Post on 02-Jan-2016
A. Steffen, 27.02.2012, Kickoff.pptx 1
Kickoff Meeting „E-Voting Seminar“
An Introduction toCryptographic Voting
Systems
Andreas Steffen
Hochschule für Technik Rapperswil
andreas.steffen@hsr.ch
A. Steffen, 27.02.2012, Kickoff.pptx 2
Cryptographic Voting Systems
• Due to repeated failures and detected vulnerabilities in both electro-mechanical and electronic voting machines, voters have somehow lost faith that the outcome of a poll always represents the true will of the electorate.
• Even more uncertain is electronic voting over the Internet which is potentially prone to coercion and vote-selling (this doesn‘t seem to be an issue in Switzerland).
• Manual counting of paper ballots is not really an option in the21st century and is not free from tampering either.
• Modern cryptographic voting systems allow true end-to-end verification of the complete voting process by any individual voter, without sacrificing secrecy and privacy.
Summary:
A. Steffen, 27.02.2012, Kickoff.pptx 3
E-Voting in my home town Schlieren
Hidden PIN
„Internet-based voting does not have tobe more secure as voting per snail mail“
Justice Department of the Canton of Zurich
A. Steffen, 27.02.2012, Kickoff.pptx 4
[In]Security Features
???
Protection fromMan-in-the-Middle
attacks
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E-Voting Website
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Voter Login
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Ballot (PHP Form)
A. Steffen, 27.02.2012, Kickoff.pptx 8
E-Voting in my home town Schlieren
PIN
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Voter Authentication
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Transmission Receipt
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Conclusion
So what?„You are not allowed to know. The exact transactionprocessing is kept secret due to security reasons“
Justice Department of the Canton of Zurich
A. Steffen, 27.02.2012, Kickoff.pptx 12
Traditional Chain-of-Custody Security
Tallying
Source: Ben Adida, Ph.D. Thesis 2006
Software VerificationSealing
Verification by proxy only
A. Steffen, 27.02.2012, Kickoff.pptx 13
Desirable: End-to-End Verification by Voter
Source: Ben Adida, Ph.D. Thesis 2006
Secrecy?Privacy?
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End-to-End Auditable Voting System (E2E)
• Any voter can verify that his or her ballot is included unmodified in a collection of ballots.
• Any voter (and typically any independent party additionally) can verify [with high probability] that the collection of ballots produces the correct final tally.
• No voter can demonstrate how he or she voted to any third party (thus preventing vote-selling and coercion).
Source: Wikipedia
A. Steffen, 27.02.2012, Kickoff.pptx 15
Solution: Cryptographic Voting Systems
Source: Ben Adida, Ph.D. Thesis 2006
A B C
A
B
C
Threshold Decryption
ElGamal / Paillier
HomomorphicTallying
Mixnet
Tamper-ProofBulletin Board
A. Steffen, 27.02.2012, Kickoff.pptx 16
Proposed E2E Systems
• Punchscan by David Chaum.
• Prêt à Voter by Peter Ryan.
• Scratch & Vote by Ben Adida and Ron Rivest.
• ThreeBallot by Ron Rivest (paper-based without cryptography)
• Scantegrity II by David Chaum, Ron Rivest, Peter Ryan et al.(add-on to optical scan voting systems using Invisible Ink)
• Helios by Ben Adida (www.heliosvoting.org/)
• Selectio Helvetica by BFH (www.baloti.ch)
• Primevote by MSE graduates Christoph Galliker and Halm Reusser(www.smartprimes.ch)
A. Steffen, 27.02.2012, Kickoff.pptx 17
Conclusion
• Modern Cryptographic Voting Systems allow true end-to-end verification of the whole voting process by anyone while maintaining a very high level of secrecy.
• Due to the advanced mathematical principles they are based on, Cryptographic Voting Systems are not easy to understand and are therefore not readily accepted by authorities and the electorate.
• But let‘s give Cryptographic Voting Systems a chance!They can give democracy a new meaning in the 21st century!
A. Steffen, 27.02.2012, Kickoff.pptx 18
E-Voting Literature and Simulators
• http://security.hsr.ch/msevote/
• Collection of MSE E-Voting seminar papers
• E-Voting Simulator based on the Paillier Cryptosystem
• E-Voting Simulator on the Damgard-Jurik Cryptosystem• Generalized Paillier, reduces to Paillier Cryptosystem with s =
1
• Threshold Decryption with Distributed Keys issued by Trusted Dealer
• Assume generator g = n+1 ( = 1, = 1)
• The Paillier Cryptosystem, presented at the BFH E-Voting seminar
A. Steffen, 27.02.2012, Kickoff.pptx 19
E-Voting Seminar Project
• Verifiable E-Voting System for Shareholder Meetings.
• Example: Novartis AG with 2‘745‘623‘000 shares
• Item 1: Approval of the Annual Report and Financial Statements yes / no / abstention (32 bit field per option)
• Voter 1550‘000‘010 sharesVoter 2500‘000‘010 sharesVoter 3400‘000‘010 sharesVoter 4350‘000‘010 sharesVoter 5300‘000‘010 sharesVoter 6150‘000‘010 sharesVoter 7100‘000‘010 sharesVoter 8 50‘000‘010 sharesVoter 9 50‘000‘010 sharesVoter 10 50‘000‘010 shares
Total 2‘500‘000‘100 shares
A. Steffen, 27.02.2012, Kickoff.pptx 20
Partial Private Keyi=N, N, T, d, n
Encrypted Ballot
v=V, c, a[], e[], z[]
E-Voting Seminar Project Tasks
Threshold KeyGeneration byTrusted Dealer
1
Public Key
n, g=n+1
Ballot Encrypt.and ZKP by Voter
v
2
Encrypted Ballot
v=1, c, a[], e[], z[]
keysize, N, T
Partial Private Keyi=1, N, T, d, n
ZKP CheckWeighted
Tallying
3
Shareholder Registryv[], w[]
Partial Decrypt.by Trustee i
4
Encrypted Tally
ct
Partial Private Keyi=N, N, T, pt, n
Partiallly Decr. Tallyi=1, N, T, pt, n
ThresholdDecryption
5
Decrypted Tally
yes, no, abstention
Paillier Cryptosystemkeysize = 1536 bitsV=10, N=5, T=3
protected channel
A. Steffen, 27.02.2012, Kickoff.pptx 21
Conditions
• Goal: Restrict effort spent on project to 90 working hours (3 ECTS)
• Programming or scripting language: Arbitrary
• Program code without whistles and bells!• No GUI required, may be a command line program.
• I/O Format: JSON• Big numbers encoded as hexadecimal strings{"v":1,"c":"2fe698..daf57e"}
• Details of interface specification to be settled among tasks
• Deliverables: Commented program code and final test run data
• Slides of final presentation