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Electronic Voting

Electronic Voting. R. Newman. Topics. Defining anonymity Need for anonymity Defining privacy Threats to anonymity and privacy Mechanisms to provide anonymity Metrics for Anonymity Applications of anonymity technology. Voting Requirements. Privacy

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Electronic Voting

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  1. Electronic Voting R. Newman

  2. Topics • Defining anonymity • Need for anonymity • Defining privacy • Threats to anonymity and privacy • Mechanisms to provide anonymity • Metrics for Anonymity • Applications of anonymity technology

  3. Voting Requirements • Privacy • Need anonymity to protect against retribution • Need privacy to protect against coersion • Authorization • Need to ensure only enfranchised vote • Need to prevent multiple voting • Verifiability • Need to make sure your vote was counted • Need to be able to verify tally is correct • Auditability is needed in case of disputes

  4. Specific Requirements • Data integrity and reliability - tamperproof • Voter anonymity and data confidentiality • Operator authentication • Documentation and assurance • Personnel integrity

  5. Specific Reqs – the ”-ilities” • System accountability • System disclosability • System availability • System reliability • Interface usability

  6. Types of Voting • Plurality Voting • One vote per voter • Candidate with most votes wins • Plurality with Run-off • Plurality voting selects top two candidates • Top two candidates have second election • Approval Voting • Voters can approve of multiple candidates • Candidate with most votes wins

  7. More Types of Voting • Instant Run-off • Candidate with fewest votes eliminated • Repeat until candidate with majority • Pairwise Elimination • Vote in tournament style • Borda Voting • Voters submit total order on candidates • Candidate with most points wins • Many more....

  8. Publically Verifiable Secret Sharing • Secret Sharing • Threshold systems • Basic versions assume: • Honest distribution • Honest reconstruction • PVSS resists • Dealer distributing incorrect shares • Anyone can verify correctness • Participants submitting incorrect shares

  9. Generic Approach - Players • Voters • Register and vote • Registrar • Validate voters • Distribute ballots • Ballot Box – Vote Certifier • Allow voters to post anonymous, verifiable ballots • Tallyer • Collect valid ballots • Post verifiable results

  10. Generic Approach - Phases • Phase I – Registering • Voter contacts Registrar, proves identity • Registrar verifies identity, gives blank ballot • Phase II – Voting • Voter prepares ballot, submits to ballot box • Ballot box validates ballot, posts ballots • Public (including voters) verify ballots • Phase III – Tallying • Tallyer combines votes on ballots, publishes results • Public verifies results

  11. Registering • Registrar gets list of valid voters • Voter sends Registrar proof of identity along with blinded ballots • Public key signature on message • Registrar verifies voter’s identity and validity • Verifies signature • Checks that name is on list of valid voters • Registrar signs blinded ballots • Typically uses cut-and-choose to detect cheating • Blinding removes association with voter

  12. Voting • Voter unblinds ballots • Voter selects ballot with candidate of choice • Voter anonymously sends ballot to Ballot Box • Ballot Box verifies ballot • Signature from Registrar • Ballot Box posts ballot • Voter can see that her ballot has been cast

  13. Tallying • Ballot Box closes polls when period is over • Tallyer collects all valid ballots • Tallyer computes results and posts • Public can validate results

  14. Registering – Alternative 1 • Registrar gets list of valid voters • Voter sends Registrar proof of identity • Public key signature on message • Registrar verifies voter’s identity and validity • Verifies signature • Checks that name is on list of valid voters • Registrar sends Voter blank ballot • Keeps digest of voters, ballots

  15. Voting – Alternative 1 • Voter marks signed ballot with choice(s) • Voter sends blinded marked ballot to Certifier • Voter signs blinded marked ballot • Certifier validates ballot • Checks signature vs. list of voters • Does not know ballot number • Signs blinded ballot • Voter unblinds ballot, anonymously sends to Tallyer • Tallyer anonymously sends receipt to voter

  16. Counting – Alternative 1 • Tallyer counts valid votes • Tallyer publishes results

  17. Registering – Alternative 2 • Registrar gets list of valid voters • Voter sends Registrar proof of identity along with blinded public key • PK used as a pseudonym • Registrar verifies voter’s identity and validity • Verifies signature • Checks that name is on list of valid voters • Registrar signs blinded public key • Blinding removes association with voter • Voter has registrar’s signature on PK certificate

  18. Voting – Alternative 2 • Voter produces ballot • Uses proper format • Signs balloot using pseudonym public key • Voter sends signed ballot to Ballot Box • Ballot sent anonymously • BB can’t link ballot to sender or to signer • BB verifies ballot • Checks signature on ballot • Checks that PK certificate signed by Registrar • BB posts valid ballots

  19. Tallying – Alternative 2 • Tallyer closes election when time is up • Tallyer combines validedated ballots • Publishes results

  20. Issues • Obtaining marked ballot that is • Not tied to the voter • Verifiable • Insuring that fraud cannot occur • Voter can only vote once • Nobody other than voter can use voter’s ballot • Only valid voters can vote • Auditability • What about write-in ballots?

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