1.
Voters, Computers, and Trust:
Designing Verifiable Elections
Stuart M. Shieber
Ben Adida
Greg Morrisett
Center for Research on Computation and Society
October 18, 2008
School of Engineering and Applied Sciences
Harvard University

2.
Secure Voting

3.
• Voting is particularly challenging:
requires secrecy and public auditability.
• Computer science enables
qualitatively novel solutions.
• Cryptography can reconcile
seemingly contradictory requirements.

4.
quot;That's for me and a
button to know.quot;
Joe, the plumber.

5.
6

6.
6

7.
6

8.
6

9.
6

10.
6

11.
6

12.
7

13.
7

14.
“When I finally saw
the results of our tests,
I thought I was going to throw up.”
Sec. of State, Ohio, last week.

15.
Fashionable Voting
http://www.cs.uiowa.edu/~jones/voting/pictures/9

16.
Fashionable Voting
http://www.cs.uiowa.edu/~jones/voting/pictures/9

17.
Fashionable Voting
http://www.cs.uiowa.edu/~jones/voting/pictures/9

18.
Fashionable Voting
http://www.cs.uiowa.edu/~jones/voting/pictures/9

19.
Fashionable Voting
http://www.cs.uiowa.edu/~jones/voting/pictures/9

20.
Fashionable Voting
http://www.cs.uiowa.edu/~jones/voting/pictures/9

21.
Fashionable Voting
http://www.cs.uiowa.edu/~jones/voting/pictures/9

22.
Fashionable Voting
10

23.
Voting is a
fundamentally
difficult problem.
11

24.
14
12

25.
14
12
1 person, 1 vote

26.
Enforced Privacy
to ensure each voter
votes in his/her
own interest
13

27.
http://www.cs.uiowa.edu/~jones/voting/pictures/ 14

28.
1892 - Australian Ballot
http://www.cs.uiowa.edu/~jones/voting/pictures/ 15

29.
The Ballot Handoff
McCain
Alice the Voter
16

30.
The Ballot Handoff
McCain
Alice the Voter
16

31.
The Ballot Handoff
McCain
Alice the Voter
16

32.
The Ballot Handoff
McCain
Alice the Voter
16

33.
The Ballot Handoff
McCain Obama
Obama
Obama
McCain
McCain
McCain
Alice the Voter
16

34.
The Ballot Handoff
McCain Obama
Obama
Obama
McCain
McCain
McCain
Alice the Voter Black Box
16

35.
Chain of Custody
19

36.
Chain of Custody
1
/*
* source
* code
*/
if (...
Vendor
19

37.
Chain of Custody
1
/*
* source
* code
Voting */
2
Machine
if (...
Vendor
19

38.
Chain of Custody
1
/*
* source
* code
Polling Voting */
3 2
Location Machine
if (...
Vendor
19

39.
Chain of Custody
1
/*
* source
* code
Polling Voting */
3 2
Location Machine
if (...
Vendor
4
Alice
19

40.
Chain of Custody
1
/*
* source
* code
Polling Voting */
3 2
Location Machine
if (...
Vendor
4
Alice
19

41.
Chain of Custody
1
/*
* source
* code
Polling Voting */
3 2
Location Machine
if (...
Vendor
4
Alice
5
Ballot Box Collection
19

42.
Chain of Custody
1
/*
* source
* code
Polling Voting */
3 2
Location Machine
if (...
Vendor
4
Alice
Results
5 6 .....
Ballot Box Collection
19

43.
Chain of Custody
1
/*
* source
* code
Polling Voting */
3 2
Location Machine
if (...
Vendor
4
Alice
Results
5 6 .....
Ballot Box Collection
Black Box
19

44.
Computers have only
obscured the process.
20

45.
Computers have only
obscured the process.
What about
computer science?
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46.
Cryptography
solving problems that initially
appear to have conflicting
requirements.
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47.
Public-Key Encryption
Customer
22

48.
Public-Key Encryption
public key
Customer
22

49.
Public-Key Encryption
public key
enc(cc number)
Customer
22

50.
Public Ballots
Bulletin Board
Bob:
McCain
Carol:
Obama
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51.
Public Ballots
Bulletin Board
Bob:
McCain
Carol:
Obama
Alice
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52.
Public Ballots
Bulletin Board
Alice: Bob:
Obama McCain
Carol:
Obama
Alice
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53.
Public Ballots
Bulletin Board
Alice: Bob:
Obama McCain
Carol:
Obama
Tally
Obama....2
McCain....1
Alice
23

54.
Encrypted Public Ballots
Bulletin Board
Alice: Bob:
Rice Clinton
Carol:
Rice
Tally
Obama....2
McCain....1
Alice
24

55.
Encrypted Public Ballots
Bulletin Board
Alice: Bob:
Rice Clinton
Carol:
Ali Rice
ce
ver Tally
ifies
he
rv Obama....2
ote
McCain....1
Alice
24

56.
Encrypted Public Ballots
Bulletin Board
Alice: Bob:
Rice Clinton
Carol:
lly
Ali ta
Rice
ce e
thTally
ver es
rifi
ifies
e ve
he n
ryo
rv ve Obama....2
E
ote
McCain....1
Alice
24

57.
How can we verify
operations on
encrypted data?
Mathematical Proofs.
25

58.
Zero-Knowledge Proof
President:
President:
Mickey Mouse
President:
Mickey Mouse
President:
Mickey Mouse
President:
Mickey Mouse
President:
Mickey Mouse
Vote For:
Mickey Mouse
Obama
Vote For:
Obama
26

59.
Zero-Knowledge Proof
President:
President:
Mickey Mouse
President:
Mickey Mouse
President:
Mickey Mouse
President:
Mickey Mouse
President:
Mickey Mouse
Vote For:
Mickey Mouse
Obama
Vote For:
Obama
26

60.
Zero-Knowledge Proof
President:
President:
Mickey Mouse
President:
Mickey Mouse
President:
Mickey Mouse
President:
Mickey Mouse
President:
Mickey Mouse
Vote For:
Mickey Mouse
Obama
Vote For:
Obama
This last envelope
likely contains “Obama”
26

61.
Zero-Knowledge Proof
President: President:
President: President:
Mickey Mouse Mickey Mouse
President: President:
Mickey Mouse Mickey Mouse
President: President:
Mickey Mouse Mickey Mouse
President: President:
Mickey Mouse Mickey Mouse
President: President:
Mickey Mouse Mickey Mouse
Vote For: Vote For:
Mickey Mouse
Mickey Mouse
McCain
Paul
Obama
Open envelopes don’t prove
anything after the fact.
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