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Usable Verifiable Remote Electronic Voting case study HELIOS 18.07.2012 SecVote Dagstuhl Comments Based on research results from the project Usable Verifiability in Remote Electronic Voting Project funded by Research conducted

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Usable Verifiable Remote Electronic Voting case study HELIOS

18.07.2012 SecVote Dagstuhl

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Comments

  • Based on research results from the project “Usable

Verifiability in Remote Electronic Voting”

– Project funded by – Research conducted by M. Maina Olembo

  • Assumptions:

– voter cast vote from trustworthy environment – voter receives authentication tokens (PWD) over secure channel

  • Focus on individual verifiability

– Cast as intended

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Overview

1. Why Helios and how Helios works? 2. Helios version 1.0 interfaces 3. Cognitive Walkthrough (KOKV2011)

1. Findings 2. Improved Interfaces

4. User study (KKOVV2011)

1. Design 2. Findings

5. Online survey

1. Design 2. Findings

6. Next steps

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Why ?

  • Proposed by Ben Adida in 2008: http://heliosvoting.org/
  • Implemented verifiable electronic voting protocol

– User interface – Opensource system – Well studied from security point of view

  • Has been used in legally binding elections
  • in academic contexts: UCL, Princeton, IACR, …
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How Helios works?

key holder 1 key holder 2 key holder 3 key holder 4 key holder 5 pk4 out of 5

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Invitation Email • Election URL • Direct Voting URL • Election Fingerprint • Email Address • Password Voting Booth • Election Fingerprint • Voting Instructions • Button: Start Press Button: Start Click 2nd URL Voting Booth • Election Fingerprint • Questions • Check Boxes • Button: Review Choices Voting Booth • Election Fingerprint • All Choices • Link: Update • Button: Encrypt Ballot Press Button: Review Choices Press Button: Encrypt Ballot Voting Booth • Election Fingerprint • Ballot Fingerprint • Button: Submit Encrypted Ballot • Button: Audit Ballot Press Button: Audit Ballot Voting Booth • Election Fingerprint • Box: Audited Ballot Information • Link: Helios Verifier • Button: Back to Choices Helios Verifier • Empty Box • Button: Verify Copy and paste Audited Ballot Information into Empty Box Helios Verifier • Box with Audited Ballot Information • Button: Verify • Result Verifying Process Press Button: Verify Press Button: Back to Choices Close Verifier to end Verifying Process Voting Booth • Election Fingerprint • Ballot Fingerprint • Panel: Email • Panel: Password • Button: Send Press Button: Submit Ballot Press Button: Send Confirmation Email • Election Fingerprint • Ballot Fingerprint Loop Click Link: Verifier Click Link: Update Independent application in separate window Helios Voting • Election ID • Election Fingerprint • Link:Vote • Link: Audit • Link: Bulletin Board • Box: Administration Click 1st URL Click Link Vote

How Helios works?

write down/ store/ print ballot fingerprint Compare

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Bulletin Board

Pseudonym/Voter’s ID1 ballot fingerprint1 Pseudonym/Voter’s ID2 ballot fingerprint2 …… ….. …. Pseudonym/Voter’s IDn ballot fingerprintn

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Important aspects

  • Separation of vote preparation/encryption and vote casting

Everyone, including auditors or election observers can verify cast as intended

  • Software commits to its encryption by displaying a hash of the

ciphertext = ballot fingerprint

To ensure that the software provides the same ciphertext for verification and vote casting

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Important aspects

  • Voter can verify as many (test) ballots as he/she wants

From the software’s perspective, it cannot encrypt the wrong candidate with a sufficiently high probability of not being detected

  • In order to ensure the secrecy of the vote, it is not possible to first

verify and then cast this ballot but needs first to be reencrypted New ballot fingerprint The voter cannot verify the encrypted ballot he finally casts but must trust the system due to previous checks.

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Individual verifiability – stored as cast

  • Use ballot finger print from vote casting
  • Verify whether is stored on the bulletin board next to the

voter’s ID / pseudonym by comparing

  • Remarks:

– Can be repeated during the vote casting phase as well as during and after the tallying phase – Voter or external observers verify that encrypted votes match to published hash values

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Properties and Assumptions

Properties Verifiability Coercionresistance Receiptfreeness Assumptions

  • Cryptography works
  • Trusted environment
  • Not coercion

resistant (voter ID tied to hash value on Bulletin Board)

  • Cryptography works
  • Trusted environment
  • (nk+1) honest key

trustee

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Helios version 1.0

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Helios version 1.0

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SecVote

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Cognitive Walkthrough [KOKV11]

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Cognitive Walkthrough [KOKV11]

  • Carried out on Helios version 1.0 and later on version 3.0

– Interfaces evaluated from voter perspective

  • How usable is it to cast and verify a vote?

