Implementation Requirements for

UK General Elections

Chris Culnane

James Heather

Steve Schneider

Sriramkrishnan Srinivasan

Zhe Xia (Joson)

Implementation Requirements

• First-Past-The-Post (FPTP) & Alternative Vote (AV)• Focus a single constituency (around 80,000 votes)• Multiple channel for vote casting (paper ballot & touch surface)• No special equipment needed (off-the-shelf hardware)• Threshold trust (distributed trust at least)• 128-bit security level• Ballot generation phase in 72 hours• Ballot tallying phase in 8 hours (10pm – 6am, 0.3s/vote)• Auditing of the ballot tallying phase in 72 hours• All votes information in a single DVD (4.7GB)• All the audit information in a single blue-ray disk (25GB)• Accessibility• Law issues

1. First-Past-The-Post (FPTP)

or

Alternative Vote (AV)

UK General Election 2010

First-Past-The-Post (FPTP)Conservative

Labour

Lib Dem X

Others

Labour

102 101

Lib Dem Conservative

99 98

Others

UK Election Reform

Alternative Vote (AV)

Conservative 1

Labour 3

Lib Dem 2

Others 4

Labour

102 101

Lib Dem

Conservative

99

200

Alternative Vote is also called Instance Runoff Voting (IRV) sometimes

Others

98

120

179

230

170

2. A single constituency

80,000 voters

3. Multiple channel for vote casting

• Paper based surface

• Hybrid touch surface

4. Off-the-shelf hardware

5. Threshold trust• Threshold key generation

without a trusted dealer

• Threshold decryption

6. 128-bit security level

Key Length ---- ECRYPT II

Key Length ---- NIST

7. Time consideration• Ballot generation in 72 hours (1.2s /

ballot)

• Ballot tallying in 8 hours (0.3s / vote)

• Verification in 72 hours

8. Data size consideration• All vote information in a single DVD

(4.7GB)

• All the audit information in a single blue-ray disk (25GB)

9. Accessibility• 5-10 candidates

• No special knowledge needed

• Accessibility for disabled voter

10.Law and patent issues

• Candidate list in the alphabetic order

• Some building blocks may be patented

Building Blocks

• Prêt à Voter ballot form (uniform ballot for both FPTP and AV)• ElGamal with re-encryption mixes (no homomorphic tally)• Verifiable shuffle (Randomised Partial Checking)• Threshold key generation without a trusted dealer• Verifiable decryption (Chaum-Pedersen proof)

Implementation Design

Election Manager

Candidate Names

Printers

Ballot SerialCandidate Names

Bulletin Board

Ballot Data

Tellers & Mix Servers

Polling Station Legal Guardian

Ballot Papers Sealed ID List

Booth

Signed Receipt

Ballot LookupVote Submission

Ballot Data, Vote

Thank you!