Download pdf - Voting Security Overview

(Electronic)Voting Security

Ben AdidaHarvard University

Workshop on Electronic VotingIDC Herzliya17 May 2009

The Point of An Election


“The People have spoken....the bastards!”

Dick Tuck1966 Concession Speech


“The People have spoken....the bastards!”

Dick Tuck1966 Concession Speech

Provide enough evidenceto convince the loser.

"That's for me and a button to know."

Joe, the plumber.

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Fashionable Voting

http://www.cs.uiowa.edu/~jones/voting/pictures/7

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


Fashionable Voting




Fashionable Voting




Fashionable Voting




Fashionable Voting




Fashionable Voting




Fashionable Voting




Fashionable Voting

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Fashionable Voting

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Voting is a fundamentally difficult problem.

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Wooten got the news from his wife, Roxanne, who went to City Hall on Wednesday

to see the election results.

"She saw my name with zero votes by it.She came home and asked me ifI had voted for myself or not."

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1 person, 1 vote

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Enforced Privacyto ensure each voter

votes in his/herown interest

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http://www.cs.uiowa.edu/~jones/voting/pictures/ 13




1892 - Australian Ballot

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The Ballot Handoff

Alice the Voter

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McCain

The Ballot Handoff

Alice the Voter

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McCain

The Ballot Handoff

Alice the Voter

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McCain

The Ballot Handoff

Alice the Voter

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McCain

The Ballot Handoff

Alice the Voter

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McCain

ObamaObamaObama

McCainMcCain

McCain

The Ballot Handoff

Alice the Voter

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McCain

ObamaObamaObama

McCainMcCain

Black Box

McCain

Chain of Custody

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Chain of Custody

Vendor

/*

* source

* code

*/

if (...

1

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Chain of Custody

VotingMachine

2

Vendor

/*

* source

* code

*/

if (...

1

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Chain of Custody

VotingMachine

2

Vendor

/*

* source

* code

*/

if (...

1

Polling Location

3

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Chain of Custody

VotingMachine

2

Vendor

/*

* source

* code

*/

if (...

1

Polling Location

3

4

Alice

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Chain of Custody

VotingMachine

2

Vendor

/*

* source

* code

*/

if (...

1

Polling Location

3

4

Alice

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Chain of Custody

VotingMachine

2

Vendor

/*

* source

* code

*/

if (...

1

Polling Location

3

Ballot Box Collection

5

4

Alice

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Chain of Custody

VotingMachine

2

Vendor

/*

* source

* code

*/

if (...

1

Polling Location

3


5

Results

.....6

4

Alice

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Chain of Custody

VotingMachine

2

Vendor

/*

* source

* code

*/

if (...

1

Polling Location

3


5

Results

.....6

4

Alice

Black Box18

The Cost of Secrecy

The Cost of Secrecy

The Cost of Secrecy

The Cost of Secrecy

The Cost of Secrecy

But Secrecy is Important.

Secret Ballot implemented in Chile in 1958.

“the secrecy of the ballot [...] has first-order implications for resource

allocation, political outcomes, and social efficiency.”

[BalandRobinson 2004]

Because we care about a meaningful result, we’ve made auditing

very difficult.

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We are left chasing evidence of correctness.

Meanwhile we destroy evidence on purpose.

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Obtaining Evidence

VotingMachine

2

Vendor

/*

* source

* code

*/

if (...

1

Polling Location

3


5

Results

.....6

4

Alice

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Obtaining Evidence

- source code audit

- Logic & Accuracy

- Parallel Testing

- Voter-Verified Paper Audit Trail

VotingMachine

2

Vendor

/*

* source

* code

*/

if (...

1

Polling Location

3

Obtaining Evidence

Polling Location

3

4

Alice

- Multiple poll watcherscompeting affiliations

- No personal electronic devicesat the polling station

- Logging all events

Obtaining Evidence

- redundant counts

- ballot box seals

- statistical auditing by partial recounts


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Results

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Fragmented, Adversarial and Indirect

- each piece of evidence coversa small segment of the chain.

- attacker knows the checks, and can try to sneak in where the chain is not covered.

- to maintain security and for practical purposes, the evidence is very indirect.

The Effect of DREs

- More to audit

- Errors can have disproportionate effects

- Software is not just for speed/efficiency,it becomes central for integrity.

Software Independence

an undetected mistake in the system does not cause an

undetectable error in the tally.

Can we getmore direct,

more end-to-end evidence?

Secret Ballot vs. Verifiability

Voting System

Alice

convince

Carl the Coercer

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Secret Ballot vs. Verifiability

Voting System

Alice

convince

Carl the Coercer

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[Chaum81], [Benaloh85], [PIK93], [BenalohTuinstra92], [SK94], [Neff2001], [FS2001],[Chaum2004], [Neff2004], [Ryan2004], [Chaum2005]

Punchscan, Scantegrity I & II, Civitas, ThreeBallot, Prêt-à-Voter, Scratch & Vote, ...

Bulletin Board

Public Ballots

Bob:McCain

Carol:Obama

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Bulletin Board

Public Ballots

Bob:McCain

Carol:Obama

Alice

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Bulletin Board

Public Ballots

Alice:Obama

Bob:McCain

Carol:Obama

Alice

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Bulletin Board

Public Ballots

Alice:Obama

Bob:McCain

Carol:Obama

Tally

Obama....2McCain....1

Alice

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Encrypted Public BallotsBulletin Board

Alice:Rice

Bob:Clinton

Carol:Rice

Tally


Alice

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Alice:Rice

Bob:Clinton

Carol:Rice

Tally


Alice

Alice verifies her vote

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Alice:Rice

Bob:Clinton

Carol:Rice

Tally


Alice

Alice verifies her vote Everyone verifies the tally

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End-to-End Verification


Polling Location

VotingMachine

Vendor

/*

* source

* code

*/

if (...


Polling Location

VotingMachine

Vendor

/*

* source

* code

*/

if (...

Ballot Box /

Bulletin Board

Alice


Polling Location

VotingMachine

Vendor

/*

* source

* code

*/

if (...

Ballot Box /

Bulletin Board

Alice

Results

.....


Polling Location

VotingMachine

Vendor

/*

* source

* code

*/

if (...

Receipt

1

Ballot Box /

Bulletin Board

Alice

Results

.....


Polling Location

VotingMachine

Vendor

/*

* source

* code

*/

if (...

Receipt

1 2

Ballot Box /

Bulletin Board

Alice

Results

.....

Open-AuditElections

Evidence-Based Elections

[email protected]

mailto:[email protected]

mailto:[email protected]