CS 40 - Lecture 6

David S. Taylor

Lecture 5 Recap

• method: a named sequence of instructions
• parameter: an input to a method
• method call: a statement that contains the method name and parameter values
• calling a method: setting the parameters and executing the method instructions

How Was the Homework?

ActiveLecture.org

1. Too easy/boring
2. Just right
3. Too hard/confusing
4. Not done yet
5. What homework?

Thanks for your feedback! (HW 2 is due tomorrow!)

Computing for Congressmen

• Computing touches the lives of all citizens
• Examples: voting machines, spam mail, credit scoring, data privacy, music sharing, etc. etc.
• Stakeholders (hardware vendors, banks, copyright holders, etc. etc.) don't give unbiased advice
• Need a basic understanding of computer science to understand risks/rewards

History of Voting Equipment

• http://www.cs.uiowa.edu/~jones/voting/pictures/
• Before ballots
• Paper ballots
• Mechanical voting machines
• Punched cards
• Electronic voting machines

Voting Machines

• Automates the counting of ballots
• Scanner: Voter marks ballot or punch card, machine tallies them
• Direct recording: Voter pushes buttons, machine tallies button pushes
• Voter verifiable paper trail: Machine prints paper tape (behind glass window)

Positive Aspects

• Direct recording: Can reduce undervote by alerting voters to skipped selections
• Some machines help people with various disabilities (but others actually make it harder...)
• Generally faster results, greater accuracy than counts by humans

What Can Go Wrong?

• 2000: Hanging chads, overvotes
• 2006 Sarasota, FL: In heavily democratic county, 18,326 voters (13%) didn't vote for either house candidate...or did they? (Undervote in neighboring Manatee County: 2 percent). Republican won seat with 363 votes.
• 2007: Team lead by UC Davis Prof. Matt Bishop breaks into every CA voting machine (http://www.sos.ca.gov/elections/voting_systems/ttbr/red_overview.pdf)

Lab: Find the Flaw

• Load VotingMachine1.a2w and click Play.
• Click on the cow and the hampster [sic] to vote for dems and reps. Each click is one vote. (They didn't have donkeys and elephants.)
• Click on the toaster to get the result.
• What is the subtle flaw in this machine? (Spoiler on next slide.)
• Answer in ActiveLecture.org.

Lab: Find the Flaw #2

• Spoiler: Click Play, then click twice on the cow, twice on the hampster, then on the toaster.
• Load VotingMachine2.a2w and click Play.
• What is the subtle flaw? Hint: look into the source code for the toaster's sayWinner method.
• How can you demonstrate the flaw to a voting official who can't read code?
• Answer in ActiveLecture.org.

Lab: Find the Flaw #3

• Load VotingMachine3.a2w and click Play.
• What is the even more subtle flaw? Hint: look into the source code for the toaster's methods.
• How can you demonstrate the flaw to a voting official who can't read code?
• Answer in ActiveLecture.org.

Attack Scenarios

• Voting machine vendor favors one party???
• Rogue employee at voting machine vendor?
• Partisan poll workers
• Fraud during data consolidation
• Setup errors, particularly with complex elections
• Defects in hardware/software

Computer Science

• Impossible to prove that software works correctly
• Impossible to prove that software hasn't been tampered with
• Developing/testing high reliability systems is expensive, time consuming
• Independent verification/fallback is indispensable

Why the Resistance?

• Voting machine vendors
  • need to make a profit
  • have not been held to high standards
• Election officials
  • have limited funds
  • are not fond of recounts
  • are not always non-partisan
• Ignorance!

What is Being Done?

• Activist groups had some success
• http://verifiedvoting.org (founded by Stanford professor David Dill)
• Many states require independent paper trail
• Some states require mandatory random spot checks
• Sep 2007: HR 811 (sponsored by Rush Holt, D-NJ) considered by congress

Reminders

• Homework #2 is due tomorrow (email to me)