials audit after each election. However, only 16
states currently require this. The security vulnerabilities we found highlight
the importance of election auditing: without audits, there may be no way to
rebut suspicion of tampering.
Electronic voting systems form a critical part of the
election process. We have far to go to ensure they are a transparent and secure
part of that process.
Matt Bishop (firstname.lastname@example.org) is a professor in the
Department of Computer Science at the University of California at Davis. He
teaches and does research in computer security and information assurance.
David Wagner (email@example.com) is a professor in the
computer science division at the University of California at Berkeley, a
cofounder of the ACCURATE center on voting, and a member of the federal
advisory committee charged with helping draft the next-generation voting