– Five experts from security, evoting and psychology – Fictitious university president election

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might be scary ? ? What to do with the ballot fingerprint / receipt ? ? O/0?

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? where ? “ … how your options where encrypted”? How to continue verifying / casting a ballot? verify/audit?

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? “ … how your options where encrypted”? ? how to continue?/ vote cast? Independent? anything to verify? what to do if it does not match? C&P is error prone

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Cognitive Walkthrough [KOKV11]

  • Carried out on Helios version 1.0 and later on version 3.0

– Interfaces evaluated from voter perspective

  • How usable is it to cast and verify a vote?

– Five experts from security, evoting and psychology – Fictitious university president election

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?

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? ! Missing instruction: comparison new: trust?

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? new ? ? verify again? ?

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Independent? ? even worse!

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Findings

Complicate (many steps) and error prone verifiability Missing: clear terminology and clear instructions Same design for verification and main voting interface Irritation to authenticate at the end of the voting process

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Improved Interfaces (1)

Clear instructions To authenticate servers

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Improved Interfaces (2)

Added verifiability step Instructions to voters

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Improved Interfaces (3)

Back and Forward Buttons

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Improved Interfaces (4)

Shortened verification code Options for voter

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Improved Interfaces (5)

Trusted institutions for verification

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Improved Interfaces (6)

Simplified results Clear instructions

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Improved Interfaces (5)

Only button

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Improved Interfaces (7)

Explanation for voter Automatically reencrypted

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Comparison

Old New

Click Audit (Drops down to give more information) Click Verify Encryption Click verify the ballot Click link to select information Rightclick and copy Click Ballot Verifier link Click on verifying institute Paste information in ballot verifier window Click Verify Close window Click close window (as in PPT) Click Back to Voting Click enter new vote button (as in PPT) Click Confirm button to reencrypt or Update to change vote [automatic]

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User Study [KKOVV2011]

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Design of the user study (lab study)

  • Mock mayoral election in Darmstadt
  • Material/Interface in German
  • 34 participants
  • Asked to put on a modified bicycle

helmet with a video camera and eye tracking

  • Participants cast a vote w/o

instructions (2 rounds)

– Would people verify? How? – Can people verify if we tell them to do so? – Instructions emphasized verifying with different techniques, different votes

  • 3 questionnaires

Note: hard for participants to take it serious as it is not a secret election due to eye tracker and log files

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General Usability (after round 1)

fully agree do not agree

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General Usability

  • 1 of 20 who answered that they verified further stated not

having noticed that the code changed (round 1)

  • 1 of the remaining 14 stated this in round 2

Most of participates noticed it

  • After round 2
  • 8 of 34 participants stated that it was not clear to them that they had

to compare the verification codes or/and the candidates

  • All stated that it was clear to them that their vote was not cast after

having verified

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How many people verified?

  • 20 of 34 participants (58%) verified in the first run (log files)

– 10 with technical background verified – 10 without technical background verified

No correlation between technical background and interest in verifying

– All did some comparison, some only very quick (eye tracking)

  • 28 of 34 (82%) claimed to have verified at least once

– Some participants confused “verifying” with double checking that their ballot was correctly filled. – 2 went to the verification page but then back without having verifieid

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Duration for vote casting

minutes From enter URL/ press enter and cast vote / entered correct credentials

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Preferred method of verification of the security code

  • Round 1:

– 17 wrote down, 9 saved, 4 printed – none compared with displayed commitment if printed or stored

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Is the authentication at the end of the voting process irritating?

fully agree do not agree

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Do people have enough information to properly verify and cast their vote?

  • 16 of 34 participants (47%): not enough information

– Participants without technical background complained that the first page (with the instructions) contained too much information at once (some didn’t even read it) – Participants with technical background wanted more information about the security of the system (papers, security proofs, statements from other institutions regarding the level of security etc.)

  • 31 of 34 participants (91%): concept of verifiability needs to

be introduced before using this kind of voting system

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Trust regarding ballot secrecy

  • Concerns about their vote secrecy….

– “The institutions can see my vote!” “… but they have strong privacy policies” – “derive vote from verification code is possible for institutes for whom else? – 26 participants (76%) answered that they were irritated by the changing verification code – 2 out of 20 in first round modified vote after having verified

  • Possible reason

– Idea behind reencrypting the ballot after verification unclear – Concept of test vote unclear

fully agree do not agree

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Trust in correct vote casting & tallying

  • Participants were not able to verify the proper tallying at all

Trust level in the proper tallying was expected to be lower than in correct vote casting

  • Possible reason: People were not aware that these are two

different concepts

fully agree do not agree

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General comments

  • “Normal people will find it too complicated.” (with technical

background)

  • “Good to know it is encrypted” (without technical background)
  • “Got confused with the different verification codes”
  • “Writing down a new security code each time annoys me.”
  • “I do not understand the idea behind the verification code”
  • “Why should I trust the verification procedure if I should not trust

the voting system”

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Findings

  • Most people are able to verify (at least with quick check)
  • People do not get the idea of test ballots to verify
  • People do not understand what they can verify and what not
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Online survey

  • Carried out to identify voters’ mental model of verifiability

– Are voters aware of verifiability? – Do they see a need to verify their votes? – Are there factors that are more likely to cause voters to verify? – What terminology is adequate to communicate verifiability to voters?

  • In Kenya and Germany

– Kenya: no postal voting, not possible to observe – Germany: 30% postal voting, possible to observe

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Design

  • Interviews carried out as a pretest
  • Refined online questionnaire
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First Findings

  • More familiar with aspects of universal verifiability

– Match number of voters to votes cast – Recount

  • Not as familiar with aspects of individual verifiability

– Seals at ballot boxes to ensure that they are not opened – Concerned about secrecy of the vote

  • General verifiability findings

– Some prefer delegating responsibility of verifying to others – More likely to verify with Internet voting than with paper based voting but

  • nly with first elections

– Verify if unexpected result (mentioned recount) – No need for traditional paper based elections because of trust in people who they know

  • More familiar terms than verifiability

– Monitor, observe

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Next Steps

  • Improve usability of hash value

– Represent hash value graphically – Identify secure enough length for hash value – Analyze what are people willing to compare

  • Explain concept of “test” votes better
  • Changes to interface based on results

– Adopt wording – Number for each hash value – Go back to empty ballot – Only ‘write down’ option – Distribute receipt for ‘stored as cast’ verifiability – Use QR code and Android app for comparison

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UNIVERSITY PRESIDENT ELECTION

https://www.presidentelection.university.com

Instructions Ballot VerificationCode VoteCasting

You can now verify whether your ballot is correctly encrypted. Click on the logo of your choice. A new window will open with the results of the verification. In order to verify your vote, the ballot will be decrypted. Once the process is finalized, your vote will be reencrypted and a new verificationcode generated. You can continue with the voting process upon successful verification. If you notice any irregularities, cancel the election process immediately and contact the election officials [Telephone number: 123456789] Institutes:

Trust in verification device or voting environment enough

Enter a new vote to proceed with the election

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Open Discussion

  • Currently: some cumbersome steps for the voter

– Check https for voting page – For each verified vote:

  • Write down hash value and compare with verification page of institute(s)
  • Check https for institute’s page

– For casting: Write down hash value and compare on board – In addition: check on bulletin board

  • Alternative: vote casting from different trusted institutions

– Check https for voting page – Could forward ballot fingerprint to delegate ‘stored as cast’ verification

  • Combination?
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Questions?

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Literature

Helios voting system: Adida, B. 2008. Webbased open audit voting. In Proceedings of the 17th symposium on security, pp. 335–348. Berkeley, CA, USA: USENIX Association.

[KOKV11] Usability Analysis of Helios An Open Source Verifiable Remote Electronic Voting System by Fatih Karayumak, Maina M. Olembo, Michaela Kauer, Melanie

  • Volkamer. In: Proceedings of the Electronic Voting Technology Workshop/Workshop on

Trustworthy Elections (EVT/WOTE), 2011.

[KKOVV11] User Study of the Improved Helios Voting System Interface by Fatih Karayumak, Michaela Kauer, Maina M. Olembo, Tobias Volk, Melanie Volkamer. In: SocioTechnical Aspects in Security and Trust (STAST), 2011 1st Workshop on , p. 3744, IEEE Digital Library, 2011. ISBN 1457711817.

[SN93] Mental models: Concepts for human computer interaction research by STAGGERS, N., AND NORGIO, A. F. Int. J. ManMachine Studies 38, 4 (1993), 587 605.